COMPARISON OF LCC SOLDER JOINT LIFE PREDICTIONS WITH EXPERIMENTAL-DATA

The ability of solder joint life-prediction algorithms to predict the failure of solder joints due to temperature-cycling induced creep-fati gue has been investigated using representative leadless chip carriers (LCCs) as the test vehicle. Four different algorithms are assessed: th e classic Coffin-Manson algorithm, a modified Coffin-Manson algorithm with dependency on peak stress, and two strain-energy based algorithms . JPL's special purpose nonlinear finite element computer program was used to dynamically simulate the solder joint response to the standard NASA temperature cycling environment, which ranges from -55 degrees C to +100 degrees C with a 4-hour period. The computed stress-strain hi story provided the inputs needed by each of the failure algorithms. To test the accuracy of the analytical predictions, three different size s of LCCs (68 pins, 28 pins, and 20 pins) were subjected to an experim ental test program using the same 4-hour temperature cycle as used in the analytical predictions. The three different sized ceramic packages , each with a 50-mil pitch, provided a range of cyclic strain ranges a nd solder fillet geometries so as to test the algorithms against reali stic electronic packaging variables. The study highlights limitations in the historical Coffin-Manson relationship, and points up possible i mprovements associated with incorporating a stress modifier into the C offin-Manson equation. This modification is also somewhat simpler and more accurate than the energy-density based algorithms, which also per formed quite well.