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.
Wafer sawing process characterization for thin die (75micron) applications
The drive for package thickness reduction has created new processing challenges with regards to thin wafer handling. While back-grinding and die attach film (DAF) lamination are now established procedures, sawing DAF-laminated wafers with wafer thickness 3 mils and below is still a significant challenge. The need is for a suitable saw process that meets the following criteria: less than 1 mil wafer chipping, low cost and high throughput. This paper elaborates work that evaluated different saw parameters and their effects on wafer chipping. 8" wafers with varied die sizes and 2 in 1 DAF-dicing material sets were used during this evaluation. The work evaluated both single and dual pass saw processes. The effects of saw parameters-feed speed, RPM and blade types are also elucidated. The results show that for thin die a dual pass saw process gives better results than a conventional single pass process. Results also show that using non-optimized saw process parameters for a given DAF material set combination could adversely affect the yield consequent assembly processes like die attach and wirebond.
Adsorption of immunoglobulin Y in supermacroporous continuous cryogel with immobilized Cu(2+) ions.
The influence of temperature, pH and ionic strength on the adsorption of Immunoglobulin Y (IgY) in IDA-Cu(2+) cryogel system was studied by batch equilibrium measurements. The adsorptive equilibrium data were obtained at 17 and 27°C, pH 5.0 and 6.5, and at ionic strength of 50 and 200mmolL(-1) NaCl. Langmuir, Freundlich and Langmuir-Freundlich models were fitted to equilibrium data, while the enthalpy of adsorption of IgY in IDA-Cu(2+) cryogel system was calculated through Van't Hoff analysis. The binding of IgY on cryogel was stronger at 27°C and lowest pH and ionic strength values, with apparent maximum adsorption capacity of 27mgg(-1). The adsorption of protein in the resin was spontaneous in all analyzed cases. The results provide valuable information to enable the improvement of IgY purification processes.