Thermal failure analysis of micro copper pillar bumps for high density flip chip packaging based on Taguchi method

The finite element method was used to study the failure behavior of the micro copper pillar bumps under the thermal cycle, and in order to simulate the influence of the main structure parameters and material properties on the cumulative plastic strain energy density,the Taguchi orthogonal experiment with three factors and three levels was designed by using the maximum cumulative plastic strain energy density of the micro copper pillar bumps as the response.The results showed that:micro copper pillar bumps corresponding to the most distant distance from the symmetrical center of the packaging was the key micro copper pillar bumps, and the crack were liable to form at the interface of solder and substrate for the key micro copper pillar bumps. The linear expansion coefficient of the underfill played the most important role but the chip thickness played the least important role in affecting the thermal failure of the micro copper pillar bumps.