Hi Charles
I agree with Werner. A fast test is not an accelerated test. Due to the
metallurgical properties of tin based alloys the possibilities of
accelerating a thermal cycling test are limited. Got some hints in a
paper:
"The Deformation Behaviour of Sn62Pb36Ag2 and its Implications on the
Design of Thermal Cycling Tests for Electronic Assemblies,"
IEEE's Transactions on Electronic Packaging Manufacturing.
January 1999
Vol. 22, no. 1,Pp. 71-79
With vibration tests we are always very cautious. If a customer wants a
norm test we do it. However, these are always qualitative tests. I
wouldn't have the courage to use these data to make a prediction of
lifetime.
In SMT it is usually not the accelerating forces that lead to a failure
of the solder joints but the bending of the PCB if the assembly tested
is in resonance. Hence the problem is not the geometry of the
components but the whole structure of the assembly, how it is fixed,
the direction of the load relative to the PCB and the frequency or the
frequency spectrum if random vibrations are applied. Because of these
reasons we usually try to gather as much information as possible and
whenever possible we measure the vibrations occurring in the
application before we start vibrations.
Best regards
Guenter
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