We use standard FR-4 laminate (Tg=130 C) to produce
1.6 mm thick double sided PCB for a telecom-switch-box
customer (laminate construction is 8X7628 with H/H
copper foil) . My customer require warpage less than
0.7% after reflow and wave soldering because the cards
need to be inserted into slots of machine racks. They
are looking for warpage less than 0.5% in three
months. We tried three different laminate vendors, but
in the end all have about 6% fall out of 0.7% after
reflow and wave soldering. My customer confirmed that
their reflow & wave process is under control. The
laminate vendors said use standard FR-4 laminate
(Tg=130 C) will lead to certain percentage fall out
of 0.7% (so that IPC-4101 defines laminate warpage
less than 1.0% for 1.6mm thick laminate).
My questions are:
1. Is it true that use standard FR-4 laminate are
sure to have certain percentage >0.7% warpage?
2. Is it true that use high Tg FR-4 laminate will
have better warpage result?
3. What material is recommended by IPC-D-275 and
IPC-D-279 for SMT board? Is high Tg preferred? (Sorry
I don't have IPC-D-275 & IPC-D-279 on hand)
Any comments will be greatly appreciated!!!
Thanks in advance!!!
Shirley Xiao
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