Beware of old AntiStatic foam - Page 1
Forum section: electronics / general

author: intabits
author_rank: Frequent Contributor
timestamp: March 21, 2021, 11:44:49 am
content: Unforunately, I wasn't aware of this previously, and maybe others aren't also...Among my most prized possions are my first two microprocessors - a pair of Signetics 2650s with ceramic packages and gold plated pins, that I bought new back in 1976.I dug them out a few months ago, just to make sure that they hadn't been lost, but I didn't take a closer look at them until today.Not only had the antistatic foam they had been stored in for 40+ years decayed to dust, it had corroded the pins of the chips away in the process. The gold plating was no obstacle.I found some discussion of this:-https://vintage-radio.net/forum/showthread.php?t=131907So to save them, (after DeOxiting and cleaning them) I'm thinking of soldering them to machined pin IC sockets like this:-It looks like the pins on these ceramic packages are not part of the leadframe, but separate pieces that are welded(?) to the frame. I hope they are welded, rather than soldered, so that they won't come adrift when I solder them to the socket.Before I do this, does anyone here have any better suggestions for saving these chips?A PCB adapter board with header pins maybe? (they don't need to be plugged into any existing socket, so the pinout can be anything)

author: Zero999
author_rank: Super Contributor
timestamp: March 21, 2021, 11:56:05 am
content: I've seen it where I work. Have you tried cleaning them with isopropyl alcohol? An ordinary detergent may help, but make sure it's properly rinsed and dried, before storage, or usage.Modern polyethylene anti-static foam doesn't decompose like this and there are polypropylene anti-static packages which are pretty good. If you can't get that, then how about putting the ICs in ordinary sockets, to protect the pins and packaging them in silver or black ESD safe bags?

author: Refrigerator
author_rank: Super Contributor
timestamp: March 21, 2021, 12:01:59 pm
content: Old foam deteriorates and gets either dry and crumbly of wet and sticky, looks like yours was the latter.You see this often in old cars where the headliner foam deteriorates as well as the foam suspension in speakers.I think it's humidity that causes this.Also make sure you plug the socket into a breadboard to keep the pins straight when soldering.

author: RoGeorge
author_rank: Super Contributor
timestamp: March 21, 2021, 12:07:00 pm
content: Have you tried using a pencil-eraser to clean the pins?It cleans almost everything, and it can be cut or pierced to clean any facet of almost any shape.

author: Refrigerator
author_rank: Super Contributor
timestamp: March 21, 2021, 12:08:52 pm
content: Quote from: Zero999 on March 21, 2021, 11:56:05 amCleaning with vinegar might be an option as well i've seen people clean battery leakage (and other corrosion) from PCB's this way.

author: tszaboo
author_rank: Super Contributor
timestamp: March 21, 2021, 12:11:05 pm
content: IPA, or ultrasonic cleaner is your friend.

author: zener
author_rank: Contributor
timestamp: March 21, 2021, 01:15:07 pm
content: An ultrasonic cleaner is NOT your friend. The ultrasonic vibrations can break the bonding wires that go betweenthe chip carrier and the silicon wafer.

author: tszaboo
author_rank: Super Contributor
timestamp: March 21, 2021, 04:50:03 pm
content: Quote from: zener on March 21, 2021, 01:15:07 pmGot any evidence to back this up?

author: Bud
author_rank: Super Contributor
timestamp: March 21, 2021, 04:56:30 pm
content: I believe it was Adrian's Digital Basement youtuber who had very good results cleaning a badly corroded PCB by soaking the affected areas with WD40 for a few hours, then brushing it.

author: Berni
author_rank: Super Contributor
timestamp: March 21, 2021, 05:01:06 pm
content: Wait are those pins just corroded or did the thin pin part disappear completely? Or are those pins just bent and such to look like it.EDIT: Sorry typo

author: intabits
author_rank: Frequent Contributor
timestamp: March 21, 2021, 05:35:13 pm
content: Thanks for the responses.Good idea about stabilizing the pins while soldering.So far, I have only applied some Deoxit, and the black munge then seems to scrape off fairly easily.Next, I'll use IPA and a toothbrush (if I had a girlfriend, I'd use hers) to get the munge off.I'll try the eraser idea on any stubborn spots."Wait are those pins just corroded or did the thin pin big disappear completely?"Not sure what you mean there, but most of the pins are definitely very, very corroded.Do people agree that soldering to a socket as shown is the best way to make these devices usable again?(I'll first test a socket to make sure the pin tops take solder well - might have to remove some plating if not)

