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Old 22nd Feb 2021, 11:30 pm   #3
Radio Wrangler
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Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 17,175
Default Re: Plastic or ceramic ICs?

No, plastic was very bad for 4000 CMOS logic.

Traces of moisture entered where the plastic was not hermetic with the legs. It dissolved phosphorus traces out of the glass passivation, and the phosphoric acid rotted the aluminium metallisation layers.

Look up 'CMOS purple plague' It's insidious in that it progresses even in stored parts.

DAvid
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