Shirley,

First, IPC-D-275 was replaced by IPC-2221 and IPC-2222 in case you weren't
aware of this.

I can't really comment on the warpage issue you are asking, but I can tell
you that
we went to the high TG (170C) and had much better soldering results for
fine pitch
and BGA components.  It was explained to me that the high TG did not "sag"
as much
during processing and lead to better solder results.  I don't know if that
is the reason,
but I can tell you our solder problems (opens/shorts/poor attach) have gone
down
since we went to TG 170C, using the same supplier base for the PWB.

Regards......DT





At 10:15 PM 5/9/00 -0700, you wrote:
>  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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