author: DrG
author_rank: Super Contributor
timestamp: March 21, 2021, 05:50:30 pm
content: Quote from: intabits on March 21, 2021, 05:35:13 pmI saw this once, with a couple of chips that were in a plastic drawer - but only a couple of chips were affected. I am sorry that I can't remember precisely, but I don't think they were on static foam at all - If they were, I do not remember it being all degraded.It puzzled me as to why a few chips would get corroded when others stored in the same environment did not. To be clear, I think you are on solid ground suspecting the degraded foam, but I just don't know.Mine were in worse shape and portions of some pins were gone:For the heck of it, I kludged the IC onto a socket and it did still workhttps://www.eevblog.com/forum/vintage-computing/sn76489-reincarnation/msg2989066/#msg2989066Personally, if I had some ICs that were extremely valuable to me, I think I would treat the pins with something like 99% isopropyl alcohol or ethanol, to remove any corrosive chemicals that might be on the pins, and store them in a plastic tube. But I don't know this for a fact. For example, in numismatics people used to use certain kind of soft PVC "flips" until learning that they could interact and damage the coins - that is well known now.If some one has some hard facts or "museum curator"-type practices, I would like to know also.Edited to add: The ICs had been in the plastic drawer for 30+ years.

author: tooki
author_rank: Super Contributor
timestamp: March 21, 2021, 06:07:24 pm
content: Quote from: intabits on March 21, 2021, 11:44:49 amOh dear, that’s rough!!At work, the component drawers are full of foam that’s decaying, but there’s no apparent corrosion. What were these chips, and their foam, stored in, and under what conditions? I suspect that there are additional factors beyond age that come into play to cause this level of catastrophic corrosion.

author: magic
author_rank: Super Contributor
timestamp: March 21, 2021, 07:09:03 pm
content: Beware that inserting the bottom pins of a female socket into another female socket will ruin the latter.I would look for a similar frame with real male pins (if such things even exist) or create one by transplanting pins. Half an hour of boring work and you're in. Well, all of that assuming that the ICs are ever meant to be used.

author: drussell
author_rank: Super Contributor
timestamp: March 21, 2021, 07:30:11 pm
content: Quote from: intabits on March 21, 2021, 05:35:13 pmToo bad you don't have access to whatever apparatus the Chinese recyclers use to weld on and polish up new pins on salvaged components when they sell all those cleaned and refurbished, sometimes remarked, sometimes even fake chips.

author: amyk
author_rank: Super Contributor
timestamp: March 21, 2021, 09:40:15 pm
content: Quote from: intabits on March 21, 2021, 11:44:49 amThey might be soldered with high-temperature solder. On the bright side, if they do come off, you're left with a DFN-40

author: Berni
author_rank: Super Contributor
timestamp: March 22, 2021, 06:07:14 am
content: Wow it does completely eat away the thin part of the pin.Would have never thought that decomposing antistatic foam could be this corrosive. Even most RTC battery leaks are not as aggressive as this.

author: intabits
author_rank: Frequent Contributor
timestamp: March 22, 2021, 08:13:07 am
content: Quote from: tooki on March 21, 2021, 06:07:24 pmThey were stored in a parts draw cabinet. Admittedly, in a room exposed more to the outside air, so with higher humidity.There's no other black foam-mounted parts in the drawers to compare with, but other parts in the drawers show no similar corrosion, and other chips stored in aluminium foil over styrofoam in the same environment are all OK. So it seems the foam (possibly plus humidity) caused it.Quote from: magic on March 21, 2021, 07:09:03 pmI wasn't aware of that. Also, the pins on those sockets are easily broken off when straightening a bent one. The leftmost one in the photo is already bent.I don't need to insert them into any standard socket, I just want to connect them up to some sort of demo/display system.So I'm starting to lean towards the idea of a PCB with header pins, like an Arduino shield.I'd just cut off the thin parts of all the pins, and just "surface mount" the chips onto traces going to the header strips.If the headers become damaged, they can be replaced without ever touching the chips. And removing the chips would be a little easier if that ever became necessary. And while I'm at it, put basic items like bypass caps & a crystal on there as well...

