Study On Process Mechanics And Thermal Reliability Of PBGA Packages

With the continuous development of microelectronic packaging technology,microelectronic devices have extensive and in-depth applications in the areas of civil, medical,aerospace and military, where those reliability is particularly important, and now electronicpackaging systems become smaller and more complex, electronic packaging reliability is animportant factor in limiting their mass-market applications. The plastic ball grid array package(PBGA) is the most commonly used ball grid array package (BGA) form, due to the complexoperating environment, there are many reliability issues to face. Therefore, it is economic tostudy the manufacturing process mechanics and reliability of PBGA package.In this thesis, the finite element based simulation technology is used for simulating theprocess mechanics and thermal reliability of PBGA package.Firstly, through analysis of traditional processes of PBGA packages, we selected two keyprocesses: die attach process and molding process for the study, then determined the processstructure model, and created the corresponding finite element model with the actual processtemperature load, simulating the process and comparing the chip warpage and residual stresssituations of PBGA packages. Finally, the effect of package materials, package structure onprocess was studied in order to optimize the process window and reduce the difficulty ofsubsequent processes.Secondly, the reliability of PBGA packages was studied under cycle temperature load,we found the temperature conversion phase (i.e., heating and cooling period) has the greatestimpact on the solder joint fatigue life. Compared to the low-temperature period,high-temperature period have a greater impact on solder joint fatigue life; By design ofexperiment (DOE) theory, the effect of packaging structure on the solder joint fatigue life wasstudied, which showed that the thickness of molding and substrate were the most important factor. On the other hand, we compared the life of three different array solder ballarrangements, which consist of the periphery array solder ball arrangement, partial arraysolder ball arrangement and full array solder ball arrangement, respectively. The partial arraysolder ball arrangement is recommended. Furthermore, we studied the effect of the workingenvironmental stability on the reliability of PBGA packages, and found the instability ofworking environment would reduce the solder joint fatigue life.