Transient Behaviour of Interface-Diffusion in Solid State Bonding and The Enhancement-Effect

Abstract

The process of solid state diffusion bonding is analized, noting the transient behaviour of interfacediffusion, which is an atom-flow along a bonded interface-boundary. A non-linear partial differential equation for the interface-diffusion is led by proposing a two-dimensional bonding model. Numerical calculations are performed with Euler method. It is indicated that an enhancement of the bonding proscess is caused by the transient behaviour when the bonding pressure is frequently removed, although it is negligible in a conventional diffusion bonding. So, "pulse-pressure bonding", in which the pressure is repeatedly applied at intervals of τ_off (pressure-off interval), is proposed according to the calculated results. Influence of τ_off on the enhancement-effect is numerically and experimentally examined. It is shown that τ_off is a very important factor as a period of "relaxation" in order to attain an effect of the transient behaviour. And also, it is suggested that the enhancement-effect becomes striking with reducing the pressure-on interval τ_on, when τ_off is suitablely determined.
It is stated in conclusion that the bonding process enhanced by the transient behaviour is successful even if τ_off is less than τ_on, that is, the pulse-pressure method can be useful to enhance the bonding process under a high vacuum condition.