author: magic
author_rank: Super Contributor
timestamp: March 22, 2021, 08:21:05 am
content: They simply are thicker than male pins that normally go into those sockets.Also, male pins have two ends and the wrong end is too thick as well.Surprising complexity for such a seemingly simple connector

author: Ian.M
author_rank: Super Contributor
timestamp: March 22, 2021, 09:18:20 am
content: This paper on gold/tin solder bond strength may be of interest:https://www.osti.gov/servlets/purl/1142490Look atAries 40-600-10flat pin headers which are readily available. If you can find stock, Aries 40-600-11 would be even nicer as that's the gold plated version. If the old pins were cropped, sanded and lightly tinned and the inside face of the fork terminals on the header was similarly tinned, after they were formed to fit the slight package over-width due to the old pin remnants, it should be possible to extract the individual pins, put them in a jig (e.g. a turned pin socket that's been oversized by reaming with a 0.55mm HSS drill bit in a pin vise) for alignment, and sweat them onto the well fluxed pin stubs.

author: intabits
author_rank: Frequent Contributor
timestamp: March 22, 2021, 01:41:26 pm
content: Thanks for the reference and detailed possible solution. It does seem a bit fiddly though, and like the machined socket idea, still involves direct connection of chip pins to socket pins, which in both cases are fairly delicate. Any pins getting damaged would mean re-subjecting the chip to soldering stresses.As mentioned, there is no need to make these able to be plugged into any standard DIP40 receptacle, so that's why I'm pretty much settled on the PCB adapter idea, which should firmly and safely mount the chip once and for all, while separating it from any possible damaged pin issues (and the header pins are stronger anyway).A manufactured PCB with white (or black?) soldermask, and silkscreen printing showing pin designations would make a nice centrepeice in a 2650 demo/display project. Some bypass caps (but no crystal) can also be fitted to the board.Thanks to all who responded.

author: rsjsouza
author_rank: Super Contributor
timestamp: March 22, 2021, 02:30:52 pm
content: Thanks for the heads up, and I am very sorry this happened to you.I have a few ancient EPROMs and some TO-18 ICs that suffered corrosion over the years. I will try the Deoxit and WD-40 to see what good can come up from it.Having moved to US I now have good access to high quality antistatic foam, but historically we did not have access to this. My dad's solution was to carefully discharge himself and then wrap the devices in aluminium foil on all his CD4000 devices and some have been stored in perfect condition for more that twenty years. I have several CMOS (and some NMOS) processors and memory stored this way as well. And yes, all them still work.This method is annoying and does not hold if you use the packaging regularly (the foil tears easily), thus I will probably keep putting most of the devices on foam but keeping a close eye as time goes on. One aspect is that I created lots silica-gel bags using coffee filters and use them copiously on the boxes where I store these parts. Hopefully this reduces the time to decay.

author: drussell
author_rank: Super Contributor
timestamp: March 22, 2021, 02:53:14 pm
content: Quote from: rsjsouza on March 22, 2021, 02:30:52 pmDon't you meanincreasesthe time to decay?

author: Ian.M
author_rank: Super Contributor
timestamp: March 22, 2021, 03:07:01 pm
content: I don't like the direct to board mounting idea - the coefficients of thermal expansion of FR4 and ceramic are very different, and there's no flex in the arrangement so you risk ripping the metalization off the package either by temperature extremes or the board flexing, at which point its game over. Originally the pins flexing could accommodate the thermal expansion difference.Also, that metalization is pretty thin - you really don't want to get non-gold alloy solder anywhere except the faces of the pin remnants as its probably severely vulnerable to leeching. (Similar to the vintage Tektronics silver on ceramic terminal strip problem.)Therefore I'd suggest using a header even if you reject my loose pins idea. You'll probably have to splay its terminals slightly or crop and file the top pins and solder with a fillet to the remaining flats.

author: DrG
author_rank: Super Contributor
timestamp: March 22, 2021, 03:28:53 pm
content: Quote from: intabits on March 22, 2021, 08:13:07 amThat situation (other chips stored right next to the chips that corroded) was also what I saw. It begs the questions as to whether the foam was the culprit. As I said before, I would also point to the foam since it is breaking down. Were there any of the same chips (2650s) nearby but not in the foam and not corroded?Other possibilities are contaminants on those chips only and also the possibility that it is a manufacturing issue. True, you are more interested in what to do now rather than how it happened.I wonder if these old cases would work for your display edit [your pcb would look better] but, at least for storage?https://chipscapes.com/collections/just-the-chips/products/intel-8008-the-first-8-bit-microprocessor-c8008

