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| Beware of old AntiStatic foam |
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| intabits:
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. |
| rsjsouza:
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. |
| drussell:
--- Quote from: rsjsouza on March 22, 2021, 02:30:52 pm ---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. --- End quote --- Don't you mean increases the time to decay? ;D |
| Ian.M:
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. |
| DrG:
--- Quote from: intabits on March 22, 2021, 08:13:07 am ---/---/ They 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. --- End quote --- That 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 |
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