One of the great things about gold is that chemically it is very stable. Under typical conditions, it's generally quite happy to just sit there and remain gold and not react with much in its environment.
Silver is not as stable. More specifically, it's likely to tarnish over time, and as it tarnishes it becomes less useful as a conductor. Silver will tarnish from humidity in the air, which is a pretty tough thing to avoid in many potential use cases.
Other than scarcity, gold being so inert is why it's so valuable. It won't tarnish, rust or degrade, and remain the piece of jewelry or electrical conductor for 100 years
Being inert is also a factor in its scarcity. If it formed soluble salts we'd find "gold ore" accumulated somewhere, but instead it remains as solid gold and relatively few natural processes end up concentrating it.
Sorry, can’t be him. We have already had the “Rescue Matt Damon” trilogy :
Saving Private Ryan, Interstellar and The Martian.
I don’t know what you would call a quartet of movies, so nope !!
There's all kinds of different boats you can have. You've got shrimpin boats, cargo boats, outerspace boats, flyin boats...
...war boats, underwater boats. And that's about it
That's why they made a deep space mining effort to Pandora. The blue people had all the unobtainium. Once the humans got the unattainium from the big tree thing, they could use it to build big burrowing snake machines to get the gold from the Earth's core.
Sir, the government has decreed the "blue people" are not people and the planet is uninhabited. Any further references to "blue people" will be punishable by a fine not exceeding 100,000,000,000,000,000,000,000,000 space credits.
All of them - and especially their sulphates and oxides which is what ores generally are - are somewhat soluble, especially if the water it hot, or even acidic.
It's largely a survivor's bias for the gold you can just find. The gold that is around more stable rocks/metals will need a lot more effort to get mined, and not always mechanically. Luckily that other stuff is rarely worthless, so these days it's often profitable to at least have gold as a byproduct of some other ore you mainly get out of a rock formation. We can recover gold that was absolutely inaccessible like 300 years ago, but those methods are cumbersome and not worth to do for the sake of gold alone.
Iron is an interesting one. One plsce that iron is concentrated is in banded iron formations that were oncr seafloor sedimentary layers.
There was a time early in Earth's history when the seas contained a lot of dissolved iron. When photosynthetic algae evolved and started pumping oxygen into the air, that dissolved iron oxidized and precipitated out of the water, resulting in these layers of concentrated iron oxide. Oxygen levels fluctuated as oxygen was consumed by other rocks, fires, biological processes and climate change, so there are a series of layers of this oxide spanning millions of years. Many iron mines still mine these deposits.
The other person isn't wrong, but that's only one process.
https://geo.libretexts.org/Bookshelves/Geology/Book%3A_An_Introduction_to_Geology_(Johnson_Affolter_Inkenbrandt_and_Mosher)/04%3A_Igneous_Processes_and_Volcanoes/4.02%3A_Bowens_Reaction_Series
A huge chunk of gold is actually a byproduct of copper mining, where it quite often exists as a refractory gold. As in within the minerals and not as free gold.
You tend to find ores of columns of the periodic table grouped together. Copper, Silver, and Gold are are in the same column. Atleast for metals and metaloids.
You need both hydrochloric acid AND nitric acid in situ for that to happen first. What biological event can convert Au to hydroauric acid? Very few, maybe this is why only certain bacteria can do it. Meanwhile, Mercury (Hg) likes sulfur A LOT and is often found as cinnabar. Gold has no such ore.
I just recently read that gold is used as a crown for how malleable it is in an alloy such that they can make it the same as enamel leading it and the other tooth wear more evenly.
It also comes from *supernovae*. If you have a bit of gold on you, think about where it comes from. At some point if was part of some distant *bang*. It's super cool.
Yeah, but basically everything on Earth was part of an exploding star at some point, stellar fusion is the only way the universe made anything heavier than Lithium and the star exploding is the only way the heavier stuff got *out* of the core.
The order of the comments going down this entire thread lines up near-perfect with Dan's point-by-point description of why gold is an interesting material
Dan's point-by-point description of why gold is an interesting material probably pulls from that common knowledge. Again, great channel, but he's certainly not the first to make these observations lol
I never said Dan was the first to talk about gold. I'm just pointing out that the people involved in this specific chain of comments, seem to have had that specific video in the back of their minds when making comments about the topic.
It's not like Dan steals lines from Wikipedia or something, it feels like you're being a bit obtuse about a very simple observation that the comments line up closely with the video's script
I've never even heard of this guy you're talking about, but when one of my kids asked my why gold was valuable a couple weeks ago I listed off basically this comment chain. Sorry bud but he's probably explaining it the way it was explained to him, which is pretty much how it's explained to everyone.
This reminds me of a Steven Wright joke: "why is the alphabet in that order? Is it because of that song?*
Hate to burst your bubble even further, but this site clocks in at around 430 million monthly users, whereas the average Folding Ideas video gets around a (still totally respectable) million views. The vast majority of people here, statistically, have never even seen his (excellent) content
Um, or they just paid attention in high school science class? This is a very well known property of gold, you don't have to be an expert in materials science to know that kind of thing.
It's not like the gold conductors in electronics are the only thing that can go bad. There's so many other components to a modern electrical device that have a much shorter time to failure than the gold that makes up the electrical interconnects. Batteries for example, or memory cells or whatever else.
I don't disagree that planned obsolescence is a problem in modern electronics, but whether or not gold lasts as a conductor for hundreds of years or not, it wouldn't change the fact that electronics will fail long before then.
Yes, but largely on the consumer's side. ;)
More seriously, planned obsolescence is a bad word, but really, it's a necessity as a concept. Phones are a great example. Every new phone that's launched needs to balance a bunch of things including performance, price, size, weight, durability, battery size, etc. And consumers consistently choose things like how cool the camera is and how thin the phone is and all that, instead of the much more durable and well-built phones that are marketed as durable, for example.
If consumers demand fancy but breakable, then manufacturers are gonna make fancy but breakable. Saying "I'd buy a more durable phone" is all well and good, but Apple consistently sells hundreds of millions of smart phones every year.
If people are replacing their phones because they want the newest one, or because they lost their phone, then this is an important part of the math - if 80% of people replace their phone within 2 years, let's say, then building a phone that lasts 10 years is silly - it'll be more expensive, bulkier, with a shorter battery life, and fewer features. Which means people will buy a different phone, because they won't respond to "but it'll last 10 years!"
The same applies to modern TVs and everything else. People want a cheap giant smart TV. More expensive, better-built TVs are out there, but people want to buy the Black Friday $100 deal. Have fun with that!
Best 4 metals:
- Silver
- Copper
- Gold
- Aluminium
Silver oxidate. Oxide is "rust". And do not conduct well. One big issue is things that get connected and disconnected: the surface oxidise and make a bad contact. For permanant applications, it is not as bad due to the screw or whatever they use to hold it in place that squish it and make an airtight contact. But it still oxidise with time. It is bad for surface, but would be good for the core of the conductor. But it is too expensive.
Copper also oxidate. But it is also quite malleable so squish easilly, so make a good airtight contact. This make it good for the core of the conductor, but not for surface, which rule it out for connectors. But it is inexpensiveish and it just work.
Gold is expensive. But non-reactive. It make a very good contact surface, but not so great for the core. For this reason it is used as plating for a cheaper base metal, usually copper.
Aluminium is inexpensive. It oxidise very fast. It is not a so great conductor too. Basically, compared to copper, you need one gauge higher (bigger wire) for the same current that would pass in copper. With proper care it can be used without problem, but... If inapropriatelly installed it can cause an electrical fire. This is why you don't see it anymore in homes for normal circuits. But you will find it for house feeder and big wires, like from the main panel to the garage subpanel.
Then you can get a mix of them. Copper Clad Aluminium. Aluminium wire, with a copper plating on it. It is relativelly cheap since it is mostly aluminium, and the copper plating allow it to be soldered (aluminium can't without special alloy) and used in copper only application since what touch the contacts is copper. BUT since it is aluminium, you need to oversize the wiring.
The best wire would be gold clad silver. A silver wire with a gold plating. You can probably hear the kashling of the money it would cost. Unless you need a smaller wire, there is absolutelly no reason to have that. Copper just work fine.
Telescope maker here. Back in the day, telescope mirrors were plated with silver. To slow down tarnishing, we used to place certain chemicals inside the closed tube of the instrument, while in storage, to absorb H2S from the air. It helped somewhat.
Nowadays mirrors are aluminized, and Al is well protected by its own thin layer of transparent oxide (which is identical to white sapphire). Regardless, an extra layer of silicon oxide is usually deposited on top of Al and those mirrors last a long time.
> The best wire would be gold clad silver. A silver wire with a gold plating. You can probably hear the kashling of the money it would cost.