author: TerraHertz
author_rank: Super Contributor
timestamp: March 22, 2021, 04:26:09 pm
content: 'Pin Rot.'Many IC leads are made of soft iron, not copper. The iron is solder, tin or gold plated after the IC package is complete. The problem is, gold and tin plating is not hermetic - it is porous. And so some kinds of old chip leads gradually corrode away on the inside, often with no external visible effect. Then you touch the lead (or the board flexes) and because nothing was holding it on but the thin plating, it fractures and falls off. Or remains as a hairline fracture if the IC was soldered into a PCB.In OP's case, the porous-gold-plated iron legs were in contact with decaying rubber, which produces many chemical breakdown products that are corrosive. Resulting in super-boosted pin rot.Rather than try to salvage that ruin, maybe better to just find a nice one on ebay and buy it?I do feel your pain. A lesson learned too late...I'm currently sorting through and repacking a quite large collection of old ICs that came to me recently. Many of the chips are in anti-static foam, some of which is decaying. But fortunately it's all the 'dry crumbly' type of decay. No corrosion encountered so far. But ALL the foam has to be removed and binned. There are better ways.

author: DrG
author_rank: Super Contributor
timestamp: March 22, 2021, 04:38:21 pm
content: This guy does make some nice displays and IC tchotchkeshttps://chipscapes.com/collections/historical-series...and you can get another (not as nice) for a not astronomical pricehttps://www.donberg.ie/descript/s/scn_2650.htmIt is interesting to watch the vintage IC market rise over the last decade....makes me a little "thirsty", not enough to get into it so late but I do like to see the history preserved.The BIN prices that never sell on $bay keep trying to push it harder....lots of boxes and boards and so many chips out there....

author: David Hess
author_rank: Super Contributor
timestamp: March 22, 2021, 07:53:33 pm
content: Quote from: intabits on March 21, 2021, 11:44:49 amThat package is a "side brazed" ceramic package. The pins are brazed onto the sides of the ceramic package in contrast to a plastic package where the plastic is molded around a lead-frame which holds the semiconductor die and includes the pins which are bent into position. There is no danger of the pins coming lose from soldering.Ceramic packages are preferred in high reliability applications because they are hermetically sealed and that extra reliability makes them more suited to expensive semiconductors.

author: intabits
author_rank: Frequent Contributor
timestamp: March 23, 2021, 12:52:45 am
content: Quote from: Ian.M on March 22, 2021, 03:07:01 pmI understand the concerns you raise, though I do struggle to visualize them actually causing problems. The header I envisage is something only about 25-30mm wide, so flexing risk would be low, and only while being (carefully) plugged into the main project board. Storage temperature would be unlikely to range outside 12C to 27C. (But then there is operating temperature)I like the adapter PCB idea for the more robust external pins and silkscreening for reference, and that could also incorporate the machined socket, or your (probably better) flat sided header idea.My major concern is to mount the chips once and for all, with no possibility of ever needing to touch them with a soldering iron again. The PCB plus DIP header/socket for the chip, with SIL headers for external connection seems to be the best answer. I'll get a DIP40 header (may even have one) and see how I feel about using that.Quote from: DrG on March 22, 2021, 03:28:53 pmNo such luck. I have only two 2650s, and they were the only chips in black foam.Quote from: TerraHertz on March 22, 2021, 04:26:09 pmNot without at least having a go with what I have.(and if that failed, I'd probably just drop the whole idea)Quote from: DrG on March 22, 2021, 04:38:21 pmI'm planning an a working, rather than a static demo/display. With leds, hex displays and keypad, etc. Also variable clock speed (2650 can go down to DC), and single stepping.Quote from: David Hess on March 22, 2021, 07:53:33 pmBrazing - that's would I should have said, something between soldering and welding.

author: coppercone2
author_rank: Super Contributor
timestamp: June 24, 2021, 10:41:49 pm
content: check old instruments with cards for this foam shit, they like using it to stabilize the cards from the top to save money on braces

