Will tin gold (90% 10% ) solder work for copper - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: April 30, 2025, 12:23:03 am
content: You can get Tin/gold solder eutectic (the cheap one on digikey, comparatively) work for mounting a part to a PCB?The tensile strenght is high. The best I can do is strip the platings so both things being joined are copper, or the PCB can possibly have ENIG gold.There is not much information about using it for non die attach operations, the only people brave enough to try were Sony, where they advertised gold solder in their MP3 player a while back, and they got attacked, but I thought it was interesting for mechanical reasons.I think it should be OK on the board side, if its ENIG. But how about the component pad or lead? Can it work on copper?? like will copper intermetallic cause problem in this alloy?

author: booscrawl
author_rank: Contributor
timestamp: May 01, 2025, 02:28:24 am
content: Are you trying to use solder as an investment? This solder costs like $30 an inch.

author: coppercone2
author_rank: Super Contributor
timestamp: May 01, 2025, 02:34:34 am
content: No this one is cheaper you are looking at the other alloy, and I still want to know what happens to the alloy not a financial and utility analysis

author: Zenith
author_rank: Frequent Contributor
timestamp: May 01, 2025, 05:11:02 am
content: Why not get in touch with Chip Quik Inc who make it? It's too expensive to experiment with.

author: bdunham7
author_rank: Super Contributor
timestamp: May 01, 2025, 05:21:00 am
content: Quote from: coppercone2 on May 01, 2025, 02:34:34 amDo you have a link to the product? The Au-Sn phase diagram is a bit complicated and it isn't clear to me what they or you are referring to when specifying the alloy as "eutectic".

author: coppercone2
author_rank: Super Contributor
timestamp: May 01, 2025, 01:41:30 pm
content: https://www.chipquik.com/store/product_info.php?products_id=630017

author: Stray Electron
author_rank: Super Contributor
timestamp: May 01, 2025, 02:45:57 pm
content: The ad that you linked to sells 90% tin and 10% gold (Sn90/10Au) solder. Not 90% gold 10% tin as you asked about in your title.I don't think that even NASA or the US Mil would be willing to pay for 90% gold solder! Personally I've never even heard of gold alloy solder and I have no idea what you would need it for, other than Audio Phoolery.I'm not sure of the point of your question anyway. All of the traditional electronic solders work for copper wire so why wouldn't they for plain copper?

author: bdunham7
author_rank: Super Contributor
timestamp: May 01, 2025, 02:50:12 pm
content: Well, here's the phase diagram. Note that the weight percentages are on top, the bottom scale and the numbers on the diagram are all in atomic percent. Sn at 90% by weight or 93.7% atomic is a eutectic point but there are several solid-state phase changes below that. I'd have to find and refer to a textbook to say much more, but I believe that at least the entire epsilon phase and everything to the right of the eta phase line is actually fairly brittle. As far as it absorbing gold or copper to a lesser degree than Sn100 IDK. I'd be interested to find out what specific application this product is intended for but I doubt it is just a better general-purpose solder where extra strength is needed. I second the idea of just asking Chipquik or Indium what the product is for.

author: coppercone2
author_rank: Super Contributor
timestamp: May 01, 2025, 08:54:38 pm
content: Its a low cost alternative to 80 percent gold 20 percent tin solder used for die bonding or some kind of wire bonding (power wire bonding? die bond repair with lesser equipment?)It has a shady reputation for this purposeI suspect somerthing like university IC prototyping where they throw out 95 percent of what they design because its R&D and the life time of a prototype is 2 days and the die bond reliability is not considered at alllike if you can crank out chips with a lithography lab (say diodes, single transistor experiments, etc)... would you care if the die can break eventually for a prototype you built to test one little idea? It would be a waste of gold unless that chip is like high power... and it might come out cheaper / more reliable then trying to maintain proper glue for die bonding.There is alot of work that IMO they might not even bother using the chip other then like a small test. Like if you are developing a process for anything small... see if you get the geometry correct and if it turns on ... its just meant to test some manufacturing or physics ideaI was reading about it a while ago when I read about Sony's mp3 player, but I lost the info. 2 years web rot is becoming alot

