Re: HP 9821 - display and tape transport issues #VintageHPComputers

Dave McGuire
 

On 2/3/20 10:35 AM, Steve Leibson wrote:
Plastic packaged chips are definitely not hermetic.
Right, they were never intended to be.

Water vapor
capillaries in between the metal/plastic interfaces, drags in
impurities, oxidizes and erodes the metal, and the chip's lead frame
falls apart or the silicon passivation layer fails.
Yes. What we're referring to here, though, is the specific type of
lead frame corrosion that seems to affect TI chips, and no others.

I had some chips
plugged into black plastic foam for five decades or so. The foam
deteriorated to powder, blackened leads, and the chips crumbled when
touched.
Yeah. Everyone stores their chips in that black foam, and we need to
stop doing that. I've eliminated most of it here, but I still have some
that I need to address.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

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