Effects of microvia build-up layers on the solder joint reliability of a wafer level chip scale package (WLCSP)

The effect of a 2-layer microvia build-up printed circuit board (PCB) on the solder joint reliability of a wafer level chip scale package (WLCSP) assembly subject to thermal cycling is investigated in this study. The 62Sn-2Ag-36Pb solder joints are assumed to be: (1) an elastic material; (2) an elastic-plastic material; and (3) a creep material described by the Garofalo-Arrhenius creep constitutive equation. The stress and strain in the corner solder joint of the WLCSP assembly are presented and compared for these three analyses. Besides, the present results are compared with those from the previous analyses on the WLCSP assembly with only one microvia build-up layer.

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