Molded flip chip BGA characterization

With the trend of electronic consumer product toward more functionality, high performance and miniaturization, IC chip is required to possess more I/Os and superior electrical characteristics and packaging is required to offer more pins out under same form factor. Thus flip chip BGA (FCBGA) package was developed to meet those requirements offering excellent electrical performance, more I/O pins accommodation and high transmission speed. In a successful FCBGA package structure development, underfill used to fill the gap between chip and substrate is the key process to mainly protect solder bumps from fatigue crack that is the major failure mode on FCBGA package. However, the underfill usually has higher material cost and worse moisture sensitivity level (MSL) performance than conventional molding compound so molded underfill material was developed to be with cost and performance effective solution. It contains smaller filler size than conventional molding compound to ensure filler can easily flow through the gap between chip and substrate which is processed like current injection-molding technology and possess higher module property than underfill to provide more robust protection to bumps. However, the first coming concern for molded FCBGA (MFCBGA) development is higher stress on chip because of higher injection-molding pressure and extra thermal stress from mismatch between compound and chip. Another concern for MFCBGA is thermal performance by using molded structure. In this paper, the MFCBGA characterization was comprehensively analyzed by finite element analysis (FEA). Various MFCBGA structures were compared with common FCBGA in thermal and stress aspects