I think the corrosion problem depends first on the metal composition of the IC pin, then the temperature and atmosphere in storage. I recently pulled ICs from boxed garage storage since 1983 and noticed the following when I reorganized them:
Motorola Ceramic ICs with square gold pins (purple ceramic color) experienced some corrosion and stickiness of the crumbly black foam they were shipped with. They were a challenge to clean up. But the Motorola plastic DIP chips (RTL logic) with rounded gold pins were in perfect condition after brushing off the same crumbled foam. Intel Ceramic ICs with tin pins (grey ceramic color) were in perfect condition even though the black foam they were shipped in turned to crumbly clumps. Hitachi and Fairchild plastic DIP ICs with tin pins in plastic antistatic tubes had darkened pins. Hitachi chip pins were almost black. This made soldering to the pin a little more difficult. But I didn't bother cleaning off the tarnish and they worked fine in a socket. I've been using them with no issues. Texas Instruments plastic DIP ICs with tin pins in plastic antistatic tubes had bright and shiny pins like they were new. I use both tubes and new foam these days and don't worry about it. I think either are good for indoor temperature and humidity. The corrosion problem definitely has happened but I think it's a problem confined to certain old chips and antistatic materials. Jerry On Mon, Oct 30, 2023, 6:53 PM <bir...@soigeneris.com> wrote: > I have chips that have been stuck in the black anti-static foam for years > and the legs are still nice and shiny. (Just checked). Perhaps it is a > particular brand of foam? > > > > Jeff Birt > > > > > > *From:* M100 <m100-boun...@lists.bitchin100.com> *On Behalf Of *Peter > Noeth > *Sent:* Monday, October 30, 2023 6:16 PM > *To:* Model 100 Discussion <m100@lists.bitchin100.com> > *Subject:* Re: [M100] Anti-static foam types > > > > I would NOT recommend the black carbonized foam for storage. We used to > use that type where I worked as a Component Level computer tech for our > "Component Inventory" many decades ago. It will turn the legs of I.C.s and > transistors black after a few months if you stick them into the foam, > requiring cleaning with a mild abrasive before soldering (risking static > damage). It may be a solution for shipment only. > > > > The other foam looks like High Density Styrofoam, as used in the building > trades for wall insulation. I have seen it both light blue and pink, used > for the purposes you mention, and have never trusted it as styrofoam is > inherently very staticy, even with anti-static additives. I have seen some > people wrap that foam in aluminum foil first before poking any leaded > components into it. This may be a shipment only solution. > > > > I have always used the plastic anti static tubes (rails) that the > manufacturers sell their components in, or the anti-static poly and > mylar bags that DigiKey and other distributors use. With "through hole" > components not being as popular as they once were, and "surface mount" > components now the "norm", your best solution would be the anti-static poly > and mylar bags easily found with an Internet search. > > > > Regards, > > > > PeterN > > > > On Mon, Oct 30, 2023 at 2:42 PM <m100-requ...@lists.bitchin100.com> wrote: > > > Message: 1 > Date: Mon, 30 Oct 2023 14:25:24 -0700 > From: Gary Weber <g...@web8201.com> > To: M100 <m100@lists.bitchin100.com> > Subject: [M100] Anti-static foam types > Message-ID: > < > caajazkoqdyapx1godpsvutedor+x1npum1isuhrv+udoman...@mail.gmail.com> > Content-Type: text/plain; charset="utf-8" > > Question for anyone out there familiar -- > > There's a few kinds of antistatic foams out there that I've come across > which have had DIP chips stuck into them for storage, and the ones I > currently have on hand is the black stuff which is very porous, and this > other very stiff stuff that almost has the feeling of styrofoam. (Not > bendable.) > > Here's the two I have on hand: > [image: image.png] > > Is anyone else familiar with the light colored antistatic "hard" foam > that's in the right of this photo? What's it called and where would you > obtain more of it? It seems to protect a DIP chip's pins much better for > long term storage or shipping and I'd like to have some on hand. > > Thanks, > > -- > Gary Weber > g...@web8201.com > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.bitchin100.com/private.cgi/m100-bitchin100.com/attachments/20231030/b21a215a/attachment.htm > > > -------------- next part -------------- > A non-text attachment was scrubbed... > Name: image.png > Type: image/png > Size: 557591 bytes > Desc: not available > URL: < > http://lists.bitchin100.com/private.cgi/m100-bitchin100.com/attachments/20231030/b21a215a/attachment.png > > > >
