Hygrothermal Fracture Analysis of Plastic IC Package in Reflow Soldering Process

The purpose of this paper is to evaluate the delamination and fracture integrity of the integrated circuit (IC) plastic package under hygrothermal loading by the approaches of stress analysis and fracture mechanics. The plastic small outline J-lead (SOJ) package with a dimpled diepad under the reflow soldering process of infrared (IR) heating type is considered. On the package without a crack, the stress variation according to the change of the design variables such as the material and shape of the package is calculated and the possibility of delamination is considered. For the model fully delaminated between the chip and the dimpled diepad, J-integrals are calculated for the various design variables and the fracture integrity is discussed. From the results, optimal values of design variables to prevent the delamination and fracture of the package are obtained. In this study, the finite difference method (FDM) program to obtain the vapor pressure from the content of moisture absorbed into the package is developed.