A novel UV-curable epoxy resin modified with cholic acid for high-frequency dielectric packaging

With the development of high-frequency communication technology, higher requirements are put forward to solder resist resin called dielectric ink that is applied to electric chips as coating, which needs high heat resistance and low dielectric properties. In this paper, different from general solder-resistance resin, cholic acid instead of acrylic acid was using to react with epoxy resin because of its unique configuration and multiple reactive sites (hydroxyl groups), after that, one mole carboxyl group would introduce four mole hydroxyl groups. All the hydroxyl groups were reacted with 1,2,5,6-Tetrahydrophthalic anhydride to produce four mole double bonds and four mole carboxyl groups. In order to adjust the acid value and increase the content of double bond of mixture, 1, 2, 3 and 4 mol glycidyl methacrylate were introduced to react with carboxyl groups. It was found that this kind of new UV-light-sensitive solid resist resin have high glass transition temperature (the highest is 144 °C), high double-bond conversion (68%) and low dielectric constant (the lowest is 2.51). Depending on above features, it is promising of the resin that can be applied for light-curing inks in high-frequency electronic packaging which requires better thermal and dielectric properties nowadays.