Abstract
We developed a method to evaluate the life of the wiring in non-solder mask defined (NSMD) solder joint pads in an LSI package. Generally, in a thermal cycling test, a package with NSMD pads has a longer life than a package with conventional pads. However, the load on the wiring in the pad in package with NSMD pads is greater than that in a package with conventional pads, so the joints with the NSMD pads may become disconnected due to failure of the wiring, not the solder. A method is thus needed to evaluate the life of the wiring. We have developed a method to measure the fatigue strength of the wiring, and we have developed a method to evaluate the life of the wiring by the finite element method. The life of the wiring in the pad is predicted by the analyzed plastic strain in the wiring and the measured fatigue strength data.
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