Delamination is a common defect in plastic-encapsulated packages (PEM), which is a separation or cracks of interfaces between two materials (EMC/metal, EMC/die, etc. in an IC package) mainly cause by the mismatch of coefficient of expansion (CTE) between the epoxy molding compound (EMC), leadframe and the dies. To solve this problem, the interfacial properties of the EMC/Cu are studied in this thesis....[ Read more ]

Delamination is a common defect in plastic-encapsulated packages (PEM), which is a separation or cracks of interfaces between two materials (EMC/metal, EMC/die, etc. in an IC package) mainly cause by the mismatch of coefficient of expansion (CTE) between the epoxy molding compound (EMC), leadframe and the dies. To solve this problem, the interfacial properties of the EMC/Cu are studied in this thesis.

The button shear test was carried out to evaluate the bimaterial interfacial properties between epoxy molding compound (EMC) and bare copper leadframe. Three dimensional finite element analysis is conducted on the button shear test sample. The fracture loads obtained from the button shear test are plug into the finite element model to determine the critical stress components and the critical distortional energy density DSED and hydrostatic energy density HSED of the interface.

The critical distortional strain energy density (strain energy density of distortion per unit volume) can be thought as a material property like K_c, G_c, or S_c for the interfacial fracture of EMC/Cu. The failure in the interface initiates when DSED > DSED, _c.

With the experimental data support, it is proved that there is a linear relationship between the critical distortional SED per square fracture load and the reciprocal of the EMC's Young's Modulus. This relationship established a universe interfacial failure criterion line for EMC/Copper leadframe of a specified shear height.

The SED ratio R has successful established the relationship between the shear height in button shear test and the critical distortional strain energy density DSED. The value of R has a physical significance that higher value of R means the fracture mode in the interface tends to mode 2 (shear) fracture whereas the lower value of R means the failure mode tends to mode 1 (tensile) fracture in the button shear test.

The thin quad flat package (TQFP) that packed with a stress chip has benchmarked the quarter three-dimensional TQFP finite element model. The quarter three-dimensional TQFP finite element analysis result and the TQFP experimental study have benchmarked the energy based interfacial failure criterion.