Fabrication of UV-induced peelable adhesives using acrylic copolymers containing photo-initiators and soybean oil based urethane acrylate oligomers

Abstract

During a typical process of silicon wafer dicing, UV-induced peelable adhesive tape is usually required to fix the wafer to ensure smooth dicing. After dicing, the adhesion strength of the tape is greatly reduced by UV irradiation to make the diced chips easy to pick up. As the wafers become thinner, the UV-induced peelable adhesive with higher peeling performance and lower residual adhesive is required. To meet the above requirements, this work presented two major improvements to the conventional UV-induced peelable adhesives. The first improvement was that the unsaturated photo-initiator 4-acryloyloxy benzophenone (ABP) was incorporated into the acrylic copolymer chain. The second improvement was developing a soybean oil based urethane acrylate oligomer (SOP-PUB-PETA) with a dual curable function (UV-induced polymerization and the addition reaction of NCO groups with OH groups) containing more cross-linking sites. A new UV-induced peelable adhesive for silicon wafer dicing was prepared by mixing ABP-containing acrylic copolymer, SOP-PUB-PETA and PETA in an appropriate proportion. Before UV curing, the NCO groups of SOP-PUB-PETA and the hydroxyl groups of ABP-containing acrylic copolymer were reacted to form a network UV-curable pressure sensitive adhesive (PSA). Under the optimal condition, the 180° peel strength of this PSA before UV curing was above 25 N/25 mm. After UV curing, a fully cross-linked adhesive film was formed and the 180° peel strength was sharply decreased to 0.03 N/25 mm. The residual adhesive was little.