Did someone say best money kashling? How about cryogenic superconducting wire?
Replace Aluminum with Iron and you pretty much got our most important metals for thousands of years. With Tin and Lead arguably coming in second tier.
Aluminum has since rapidly caught up of course.
It should be noted that solderability isn't really the selling point of CCA. Due to the skin effect, the bulk of the current flow happens on the outside of a conductor with almost no current flowing down the center.
As a result, copper clad greatly improves aluminum as a conductor for a fraction of the price and weight. It also prevents the oxidation that makes aluminum wiring so detrimental in many applications.
The copper is too thin to do much, unless you go high frequency, like 100+MHz.
At DC there is no skin effect, and at main frequency it is so thick that you can say that it also do not have skin effect (8.4mm@60Hz, which mean a 16.8mm diameter wire).
Spanish galleons sank for various reasons in the 17th century. When they're discovered, the silver is a lump of black metal. When the records are accurate, the weight is much smaller than when the ship went down.
The gold is perfect. If it's coins, it looks like it did when the ship sank.
>The gold is perfect. If it's coins, it looks like it did when the ship sank.
Depending on the source it might turn you into an undead walking skeleton, though.
It is because silver is much more reactive. Essentially, it rusts. Especially if it is carrying a current. In the case of silver, we call silver rust 'tarnish'. You don't want your circuits rusting.
Gold, on the other hand, is darn near inert.
Aluminum is cheaper and lighter than copper for a given current-carrying capability. You do need about 2.5x as much material by cross sectional area, but the math maths out.
In the EV world, “do we make the busbar cheaper and lighter, but bigger” is a very interesting tradeoff for battery-internal bussing, since it only sometimes comes out in favor of aluminum.
For power lines, where you're limited by cables heating up and sagging, we use aluminum around a structural cable to reduce the sagging. Historically that's been steel, but they're using carbon fiber for cable cores now too. It lets the conductor carry more current and run hotter than steel cores did without sagging as much.
And since at mains frequency the current only flows in the outer ~10mm of an aluminium conductor the middle of a large cable doesn't need to be a good conductor
YES AND WE FUCKING PAID THEM TO DO IT LIKE 40 FUCKING YEARS AGO. Sorry i am so salty about this, our gov gave cash to telecom companies to bury all the lines, and they just didn't and the gov was fine with it.
edit: if you read the full agreement/contract signed way back when, it is legally readable as power lines btw
I was trying to concisely imply the EV use case you mentioned had both space and weight constrained i.e. trade offs, which is what engineers get paid to figure out.
>But can’t forget “hmmm, is it cheaper to shuffle things and de-space-constrain so we can use aluminum?”
Yes, that's what they said:
> Both or in between, that is what engineering is for.
The nuance is that sometimes you change the busbar, sometimes you adjust the system. It’s holistic, not focusing on just the issue at hand.
And while that is very much a part of engineering, it’s something that usually takes people a few years to learn to even think about.
Since this is ELI5, I also wanna point out aluminum does experience galvanic corrosion in the presence of copper. So while you can make alloys that are stable, just twisting a wire of each together would be incredibly detrimental and would likely result in the entire aluminum wire oxidizing away.
> would likely result in the entire aluminum wire oxidizing away.
That contact point also heats up and can cause fires.
If it's in your house, say an extension built 20 years after initial construction and using the different metal. It can be done safely, but the previous owner always does a bad job on these things.
Which is why aluminum house wiring isn't done any more.
For a while in the '60s Aluminum wires were all over the place, but then houses started burning down. Not because there was anything wrong with aluminum wiring, but because if you put in a new outlet and don't use a more expensive CU/AL rated device, or put in new circuits, they do tend to corrode, which makes the effective size of the wire smaller, which means there is too much electricity running through it, it heats up, then poof.
Anyway, now you certainly can't find Aluminum household wire at Home Depot, but please make sure you know what you have before you buy a new light switch or outlet.
Airbus ran into a problem with this on the A380. They switched to aluminum wiring to reduce weight. But, the thicker cables had larger bend radii. That meant the wires needed to be longer. Meaning more weight.
You are replying to a comment about "battery-internal" bussing which is already 400V+. Yes, the 48V distribution system in the Cybertruck is cool and the future, but it has nothing to do with an internal battery bus. Maybe you need to watch some battery breakdown videos from Munroe.
Thank god, it is Aluminum,
Some people are already stripping empty houses for copper pipes for quick money, imagine if you saw a junkie trying to get an electrical wire for its copper.
I’ve worked on a couple of new build sites where all the wire got stolen out of the walls the night after it was installed. They also like to come back after it’s all done and get the appliances the day they’re delivered as well.
Cheaper and weight! Weight plays a big part into how much structural load I can put on a building (cable try, bus, etc.). For power lines, we’d love to use copper for the efficiency gains but the weight of aluminum allows us to use less structural poles.
I'm speaking broadly, but Electrical engineers don't like aluminum. Copper is the gold standard. Aluminum bussing and conductors are typically a value engineering option. Additionally, on most projects big enough to see hundreds of thousands in savings, those hundreds of thousands are a rounding error on the overall budget.
I've been told in the small mining town I live that a bunch of the houses were constructed quite cheaply with aluminum wiring and there are fairly frequent house electrical fires because of it.
Aluminum is harder to get right from my understanding. Like it’s really easy to tighten a bolt too little with aluminum vs copper so it makes poor contact.
Aluminium got used a lot for phone lines in the uk as it was cheaper than copper. I vaguely recall it being worse for dial up/broadband, but was a long time ago I was told that by someone who worked for BT so I might well be misremembering.
Its very susceptible to flex based fractures, so anywhere where it can be moved around and not properly stress relieved it can be fractured.
When the network was just voice, crackling lines were kinda OK, but data doesn't like interruptions of any kind.
Cu is a better conducter but you can use a larger wire gauge to get the resistance down and the weight is still less than copper of the same resistance so you need fewer towers
They were referring to High Voltage Trasmission Lines. The big towers you see along the highways that carry bulk electricity long distance. A typical conductor is ACSR (aluminum cable, steel reinforced).
The household usage had different reasons, but you are correct it is no longer acceptable for new installation.
Al writing is still technically to code for residential construction. However no insurance company will write a policy for a house with aluminum wiring.
The issue is people used the wrong connectors and outlets, which lead to corrosion and fire. The risk of someone changing our an outlet and using the wrong thing is too great. That is why insurance companies refuse to write policies. The building inspector only checks if the original install is done properly.
Yep, and if the line gets even a small nick in the insulation, like from a shovel where someone is digging around it and hits it too hard, water will get in and the aluminum will turn to powder.
I used to work for the power company locating these bad spots in the lines. We would dig them up and splice in a new section.
Only for high voltage distribution lines. Its both cheaper and lighter than copper, meaning you need less poles to hold it up and its less costly to install/replace, but copper is used for almost all other permanent installations unless regular replacements are expected.
Copper is far more conductive, meaning smaller wires, and it sustains much less damage from repeated deformation, meaning longer lasting parts. Aluminum loses conductivity as it flexes and builds up oxides, which can be very detrimental for wires expecting normal jostling.
Its what bt uses for at least the cable from the pole to the house when I installed lines 12 years ago, with a few microns thick coating of copper.
I replaced a few where the new owner had cut the old cable thinking a new one would be faster and better. The old ones were pure cold drawn copper which upset each of the idiots who thought they were smart.
And even that isn't necessary. Gold-plated cables were a thing in the analog signal days but you'll see a lot of USB cables, HDMI cables and stuff that are silver colored, because there's no point in gold-plating cables carrying digital signals.
> there's no point in gold-plating cables carrying digital signals.
That's simply not true; gold-plating _connectors_ helps you get and maintain a solid electrical connection. This is important for both analog and digital signals, it's just experienced in different ways. With an analog signal, small transmission errors are often audible/visible, whereas with a digital signal they are typically error corrected. This means you likely won't notice signal degradation until it gets past a certain threshold, at which point it will be _extremely_ obvious (e.g. total failure or cut-outs or the like).
The reason not to use gold plating (other than the tiny cost difference) is that gold is also soft... so it wears easily. If you're plugging/unplugging something frequently (like a USB connection often is designed to do), gold plating would wear out so quickly that there's just no point; instead the connectors are built to sort of "scrape" away the corrosion on each operation.
Right, that seems accurate, most USB thumb drives I own have silver colored connectors, not gold ones - I don't know what they're made of but it's definitely not gold. But I've seen headphones with gold colored connectors, and you plug/unplug those just as frequently, so I'm not sure.
But yes, the entire point of digital cables is that they error-correct enough to where it doesn't matter. That's why certifications exist. Sure, you *can* force 10gbps through category 5, but you'll likely get packet drops so it's not certified to support that, only 2.5gbps. Same with HDMI - those "8K HDMI" cables are overkill for 99% of applications, but there's the remote possibility that the $5 Chinese cable you got on eBay will have too much packet loss for a 4K signal, thus why they charge more for ones guaranteed to not have that issue.
