A novel CO2 based UV-induced peelable adhesive for wafer dicing

Poly (propylene carbonate) diol with double-bonds on the side chains (PPCAGE) was synthesized form CO₂, propylene oxide (PO), polyether diol (PPG) and allyl glycidyl ether (AGE). Then, three kinds of CO₂ based polyurethane oligomers (PPCAGE-PU) (PPCAGE-PUA, PPCAGE-PUB and PPCAGE-IPDI, respectively) with different contents of double bond were prepared through the reaction of PPCAGE, isophorone diisocyanate (IPDI) and hydroxyethyl acrylate (HEA). The content of -NCO was adjusted by varying the ratio of -NCO terminated prepolymer and HEA. Acrylate copolymer with side double bonds and hydroxyl groups (GMA-PSA) was synthesized by the ring-opening reaction of glycidyl methacrylate (GMA) and acrylate copolymer (PSA) containing -COOH and -OH. CO₂ based UV-induced peelable adhesive was prepared by mixing PPCAGE-PU, GMA-PSA, active diluent and photoinitiator. The structure of PPCAGE was confirmed by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (¹H NMR). The reaction of PPCAGE-PUB and GMA-PSA was monitored by FT-IR, companied by the titration of -NCO and epoxide. The molecular weight of PSA and GMA-PSA was determined by gel permeation chromatography (GPC). The surface morphology of the adhesive was observed by scanning electron microscopy (SEM). The viscoelasticity of adhesive was measured by real-time rheology. The 180° peel strength, micro-surface morphology, gel content, unsaturation conversion and glass transition temperature of UV-induced peelable adhesive were characterized. The results showed that the peel strength of adhesive was 17.82 N/25 mm before UV curing. After UV curing, the surface morphology changed from smooth to rough, the peel strength decreased to 0.08 N/25 mm and the modulus of the PSA increased due to the cross-linking. DSC results showed that the glass transition temperature increased after UV curing.