A new leadframe design solution for improved popcorn cracking performance

A new leadframe design solution is proposed as one of the synergistic factors toward improving popcorn-cracking performance of plastic packages. The impact of the leadframe design on package stresses and thermal resistance was analyzed by finite element modeling (FEM) and further verified experimentally. An atomic force microscope (AFM) and the contact angle method were used to characterize surfaces before and after plasma cleaning. The new leadframe design was effective in reducing popcorn cracking sensitivity, package stresses, warpage and delamination. By incorporating the leadframe solution in a level 5 classified Cu-alloy leadframe 144L quad flat package (QFP), it was able to achieve a level 3 classification without plasma cleaning and changing of packaging materials. An AFM technique was used in a novel attempt to characterize surface cleanliness and to correlate with contact angle measurements.