Subject: | |
From: | |
Date: | Wed, 12 Jul 95 15:34:13 EST |
Content-Type: | text/plain |
Parts/Attachments: |
|
|
I have a customer who is experiencing excessive warpage
after reworking BGAs. The PCB is a .062" thk - 10 lyr made
from 140'C Tg FR-4. He uses forced hot air under the BGA
device that heats only the region/area where the device is
located. I discussed with him the issues
(stress/TCE/expansion/contraction) that he may be
encountering by heating only specific areas. I also stressed
issues associated with controlled heat rise and cooldown of
PWAs. His next tests will be to heat the entire board
slightly below component degradation temperatures then
perform his BGA rework procedure. Once rendered he was going
to allow the entire PWA to cooldown at a slow rate to
minimize any potential stresses that could happen during
rapid cooling.
Since I'm a fabricator and don't completely understand
the assembly/rework issues, I thought I would throw this up
for suggestions.
Any responses will be greatly appreciated.
Thanks in advance.
Dave Hoover
Senior Process Engineer
Hadco Corp/Tech Center Two-Watsonville, CA
[log in to unmask]
|
|
|