author: TerraHertz
author_rank: Super Contributor
timestamp: June 25, 2021, 02:44:16 am
content: Quote from: intabits on March 22, 2021, 08:13:07 amAh ha. I think that's the culprit. The foam itself degrades and produces some potentially corrosive substances but it seems they are not very mobile. Moisture multiplies the effect greatly by acting as a solvent and transporter.Thin gold plating is porous. The underlying metal of the pins is an iron alloy. Without moisture the corrosive substances don't transport into the pores and reach the iron. Moisture alone will make gold plated surfaces on old chips corrode - but it's simple rust that starts in the pores and bubbles off the gold plating.Add water transporting corrosives into the pores, and the mess in your photos is the result. Very sad.I'm currently sorting out a quite vast quantity of moderately mixed ICs. It's an old collection, had been in plastic parts drawers in a dry location. Most of the ICs are loose, some in black foam, some al-foil wrapped. They are old enough that some of the loose ones have a dark silver-tarnish appearance to the pins. That's OK, not corrosion. Most are still shiny. Of the ones in black foam _most_ are still fine, but now and then I come across one or two that are a little corroded where in contact with the foam. Some of the foam is very decayed and falls apart into dust.But so far nothing like your pics. I suspect the differentiating factor was the low humidity storage conditions of this collection.As I sort them, ALL are ending up in stacks of 20 or less wrapped in alfoil, placed in small yellow paper envelopes in rows in boxes. It's an extremely dense and versatile storage system, easy to keep in good sorted order. The boxes have lids, so it's pest and dust proof.Quote from: coppercone2 on June 24, 2021, 10:41:49 pmThat's urethane foam rubber, the bane of restorers of old equipment. It decays to a sticky gunk, falling apart into small pieces that get all through the equipment, and is extremely corrosive to many metals. It's a 'remove on sight' menace.The black antistatic foam otoh, seems to be something else. Not sure of its composition, other than probably containing a lot of carbon powder additive to make it conductive.

author: coppercone2
author_rank: Super Contributor
timestamp: June 25, 2021, 07:05:53 am
content: are you sure its not that mixed with carbon and freeze dried or something like softee ice cream

author: Zero999
author_rank: Super Contributor
timestamp: June 25, 2021, 07:45:20 am
content: Quote from: tszaboo on March 21, 2021, 04:50:03 pmObviously the person who posted doesn't have any evidence and nor do I but, it's plausible ultrasound could damage come components. I belive most DIPs should be fine, as the bond wires will be secured by the encapsulation, but metal can packages might be vulnerable, as well as some crystals and oscillators.Quote from: coppercone2 on June 25, 2021, 07:05:53 amIt's a commmon problem. I've seen it on new, old stock, components where I work. I think the old ant-static foam is made of celulose, which produces corrosive decomposition products.

author: Ian.M
author_rank: Super Contributor
timestamp: June 25, 2021, 08:59:40 am
content: The O.P. had a pair of side-braze CERDIP package MCUs. CERDIPs and other ceramic IC packages will almost invariably have unsupported 'naked' bond wires in the cavity running from the leadframe or leadout metalization to the die. If the ultrasonic cleaner hits a mechanical resonant frequency of any of the bond wires, failure is highly likely.

author: coppercone2
author_rank: Super Contributor
timestamp: June 25, 2021, 04:17:06 pm
content: you can reduce power level by increasing bath temperature and then dampening it with extra items to make it saferhigher temp = more soap action, it should compensate for the loss due to other materials absorbing energy in the tank

author: helius
author_rank: Super Contributor
timestamp: June 28, 2021, 03:01:11 pm
content: Another way of reducing power level in an ultrasonic cleaner is by using beakers suspended inside the tank. There are custom lids to hold them suspended like this. You then hang your delicate parts in the beaker, and the beaker attenuates the vibrations by absorbing some of the energy.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: June 28, 2021, 06:49:09 pm
content: Good Morning Intabits, I too have ICs stored in antistatic foam that is crumbling, but no corrosion. How about putting your ICs into some high quality ZIF sockets instead of soldering them?

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: June 28, 2021, 09:15:12 pm
content: It's not just anti-static foam that deteriorates, but all foam. I recently dug several of my old HP calculators out of the closet (HP-25, HP-41) and the foam lining in both of the cases had deteriorated and left a black mess on the keyboards of both calculators.

author: rdl
author_rank: Super Contributor
timestamp: June 29, 2021, 12:45:19 am
content: Back in 2004 I bought a sheet of conductive foam from Jameco. The sheet was about 2'x3' and it wasn't cheap. About $30 I think. The plasticky part is shiny and the sheet was very stiff. It didn't bend when held horizontally by one edge. Now, 17 years later it's still fine. I suspect it's made from polyethylene or polypropylene - not some kind of urethane.

author: intabits
author_rank: Frequent Contributor
timestamp: July 04, 2021, 07:55:58 pm
content: Quote from: BILLPOD on June 28, 2021, 06:49:09 pmI'm not sure how you mean to do that.Most of the pins are corroded away, so there's nothing left to go into any sort of socket.