基于细观力学方法的底部充填封装芯片接合层的热应力计算

底部充填是一种用来提高电子产品在恶劣环境下工作的稳定性及可靠性的技术，是电子制造产业的常用方法．本文基于细观力学方法建立了计算底部充填封装芯片热应力的方法．针对底部充填封装芯片焊锡-充填物接合层的结构特点，我们建立了接合层的均一化模型，并从理论上推导了接合层的等效弹性常数、热膨胀系数和导热系数．运用该均一化模型，我们对封装芯片工作产热导致的热传导和热应力问题进行了有限元数值模拟，计算的结果与接合层未均一化的模型具有较好的一致性，而计算效率极大提高，显示了该方法在计算底部充填封装芯片热应力方面的可行性．

Thermostress Calculation for Interconnection of IC Package with Underfill Based on Meso-Mechanics Models

Underfill is widely used in electronics industry to enhance the stability and reliability of electronic products working in harsh environments. In this paper, thermostresses are calculated for the interconnection of IC package with underfill based on the meso-mechancis models. Utilizing the periodic characteristics in the structure of the solder-underfill interconnection, a homogenization model is established. The equivalent modulus, coefficient of thermal expansion (CTE), and the thermal conductivity are deduced theoretically. The homogenization model is then used to calculate the temperature and the thermo-stresses for the problem of heat generation by the working chip using finite element (FE) simulations. The proposed method generates results that agree well with the conventional FE simulations without interconnection homogenization, and at the same time possesses much higher computational efficiency. The results demonstrate the feasibility of the proposed method in the thermostress calculation of electronics.