Impact of Lead Free Solder Joint Orientation on Multi-terminal Passive Components During FCBGA Board Level Reliability

Multi-terminal passive components like interdigitated capacitors (IDCs) are a key enabler for power supply decoupling and controlling transient chip responses at high frequency for improved performance and functionality. To ensure higher performance is achieved, the integrity of the solder joint connecting the passive component to the organic build-up substrate in a flip chip ball grid array (FCBGA) application requires a methodical investigation. Based on the scarcity of SAC305 passive component solder joint fatigue characteristic life in the literature, this paper attempts to study this deficiency. As such a daisy-chain FCBGA substrate was designed to evaluate the characteristic solder joint fatigue life of ten-terminated (10-T) 0805 chip capacitors in-situ in a board level reliability (BLR) environment. The test vehicle featured multiple chip capacitors with varied locations and orientations to study the impact of layout design under temperature cycling conditions (125°C to -40°C). Finite element models show early potential for correlation to observed fatigue failures, and suggest a strategy for optimum placement of IDCs based on the cyclic strain mismatch between the substrate and capacitor body. Results can form a basis for a more upfront and robust chip capacitor layout design process where improved IDC solder joint reliability characteristic life can be enabled.