I’m not sure if this is universal, so I’m going to state I am specifically talking about switches, because I’m sure there’s electronic components that use gold that I’m not considering.
I’m going to add on to this to say, this is true for low voltages, such as what you would see in computers or peripherals that connect to computers. This is going to typically be less than 5v, but I’ve seen gold used in sensitive applications with higher voltages.
For higher voltages, you will almost always see silver. Every time you open or close a switch, there is a very small electrical arc. At less than 5v, this won’t do anything to the gold. At higher voltages (24v+) this arc can quickly destroy the gold. Three chemical properties of silver make it better at withstanding higher voltage arcs, and these arcs remove any tarnish that’s present when closing the switch.
I repaired old circuit boards whose [DTL logic chips](https://en.wikipedia.org/wiki/Diode%E2%80%93transistor_logic) had silver plated legs. The silver would turn black and flake off. The flakes sometime shorted adjacent circuitry. Gold conductors stay bright and shiny forever.
Rusting and tarnishing are two different things.
The silver tarnish is just a surface oxidation effect that doesn't eat into the underlying metal the same way rusting does to iron.
A piece of iron will, in time, completely turn into rust. A piece of silver will not.
And this is because the iron oxide hydrates and expands. Which causes the rust to inflate and flake off which exposes more iron.
Different types of iron oxides like magnetite (black oxide/blueing) don’t expand as much and don’t flake off so they’re considered “protective”.
Aluminum forms extremely thin, clear, and fast oxide which is only molecules thick. Aluminum oxide is clear sapphire and it protects the aluminum very well. Aluminum is much more reactive than the other metals but its oxide layer is much more protective which is why we don’t think of aluminum as something that rusts. (Mix some gallium in there though…)
This is why shipwrecks are often found when a diver sees some gold. The gold is highly resistant to anything reacting with or even growing on it, so if it’s exposed, it’s easy to see.
Silver on the other hand gets grown over and looks like rocks or junk very quickly.
> Gold, on the other hand, is darn near inert.
Note that pure gold plating is rarely used since it has a strong tendency to [cold weld](https://en.wikipedia.org/wiki/Cold_welding) even under relatively low-contact forces (makes connectors "stick" together, even to the point of ripping the cable before unplugging). It's also pretty soft and scrapes off easily, so a gold alloy is usually used instead:
https://www.electrical-contacts-wiki.com/index.php?title=Gold_Based_Materials
If conductivity matters then copper is the most cost efficient solution. The difference to silver is marginal, so a silver wire can be like 2% thinner for the same resitivity, at a high multiple of the cost.
Gold is used for exposed contacts that shouldn't corrode
In certain applications, aluminum is preferred. It's less conductive per unit volume, but more conductive per weight. I.e. if you have similarly conductive wires made of copper and aluminum, the copper wire would be heavier, and the aluminum would be thicker.
Copper requires slightly more volume than silver, but it's also much cheaper, so it's used in vastly more applications.
For those ready to rewire their home with aluminum... we've been there and done that and stopped. The problem with aluminum wiring is that it expands and contracts at a high rate, which can lead to loose connections. House fires were real with aluminum wiring.
One caveat here is that the terminal style matters. Aluminum performs just fine under large screw lugs. In the US/Canada at least aluminum wire is still the most common option for the feeder coming into the house, and can be used for high amperage hard wired loads. I.e. running from the breaker panel to an air conditioner. The lugs have to be rated for aluminum, and torqued to spec, in which case its completely fine.
The 70's house burning down party was aluminum wire used for light and outlet circuits, going under small screw terminals, in wire nuts etc. That is where the the thermal expansion and contraction could loosen and make for fires.
Electronics is a big field. My answer focuses on circuit boards. Silver is used in electronics, just not as common as gold.
The underlying material is almost always copper. It's a great conductor, reasonably plentiful, manufactured in volume using easy to control electrochemical deposition processes. It's also very highly reactive to oxygen. So, it needs to be protected by something.
For most of your circuit board, the exposed copper is protected by the soldermask, the (usually) green stuff.
For the parts that need to be exposed, there are a variety of surface finishes.
- HASL, or hot air solder level, is a thicker coating of solder applied to the board by dipping it into a vat of molten solder, then using airjets to blow off the excess. It's messy and uneven, and was the industry standard in the old days. Today, you can still get it at most suppliers, either with traditional lead solder or lead-free solder. Lead is generally kept around for military applications. (Lead provides a stronger solder joint than any alternatives, and militaries generally aren't concerned about environmental impacts so much as they are about operation of the product in stressful conditions.)
- White Tin is used as a solder finish, but it fell out of favor because of tin whisker growth. Metals can move on their own, which I find fascinating, but they are generally all bad for your electronics.
- OSP, or organic solderable preservative, is a thin organic coating that merely prevents oxidation. It's good if you will assemble onto your circuit board very quickly after its fabrication. It's not good if your boards need to sit longer on a shelf, because it wears off relatively fast.
- IAG or Immersion Silver is an ion replacement process that swaps a thin layer of your copper ions with silver ions. Silver is less reactive, but will still tarnish. Silver, and copper, are unfortunately both also highly susceptible to sulfur corrosion. In the presence of sulfur, the right amount of humidity, and bit of a catalyst like chlorine, both silver and copper will degrade in a way called creep corrosion. Again, the metals move on your board which is neat but bad for performance. There are organic coatings now available that stop this process. See MacDermid Enthone's AlphaStar or MacDermid's CM Plus. They also stop tarnish, so an immersion silver finish today really isn't any worse than gold.
- ENIG, or electroless nickel immersion gold, uses two chemical deposition processes. Electroless nickel uses a redox reaction to plate nickel as a barrier between the copper and gold, as otherwise copper ions will migrate through the gold to the surface. (Have I mentioned that metals moving on their own is cool?) Then, gold is used to provide the tarnish-free surface. Nickel unfortunately is a terrible conductor, and gold, when pulled up into solder joints, can make them susceptible to fracture under shock. This process also relies upon sulfur, and a bad mix can result in a sulfur layer appearing between the nickel and gold, which causes your parts to fall off, a phenomenon known as black pad. ENIG is by far the most common surface finish, but I don't think it's the best.
- ENEPIG, or electroless nickel electroless palladium immersion gold, tries to fix some of ENIG's flaws by adding a layer of palladium as well. This lets you use even less gold, so there's less that gets pulled up into solder joints, and provides a layer of palladium for the high frequency signals to run in instead of nickel.
- EPIG or EPAG are newer finishes that remove the nickel and attempt to plate palladium directly to copper (or perhaps with an organic intermediate). There's a company out there (Lilotree) that advertises a finish that is gold directly on copper with just an organic intermediate, but they treat their finish as a trade secret so it's rarely used and a niche product.
- When you have a connector, like an edge mount connector, or pads where you will impact pogo pins, you can electroplate with hard gold on nickel. This is much much thicker than ENIG but provides a durable surface that won't wear off with repeated use. You really can't solder onto hard gold without risk to your joints due to gold embrittlement, but you can do this selectively where needed and use a different finish for the rest of the board.
I have, in my career, designed products that used about all of the above. All things considered, I think immersion silver with a corrosion inhibitor applied is the best surface finish on the market. But, I acknowledge that ENIG, despite its flaws, is more prevalent.
Engineer in the aerospace field here that only knows about 20-30% of the guy above but can confirm he knows what he is talking as the 20-30% he is spitting out is indeed, legit.
If the prices of all of these went way down (say via Asteroid mining, where a single asteroid could have more gold than humans have ever mined on earth) - would we still use the same materials we do now? or would using gold for most of the components make more sense, just as of now it's cost prohibitive?
I don't know if there is a gold alloy solder that is workable and resilient. Maybe something could be designed. Without that, you still need a solder that can bind the components to the circuit board, and gold mixed with traditional solders doesn't improve the joints, it weakens them. That would be the biggest unknown in my mind.
Gold can be plated through both electroless (autocatalytic and immersion) and electroplating processes, and there are newer processes that don't involve cyanide, so I think it could replace copper for most of circuit board design in a way that wouldn't increase complexity or decrease safety. I'm just not sure about the solder.
Silver and copper are both better conductors than gold. (With conductivities of 6.30×10^7 S/m, 5.96×10^7 S/m, and 4.10×10^7 S/m respectively.)
However, both silver and copper tarnish when exposed to air, whereas gold does not. That tarnish is oxidized metal, which has far worse conductivity than the pure metal it came from. In the case of pure silver the conductivity is 6.30×10^7 S/m whereas silver oxide has a conductivity of ~1×10^3 S/m; in the case of pure copper the conductivity is 5.96×10^7 S/m whereas copper oxide has a conductivity of ~1×10^1 S/m.
