Preparation of UV Debonding Acrylate Adhesives by a Postgrafting Reaction

Abstract

UV debonding acrylate adhesive (UDAA) plays a crucial role in the semiconductor industry, where its excellent adhesion is required to ensure the stability of silicon wafers and leave no residue on the surface after UV irradiation. The necessary UV debonding is achieved through the formation of rigid networks by the reactions of all the vinyl groups in the system. Acrylate copolymers with vinyl groups are typically obtained by the grafting reaction of isocyanate with a side-chain hydroxyl comonomer. However, these grafting reactions easily fail due to early cross-link formation. In this study, we illustrate a straightforward method for preparing UDAA by conducting a postgrafting reaction after one-step mixing of isocyanate functional monomer (IPDI-H) and hydroxyl acrylate copolymers (BA-H), thereby skipping the abovementioned vinyl grafting process. The chemical structures of the synthesized IPDI-H and BA-H were confirmed using Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H-NMR) analysis. Gel permeation chromatography (GPC) was employed to determine their molecular weights, while differential scanning calorimetry (DSC) was used to determine their glass transition temperatures. The postgrafting reactions successfully introduced vinyl groups onto the polyacrylate copolymer chains, resulting in high bonding strength during use and a significant decrease in peeling strength after UV irradiation. Rheological methods, including the three-interval thixotropy test (3ITT) and tack test modes, were employed to characterize a series of acrylate UV debonding adhesives. The recovery percentage of the storage modulus in the 3ITT mode indicated that a 0.6 wt% isocyanate curing agent made the UV debonding adhesives resistant to deformation. From the maximum normal force in the tack test mode, it was found that UDAA with 10 wt% PETA monomer and 30 wt% C5 tackifying resin exhibited excellent combined adhesion and debonding properties, which were further confirmed by peel strength tests. Microscope images of the wafer surfaces after removing the adhesive tapes demonstrated the excellent UV debonding properties achieved after 40 s of UV irradiation through the postgrafting reaction. The prepared UDAA has excellent properties; the peel strength can reach 15 N/25 mm before UV irradiation and can be reduced to 0.5 N/25 mm after ultraviolet irradiation. This research establishes a comprehensive method for understanding and applying UDAA in various applications.