基于硅凝胶灌封温循载荷下的键合丝疲劳失效机理仿真分析

Simulation Analysis of Fatigue Failure Mechanism of Bonding Wire Under Silicone Gel Encapsulation and Temperature Cycling Loads

针对某型混合集成电路在温度循环试验后出现的硅凝胶灌封区域键合丝疲劳失效,对键合丝的键合强度和疲劳断裂失效进行了试验分析,建立了单根键合丝和硅凝胶局部灌封区域的有限元简化模型,拟合了硅凝胶材料的本构模型参数,基于ANSYS Workbench软件对不同胶体材料参数条件和温循载荷作用下的键合丝应力分布情况进行了热力耦合仿真分析,并基于仿真结果对混合集成电路的硅凝胶灌封工艺进行了优化和加严温度循环试验。仿真和实验结果表明,键合丝第一键合点颈部和第二键合点根部的应力值较大,存在明显的塑性应变,与疲劳断裂失效分析一致;通过减小硅凝胶的热膨胀系数和灌封体积的方式进行工艺优化后,键合丝的应力值显著减小,样品经过温度循环试验后实测良率从167%提升至100%。研究结果对于提高硅凝胶灌封区域中的金丝键合疲劳强度有一定的指导意义。

Aiming at the fatigue failure of the bonding wire in the silicone gel encapsulation area for a hybrid integrated circuit after the temperature cycling test,the bond strength and fatigue fracture failure of the bonding wire were tested and analyzed.A simplified finite element model of a single bonding wire and local encapsulation area of silicone gel was established,and the constitutive model parameters of the silicone gel were fitted.Based on the ANSYS Workbench software,the thermal-mechanical coupling simulation analysis of the stress distribution of the bonding wire under different gel material parameters and temperature cycling loads was carried out.According to the simulation results,the silicone gel encapsulation process was optimized,and the tightened temperature cycling test was conducted.The simulation and experimental results show that the stress values of the neck of the first bonding point and the root of the second bonding point are relatively larger,and there is obvious plastic strain,which is consistent with the fatigue fracture failure analysis.After process optimization by reducing the thermal expansion coefficient and the encapsulation volume of the silicone gel,the stress of the bonding wire is significantly reduced,and the measured yield of the samples is increased from 167%to 100%after the temperature cycling test.The research results have certain guiding significance for improving the fatigue strength of the bonding wire in the silicone gel encapsulation area.