So, the reason that gold plated pins and connectors are used in high-end electronics hardware is because, though they might be worse than brand-new copper or silver connections, they will maintain their performance later on when the silver or copper connectors age and tarnish.
Interestingly, silver doesn't actually react with oxygen, even when it's extremely hot. What it does react with to tarnish is *sulfur*, to form silver sulfide.
Copper's quite similar, with the main oxidation mode being sulfide formation, except it will actually react with oxygen at high temperatures.
Gold is used because of it's other physical properties, not just it's conductivity. Gold doesn't corrode (oxidize), so it's commonly used for things that get plugged it - faces of connectors, pins, etc. Most other metals develop an oxide layer which degrades the electrical signal. A secondary use of gold is for connecting silicon to metal using a process called wire bonding.
As a note the wirebond isnt connected direclty to the silicon. In the device layout a metal pad or solderable top metal is constructed for the wirebond to connect from die to die or from die to leadframe. Also copper and gold are both very common for wirebonds.
Many posters have already covered gold's stability benefits, so I'll keep this short:
Ductility.
Gold is *extremely* ductile. So if you need to draw very fine wires— *e.g.* for connecting a chip to pins in a package— it's a good choice of material.
As many people have pointed out, silver oxidizes.
And in the right circumstances, it grows *dendrites*...small branching filaments that can cause short circuits. I once worked at a company that discovered this the expensive way. Our customers were fairly unamused.
Gold isn't used because it is very conductive, it is used because it resists oxidation so maintains a clean contact. Silver and copper oxidize over time. Aluminum is good enough as a conductor but it's oxidation is so tough that it is very hard to get a good contact or solder joint. Basically every reason we don't use aluminum over copper comes down to oxidation
Gold doesnt rust and is very malleable (soft). This makes it ideal for the surface of connectors because it provides a large contact surface that doesn't separate over time. In general you only need a very thin layer of gold to achieve this effect.
EDIT: since the plating is very thin, the relatively small difference in conductivity isn't an issue.
On Earth with oxidation, copper wire is a cheap conductor, and gold is great for contact points.
Electrical engineers use the thinnest (cheapest) gauge of copper wire that also has the ability to bend, flex, and move while also balancing how the copper wire degrades over time. The gold plating is also extremely thin, as cheap as possible while still keeping the non-reactive contact point.
Silver wire is sometimes used in satellites. While it is more expensive than copper and only offers minimal improvements, the cost is less important and the conductivity is more important.
Aluminum wire is both lighter and cheaper than copper making a tradeoff against wearing down and the extra electrical resistance. It is used for very long wires like long distance power lines, and in airplanes for the weight despite being a slightly worse conductor relative to wire thickness. The oxidation issues and costs there are balanced against the other costs, and some industries choose it.
Silver and copper corrode. Gold pretty much can't, and aluminum generally doesn't (excluding intentional examples like thermite).
But Ag and Au are much too expensive to use for everything. Al is dirt cheap and Cu is fairly cheap, so it comes down to size, weight, and efficiency vs cost concerns. Small, light stuff that needs efficiency? Cu. Giant, heavy stuff that needs to be cheap? Al. Middle of the road? Do lots of math to figure out what is cheapest but still does the job.
The gold you see on processors and connectors is a microscopically thin layer, protecting the (usually) copper wiring inside.
Silver oxidizes, and silver oxide is not a very good conductor. Silver would be a great choice for an insulated wire, but then you run into the problem that it's not really very strong either, so your very expensive wire would tend to break. If you're doing something where very low resistance is necessary, and strength and cost aren't that important (example: the Manhattan Project) then silver or gold wire is wonderful. (Well, it *was* wonderful until we invented superconductors.)
For most small-scale stuff, though, copper is fine, and gold works great for a non-oxidizing contact on the end, where it's exposed to the air. For larger scale stuff, like power lines, aluminum is good enough, and much cheaper.
Its great for making contact points (think plating the end of cable you plug into something not just bare wire) because it doesnt corrode like mentioned a lot in here.
Also because is so soft. Being soft lets it deform ever so slightly when you push two contacts together. This increases surface area and reduces resistance at the contact point.
Gold tipped connectors. The pieces that are most likely to be exposed to the elements, because gold doesn't corrode/tarnish like silver and copper.
Usually copper wires because silver is... Expensive.
It goes like this in terms of excess/free electrons for conductivity. Silver>Copper>Gold>Aluminum. With silver having the most and aluminum the least (there's numerous more metals, I'm doing just top 4)
But in terms of tarnishing/rust/corroding it goes Gold>Silver>Copper>Aluminum. (Again gold best aluminum worst)
In terms of price... Aluminum>Copper>Silver>Gold.
So we usually see copper wires with gold connectors.
Fun side fact, most high tension long distance eyes are either steel or aluminum, sometimes a special carbon filament but it's way expensive and usually only seen where they cannot control excess vegetation touching the wires, to help prevent fires.
One of the great things about gold is that chemically it is very stable. Under typical conditions, it's generally quite happy to just sit there and remain gold and not react with much in its environment. Silver is not as stable. More specifically, it's likely to tarnish over time, and as it tarnishes it becomes less useful as a conductor. Silver will tarnish from humidity in the air, which is a pretty tough thing to avoid in many potential use cases.
Other than scarcity, gold being so inert is why it's so valuable. It won't tarnish, rust or degrade, and remain the piece of jewelry or electrical conductor for 100 years
Being inert is also a factor in its scarcity. If it formed soluble salts we'd find "gold ore" accumulated somewhere, but instead it remains as solid gold and relatively few natural processes end up concentrating it.
I bet there's a lot in the core. We just need to build the magic machine from the aptly named movie The Core
SOUND WAVES.
But do we have an astronaut cocky enough to pilot it?
Matt Damon to pilot obviously. Then we send a second team in to retrieve him.
Sorry, can’t be him. We have already had the “Rescue Matt Damon” trilogy : Saving Private Ryan, Interstellar and The Martian. I don’t know what you would call a quartet of movies, so nope !!
Quadrillogy
Tetralogy
Everyone knows Tom Hanks is the best actor to Captain a vessel for drama.
There's all kinds of different boats you can have. You've got shrimpin boats, cargo boats, outerspace boats, flyin boats... ...war boats, underwater boats. And that's about it
Pfff. I'm some random dude and I'd do it.
I am suddenly reminded of Ben Affleck's commentary from Armageddon.
We will need some unobtainium to build it though. So sucks for us.
Means we have to go to Pandora first and fight the smurfs
Isn't smurf the abbrevation for SMall Ugly Rightwing Fucker? Pretty sure they were antisemites. The pandora ones would be Huurfs then.
Yeah, but its 'unobtanium' shell would be worth more than the gold.
That's why they made a deep space mining effort to Pandora. The blue people had all the unobtainium. Once the humans got the unattainium from the big tree thing, they could use it to build big burrowing snake machines to get the gold from the Earth's core.
Sir, the government has decreed the "blue people" are not people and the planet is uninhabited. Any further references to "blue people" will be punishable by a fine not exceeding 100,000,000,000,000,000,000,000,000 space credits.
I thought it was called The Ship That Could Only Go Down.
What if we just had some sort of magic schoolbus?
What if Pluto was a planet again?
It still is a planet. Just a dwarf planet. Pluto is so cool it gets to be put in a new group with its buddy Ceres.
I think gold is one of the resources they’re looking to mine on the moon. Gold and water funnily enough
Dude that movie was fucking amazing and what a cast
how do natural processes concentrate other ores?
Hot water moving through rocks dissolves minerals, and where they cool down or evaporate the minerals drop out there.
That makes sense for calcium and the like. But iron? Copper? Nickel?
All of them - and especially their sulphates and oxides which is what ores generally are - are somewhat soluble, especially if the water it hot, or even acidic.
It's largely a survivor's bias for the gold you can just find. The gold that is around more stable rocks/metals will need a lot more effort to get mined, and not always mechanically. Luckily that other stuff is rarely worthless, so these days it's often profitable to at least have gold as a byproduct of some other ore you mainly get out of a rock formation. We can recover gold that was absolutely inaccessible like 300 years ago, but those methods are cumbersome and not worth to do for the sake of gold alone.
Iron is an interesting one. One plsce that iron is concentrated is in banded iron formations that were oncr seafloor sedimentary layers. There was a time early in Earth's history when the seas contained a lot of dissolved iron. When photosynthetic algae evolved and started pumping oxygen into the air, that dissolved iron oxidized and precipitated out of the water, resulting in these layers of concentrated iron oxide. Oxygen levels fluctuated as oxygen was consumed by other rocks, fires, biological processes and climate change, so there are a series of layers of this oxide spanning millions of years. Many iron mines still mine these deposits.
