has anyone here used indium to solder to a non metal - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: September 30, 2024, 07:24:55 am
content: I read alot of tall tales about being able to wet indium to many surfaces.I cut a small strip of indium metal, and I also mixed up some indium/tin (50/50) in a smelt and planished it into some stripsI had four samples, 2 alumina and 2 microscope slides made out of glass. I washed them, soaked 1/2 in HCl and the other half in sodium hydroxide. I also soaked the solder in hydrochloric acid. Everything was washed in acetone too after being rinsed in distilled water, and it appeared to pass the "no bead" test.I then heated them up and tried two different methods of application, one was to try to "feed" solder into it like soldering from a thin strip (1mm) and the other way was a preform, that is to put a flattened piece ontop of the substrate and then heat itAnyway, in all cases, absolutely nothing happened. Its identical to feeding normal lead solder. With the preform I thought it was working, but actually as soon as I touched it to try to see what happens if I scrape it, it balled up into a lump and there was zero wetting.I regard this as a total fail, it may be possible with ultrasonic but I have trouble believing the claims that its possible to use pure indium to solder glass with. I am not even seeing a HINT of any sort of adhesion.I see you can buy a 'nickel felt' to help apply it. I have a feeling its a waste of money to try.

author: coppercone2
author_rank: Super Contributor
timestamp: October 01, 2024, 02:27:30 am
content: I got some sort of ultrasonic wand, I wanna see what happens if you poke it, and possibly make a butane heated tip for it to make a poor mans ironThe idea is to use a blower to keep the shaft / module cool and a ceramic coupler between the soldering iron tip and the shaft, to limit heat going into the crystals

author: coppercone2
author_rank: Super Contributor
timestamp: October 08, 2024, 10:22:59 pm
content: it looks like you can drill into rubber with the ultrasonic wand. They use a special transformer instead of a piezo material.what a bizzare contraptionit looks like I can wet a microscope slide with indium that hangs on OK, but it keeps breaking. I need to try with a hot plate and lower ultrasonic settings. You can drag the wand through the molten indium and under neath it looks like a mirror

author: coppercone2
author_rank: Super Contributor
timestamp: October 10, 2024, 12:12:40 am
content: it looks like it works with indium, I made a T-joint between two ceramic heat spreader tiles.that is so weird, there is actually a fillet.wtf

author: coppercone2
author_rank: Super Contributor
timestamp: June 26, 2025, 01:15:09 am
content: I bought the nickel felt (China) with which to build a nickel felt applicator.Might as well be mageweave cloth and mithrilI wonder what the people using Indium actually use. I bet there is something not documented online that is 10x cheaper and easier. Maybe people stopped using indium all together after Indium suggested you need this strange material.

author: coppercone2
author_rank: Super Contributor
timestamp: July 07, 2025, 09:50:14 pm
content: well it kind of looks like felt and bends like a soft sheet of lead or something. Feels like felt. Cuts OK with electricians scissors.I wonder if they mean plated carbon fiber felt, instead of sintered pure nickel felt. I guess I need to try it.

author: coppercone2
author_rank: Super Contributor
timestamp: July 07, 2025, 10:20:19 pm
content: Does anyone know how this applicator should look?Should I have a strip of nickel felt hanging off the end flapping in the breeze, or should it be draped around some kind of substrate.I either thought to bend a U and fasten it to a thin stainless steel spatula, or just attach it to a stick so its just hanging off by 1/2 a cm.

author: langwadt
author_rank: Super Contributor
timestamp: July 07, 2025, 10:23:01 pm
content: https://documents.indium.com/qdynamo/download.php?docid=20

author: coppercone2
author_rank: Super Contributor
timestamp: July 07, 2025, 10:25:04 pm
content: I saw that, but unfortunately all records of what it actually is are missing."Apply indium to the heated non-metallic using anindium-plated nickel felt applicator. Rub gently untilthe non-metallic is coated with a thin film of indium"I don't understand if the applicator should be like loose or fastened to something. I can bend a spatula into a U shape, and fasten the nickel felt to it. Then I can apply pressure because when I press the stainless will press it. Or I can just tie it to a stick so its like a 'paint brush.I only have like 1 square inch so I don't want to waste it. While its porous, the felt itself.. handles much like a thin sheet of very soft lead or indium metal. Its not nearly as soft as real felt. I thought it would be like puffy, but IMO its pretty much a porous textured soft sheet metal.I am guessing it should have a backer, since it does say to "rub" but its pretty ambiguous. The way that seems logical to me is to have it against a flat, much like a sanding pen. Sanding pens are kind of like chisel shaped.Its very much like solder wick which has been used but is softer.

author: coppercone2
author_rank: Super Contributor
timestamp: July 07, 2025, 10:40:17 pm
content: I am thinking of how to make a applicator too. I have a set of stainless spatulas, I though to grind the end so it has two notches so the top part can be secured with a O-ring. And to solder on a shim down the middle which extends to almost the bottom, so the felt can be curled over and pressed down by it. If I can stand to waste a little more felt, I can make it work with 2 o -ringsOr to make it like a trowel

author: coppercone2
author_rank: Super Contributor
timestamp: July 08, 2025, 04:28:18 am
content: OK I made the thing I drew out of stainless.The nickel felt did not really wanna wet. I made a hot pool of indium on a hot plate (ceramic) and kept rubbing it like a kind of scratch brush. After a while it stated to work. Takes some effort.Anyway now its like a layer of indium stuck to it.I cleaned a microscope slide with IPA spray and a wipe, let it warm up on the plate, and I was able to "paint" the indium on it with a gentle enough scratching back and forth motion. For the glass it seemed to coat it good without much effort or scratching really.IDK if that is how its supposed to be but it does seem to work. I will try it on alumina later.

