Die attach film application in multi die stack package

The trend for package miniaturization has created challenges to conventional die attach process. When wafers need to be thinned down beyond 100 mum, challenges in die attach process become great and die attach paste may not be suitable in most cases [Paydenkar, 2004]. The selection of die attach material becomes critical to ensure package robustness and reliability. When die paddle of a package is reduced to less than 0.3mm, the control of bleed out of paste becomes critical. The rheology of paste results in creeping of the material to the edge of die and contaminate the bonding pad when the die is placed and seated upon a certain amount of dispensed paste. New generation of die attach material has been introduced amid this complication, die attach film (DAF) is commonly used for thin die stacked package (< 100 mum). DAF replaces paste in stacked packages for its good control of paste bleed, creeping effect to die edge and also consistent bondline thickness (BLT) at desired thickness. New generation of DAF tape incorporates wafer dicing tape and adhesive in one, namely the dicing die attach film (DDAF), which is mounted onto the back of wafer. The wafer which is mounted with DDAF was diced into the predetermined die size and the diced chip was picked and placed directly to a leadframe or substrate with adhesive at the back . Today, DDAF has been proved to reduce manufacturing process steps and improve productivity. The gain in productivity has improved total package cost, irrespective of the higher material cost when conventional die attach paste is replaced by DDAF