LQFP和eLQFP热机械可靠性的有限元分析

Finite Element Analysis on Thermo-Mechanical Reliability of LQFP and eLQFP

封装形式的差异性对产品可靠性具有重要影响。基于有限元法,对比分析了薄型四方扁平封装(LQFP)和载体外露薄型四方扁平封装(eLQFP)在室温和回流焊温度下的翘曲、芯片和粘片胶的应力水平以及各材料界面应力分布。研究表明,LQFP的翘曲比eLQFP的大,但芯片和粘片胶上的最大应力无明显差别;eLQFP在塑封材料与芯片有源面界面的应力水平比LQFP的大;eLQFP在芯片与粘片胶界面、粘片胶与芯片载体界面的剪切应力比LQFP的大,但eLQFP在芯片与粘片胶界面、粘片胶与芯片载体界面的剥离应力比LQFP的小;eLQFP在塑封材料与芯片载体镀银区界面的应力水平高于LQFP的应力水平,由于塑封材料与镀银芯片载体的结合强度弱,eLQFP更易发生界面分层。

The reliability of microelectronic packages is closely related with package type. Based on the finite element method, warpage, stress on chip and die attach as well as interracial stresses of lowprofile quad flat package （LQFP） and exposed-pad low-profile quad flat package （eLQFP） at room temperature and reflowing temperature were comparatively investigated. The results show that the warpage of LQFP is larger than that of eLQFP, and the package difference has little influence on the stress of chip and die attach. The interracial stresses along epoxy moding compound （EMC） /chip interface for eLQFP are higher than that for LQFP. And the interfacial shear stresses for eLQFP along chip/die attach interface and die attach/chip pad interface are higher than that for LQFP. However, the interfacial peeling stresses present opposite situation. The interfacial stresses along EMC/silver plated chip pad interface for eLQFP are higher than that for LQFP, due to the intrinsic weak adhesion between EMC and silver plated chip pad. The interfacial delamination is more prone to occur for eLQFP compared with LQFP.