Impact of Structural Parameters on the Warpage of fcBGA Packages with Indium Thermal Interface Material

This paper presents a comprehensive study on the warpage of large-sized flip-chip ball grid array (fcBGA) packages with indium thermal interface material (TIM), through both finite element analysis (FEA) simulation and lab characterization using engineering samples. The stress and warpage of the package are investigated in detail under different temperature conditions. At room temperature, due to the impact of metal bonding, the warpage profile of the package is significantly affected by the indium sheet, which shows a W shape. With the temperature increasing, the indium bonding is weakened, thus the impact of the indium sheet on the warpage in the die area decreases. When the temperature rises above the melting point of indium, the die and indium sheet separate, and the warpage exhibits a smiling face at a high temperature of 245°C. Key structural parameters are examined in this paper to understand their impact on package warpage, and an optimal design is then achieved. This study provides a good reference for large fcBGA packages with indium TIM.