Study of Bondable Laser Release Material Using 355 nm Energy to Facilitate RDL-First and Die-First Fan-Out Wafer-Level Packaging (FOWLP)

A thorough evaluation on selecting a bondable laser release material for redistribution layer (RDL)-first and die-first fan-out wafer-level packaging (FOWLP) is presented in this article. Four laser release materials were identified based on their absorption coefficient at 355 nm. In addition, all four of these materials possess thermal stability above 350 degrees C and pull-off adhesion on a Ti/Cu layer greater than 8 psi, further illustrating their compatibility in FOWLP. To further evaluate these materials, focus ion beam (FIB) inspection was used to examine the profile of a single-pulse laser ablation region, ensuring free penetration of 355-nm laser energy. With a designated die bonding test vehicle, die shift less than 1.5 mu m and rotation less than 0.02 degrees before and after molding was achieved with the material bondable at temperatures lower than 200 degrees C. Furthermore, this same material required a laser energy of less than 3 W for laser release. A bondable laser release material that eliminates the requirement for a die attach material from the traditional process flow facilitates the development of cost-effective FOWLP.

Automated summary

This article presents a thorough evaluation of four bondable laser release materials for RDL-first and die-first FOWLP, based on absorption coefficient, thermal stability, and pull-off adhesion. Through FIB inspection and die bonding test, it was demonstrated that a specific material achieved excellent packaging results at lower temperatures.