Modeling and Design for System-Level Reliability and Warpage Mitigation of Large 2.5D Glass BGA Packages

Glass has emerged as an alternative substrate technology to overcome the shortcomings of silicon and organic substrates for high-performance systems. Glass has been demonstrated to have superior electrical properties than silicon with lower losses and can accommodate high-density wiring owing to micron-scale lithographic design rules. Further, glass can be tailored for a wide CTE range of 3 ppm/°C to 9.8 ppm/°C. This unique property brings design flexibility to address board-level reliability challenges and directly assemble large glass interposer packages to boards without the need for an intermediate organic package.This paper investigates the system-level reliability of 2.5D glass BGA packages of different sizes and with different core CTEs. Finite-element models were developed to predict the fatigue life and package warpage as a function of glass CTE. The contradicting core CTE requirements to achieve board-level reliability (BLR) and minimize yield loss by warpage control are highlighted. Based on the high-CTE requirements for BLR and low CTE requirements for warpage control, optimum range of glass CTEs to achieve system level reliability was extracted for different package sizes. Other solutions to achieve system-level reliability such as solder volume control and use of low-temperature solders are also discussed.