Mechanistic-Based Reliability Evaluation Of FC-PBGA Under Thermal And Flexural Loading
Authors: A.Shirazi, H.Lu and A.Varvani-Farahani Company: Department of Mechanical Engineering, Ryerson University Date Published: 5/17/2010
ICSR (Soldering and Reliability)
Abstract: Thermal and mechanical behavior of a flip chip plastic ball grid array (FC-PBGA) assembly may be investigated with analytical methods. This paper presents new analytical solutions for the evaluation of thermal warpage, mechanical deflection and interfacial stresses-strains in adhesively bonded trilayer structures including assemblies and its constituents such as the IC (Integrated Circuit) chip, substrate laminate, printed circuit board (PCB), underfill layer and board level solder joints. It is a challenging task to obtain internal interfacial stresses-strains in a package experimentally, yet these parameters are essential to the understanding and improvement of the reliability of individual layers and the entire package. The new analytical solutions are developed with less restriction as compared with those of the existing analytical models, thus giving enhanced accuracy to such evaluation if the materials thermal and mechanical properties are known and certain. Furthermore, this paper presents a novel hybrid experimental-analytical inverse method (HEAIM) that is formulated based on the above analytical structure models. With experimentally measured global structural deformation of a package subjected to a thermal cycle, HEAIM is capable of inversely evaluate and characterize the thermal properties and the temperature dependent constitutive behavior for individual layers of the package. Both analytical model and inverse method as proposed can provide pertinent guidance to design for reliability of complex layered structures at different levels of packaging, such as the modules, substrates, PCBs and board-level assemblies, etc.