| Modern electronics advance towards complex, high density, high speed, thinner and lighter products for portability. Reliability concerns arise due to the use of BGAs and CSPs in portable electronics. Underfilling the components offers a solution for the reliability concerns, however increases the unit manufacturing cost due to materials, capital equipment and process time. Although underfill often increases the reliability of the package, the use of wrong underfill could be detrimental to the reliability. Therefore, material selection becomes important in spite of high testing costs and time associated with it.A systematic underfill selection approach has been presented in this research work to characterize and identify promising materials for the process. The selection methodology presented in this work aims to cut down the costs in underfill selection through simpler and innovative non assembly tests. The drop and thermal cycling tests on assemblies were also done in this research work to test the relevance of the selection methodology. In addition to the development of the selection methodology, the effect of moisture on the adhesion strength of the underfills was extensively studied with a DOE. Two soldermask surfaces, PR77 and PSR4000, were tested with five different corner &edge bond materials and six capillary underfills after varying degree of exposure to moisture. The adhesion to PR 77 soldermask was greater compared to PSR 4000 soldermask surface and statistically verified. The identification of soldermask as a factor affecting the soldermask is an important addition to the existing literature. |
