Analyses of Delamination Arrest Effect of Dimples on Interface in LSI Package.

The arrest of delamination between the die pad and the resin is expected to be an efficient method to prevent resin cracking of LSI packages. In some LSI packages, dimples properly arranged on the die pad surface prove to be efficient for the arrest of delamination. In this study, the effect of dimples is examined based on BEM analyses of LSI package under conditions of uniform temperature variation and vapor pressure. To evaluate this effect, the stress intensity factor K1 for an interface crack is calculated considering the contact of interface crack surfaces. The following results are obtained. (1)Ki. values for an interface crack along a dimple significantly decrease under both of the above conditions. (2) The decrease in Ki is mainly due to the contact of crack surfaces under uniform temperature variation and the change in the direction of crack extension along a dimple under vapor pressure condition. (3) The effect of delamination arrest increases as the dimple depth increases.