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| From [log in to unmask] Wed Sep 25 08: |
37:56 1996 |
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While answering another technet question on buried via, I had one of my
own.
In the late 1980's, I recall seeing a study (IBM-Endicott?) which
demonstrated that the most reliable via thickness with respect to Z-axis
expansions was something like .5 - .7 mil. Was this just wishfull
thinking?
If this is so, why have we not pursued it as a standard? If it is a
better thru hole, wouldn't I (now a consumer of PWBs) want that? And
wouldn't every PTH house like to reduce their plating times by 30%?
Is a possible answer: The extra copper is to ensure coverage. I have
known boards with copper thickness of .4-.6 mil to have problems with
blow holes in the assembly process.
George Franck
Raytheon E-Systems
Falls Church Va
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