Effect of integrated heat spreader on thermal performance and bump joint reliability for flip chip packages

Thermal simulation had been conducted on flip chip packages with copper heat spreader and better thermal performance was achieved. The copper heat spreader was able to enhance the heat spreading from the die but thermal performance was affected due to the thin layer of thermal interface materials. It was observed that thermal performance gain can be as high as 30% from heat spreader. Ansys thermo-mechanical simulation showed that heat spreader was reduced the overall package warpage but stresses in the solder bump increased due to the stiffer heat spreader. The solder bump joint fatigue life of the heat spreader package was subsequently reduced. A sub-modeling technique was developed in a three dimensional true symmetry global model at the critical joint location to find out the fatigue life of the package.