Ic Chip Package Thermal - Structural Numerical Simulation Analysis And Design Optimization

Base on the theory of heat exchange, thermal elasticity mechanics and structural optimization, this paper presents a thermo-mechanical analysis of a plastic ball grid array (PBGA) package design, with emphasis on the package warpage, thermally induced stress and the second of level solder joint reliability. And a new design method involving thermal and thermo-mechanical characterizations is developed to optimize the geometric parameters and material properties of PBGA package.A 2-D finite element stress analysis of full-matrix and perimeter PBGA solder joints, based on FE method has been carried out to study the most critical the solder joint with a local temperature load. The results indicate that the ball nearest to the die has the highest magnitude of the stress and hence is the most critical. And it is consistent with conclusion of the literatures. The results are expected to act as database for the stress-strain and fatigue life of the solder balls.The 3-D mold is loaded by three modes, which are Constant Power Generation in the Die, Accelerated Thermal Cycling and ATC with Superimposed Constant Power Generation in the Die. And the warpage of PBGA package is studied. The results show that temperature and thermal stress distribution are consistent with the experimental result. The fatigue life of solder joint is estimated by the Engelmaier's approach. The third load mode is better than departed literatures, then the result of thermal stress-strain and fatigue life are more importance to the package. The results are compared with the second results loaded by ATC, is shows that they have consistent completely with thermal stress and temperature distribution direction. The work is more comprehensive than previous researcher.In this paper, PBGA package optimization design is realized with object of minimum weight and minimum the maximum thermal stress, from the geometric parameters and material properties by using the APDL commercial software ANSYS programming technique. Design variable is analyzed to the effect of thermo-mechanical characterizations. The results show that the lesser elasticity module and Coefficient of Thermal Expansion can availably reduce thermal stress, affect the package warpage and the solder joint reliability are the substrate thickness and the die thickness. The optimized results in the first group have more effect. The weight of package is reduced to 18.04%, and the maximum thermal stress is reduced to 23.63%. FEM numerical simulation technique is feasible and effectual in the electronic package design. The results are expected to act as database for improving reliability of package and optimized design.