Photo-Cross-Linkable Unsaturated Polyesters as Aqueous Depolymerizable Adhesives

Unsaturated polyesters (UPEs) are an established class of thermosetting polymers with widespread industrial use; however, their application as temporary bonding and debonding (TBDB) adhesives in advanced semiconductor manufacturing remains unexplored. This study presents an approach using UPEs as TBDB adhesives for silicon wafer processing applications. A compositional range of UPEs demonstrated tunable viscosity, cross-link density, thermomechanical properties, and adhesion strengths to glass and silicon. Formulation of the UPE resins without reactive diluents enabled fundamental insight into the reactivity of the fumarate unsaturated site over a range of curing times and temperatures. Photorheology confirmed fumarate curing kinetics and showed significant acceleration with increasing temperature. Additionally, heating the UPE resins reduced their melt viscosities, which improved the processability into thin adhesive films. As expected, cross-link density and corresponding storage moduli were correlated directly with the concentration of unsaturated sites in UPE compositions, and lower cross-link density compositions rapidly hydrolyzed into soluble species within minutes in basic water. UPEs establish a platform for TBDB adhesives that provides the thermal stability required in packaging while eliminating the harsh solvents used in the synthesis, processing, and removal of conventional TBDB systems. UPEs enable environmentally friendly, water-based removal, which delivers a cost-effective, sustainable adhesive technology for next-generation electronic devices.