Solder Not Adhering to Eyelets

[jam-mill]

I've encountered a number of eyelets, in a batch of 500, where solder just flows through them and does not stick. Applying flux did not help. Any ideas?

[Winder]

Try burnishing with a fine grit sandpaper ... 600 maybe ... to remove oxidation.

[jam-mill]

Try burnishing with a fine grit sandpaper ... 600 maybe ... to remove oxidation.

Thank-You for the tip!

[Matt J]

Try burnishing with a fine grit sandpaper ... 600 maybe ... to remove oxidation.

That's something I like to do. Try using Mitchell abrasive chord. You can get it from Stewart MacDonald and a couple of other online retailers. It comes in different thicknesses you can try.

- Matt J.

[JD0x0]

Try burnishing with a fine grit sandpaper ... 600 maybe ... to remove oxidation.

It also gives a rougher surface to adhere to. Just like how you would rough up a glossy surface that you're trying to paint to get better adhesion, I believe the same principal applies to solder, to a degree.

[R.G.]

You know how water "wets" some surfaces, not others? Water rolls off a freshly waxed car, but clings in a continuous sheet to a car that's got oxidized, dull paint.

Same with solder. The electrochemical nature of molten solder is such that it will "wet" some surfaces and not others. The process of solder wetting is NOT mechanical, in that a rougher surface gives a better grip. It's closer to a very thin layer of alloying with the the underlying metal. The solder won't wet, or dissolve a layer of metallic oxides, or paint, or oils or dirt, or a vast number of other things. to get solder to wet reliably, you must expose a clean metallic surface. Abrading with fine sandpaper is one way. I prefer 0000 steel wool. It's common for "brass" things in the marketplace to be some other base metal (iron or steel) with a thin layer of brass-ish or copper-ish plating. Often this is then covered with a clear paint layer to preserve the "shiny new" look. But this same coating can make it nearly impossible to solder to.

If the eyelets are still loose, soak them in paint remover (for most paints) or acetone (for lacquers and epoxies) and test for when they will solder well >> before << putting them in boards.

Flux will chemically remove a very thin layer of metal oxide and its residues won't then impede solder from doing its wetting/bonding. It also prevents oxygen from getting to the heated joint and making new oxide faster as the soldering progresses.

So I'd recommend: (1) try paint stripping them. If that solders well, do a whole batch and you're done. (2) or just toss them and go get eyelets where you bought them before and the worked well. If your time is anywhere near as valuable to you as mine is to me, I'd chalk it up to experience, toss the junk eyelets and go buy good ones. And I'd never, ever use another batch of eyelets that I hadn't tested for solderability before putting them into eyelet boards.

[jam-mill]

You know how water "wets" some surfaces, not others? Water rolls off a freshly waxed car, but clings in a continuous sheet to a car that's got oxidized, dull paint.

Same with solder. The electrochemical nature of molten solder is such that it will "wet" some surfaces and not others. The process of solder wetting is NOT mechanical, in that a rougher surface gives a better grip. It's closer to a very thin layer of alloying with the the underlying metal. The solder won't wet, or dissolve a layer of metallic oxides, or paint, or oils or dirt, or a vast number of other things. to get solder to wet reliably, you must expose a clean metallic surface. Abrading with fine sandpaper is one way. I prefer 0000 steel wool. It's common for "brass" things in the marketplace to be some other base metal (iron or steel) with a thin layer of brass-ish or copper-ish plating. Often this is then covered with a clear paint layer to preserve the "shiny new" look. But this same coating can make it nearly impossible to solder to.

If the eyelets are still loose, soak them in paint remover (for most paints) or acetone (for lacquers and epoxies) and test for when they will solder well >> before << putting them in boards.

Flux will chemically remove a very thin layer of metal oxide and its residues won't then impede solder from doing its wetting/bonding. It also prevents oxygen from getting to the heated joint and making new oxide faster as the soldering progresses.

So I'd recommend: (1) try paint stripping them. If that solders well, do a whole batch and you're done. (2) or just toss them and go get eyelets where you bought them before and the worked well. If your time is anywhere near as valuable to you as mine is to me, I'd chalk it up to experience, toss the junk eyelets and go buy good ones. And I'd never, ever use another batch of eyelets that I hadn't tested for solderability before putting them into eyelet boards.

R.G - Thank-You for the detailed post. Having built three amps from the batch of eyelets, encountering soldering issues was completely unexpected. Granted that more than a year has elapsed during that build period. So, it seems, that over time, some of the eyelets have oxidized despite being stored in a sealed plastic bag in a relatively dry environment. No telling how long they were in Mouser's possession prior to purchase either. Regardless, the abrading method mentioned in a previous post seems to be doing the trick and is not costly time-wise. Thanks again for the edification - much appreciated!

-jack

[statorvane]

Try soaking them in white vinegar (acetic acid). It'll etch the surface some and may help. Should only take a few minutes to see if this works for you.

[R.G.]

Ah. If this batch has soldered well before, it is indeed oxidation that's "poisoning" the surface. Abrasion or chemical stripping of the oxide is good. For some reason I read your post as it being a new batch.

As a side note, acid or zinc chloride fluxes will nicely take care of an oxidation layer like that - but never, ever use these fluxes. The unavoidable residue from acid/zinc fluxes will corrode the soldered parts badly.

One approach I've used that seemed to work was brass polish, sold as "Brasso" in supermarket cleaning products aisles. It removes brass tarnish quickly, but leaves an oil layer. You can then remove the remaining oil with strong solutions of dishwashing liquid or a solvent, like maybe rinsing in a small bowl of acetone. Another is to use "Bon Ami" scrubbing powder, another cleaning aisle product. I use Bon Ami to clean copper PCB stock before etching.