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From [log in to unmask] Wed Oct 16 14: |
50:10 1996 |
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We conducted two lenghly tests, temperature cycling and thermal shock,
where we encountered problems with unfilled via holes on 6-layer MLBs,
approximately .062 thickness. First our via holes were approximately
.035". The temperature range was -65C to 125C. Test time per cycle
was 3-hrs. for temperature cycling and 42-min. for thermal shock.
Results: failures started occurring on the thermal shock boards at
440 cycles and 373 cycles on temperature cycled MLBs. Once the via
holes were filled with solder no more via hole failures were
experienced through 7650 shock cycles and 4910 temperature cycles, end
of test sequence.
The above data was for bare MLBs. We also had two different conformal
coatings in our tests. One an epoxide type coating which performed the
same as the bare MLBs for via holes however we were surprised with the
performance of Parylene-c coated MLBs. We never experienced any via
hole failures with these boards in the unfilled state through 7650
shock and 4910 temperature cycles.
Regards,
Arny Andrade
Sandia National Laboiratories/California
[log in to unmask] at CASMTP
______________________________ Reply Separator _________________________________
Subject: via data
Author: [log in to unmask] at casmtp
Date: 10/9/96 12:02 PM
Is there any research on finished via structure and the integrety of
the connection; specifically tented or plugged vias vs. non-tented
vias (lpi solder mask) filled with solder.
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