Warpage Simulation Including the Effect of Molding Compound Cure Shrinkage

Warpage control is the fundamental requirement for the packaging. The accurate prediction of warpage by finite element simulation becomes very critical during design stage. Intrinsic warpage is largely driven by coefficient of thermal expansion (CTE) mismatch of packaging material. Cure shrinkage is one of the important features of the epoxy molding compound (EMC) and plays a very important role in warpage characterization. In previous simulation works, the cure shrinkage is combined with thermal shrinkage to obtain the total shrinkage of EMC, then derive the equivalent CTE from molding temperature to room temperature. One step warpage simulation is conducted by using this equivalent CTE to simulate the warpage at room temperature. But the warpage simulation accuracy is limited. In this paper, a multi-steps warpage simulation is proposed. Warpage caused by EMC cure shrinkage and by CTE1 and CTE2 are simulated separately. The final warpage is the combination of all warpages. The warpage of the EMC/Cu bi-layer beam specimens is measured and simulated by using both one-step and multi-steps methods. The simulation results are correlated with the warpage measured. Good agreement between measured warpage and multi-steps simulated warpage is obtained.