Elasto-Plastic Analysis Of Popcorn Failure Caused By Cavitition Unstable Growth In Plastic IC Packaging Material

The rapid development of high-density integrated electronic technology sets a higher request to reliability of electronic packing. During the solder-reflow process, popcorn failure of plastic electronic packages has a strong impact on proportion of qualified products, which is one of the hottest research points. In this paper, elasto-plastic analysis of popcorn failure was made and the numerical results were given by using nonlinear materials'finite deformation theory. The main results contain as follows:1. Thermal analysis of polymer materials(GR9810 and KL-G900HC) used in package devices such as QFP, BGA etc. was carried out. The coefficients of thermal expansion and glass transition temperature were obtained, which provide necessary lab support for applying finite deformation theory about unstable void growth to analyze popcorn failure.2. Popcorn failure about seven kinds of typical polymer materials which have different strain energy functions under elastic stage was analyzed according to finite deformation theory about unstable void growth. Analytical relationships were gained between void growth and the sum of the vapor pressure and thermal stress. Numerical analyses show that popcorn failure is related to stored energy function closely. The relations between critical values and energy storage forms were discussed when popcorn failure occurred. If popcorn failure didn't happen, we added failure criterions of ultimate elongation to discuss the probability of popcorn failure.3. The assumption of materials' incompressibility was revised to compressibility when the effect of temperature change on the volume of polymer materials was taken under consideration, and the generalized temperature-dependent relationship forσ?f was given. Critical traction and void growth for popcorn failure were discussed by measurement of thermal expansion coefficient.4. In view of the problem of popcorn failure, the void growth behavior of polymer materials which have typical strain energy functions respectively was analyzed according to by using elasto-plastic stability theory. The governing equations of void growth considering elasto-plastic property were given. The elasto-plastic analysis and elastic analysis of popcorn failure about polymer materials was carried out.The chapter 2 to chapter 5 of this paper make the present theoretical research on popcorn failure systematic. The chapter 6 makes theoretical research on popcorn failure further. In addition, this paper can promote harmonization of theories research on void formation and growth, and bring stability theory of finite deformation into boarder use in engineering.