Thermal analysis and electromigration behaviour in BGA packages: investigating the impact of electric current and resultant Joule heating on temperature distribution

Abstract

Ball Grid Array (BGA) packages, integral to modern electronics for their high density and reliability, face significant challenges related to electromigration and thermal management. This research investigates the impact of electric current and resultant Joule heating on the temperature distribution within BGA solder balls, which is essential for understanding and mitigating performance degradation caused by electromigration. Electromigration in BGA solder balls results in the migration of metal atoms under high-density currents and it is accelerated by current crowding which leads to void formation and intermetallic compound growth. Joule heating further intensifies these effects by increasing local temperatures. To address this problem, a six-layer organic stack-up BGA substrate was designed, incorporating various pitch sizes and microvia configurations to facilitate current delivery pathways. Temperature sensors were strategically integrated into the substrate to monitor the solder ball's temperature during electromigration tests. Advanced finite element simulations were employed to analyze temperature and current distribution, providing insights that are difficult to obtain through practical experiments. These simulations accurately represented the copper traces, core vias, micro-vias, solder balls, and the overall substrate stack-up, predicting temperature hotspots and temperature distribution at BGA substrate. The findings from this research indicate a good correlation between temperature readings obtained from sensors placed on the BGA substrate and the results from simulations. The finite element analysis highlights the temperature gradient within the substrate and its impact on the sensor readings, based on their placement. This gradient is crucial for accurately interpreting the thermal profile of the BGA packages in particular for the solder joint itself. The study provides a methodology to predict the actual temperature of the solder ball under test by aligning sensor measurements with simulation data. This methodology is essential for accurately modeling and understanding the electromigration behavior in BGA solder joints.