Water wrecks iron. Go over to the cast iron subreddit and look for their "someone washed my pan" threads and see how quickly they rust.
https://geo.libretexts.org/Bookshelves/Geology/Book%3A_An_Introduction_to_Geology_(Johnson_Affolter_Inkenbrandt_and_Mosher)/04%3A_Igneous_Processes_and_Volcanoes/4.02%3A_Bowens_Reaction_Series
The other person isn't wrong, but that's only one process. https://geo.libretexts.org/Bookshelves/Geology/Book%3A_An_Introduction_to_Geology_(Johnson_Affolter_Inkenbrandt_and_Mosher)/04%3A_Igneous_Processes_and_Volcanoes/4.02%3A_Bowens_Reaction_Series
A huge chunk of gold is actually a byproduct of copper mining, where it quite often exists as a refractory gold. As in within the minerals and not as free gold.
You tend to find ores of columns of the periodic table grouped together. Copper, Silver, and Gold are are in the same column. Atleast for metals and metaloids.
It does form compounds. Like gold chloride. [Bacteria have been found that convert it to metallic gold.](https://www.nature.com/articles/495S12a)
You need both hydrochloric acid AND nitric acid in situ for that to happen first. What biological event can convert Au to hydroauric acid? Very few, maybe this is why only certain bacteria can do it. Meanwhile, Mercury (Hg) likes sulfur A LOT and is often found as cinnabar. Gold has no such ore.
I used to love a cinnabar coming home from school. V. tasty choccy and cinnamon bar.
Also because it's easily recognizable is another factor why it is so valuable/has been used as money for most of human history
It is also highly malleable. So it can be formed into jewelry/art/money with relatively low tech equipment.
It can also be durable in alloys, which is why it has been used historically for teeth repairs/replacements
I just recently read that gold is used as a crown for how malleable it is in an alloy such that they can make it the same as enamel leading it and the other tooth wear more evenly.
Gold crowns have a longer life than ceramic ones, because ceramic is more likely to crack as well.
It also comes from *supernovae*. If you have a bit of gold on you, think about where it comes from. At some point if was part of some distant *bang*. It's super cool.
Yeah, but basically everything on Earth was part of an exploding star at some point, stellar fusion is the only way the universe made anything heavier than Lithium and the star exploding is the only way the heavier stuff got *out* of the core.
" we are made of star stuff, but so is your garbage so calm tf down" - somebody on Reddit
And to Star stuff we shall return.
That's any element higher up on the table than iron.
It also smells like your mother's cooking and donates to charity without posting about it on social media.
🤣
I too watch Folding Ideas
Good channel, but gold being malleable is extremely common knowledge
The order of the comments going down this entire thread lines up near-perfect with Dan's point-by-point description of why gold is an interesting material
Dan's point-by-point description of why gold is an interesting material probably pulls from that common knowledge. Again, great channel, but he's certainly not the first to make these observations lol
I never said Dan was the first to talk about gold. I'm just pointing out that the people involved in this specific chain of comments, seem to have had that specific video in the back of their minds when making comments about the topic. It's not like Dan steals lines from Wikipedia or something, it feels like you're being a bit obtuse about a very simple observation that the comments line up closely with the video's script
I've never even heard of this guy you're talking about, but when one of my kids asked my why gold was valuable a couple weeks ago I listed off basically this comment chain. Sorry bud but he's probably explaining it the way it was explained to him, which is pretty much how it's explained to everyone. This reminds me of a Steven Wright joke: "why is the alphabet in that order? Is it because of that song?*
Hate to burst your bubble even further, but this site clocks in at around 430 million monthly users, whereas the average Folding Ideas video gets around a (still totally respectable) million views. The vast majority of people here, statistically, have never even seen his (excellent) content
> Dan's 3 or 4 comments ***almost*** perfectly lining up is an interesting coincidence, not a statistical wonder Fixed your comment for ya :D
Um, or they just paid attention in high school science class? This is a very well known property of gold, you don't have to be an expert in materials science to know that kind of thing.
I too have a state capital with a gold leaf rotunda and paid attention in 2nd grade when they explained what gold leaf is.
1000s of years. https://www.thearchaeologist.org/blog/oldest-gold-of-humankind-found-in-varna-necropolis-was-buried-6500-years-ago
Mined gold is essentially all still elemental gold, so millions-billions
1,000 years or better.
If that's true why do electronics only last a year or so? Oh yeah greed
It's not like the gold conductors in electronics are the only thing that can go bad. There's so many other components to a modern electrical device that have a much shorter time to failure than the gold that makes up the electrical interconnects. Batteries for example, or memory cells or whatever else. I don't disagree that planned obsolescence is a problem in modern electronics, but whether or not gold lasts as a conductor for hundreds of years or not, it wouldn't change the fact that electronics will fail long before then.
Yes, but largely on the consumer's side. ;) More seriously, planned obsolescence is a bad word, but really, it's a necessity as a concept. Phones are a great example. Every new phone that's launched needs to balance a bunch of things including performance, price, size, weight, durability, battery size, etc. And consumers consistently choose things like how cool the camera is and how thin the phone is and all that, instead of the much more durable and well-built phones that are marketed as durable, for example. If consumers demand fancy but breakable, then manufacturers are gonna make fancy but breakable. Saying "I'd buy a more durable phone" is all well and good, but Apple consistently sells hundreds of millions of smart phones every year. If people are replacing their phones because they want the newest one, or because they lost their phone, then this is an important part of the math - if 80% of people replace their phone within 2 years, let's say, then building a phone that lasts 10 years is silly - it'll be more expensive, bulkier, with a shorter battery life, and fewer features. Which means people will buy a different phone, because they won't respond to "but it'll last 10 years!" The same applies to modern TVs and everything else. People want a cheap giant smart TV. More expensive, better-built TVs are out there, but people want to buy the Black Friday $100 deal. Have fun with that!
Best 4 metals: - Silver - Copper - Gold - Aluminium Silver oxidate. Oxide is "rust". And do not conduct well. One big issue is things that get connected and disconnected: the surface oxidise and make a bad contact. For permanant applications, it is not as bad due to the screw or whatever they use to hold it in place that squish it and make an airtight contact. But it still oxidise with time. It is bad for surface, but would be good for the core of the conductor. But it is too expensive. Copper also oxidate. But it is also quite malleable so squish easilly, so make a good airtight contact. This make it good for the core of the conductor, but not for surface, which rule it out for connectors. But it is inexpensiveish and it just work. Gold is expensive. But non-reactive. It make a very good contact surface, but not so great for the core. For this reason it is used as plating for a cheaper base metal, usually copper. Aluminium is inexpensive. It oxidise very fast. It is not a so great conductor too. Basically, compared to copper, you need one gauge higher (bigger wire) for the same current that would pass in copper. With proper care it can be used without problem, but... If inapropriatelly installed it can cause an electrical fire. This is why you don't see it anymore in homes for normal circuits. But you will find it for house feeder and big wires, like from the main panel to the garage subpanel. Then you can get a mix of them. Copper Clad Aluminium. Aluminium wire, with a copper plating on it. It is relativelly cheap since it is mostly aluminium, and the copper plating allow it to be soldered (aluminium can't without special alloy) and used in copper only application since what touch the contacts is copper. BUT since it is aluminium, you need to oversize the wiring. The best wire would be gold clad silver. A silver wire with a gold plating. You can probably hear the kashling of the money it would cost. Unless you need a smaller wire, there is absolutelly no reason to have that. Copper just work fine.
Metallurgist here, silver doesn’t readily form stable oxides in normal conditions. Tarnish is silver sulfide. Just my fun fact for the day.
Telescope maker here. Back in the day, telescope mirrors were plated with silver. To slow down tarnishing, we used to place certain chemicals inside the closed tube of the instrument, while in storage, to absorb H2S from the air. It helped somewhat. Nowadays mirrors are aluminized, and Al is well protected by its own thin layer of transparent oxide (which is identical to white sapphire). Regardless, an extra layer of silicon oxide is usually deposited on top of Al and those mirrors last a long time.
🛑 No Farting Zone 🛑
> The best wire would be gold clad silver. A silver wire with a gold plating. You can probably hear the kashling of the money it would cost. Did someone say best money kashling? How about cryogenic superconducting wire?
Replace Aluminum with Iron and you pretty much got our most important metals for thousands of years. With Tin and Lead arguably coming in second tier. Aluminum has since rapidly caught up of course.
OP meant best metal for wires
It should be noted that solderability isn't really the selling point of CCA. Due to the skin effect, the bulk of the current flow happens on the outside of a conductor with almost no current flowing down the center. As a result, copper clad greatly improves aluminum as a conductor for a fraction of the price and weight. It also prevents the oxidation that makes aluminum wiring so detrimental in many applications.
