Effects of Heatsink Application and PCB Design Variations on BGA Solder Joint Reliability

The ever-increasing performance demand on advanced semiconductor devices such as networking processors has been driving the continued growth of body size, complexity, and power consumption of these devices. For thermal management, new thermal interface materials may be needed and some of these materials require higher pressure to achieve the desired thermal performance. On the printed circuit board side, both layer count and thickness are increasing for new systems and a new generation of materials is also needed. All of these factors pose new challenges to solder joint reliability and the fatigue life models require fresh assessment and validation. In this work, we use finite element simulation to investigate and correlate the reliability performance of solder joints in near-product designs in multiple configurations. In the first configuration, the effects of heatsink loading are evaluated. Strain and stress distribution in the solder joints arrays will be analyzed. The results will be used to interpret real-life testing results from both configurations, one with heatsink and one without. Secondly, PCB materials from the same electrical performance group are evaluated. The same component is mounted on three PCB materials with identical layout and all assemblies are tested with the same temperature cycling test. Lifetime differences will be discussed and compared with simulation results. Lastly, effects of PCB thickness will be evaluated in a similar fashion where two thicknesses are tested and compared, again using the same component test vehicle and acceleration testing condition. Results from these studies will provide realistic assessment of solder joint reliability in some of the most challenging application conditions and will be important for improving field lifetime models. For component and system qualification, these data will also help identify important areas of focus to ensure qualification tests are properly executed.