author: coppercone2
author_rank: Super Contributor
timestamp: May 02, 2025, 03:53:43 am
content: Oh right and they also talk about lid on transistor enclosures.I think the main idea other then high tensile strength, is that its OK with bonding to thick gold.And I think in general gold bearing solders are vacuum-solder friendly (fluxless). I think some alloys don't like being fluxless even in a vacuum. And I assume that the gold might prevent alot of surface oxidation on the wire, so it stores nicely and vacuum solders nicely because its oxide free-er.I get what you are saying, since that its mainly tin, its logical to think about it being close to 100% tin solder from the point of view of solubility.and I have no idea what that diagram is lolBut how about some kind of test? Does thermal aging help? I thought maybe to solder two PCB together, leave it on a hot plate, and then try before and after tear testing after some period of time (put it in a vise and toque it). I can't do a pull test, but if they are soldered with a lap joint between two boards, I can definitely try to twist it with a hand vise attached to it. I am definately not looking to build any machinery, so a test would need to be performed with hand tools, if I were to do it. Or strike it with a hammer to try to 'pop' something off with a chisel.I don't have any interest in a pull testing machine or torque machine building. Are there any possibilities left?I could solder a segment of copper rod to a copper clad board and chisel it, and see how it does compared to a normal solder mounted one. I just mean maybe a 1/2 centimeter tall 3/16 copper cylinder that is sanded flat and soldered to a PCB (no hole). This one sounds pretty good?? Its like a battering ram. If something funny was going on, maybe I could tell by how hard I need to strike it to knock it off.

author: coppercone2
author_rank: Super Contributor
timestamp: May 02, 2025, 04:13:35 am
content: Or maybe to 'age' it, just reflow it for way too long? Normally your solder joint would be completed in a few seconds right, so what if you left it on a hot plate so it stays molten for like 1 minutes? 5 minutes? If anything bad is happening from diffusion ,it should occur way too much and make a instantly crappy joint once you let it solidify? And then after doing that leave it on near molten temperature for another substantial time period.And do the same thing for the electronics solder one, for comparison.That seems like it would magnify problems ?And instead of a chisel, how about using a copper hex standoff, and then putting a torque wrench on it? I have those torque wrenches with the 'dial' which measures torque (non ratchet). It should show me the force it breaks at. And I could clamp the PCB to a work table.

author: Zenith
author_rank: Frequent Contributor
timestamp: May 04, 2025, 09:22:44 pm
content: Quote from: Stray Electron on May 01, 2025, 02:45:57 pmGold solder is used for jewellery. In this case it seems to be sold as a heat spreader material.Quote from: Stray Electron on May 01, 2025, 02:45:57 pmI thought it was mechanical strength, as in shock and vibe. I'd have thought putting together circuits to withstand shock and vibe was a well understood area, and they'd found cheaper ways to do it than gold solder.

author: coppercone2
author_rank: Super Contributor
timestamp: May 04, 2025, 09:37:05 pm
content: i mean, the tensile strenght is 2x normal solder. the 80% is 4x. No matter what you do thats not a small numberLike 100% strength increase is not ignorable

author: jpanhalt
author_rank: Super Contributor
timestamp: May 04, 2025, 11:08:35 pm
content: You are confusing people. 90% 10% gold tin and 90% 10% tin gold are two completely different alloys. Maybe you should divide that discussion into two different threads?Quote from: coppercone2There is also discussion of the gold-tin eutectic alloy -- a 3rd thread?

author: coppercone2
author_rank: Super Contributor
timestamp: May 04, 2025, 11:20:02 pm
content: I fixed the thread tittle to be 90 percent tin 10 percent gold (cheap solder)Maybe someone else is interested in the 80/20 gold/tin but its not affordable for me. Unless it is with some badass part like a diamond substrate resistor that can do 100w in 1210 ($500 each). That one will get its own threadhttps://www.smithsinterconnect.com/getmedia/d475db53-ecb7-4b39-8183-2de634689e1d/CcT0603D.pdf300whttps://www.smithsinterconnect.com/getmedia/b62cd76b-ef3e-480a-9ffb-5b814ce4ac01/CT2010D.pdflittle solid silver gold plated water cooled heat exchanger for that one lol

author: jpanhalt
author_rank: Super Contributor
timestamp: May 04, 2025, 11:34:22 pm
content: We all work within the constraints of this forum:You didn't fix the title enough.

author: coppercone2
author_rank: Super Contributor
timestamp: May 04, 2025, 11:38:26 pm
content: it says for meWill tin gold (90% 10% ) solder work for copperit must not be updating something for you

author: tooki
author_rank: Super Contributor
timestamp: May 05, 2025, 07:32:57 am
content: Folks: when a thread is renamed by editing the original post, it does NOT edit the titles of existing replies. And if one replies to a reply (with the button on that reply), the reply’s title is used, not the thread title.