Hi Gaby,
I would recommend, that you require thatmthe coupons on the panels for your
 PCBs contain the smallest hole diameter drilled for your PCBs. Depending on
drilled PTH diameter and PCB thickness (Smaller diameters & thicker PCBs are
worse), good plating may require special plating solutions allowing plating
at lower plating current densities.  I, of course, assume that your PCB
vendor has vibrators in place on the plating frames for all wet processing to
avoid entrapped air and/or hydrogen bubbles in the PTHs.
But, the integrity of the plating in small vias does not only involve the
plating thickness, but also the quality of the copper deposited. The deposit
also requires adquate strength and ductility to survive solder assembly.
While tensile strength and fatigue ductility measurements of mandrel samples
plated concurrently with your product give some indication, the copper
plating quality on the PTH will almost always be below the properties from a
mandrel sample.
That is why testing is done-- the new IST test is quick and correlates, at
least qualitatively, with thermal cycling.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
23 Gunther Street                                 In December:                                               7 Jasmine
Run
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Phone & Fax: 973-543-2747                         Phone: 904-437-8747, Fax: 904-437-8737
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