Mechanical properties of UV-curable polyurethane acrylate used in packaging of MEMS devices

Research has concentrated on thermally cured packaging materials, with little effort directed at UV-curable systems. The aim of this work is to study the characteristics of a UV-curable Polyurethane Acrylate (PUA) processed under different UV curing conditions, as well as to monitor changes in its properties upon aging under room temperature conditions and in corrosive solvent environments. The PUA system was observed to possess a dual cure mechanism. Different UV conditions yield PUA with varying modulus; however, the modulus eventually converge and approach a plateau with prolonged staging under ambient conditions, due to interaction with moisture. Annealing was found to assist in accelerating moisture cure reaction, which facilitates stable material properties within a shorter ambient staging time. In addition, the degradation in properties occurring when cured materials come into contact with a corrosive solvent environment was also studied. (c) 2005 Elsevier B.V All rights reserved.