> =A0 =A0- Can you reference any reputable source that
> supports your claim?

Elementary, my dear Watson, - any schoolbook on Physics, I almost
sure. But, please, take it easy, "claim" is not the best word to
describe my humble statement that the highest quality you company is
well known for "does not allow" you to implement sub-standard
technologies :-)

Imagine a connector's pin is soldered to the PCB's other side single
copper layer without the pin being bent.

You know that every material in the world expands or contracts as its
temperature changes. The expansion is expressed in ppm/=B0C or parts per
million per =B0C  - coefficient of thermal expansion (CTE) . This
expansion has a second property, called Young's Modulus, defined as
how hard a material pushes when it expands.

The connector's pin material may have CTE different to that of SnPb.
When temperature excursions occur, due to changes in either ambient
conditions or the power dissipated by the circuit, these materials
will expand differently, leading to the creation of stresses.

The mismatch in thermal expansion will cause shear stress between the
solder and the connector's pin. After a sufficient number of thermal
cycles, the stress will eventually lead to work hardening of the
solder, which results in cracking of the solder joint itself. The
resulting intermittent electrical conductivity is unacceptable in
today's high reliability electronics applications.

The shear stress between the solder and the connector's pin is roughly
proportional to the thickness of the solder cone and the thickness of
connector's pin. In case of perpendicular surfaces the SnPb thickness
can be a few millimetres, in case of parallel surfaces it can be a few
microns, that is hundreds times less.

Of course, bent connector's pin (if the bending permitted) may not be
flat, but still the "effective thickness" of SnPb in this case is much
less compared to that in the case of non-bent pin.

Best Regards.

-- =

http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist