Synthesis and properties of UV-curable hyperbranched polyurethane and its application in the negative-type photoresist

UV-curable hyperbranched polyurethane (UV-HBPU) containing carboxyl groups was synthesized from isophorone diisocyanate (IPDI), diethanolamine (DEOA), polyethylene glycol (PEG-400), hydroxyethyl acrylate (HEA), and 2,2-bis (hydroxymethyl) propionic acid (DMPA). The UV-HBPU was used as a negative-type photoresist for a printed circuit board (PCB). Fourier-transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1HNMR) spectroscopy of UV-HBPUs indicated that the synthesis was successful. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed that the thermal stability of the UV-HBPUs decreased as the HEA content increased. The polymer exhibited excellent photoresist properties, and the resolution of circuits based on this negative-type photoresist reached 10 μm.