Investigation of failure mechanism in packaging of inkjet printer head

Abstract

Encapsulation failures in inkjet print head assembly were studied with four approaches. The impact of ultraviolet (UV) cure and post cure conditions on the mechanical properties of Polyurethane Acrylate (PUA) encapsulant was first studied. The investigation was continued by probing the interaction between PUA, processed using different UV curing conditions, with moisture and ink. The manner by which PUA properties degraded upon soaking in solvent was investigated. Electrified ink immersion (EII) testing was conducted to determine the barrier layer properties of the PUA. Finally, with the finite element (FE) modeling, moisture distribution and swelling induced stress in the print head package was determined by inputting all relevant parameters obtained from various experiments. Design parameters were varied to understand the effect modulus and encapsulant thickness to the swelling stress and hence to package reliability.