author: coppercone2
author_rank: Super Contributor
timestamp: July 09, 2025, 02:15:28 am
content: Using my nickel scraper thing, I managed to solder a laboratory slide to a alumina substrate (the one with score marks in it)I don't know what makes it chooch, first it was just giving like dark stains but then after I rubbed it a bunch it seemed to spread easier and I painted the entire surface, and the middle of a laboratory slide. I used a razor blade to scrape most of the indium off to leave a film, and then I noticed some areas where it did not peentrate, so i rubbed it more on those areas and then cleaned it again with razor till I can pull it off leaving like a thin film.I then put a strip of indium on the middle of the ceramic and spread it out a little bit with the nickel thingI used a titanium clamp to pick up the slide, rotate it and place it down to make a lap joint.It is very easy to scrape excess indium off the glass with a razor if it spills or whatever when coldLater I will reheat it, separate it, and scrape it mostly off with the razor, and attempt to do an actual solder joint using indium tin solder 5050 onto the indium "plate" layer.The indium tin melts at a much lower temp then the pure indium, but its less sticky supposedly.

author: coppercone2
author_rank: Super Contributor
timestamp: July 09, 2025, 05:56:11 am
content: It seems that when I solder with indium tin, it eats the indium very easily. I guess you need precise control of iron, mine does not go that low. You might need a digital iron.I am doing another experiment with solder, to solder to carbon. C-Solder does it. Its a mere 150 euro for 3 feet. I believe its SAC305 with some chromium mixed in.https://pubs.acs.org/doi/10.1021/acsnano.5b02176I will be doing a experiment to heat some solder up with chromium or nickel dust, to see if I can get it to dissolve. I can leave it on the hot plate for a while.

author: coppercone2
author_rank: Super Contributor
timestamp: July 09, 2025, 07:13:50 am
content: That ceramic to glass joint I made came apart too easily. And it was peeling too easily.And for some reason there turned out to be a big gap, I thought it was flush. I don't know where it came from, maybe I lifted it a little when I was doing the corners.I melted it again and added more indium and ran over it with my ultrasonic wand. I feel like something happened because the wand... made like crud appear.I 'peened' the entire surface with the wand and then I went over it with the razor blade, and a few empty spots showed up. I got more indium and used the wand to patch them, then ran the razor blade again..Then I got a uniform surface that looked like a dull tin plate.I cleaned it with alcohol and rubbing, and then I managed to make two solder joints with the indium/tin alloy using a normal soldering iron and some low temp flux. On the DMM it measures similar to how a electroless copper would measure.I think it needs to be really clean to work well with just the felt. The felt is still useful for spreading it though. I can try alkali cleaning next time, isntead of just isopropyl alcohol. But with ultrasonic it looks like enough.. the tin/indium solder point on the indium coating are like tough and look good this time. sssssSo the felt is not a cure all, it might work good if its totally clean, but I was not even wearing gloves, for this situation you need the sonicsAnother thing that would be useful is a hole in the table for the hot plate, so its easier to work on it.I am so bad with processes that need to be clean.I wonder why the ultrasonic makes the indium so... drossy. It like instantly forms dross on the highest power level. When its set to medium its more like welding where the impurities appear on top.I may buy a block of indium instead of a sheet.I made a new solder joint between two alumina sheets with a lap joint. The 2nd alumina sheet was not cleaned, and it was more difficult to tin. It took 3 passes with the ultrasonic, some scrubbing with the nickel brush (which developed a black stain on it, which was removed via alot of rubbing) and 2 razor blade scrapes before it had a coating of indium that looked like properly adhered after a razor blade scrape. I then used titanium tongs to flip it over and make a lap joint.So the less you clean the more work you have to do. Next experiment I will wear gloves, clean them with oven cleaner and distilled water, and see how much easier it is. And then I can try hot caustic, but that is alot of work.

author: coppercone2
author_rank: Super Contributor
timestamp: July 12, 2025, 08:33:48 am
content: I bought the tools to cut up some alumina stock I have so I can make test pieces to measure the strenght of the solder joint without risking cracking substrates. I intend to solder two cylinders together and try to torque it apart

author: coppercone2
author_rank: Super Contributor
timestamp: July 17, 2025, 01:27:28 am
content: oven cleaner and distilled water worked great for making some alumina blocks solderable

author: Funn_Indication
author_rank: Newbie
timestamp: September 09, 2025, 08:19:11 am
content: It seems like you’ve encountered a common issue with indium not adhering well to glass substrates, despite your cleaning efforts. The oxide layer on both the indium and the glass surface could be the main cause of the problem, preventing proper wetting. While your cleaning process with HCl and sodium hydroxide seems good, the oxide layer might not have been fully removed. For glass, using HF (hydrofluoric acid) might be more effective in cleaning and activating the surface. Ultrasonic cleaning could also help, especially when combined with a suitable flux to enhance adhesion. If you're using nickel felt to apply the indium, it's important to ensure you're using the right temperature and flux, as this could also affect how well the indium adheres. Overall, it’s not surprising that it didn’t work with just the methods you tried, as pure indium can be tricky to work with on glass. It may take some more trial and error, particularly with flux and surface prep. Keep experimenting, and consider using a reducing atmosphere to help prevent oxidation while you’re working with indium.