Assessment of Die Attach Film for Thin Die and SiP Applications

The drive for package miniaturization and die thickness reduction has created new challenges for conventional die attach paste materials. Die attach film (DAF) is seen as a potential candidate especially in applications requiring die thickness =100 mum. However, processing of DAF materials also presents certain difficulties especially in dicing of DAF-laminated wafers. This paper outlines the challenges and process optimization carried out for 5 different DAF materials. Process feasibility study and dicing optimization were conducted on 100 mum thick wafers. Subsequently the DAF materials were assembled into a ball grid array (BGA) package and subjected to reliability testing (Moisture Sensitivity Level 3, Unbiased Highly Accelerated Temperature and Humidity Stress Test and Temperature Cycling). Results showed that minimum chipping and whisker formation can be achieved using a 2-step dicing process with optimized cutting depths and feed rate. It was also found that optimum adhesion of the DAF material to both the dicing tape and die backside is necessary to prevent "flying die" during dicing and die pick-up problem during die attachment. Positive results for 2 DAF materials were obtained from reliability performance assessment. These findings show that there is a robust DAF material and process for thin die and System-in-Package (SiP) applications.