Organic Thermal Interface Materials Delamination Analysis of Large Size FCBGA Package during Reflow Process

Thermal interface material(TIM) delamination of large size flip-chip ball grid array package is a common problem. In this paper, we analyzes the cause and mechanism of organic TIM delamination by means of acoustic microscope, ultrasonic cutting technology and finite element analysis. We found that the package would have insufficient TIM coverage ratio due to micro-cracks after lid attach and the ball attach process would lead to a further degradation in TIM coverage ratio. If the original TIM coverage of the chip is too low, the TIM stress will increase when reflow at high temperature, causing the TIM to necking until snap. In the process of reflow and temperature drop to room temperature, the TIM cannot be restored to its initial state due to severe cracks and holes in the interior, which will make the TIM produce large gap and irreversible delamination, which will block the cooling channel of the package, and affect the normal use of the product.