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August 2003

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Fri, 15 Aug 2003 15:19:19 -0500
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After subjecting samples to 1000 cycles of +85, -40 deg C with 30 min
dwells I am inspecting the solder for cracks holes or voids.
I notice that there are some cracks on the edges of SMT components
(resistors and caps, no damage on the IC connections), IPC-SM-785 states
that the crack must propagate through the entire solder connection to be
considered a failure, also on my THP connector the solder
appears "crinkly" - Friday afternoon tech talk!

This is a mixed board, SMT reflow then THP wave using a pcb pallet to
protect the SMT parts.

I am wondering what would be the first step to determine what part of the
soldering process should be reviewed.
My first thought is that the larger SMT pads are picking up too much heat
during the wave process and the solder is getting brittle. The reason I
think this is that the IC leads have perfect - still shiny - solder
connections.

Thanks for any thoughts,
Jason

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