| Inkjet printing technology has been widely utilized for document and photo printing. Additionally, non-graphic-arts uses of inkjet printing are developing as a technique for depositing and patterning functional materials in the liquid phase, such as biomaterials, photo resist, and dielectric materials, to a substrate. Epoxy resins are commonly used adhesives between passivated substrates and polyimide films in an inkjet printing head. Although such adhesive layers have high fracture toughness with fracture energies in excess of 500 J/m2, the silica/adhesive interface and the adhesive itself is susceptible to accelerated debonding in a complex chemical environment at high temperature. Debonding is frequently further accelerated by cyclic loading due to heating and cooling cycles, resulting in serious reliability concerns.; The effects of debond growth rate, solution pH and temperature on the interfacial and cohesive adhesion of silica/adhesive/polyimide thin layered systems are examined under different loading mode mixities typical for a range of inkjet printing heads. The relationship between the debond growth rate (da/dt) and the applied strain energy release rate (G) was evaluated using fracture mechanics techniques. The silica/adhesive interface is found to be susceptible at low da/at (<10-7 m/s) in higher pH environments and higher temperatures. However, if da/dt is higher than 10-7 m/s, the adhesive will experience cohesive failure, and the debonding mechanism is determined by pH value and temperature of the environment. Finally, subcritical crack growth process and debond path selection are described in terms of a competing-reaction mechanism. The ability to predict fracture behavior may be used to establish environmental parameters in order to enhance the reliability of inkjet printing heads. |
