Hi Gavin,
You are not clear whether you talk about the adhesion of the pad to the PCB
or a solder joint to the pad. For the adhesion of copper foil to the epoxy
matrix, it is the peel strength that is normally used--reason : pads are not
loaded in straight-up tension, but in some sort of peeling mode. A typical
requirement is about 6 lb/in; that is if your pad is peeled along its long
dimension and it is 25 mils wide, you should need something like 0.15 lb of
peel force. On the other hand, when component leads soldered to pads are
pulled (the pad is somewhatpeeled/pulled because of the assymetric attachment
of the leads, you get something in the range of 2000 to 5000 grams before
failure which is typically in the solder.
I hope this helps.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask]

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