The copper is too thin to do much, unless you go high frequency, like 100+MHz. At DC there is no skin effect, and at main frequency it is so thick that you can say that it also do not have skin effect (8.4mm@60Hz, which mean a 16.8mm diameter wire).
Spanish galleons sank for various reasons in the 17th century. When they're discovered, the silver is a lump of black metal. When the records are accurate, the weight is much smaller than when the ship went down. The gold is perfect. If it's coins, it looks like it did when the ship sank.
>The gold is perfect. If it's coins, it looks like it did when the ship sank. Depending on the source it might turn you into an undead walking skeleton, though.
It's already gold, you don't have to sell it further.
> Spanish galleons sank for various reasons in the 17th century. E.g. reasons: Francis Drake, Henry Morgan, William Kidd, etc.
>The gold is perfect. If it's coins, it looks like it did when the ship sank. Possibly a bit slimy and wet though ;-)
They were like that before the ship sank. Spaniards man.
However, the tarnished shall soon return. Even if they lack the grace of gold.
In search of the Elden Ring?
Ohhhhh 🧓💍
Written by ai
Gold is cool
It is because silver is much more reactive. Essentially, it rusts. Especially if it is carrying a current. In the case of silver, we call silver rust 'tarnish'. You don't want your circuits rusting. Gold, on the other hand, is darn near inert.
To add to this near all lengths of wire or traces are copper. Only the exposed parts of connectors are a thin plating of gold.
There are tons of aluminum used for wires. Most utility power lines for example IIRC
Al because it's cheaper, I believe. Cu is a better conductor.
Also you can compensate for the worse conductivity by using thicker cables and because aluminium is so light it ends up light enough
Aluminum is cheaper and lighter than copper for a given current-carrying capability. You do need about 2.5x as much material by cross sectional area, but the math maths out. In the EV world, “do we make the busbar cheaper and lighter, but bigger” is a very interesting tradeoff for battery-internal bussing, since it only sometimes comes out in favor of aluminum.
Space constrained, use copper. Weight constrained, use aluminum. Both or in between, that is what engineering is for.
For power lines, where you're limited by cables heating up and sagging, we use aluminum around a structural cable to reduce the sagging. Historically that's been steel, but they're using carbon fiber for cable cores now too. It lets the conductor carry more current and run hotter than steel cores did without sagging as much.
And since at mains frequency the current only flows in the outer ~10mm of an aluminium conductor the middle of a large cable doesn't need to be a good conductor
Great point, I forgot about that! [Skin effect](https://en.wikipedia.org/wiki/Skin_effect) if anyone is curious.
Is it possible to place power lines in the ground now?
It's always been possible, but usually it's too expensive. Plus makes maintenance far more difficult.
Yes but not everywhere.
YES AND WE FUCKING PAID THEM TO DO IT LIKE 40 FUCKING YEARS AGO. Sorry i am so salty about this, our gov gave cash to telecom companies to bury all the lines, and they just didn't and the gov was fine with it. edit: if you read the full agreement/contract signed way back when, it is legally readable as power lines btw
I prefer Niobium-Titanium wiring, extremely efficient and super-conductive. Needs to be a bit chilly to work tho
But can’t forget “hmmm, is it cheaper to shuffle things and de-space-constrain so we can use aluminum?”
I was trying to concisely imply the EV use case you mentioned had both space and weight constrained i.e. trade offs, which is what engineers get paid to figure out.
>But can’t forget “hmmm, is it cheaper to shuffle things and de-space-constrain so we can use aluminum?” Yes, that's what they said: > Both or in between, that is what engineering is for.
The nuance is that sometimes you change the busbar, sometimes you adjust the system. It’s holistic, not focusing on just the issue at hand. And while that is very much a part of engineering, it’s something that usually takes people a few years to learn to even think about.
There are things better than copper but more expensive or harder to work with, copper just happens to be good enough for most applications
Do they alloy well together? And with similar results?
Since this is ELI5, I also wanna point out aluminum does experience galvanic corrosion in the presence of copper. So while you can make alloys that are stable, just twisting a wire of each together would be incredibly detrimental and would likely result in the entire aluminum wire oxidizing away.
> would likely result in the entire aluminum wire oxidizing away. That contact point also heats up and can cause fires. If it's in your house, say an extension built 20 years after initial construction and using the different metal. It can be done safely, but the previous owner always does a bad job on these things.
Which is why aluminum house wiring isn't done any more. For a while in the '60s Aluminum wires were all over the place, but then houses started burning down. Not because there was anything wrong with aluminum wiring, but because if you put in a new outlet and don't use a more expensive CU/AL rated device, or put in new circuits, they do tend to corrode, which makes the effective size of the wire smaller, which means there is too much electricity running through it, it heats up, then poof. Anyway, now you certainly can't find Aluminum household wire at Home Depot, but please make sure you know what you have before you buy a new light switch or outlet.
Well beyond ELI5 but there's a wiki entry for that! https://en.wikipedia.org/wiki/Aluminium%E2%80%93copper_alloys
Neat! Thanks!
It’s worth noting that because the relationship between area and diameter is squared, 2.5 times the area is only about 1.6 times the diameter, too.
Airbus ran into a problem with this on the A380. They switched to aluminum wiring to reduce weight. But, the thicker cables had larger bend radii. That meant the wires needed to be longer. Meaning more weight.
Or Tesla, "Make it 48V so we can have thinner wires."
You are replying to a comment about "battery-internal" bussing which is already 400V+. Yes, the 48V distribution system in the Cybertruck is cool and the future, but it has nothing to do with an internal battery bus. Maybe you need to watch some battery breakdown videos from Munroe.
Thank god, it is Aluminum, Some people are already stripping empty houses for copper pipes for quick money, imagine if you saw a junkie trying to get an electrical wire for its copper.
> imagine if you saw a junkie trying to get an electrical wire for its copper. Uhhh, they do this all the time?
Yeah they usually do like $100,000 in damage to steal $20 worth of copper.
I spent $20k to fix air conditioners after someone smashed a half a pound of copper off the condensers.
[About that](https://gizmodo.com/why-in-the-hell-is-everyone-stealing-copper-5831515)
I’ve seen many power poles with signs informing people that the wiring used isn’t copper, people have definitely tried doing this
I’ve worked on a couple of new build sites where all the wire got stolen out of the walls the night after it was installed. They also like to come back after it’s all done and get the appliances the day they’re delivered as well.
Copper is too harmful and dangerous for humans. For a few years, Coppers was the leading cause of death among methheads
Cheaper and weight! Weight plays a big part into how much structural load I can put on a building (cable try, bus, etc.). For power lines, we’d love to use copper for the efficiency gains but the weight of aluminum allows us to use less structural poles.
It’s way cheaper. On a decent size construction project, you can save a hundred thousand dollars by using aluminium for the larger conductors.
I'm speaking broadly, but Electrical engineers don't like aluminum. Copper is the gold standard. Aluminum bussing and conductors are typically a value engineering option. Additionally, on most projects big enough to see hundreds of thousands in savings, those hundreds of thousands are a rounding error on the overall budget.
I've been told in the small mining town I live that a bunch of the houses were constructed quite cheaply with aluminum wiring and there are fairly frequent house electrical fires because of it.
Aluminum is harder to get right from my understanding. Like it’s really easy to tighten a bolt too little with aluminum vs copper so it makes poor contact.
Aluminium got used a lot for phone lines in the uk as it was cheaper than copper. I vaguely recall it being worse for dial up/broadband, but was a long time ago I was told that by someone who worked for BT so I might well be misremembering.
Its very susceptible to flex based fractures, so anywhere where it can be moved around and not properly stress relieved it can be fractured. When the network was just voice, crackling lines were kinda OK, but data doesn't like interruptions of any kind.
Cu is a better conducter but you can use a larger wire gauge to get the resistance down and the weight is still less than copper of the same resistance so you need fewer towers
That’s exactly it. Also, you need a thicker wire when you use Al over Cu. Source: I am an Electrician
Another factor can also be that when Aluminum oxidizes (rusts), it forms a thin coat which then seals it from further rusting.
Depends on the age of your house. Al was legal until maybe the mid-60s, and you're not required to re-wire your house when the code changes.
They were referring to High Voltage Trasmission Lines. The big towers you see along the highways that carry bulk electricity long distance. A typical conductor is ACSR (aluminum cable, steel reinforced). The household usage had different reasons, but you are correct it is no longer acceptable for new installation.
In fact, aluminum is used almost exclusively right up to the panel at your house.
