The invention discloses alkali-soluble hyperbranched photosensitive organic
silicon prepolymer and a preparation method thereof. The preparation method comprises the following steps of: (1) adding organic
silicon, polyisocyanate,
carboxylic acid or anhydride containing an
active group and a catalyst to a first reactor and reacting for 3-7 hours at the temperature of 50-60 DEG C; (2) adding a hydroxyl-ended hyperbranched
polymer (HPB-OH) and a catalyst to a second reactor, then, adding a product in the first step, and reacting for 2-5 hours at the temperature of 30-70 DEG C; (3) adding the polyisocyanate, a
gadoleic acid-hydroxyl ester compound, the catalyst and a
polymerization inhibitor to a third reactor, and reacting for 5-8 hours at the temperature of 40-80 DEG C; (4) reacting the product in the second step, the product in the third step, the catalyst and the
polymerization inhibitor for 2-6 hours at 30-80 DEG C; and (5) cooling to
room temperature, discharging and keeping in a dark place for standby. The invention has the advantages that: (1) the synthesized alkali-soluble hyperbranched photosensitive organic
silicon prepolymer has better high
temperature resistance, better
photosensitivity, better flexibility, higher light reaction activity and lower
viscosity; (2) solder
resist ink prepared by the
prepolymer is developed by a diluted alkali solution, therefore, the environmental
pollution caused by largely using an
organic solvent is avoided; and (3) the synthetic method is simple and is easy to operate, and raw materials are cheap and are easy to obtain.