Hi Technet,

I recently received some boards that were warped outside the IPC
specifications and I complained about it to the manufacturer. Their
answer is that the problem was caused by variations in laminate and
prepreg, where the operater didn't do the prescribed
material-inspections.
They will rework the boards by applying pressure at a temperature
higher then Tg, to release the stresses in the material.

Some questions:
Whats' the proper way for a bare board manufacturer to control the
quality of laminates and prepregs with regards to flatness ?  Is it
common practice to rely on an incoming inspection ?
If a board is flattened, will it remain flat after soldering ?  I know
that with an unblanced design the problem will always re-occur, but I'm
not sure what will happen when it's the laminate-quality that caused the
problem.

Daan Terstegge
Thales Communications
Unclassified mail
Personal Website: http://www.smtinfo.net

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