The constriction resistance model is employed for the thermal analysis at the solder ball joint of a Ball Grid Array (BGA) package. The behavior of heat dissipation in solder joint is also analyst through Finite Element Modeling (FEM) and compared with the analytical model. The principle of constriction and spreading resistances is analyzed in detail because of the geometrical complexity encountered in BGA solder joints. The total resistance across the solder joint includes the internal resistance and external resistance. The internal resistance, which is the main focus of the analysis, consists of material resistance and constriction resistance. It is a function of material conductivity, thermal boundary conditions and geometric parameters. FEM solutions are in good agreement with analytical results of thermal resistance for single solder ball joint and multiple solder ball joints. The analytical resistance provides an accurate prediction on the temperature drop across the array of solder balls and hence the overall performance of the BGA packages. The pitch size is the main parameter in the investigation to study the heat dissipation of solder ball joints.

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