Daan

You've already heard that the boards will likely warp when they go above Tg (such as during reflow).  But I'd have another concern with these.  You've already been told the material was not manufactured properly.  What assurances do you have that whatever is wrong with the material will not manifest itself in some other way.  For instance if the material is prepreg is defective because the thicknes of resin coating on the glass is uneven, what other implications, beyond warpage, does that mean in your final product?

Mike McMaster
RF Product Engineer
Merix Corporation
503-992-4263

----------
From:   d. terstegge[SMTP:[log in to unmask]]
Reply To:       TechNet E-Mail Forum.;d. terstegge
Sent:   Thursday, May 22, 2003 1:13 AM
To:     [log in to unmask]
Subject:        [TN] Bad laminate and warped board

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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