Thermal/mechanical analysis of novel C-TSOP using nonlinear FEM method

Abstract

This paper describes a novel ceramic thin-small-outline package (C-TSOP) to meet the thermal performance and long-term reliability considerations of low-pin-count and high-performance electronic devices, especially for memory devices. To improve the disadvantages of molding compounds and simplify the fabrication process, the molding compound is replaced by a ceramic-like stiffener which is adhered to the leadframe by tape or adhesive. The ceramic-like stiffener would overcome the low thermal conductivity problem of molding compound in a conventional lead-on-chip TSOP (LOC-TSOP) and increase the thermal dissipation efficiency. In this paper, 3D nonlinear finite element models of both the conventional and novel LOC-TSOPs have been established. Various heat generation scenarios are applied to the 3D nonlinear models under natural convection conditions for evaluation of heat dissipation capability and thermal resistance of the packages. Moreover, the material properties and solder joint reliability of the packages are also investigated. In order to compare solder joint reliabilities of the novel and conventional LOC-TSOPs, a nonlinear finite element method is used to analyze the physical behaviors of packages under thermal loading conditions. The thermal fatigue life of the solder joints has been estimated in terms of equivalent plastic strain. The results are compared to the experiments in the literature in order to verify the accuracy of the finite element models. From the results, it can be concluded that the novel C-TSOP package implies excellent thermal performance and solder joint reliability.