Dear All,

I am only an occasional subscriber to the Technet but I have found it very useful
in the past when I have a technical query.

I am using multi-layer boards in aerospace applications and I am having to weed out
latent PCB defects by stress screening the bare boards. My current stress screening
in a HALT chamber uses a temperature range of -40 deg C to +125 deg C, 35 deg C /
min ramp rate, for 5 cycles.  The board supplier then performs continuity tests and
this confirms hard faults on 0% to 20% of boards. I am concerned that I may not be
precipitating all latent faults and I am interested to know if I could use a wider
range of temperature extremes.

Can anyone tell me if FR4 boards may experience damage in the region -40 to -70 deg
C or above +125 deg C?

Best regards

Terry Exell
BAE SYSTEMS
Plymouth, UK



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