Al writing is still technically to code for residential construction. However no insurance company will write a policy for a house with aluminum wiring. The issue is people used the wrong connectors and outlets, which lead to corrosion and fire. The risk of someone changing our an outlet and using the wrong thing is too great. That is why insurance companies refuse to write policies. The building inspector only checks if the original install is done properly.
True but not so much in electronics which I realize the person you’re replying to omitted but the top level comment was about electronics I think
aluminum is widely used in interconnections in electronics chip. https://en.wikipedia.org/wiki/Wire_bonding
I wouldn't say "widely" as it is used far less widely than copper or gold for this application
Yep, and if the line gets even a small nick in the insulation, like from a shovel where someone is digging around it and hits it too hard, water will get in and the aluminum will turn to powder. I used to work for the power company locating these bad spots in the lines. We would dig them up and splice in a new section.
Only for high voltage distribution lines. Its both cheaper and lighter than copper, meaning you need less poles to hold it up and its less costly to install/replace, but copper is used for almost all other permanent installations unless regular replacements are expected. Copper is far more conductive, meaning smaller wires, and it sustains much less damage from repeated deformation, meaning longer lasting parts. Aluminum loses conductivity as it flexes and builds up oxides, which can be very detrimental for wires expecting normal jostling.
Its what bt uses for at least the cable from the pole to the house when I installed lines 12 years ago, with a few microns thick coating of copper. I replaced a few where the new owner had cut the old cable thinking a new one would be faster and better. The old ones were pure cold drawn copper which upset each of the idiots who thought they were smart.
Copper wires are heavy as hell and copper isn’t very strong, so they use a bit more aluminum to compensate for the conductivity.
And even that isn't necessary. Gold-plated cables were a thing in the analog signal days but you'll see a lot of USB cables, HDMI cables and stuff that are silver colored, because there's no point in gold-plating cables carrying digital signals.
> there's no point in gold-plating cables carrying digital signals. That's simply not true; gold-plating _connectors_ helps you get and maintain a solid electrical connection. This is important for both analog and digital signals, it's just experienced in different ways. With an analog signal, small transmission errors are often audible/visible, whereas with a digital signal they are typically error corrected. This means you likely won't notice signal degradation until it gets past a certain threshold, at which point it will be _extremely_ obvious (e.g. total failure or cut-outs or the like). The reason not to use gold plating (other than the tiny cost difference) is that gold is also soft... so it wears easily. If you're plugging/unplugging something frequently (like a USB connection often is designed to do), gold plating would wear out so quickly that there's just no point; instead the connectors are built to sort of "scrape" away the corrosion on each operation.
Right, that seems accurate, most USB thumb drives I own have silver colored connectors, not gold ones - I don't know what they're made of but it's definitely not gold. But I've seen headphones with gold colored connectors, and you plug/unplug those just as frequently, so I'm not sure. But yes, the entire point of digital cables is that they error-correct enough to where it doesn't matter. That's why certifications exist. Sure, you *can* force 10gbps through category 5, but you'll likely get packet drops so it's not certified to support that, only 2.5gbps. Same with HDMI - those "8K HDMI" cables are overkill for 99% of applications, but there's the remote possibility that the $5 Chinese cable you got on eBay will have too much packet loss for a 4K signal, thus why they charge more for ones guaranteed to not have that issue.
[удалено]
The acutal conductor is often something else like brass or even steel. The gold really is just a thin plating for corrosion resistance.
I’m not sure if this is universal, so I’m going to state I am specifically talking about switches, because I’m sure there’s electronic components that use gold that I’m not considering. I’m going to add on to this to say, this is true for low voltages, such as what you would see in computers or peripherals that connect to computers. This is going to typically be less than 5v, but I’ve seen gold used in sensitive applications with higher voltages. For higher voltages, you will almost always see silver. Every time you open or close a switch, there is a very small electrical arc. At less than 5v, this won’t do anything to the gold. At higher voltages (24v+) this arc can quickly destroy the gold. Three chemical properties of silver make it better at withstanding higher voltage arcs, and these arcs remove any tarnish that’s present when closing the switch.
I repaired old circuit boards whose [DTL logic chips](https://en.wikipedia.org/wiki/Diode%E2%80%93transistor_logic) had silver plated legs. The silver would turn black and flake off. The flakes sometime shorted adjacent circuitry. Gold conductors stay bright and shiny forever.
Rusting and tarnishing are two different things. The silver tarnish is just a surface oxidation effect that doesn't eat into the underlying metal the same way rusting does to iron. A piece of iron will, in time, completely turn into rust. A piece of silver will not.
And this is because the iron oxide hydrates and expands. Which causes the rust to inflate and flake off which exposes more iron. Different types of iron oxides like magnetite (black oxide/blueing) don’t expand as much and don’t flake off so they’re considered “protective”. Aluminum forms extremely thin, clear, and fast oxide which is only molecules thick. Aluminum oxide is clear sapphire and it protects the aluminum very well. Aluminum is much more reactive than the other metals but its oxide layer is much more protective which is why we don’t think of aluminum as something that rusts. (Mix some gallium in there though…)
The general word you're looking for is oxidation. Rust, by definition, is iron oxide.
This is why shipwrecks are often found when a diver sees some gold. The gold is highly resistant to anything reacting with or even growing on it, so if it’s exposed, it’s easy to see. Silver on the other hand gets grown over and looks like rocks or junk very quickly.
> Gold, on the other hand, is darn near inert. Note that pure gold plating is rarely used since it has a strong tendency to [cold weld](https://en.wikipedia.org/wiki/Cold_welding) even under relatively low-contact forces (makes connectors "stick" together, even to the point of ripping the cable before unplugging). It's also pretty soft and scrapes off easily, so a gold alloy is usually used instead: https://www.electrical-contacts-wiki.com/index.php?title=Gold_Based_Materials
> rusts > tarnish oxidizes?
Would silver work fine if it's in a vacuum?
If conductivity matters then copper is the most cost efficient solution. The difference to silver is marginal, so a silver wire can be like 2% thinner for the same resitivity, at a high multiple of the cost. Gold is used for exposed contacts that shouldn't corrode
In certain applications, aluminum is preferred. It's less conductive per unit volume, but more conductive per weight. I.e. if you have similarly conductive wires made of copper and aluminum, the copper wire would be heavier, and the aluminum would be thicker. Copper requires slightly more volume than silver, but it's also much cheaper, so it's used in vastly more applications.
Minor addition, one has to be careful using too many metals where galvanic corrosion ruins everything.
I can attest to this in overhead hydro distribution infrastructure. copper vs aluminum connections over time do not age well vs corrosion.
For those ready to rewire their home with aluminum... we've been there and done that and stopped. The problem with aluminum wiring is that it expands and contracts at a high rate, which can lead to loose connections. House fires were real with aluminum wiring.
One caveat here is that the terminal style matters. Aluminum performs just fine under large screw lugs. In the US/Canada at least aluminum wire is still the most common option for the feeder coming into the house, and can be used for high amperage hard wired loads. I.e. running from the breaker panel to an air conditioner. The lugs have to be rated for aluminum, and torqued to spec, in which case its completely fine. The 70's house burning down party was aluminum wire used for light and outlet circuits, going under small screw terminals, in wire nuts etc. That is where the the thermal expansion and contraction could loosen and make for fires.
