[vcf-midatlantic] How to best store vintage ICs
hjohnson at retrotechnology.info
Tue Dec 17 12:15:34 EST 2019
Henry S. Courbis (and others) suggest "antistatic foam is better than
nothing" and suggests sealed antistatic bags to store the antistat'ed
ICs. Also suggested are antistatic IC tubes, which Bill Degnan correctly
states are superior. But many people (including Henry, myself) end up,
piling chips in black anti-stat foam "in a shoebox", as he posts.
I'm not ragging on Henry; everyone has these problems and uses the
solutions reasonably available. Or we inherit collections of chips
stored this way. Due to my age it's clear to me, these are serious
problems over a few decades. Since many vintage computers and components
are 40, 50 or more years old, it's a more serious problem for those
Some science and engineering of materials comes into play when dealing
with old IC's and their storage. If such discussions are not of
interest, stop reading here.
I don't have a specific Web page, about problems with "black rust" AKA
"silver oxide". But many have observed that certain TI (Texas
Instrument) IC's from the 1980's 90's have had IC pins turn black and
become brittle. In sockets these IC's must be replaced; soldered in they
seem to mostly perform OK (until they don't). Other ICs in general may
suffer similar brittle-rust-pin problems. I don't have a factual
scientific finding on the chemistry of the problem But there's no doubt
problems occur for certain runs, brands, and eras of IC's.
Solutions to the old chips that rust-out? one simply avoids them. They
now stand out with their black and sometimes brittle "legs". My
expedient (described on the Web page cited) was to use De-Oxit per pin
and socket and pray.
Antistatic-plastic tubes are available and not overly expensive in bulk.
One accumulates these or just buys them. Replacement every few decades
is simply a fact, because they *break up* otherwise. Other than the
tube's decay, I'm not aware they cause other problems.
I and others have seen chips, stored for decades in antistatic foam,
fall apart when pulled out. We have all seen such foam become dust or
mud. So, it's a problem. I'll detail what I know.
I did some research several years ago about the nature of black
antistatic foam. I had to recover chips stored since the 1970's in black
foam in a cardboard box; others were packaged in individual little
hard-plastic containers, also with black foam.
The classic conductive material in these foams, appears to be
carbon-black. Some carbon-black is produced by burning (with acids I
believe) *sugar*. Consequently, some resulting carbon black contains
sugar and acid. Over time and in the presence of oxygen and moisture,
these contribute to *corrosion*. And over decades, the base material of
anti-static "foam" degrades, as does almost any plastic. When these
anti-static foams are cheaply produced, these problems seem to occur
Antistatic foam is intended to be a temporary storage, generally, for
transport. I'm sure someone with more industrial knowledge, can inform
me about long-term storage methods. I'm generally aware, those involve
sealed plastic and antistatic or conductive baggies. There's likely
other and better (or worse) materials used in storage in recent years.
Among the decades-old ICS, I observed there was much less damage among
the individual containers than in the "black foam in a box" items. I
hypothesize that the somewhat sealed containers reduced oxygen and
moisture exposure. I left those items alone.
The chips stored in sheets of crumbling black foam? As an expedient, I
repackaged them in "aluminum wool" sheets and sealed anti-stat bags.
"aluminum wool" is like steel wool, only made from aluminum. It was
awful, cheaply made, crumbly stuff. But it wont' rust or induce rust in
other metals, and it provides conductive protection. Instead of
'cardboard boxes" I used acid-free archival boxes. Most cardboard is
full of acids, from the paper-making process. Again - these choices were
an expedient of time and cost.
I didn't and don't have cheap solutions to these "black-foam" problems;
but I've not looked lately. I'm glad the subject came up for discussion
(if anyone has read this far).
I don't know of a better and relatively cheap material to use as an
antistatic embedded "pad", than the black (and pink) foamed plastics in
current use. It seems prudent to replace the foam every several years,
and to sealed-bag such things: yet I don't follow my own advice out of
convenience. Conductive tubes are reasonable for batches of like chips;
inconvenient for individual chips.
IF somone has factual/engineering data about some modern material
alternatives, I'd love to hear about it. Don't forget the material facts.
Regards, Herb Johnson
Herbert R. Johnson, New Jersey in the USA
http://www.retrotechnology.com OR .net
preserve, recover, restore 1970's computing
email: hjohnson AT retrotechnology DOT com
or try later herbjohnson AT retrotechnology DOT info
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