Preventing socketed chip corrosion?

Question

I spent a couple hours repairing an Amiga A3000 that wouldn't boot yesterday. The fix was to remove Kickstart ROMs, clean the DIP leads and sockets with contact cleaner, and re-insert. Apparently a small corrosive film was preventing good contact between ROMs and sockets.

The A3000 had been stored and unused for about 9 months. While it is stored indoors in a cool and relatively dry place, my home is subject to significant humidity levels for much of the year.

The DIP chips (EPROMs, in this case) and sockets (decent quality, dual wipe) are typical of what you will find in most retro computers. I am wondering about upgrades or workarounds to minimize this problem in places with humidity.

What can be done to minimize the appearance of this type of corrosion affecting socketed chips?

Answer 1

As already stated, there is no solution. I am a collector/restorer of stand up video arcade machines and pinball machines, and these all suffer from corrosion. Even after I have cleaned and restore a game, a chip can get corrosion after a year. The one thing I do, is I collect and throw any desiccant bags I come across into each machine cabinet to help prevent moisture. I have like 10 in each cabinet. Desiccant bags are those little sacks of stuff you find when you get new electronics. That is why they include them in the packaging. I'd find a couple small bags and put them inside the Amiga case somewhere that they wont affect the electronics in any way.

Answer 2

Low humidity helps, but beyond that there are no good solutions. You can coat the exposed parts with a protective seal but then they become difficult to maintain.

Preventative maintenance is an option. Periodic cleaning with isopropanol will help. In fact after handling the parts try to clean them with alcohol to remove skin oils and other contaminants that can become oxidised or cause corrosion.

Answer 3

It may be hard to find this info, but see if you can find sockets with contacts composed of the same material as your chip's pins.

If the pin and socket are different metals, and it's a moist environment, you can get galvanic corrosion. (This is why gold-plated contacts can be a bad idea; the gold itself will not corrode or oxidize, but base metals in contact with it will.) Here's a blog post with a compatibility table; to summarize, iron, nickel, tin and lead are more or less compatible, but copper introduces some risk, and silver and gold are riskier still.

Answer 4

Once corrosion has started on the contacts, there's not much you can do to prevent it. Re-seating chips might or might not help for a while depending on storage conditions. Be aware that chemical anti-oxidation sprays are often acid-based to dissolve oxides plus some oil-based corrosion protection that tends to attract dust and can make matters even worse long-term. Thorough cleaning with alcohol would be a better option.

You can replace old sockets with new ones to at least reestablish factory-new condition and give the equipment a new lifespan (I consider that the best option. If you use good quality replacements, you can expect quite some life out of them.)

You can also remove the sockets completely and solder chips directly to the PCB, this would be a once-and-for-all solution with obvious consequences. Thinking that one through, it is maybe a bit of a drastic measure, but how many new ROM versions (which justified the sockets in the first place) would you expect to be released in the next 30 years?

Depending on the circuitry, it might also be possible to replace sockets and EPROMS with soldered pin-compatible flash chips. Would give you the best of both worlds. I did that to some of my computers (Cambridge Z88, for example) that had soldered-in ROM chips for an easier upgrade.

Answer 5

Not all desiccant bags are create equal. Silica Sand Beads only adsorb moisture and stick to surface. Expanding Polymer bags absorb and can pull moisture into bag in enclosed spaces. check it out.

https://www.youtube.com/watch?v=0U6kIsGj9X8&t=5s&ab_channel=SteelCamel