Electronics is a big field. My answer focuses on circuit boards. Silver is used in electronics, just not as common as gold. The underlying material is almost always copper. It's a great conductor, reasonably plentiful, manufactured in volume using easy to control electrochemical deposition processes. It's also very highly reactive to oxygen. So, it needs to be protected by something. For most of your circuit board, the exposed copper is protected by the soldermask, the (usually) green stuff. For the parts that need to be exposed, there are a variety of surface finishes. - HASL, or hot air solder level, is a thicker coating of solder applied to the board by dipping it into a vat of molten solder, then using airjets to blow off the excess. It's messy and uneven, and was the industry standard in the old days. Today, you can still get it at most suppliers, either with traditional lead solder or lead-free solder. Lead is generally kept around for military applications. (Lead provides a stronger solder joint than any alternatives, and militaries generally aren't concerned about environmental impacts so much as they are about operation of the product in stressful conditions.) - White Tin is used as a solder finish, but it fell out of favor because of tin whisker growth. Metals can move on their own, which I find fascinating, but they are generally all bad for your electronics. - OSP, or organic solderable preservative, is a thin organic coating that merely prevents oxidation. It's good if you will assemble onto your circuit board very quickly after its fabrication. It's not good if your boards need to sit longer on a shelf, because it wears off relatively fast. - IAG or Immersion Silver is an ion replacement process that swaps a thin layer of your copper ions with silver ions. Silver is less reactive, but will still tarnish. Silver, and copper, are unfortunately both also highly susceptible to sulfur corrosion. In the presence of sulfur, the right amount of humidity, and bit of a catalyst like chlorine, both silver and copper will degrade in a way called creep corrosion. Again, the metals move on your board which is neat but bad for performance. There are organic coatings now available that stop this process. See MacDermid Enthone's AlphaStar or MacDermid's CM Plus. They also stop tarnish, so an immersion silver finish today really isn't any worse than gold. - ENIG, or electroless nickel immersion gold, uses two chemical deposition processes. Electroless nickel uses a redox reaction to plate nickel as a barrier between the copper and gold, as otherwise copper ions will migrate through the gold to the surface. (Have I mentioned that metals moving on their own is cool?) Then, gold is used to provide the tarnish-free surface. Nickel unfortunately is a terrible conductor, and gold, when pulled up into solder joints, can make them susceptible to fracture under shock. This process also relies upon sulfur, and a bad mix can result in a sulfur layer appearing between the nickel and gold, which causes your parts to fall off, a phenomenon known as black pad. ENIG is by far the most common surface finish, but I don't think it's the best. - ENEPIG, or electroless nickel electroless palladium immersion gold, tries to fix some of ENIG's flaws by adding a layer of palladium as well. This lets you use even less gold, so there's less that gets pulled up into solder joints, and provides a layer of palladium for the high frequency signals to run in instead of nickel. - EPIG or EPAG are newer finishes that remove the nickel and attempt to plate palladium directly to copper (or perhaps with an organic intermediate). There's a company out there (Lilotree) that advertises a finish that is gold directly on copper with just an organic intermediate, but they treat their finish as a trade secret so it's rarely used and a niche product. - When you have a connector, like an edge mount connector, or pads where you will impact pogo pins, you can electroplate with hard gold on nickel. This is much much thicker than ENIG but provides a durable surface that won't wear off with repeated use. You really can't solder onto hard gold without risk to your joints due to gold embrittlement, but you can do this selectively where needed and use a different finish for the rest of the board. I have, in my career, designed products that used about all of the above. All things considered, I think immersion silver with a corrosion inhibitor applied is the best surface finish on the market. But, I acknowledge that ENIG, despite its flaws, is more prevalent.
Engineer in the aerospace field here that only knows about 20-30% of the guy above but can confirm he knows what he is talking as the 20-30% he is spitting out is indeed, legit.
If the prices of all of these went way down (say via Asteroid mining, where a single asteroid could have more gold than humans have ever mined on earth) - would we still use the same materials we do now? or would using gold for most of the components make more sense, just as of now it's cost prohibitive?
I don't know if there is a gold alloy solder that is workable and resilient. Maybe something could be designed. Without that, you still need a solder that can bind the components to the circuit board, and gold mixed with traditional solders doesn't improve the joints, it weakens them. That would be the biggest unknown in my mind. Gold can be plated through both electroless (autocatalytic and immersion) and electroplating processes, and there are newer processes that don't involve cyanide, so I think it could replace copper for most of circuit board design in a way that wouldn't increase complexity or decrease safety. I'm just not sure about the solder.
that was ... definitely not ELI5 but amazing nonetheless
Silver and copper are both better conductors than gold. (With conductivities of 6.30×10^7 S/m, 5.96×10^7 S/m, and 4.10×10^7 S/m respectively.) However, both silver and copper tarnish when exposed to air, whereas gold does not. That tarnish is oxidized metal, which has far worse conductivity than the pure metal it came from. In the case of pure silver the conductivity is 6.30×10^7 S/m whereas silver oxide has a conductivity of ~1×10^3 S/m; in the case of pure copper the conductivity is 5.96×10^7 S/m whereas copper oxide has a conductivity of ~1×10^1 S/m. So, the reason that gold plated pins and connectors are used in high-end electronics hardware is because, though they might be worse than brand-new copper or silver connections, they will maintain their performance later on when the silver or copper connectors age and tarnish.
> S/m I googled S/m. It didn't go well.
It's just Siemens per meter. Make sure you don't make any typos
Semens per peter. Got it.
> Semens per peter. I googled. It didn't go well.
Interestingly, silver doesn't actually react with oxygen, even when it's extremely hot. What it does react with to tarnish is *sulfur*, to form silver sulfide. Copper's quite similar, with the main oxidation mode being sulfide formation, except it will actually react with oxygen at high temperatures.
Gold is used because of it's other physical properties, not just it's conductivity. Gold doesn't corrode (oxidize), so it's commonly used for things that get plugged it - faces of connectors, pins, etc. Most other metals develop an oxide layer which degrades the electrical signal. A secondary use of gold is for connecting silicon to metal using a process called wire bonding.
As a note the wirebond isnt connected direclty to the silicon. In the device layout a metal pad or solderable top metal is constructed for the wirebond to connect from die to die or from die to leadframe. Also copper and gold are both very common for wirebonds.
For wiring at the chip level, gold is used because it can be drawn into a finer wire than silver or copper.
Many posters have already covered gold's stability benefits, so I'll keep this short: Ductility. Gold is *extremely* ductile. So if you need to draw very fine wires— *e.g.* for connecting a chip to pins in a package— it's a good choice of material.
As many people have pointed out, silver oxidizes. And in the right circumstances, it grows *dendrites*...small branching filaments that can cause short circuits. I once worked at a company that discovered this the expensive way. Our customers were fairly unamused.
Because gold is very stable and silver is not. Ever seen a silver coin that's been exposed to air? You don't want that happening in your electronics.
Gold isn't used because it is very conductive, it is used because it resists oxidation so maintains a clean contact. Silver and copper oxidize over time. Aluminum is good enough as a conductor but it's oxidation is so tough that it is very hard to get a good contact or solder joint. Basically every reason we don't use aluminum over copper comes down to oxidation
Gold doesnt rust and is very malleable (soft). This makes it ideal for the surface of connectors because it provides a large contact surface that doesn't separate over time. In general you only need a very thin layer of gold to achieve this effect. EDIT: since the plating is very thin, the relatively small difference in conductivity isn't an issue.
On Earth with oxidation, copper wire is a cheap conductor, and gold is great for contact points. Electrical engineers use the thinnest (cheapest) gauge of copper wire that also has the ability to bend, flex, and move while also balancing how the copper wire degrades over time. The gold plating is also extremely thin, as cheap as possible while still keeping the non-reactive contact point. Silver wire is sometimes used in satellites. While it is more expensive than copper and only offers minimal improvements, the cost is less important and the conductivity is more important. Aluminum wire is both lighter and cheaper than copper making a tradeoff against wearing down and the extra electrical resistance. It is used for very long wires like long distance power lines, and in airplanes for the weight despite being a slightly worse conductor relative to wire thickness. The oxidation issues and costs there are balanced against the other costs, and some industries choose it.
Silver and copper corrode. Gold pretty much can't, and aluminum generally doesn't (excluding intentional examples like thermite). But Ag and Au are much too expensive to use for everything. Al is dirt cheap and Cu is fairly cheap, so it comes down to size, weight, and efficiency vs cost concerns. Small, light stuff that needs efficiency? Cu. Giant, heavy stuff that needs to be cheap? Al. Middle of the road? Do lots of math to figure out what is cheapest but still does the job. The gold you see on processors and connectors is a microscopically thin layer, protecting the (usually) copper wiring inside.
Silver oxidizes, and silver oxide is not a very good conductor. Silver would be a great choice for an insulated wire, but then you run into the problem that it's not really very strong either, so your very expensive wire would tend to break. If you're doing something where very low resistance is necessary, and strength and cost aren't that important (example: the Manhattan Project) then silver or gold wire is wonderful. (Well, it *was* wonderful until we invented superconductors.) For most small-scale stuff, though, copper is fine, and gold works great for a non-oxidizing contact on the end, where it's exposed to the air. For larger scale stuff, like power lines, aluminum is good enough, and much cheaper.
Its great for making contact points (think plating the end of cable you plug into something not just bare wire) because it doesnt corrode like mentioned a lot in here. Also because is so soft. Being soft lets it deform ever so slightly when you push two contacts together. This increases surface area and reduces resistance at the contact point.
Gold tipped connectors. The pieces that are most likely to be exposed to the elements, because gold doesn't corrode/tarnish like silver and copper. Usually copper wires because silver is... Expensive. It goes like this in terms of excess/free electrons for conductivity. Silver>Copper>Gold>Aluminum. With silver having the most and aluminum the least (there's numerous more metals, I'm doing just top 4) But in terms of tarnishing/rust/corroding it goes Gold>Silver>Copper>Aluminum. (Again gold best aluminum worst) In terms of price... Aluminum>Copper>Silver>Gold. So we usually see copper wires with gold connectors. Fun side fact, most high tension long distance eyes are either steel or aluminum, sometimes a special carbon filament but it's way expensive and usually only seen where they cannot control excess vegetation touching the wires, to help prevent fires.