STUDY ON ADHESION OF DICING DIE ATTACH TWO-IN-ONE FILM FOR 3-D STACK PACKAGING
Authors: Shijian Luo, Ph.D. and Tom Jiang, Ph.D. Company: Micron Technology Inc. Date Published: 11/1/2006
IWLPC (Wafer-Level Packaging)
Abstract: Recently, dicing die attach two-in-one film (DDF or DDAF) has been developed for 3-D stack packaging application. When DDAF is used, a wafer is laminated on DDAF film, then diced, UV cured (if the dicing tape is a UV tape), and die-picked and attached. During die picking, easy release and clean separation between the die bonding film and dicing film is critical. In this paper, the adhesion between the die attach film layer and UV dicing film layer of one DDAF material was investigated. UV intensity and UV dosage affected the adhesion. When the tape was cured under high UV intensity light, there were some hot spots on the two-in-one film, and die pick became more difficult for these locations than the other areas. The hard to pick areas were randomly located on the wafer. For a low intensity UV curing system, the UV dose (curing time) had a significant affect on adhesion. There was an optimal UV dose for easy release of the die bonding adhesive layer and UV dicing tape layer. Wafer lamination temperature and time affected the adhesion as well. When wafers were laminated onto the DDAF at a higher temperature (65°C), and left on the chuck at this temperature for a long time, the separation between die attach adhesive layer and UV dicing film layer became more difficult. The die picking force increased continuously with the tape age at room temperature before lamination. This indicates that inherent adhesion between die attach adhesive layer and dicing film, which can not be diminished by UV curing, increases continuously with the tape age at room temperature before UV curing. The increased adhesion between the die bonding film layer and UV dicing tape vs. aging time before UV curing is mainly due to the interaction (inter-diffusion and mixing) of the UV adhesive layer on UV dicing tape with the die bonding adhesive layer. The adhesion between the two layers did not increase with aging time after UV curing, as the adhesive layer on the UV dicing tape had been cured, thus limiting the inter-diffusion of the two layers.
Key words: adhesion, die attach film, dicing film.