I would be concerned about bringing the resin above it's Tg for this 
length of time in an unsupported fashion.  If the boards were just in a 
rack you may be inviting warp.  If they were stacked under weight this 
may not be a problem.  I would suggest for safety's sake having this 
board built on FR-4 with a minimum Tg 170.  This material is very 
readily available.


On Feb 4, 12:03am, Ulrich Korndoerfer wrote:
> Subject: PCBs at 150°C for more than 2 hours
> Hi TechNetters!
> 
> We use a multilayer pcb made from basically FR4 with a Tg of 135°C.
> There are pths, blind microvias, buried vias and some fine line wiring
> (only on top and bottom). One of our processing steps in building up 
the
> assembly (after smd-soldering both sides and cleaning) is die attach
> with an adhesive. The recommended curing cycle of the adhesive is 1 h
> (actual it may be 2h ore more) at 150°C and is done in a convection 
oven
> under normal atmosphere.
> 
> I am interested in the cons of above curing temperature and time. Are
> there any reliability issues concerning the pcb? To my knowledge,
> laminating the pcb's by the manufacturer is done at even higher
> temperatures (although under vacuum).
> 
> Any comments are welcome.
> 
> Ulrich Korndörfer
> 
> 
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>-- End of excerpt from Ulrich Korndoerfer



-- 
Thomas Ingham
Eastern Regional Sales Mgr.
Details Inc.
714-630-4077
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