Analysis of the formation process of the bonded area in the solid state bonding and its prediction

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The solid state bonding process is not only influenced by the bonding pressure and temperature but also by the surface roughness. When the faying surfaces are pressed each other, the voids dre formed on the bond-interface due to the surface roughness. Thus, we cannot achieve the full intimate contact (adhesion) immediately after pressing the faying surfaces. In this study, we analyzed the process of the void shrinkage by the computer simulations. Also, we developed the algorithm to estimate the bonding process under the extend conditions of the pressure and temperature. Besides, we produced the algorithm for determining the optimum bonding conditions by taking account of the scattering of the surface roughness. The main results obtained is as follows.1) the void shrinkage process is controlled by the pressure and temperature. the activation energy of the void shrinkage is obtained by 1n(T/t_v)-(1/T) plots, where T is the absolute temperature, and t_v the time required to attain the void shrinkage of a certain volume. 2) When the void shrinkage is dominantly controlled by the diffusion, the stress exponent n for the time tv is in the range of -1 to -0.3 ( n is not less than - 1 ). 3) The void shrinkage is largely influenced by the spacing between the voids. 4) The introduction of fine surface asperities promotes the bonding process. 5) The spacing between the voids changes during bonding. This is due to the scattering the surface roughness. This is exactly estimated by the overlap process of the profiles of the faying surfaces. 6) By taking account of the change in the void spacing, it is possible to estimate the complete bonding time if the scattering is not so large. 7) It is found that the algorithm developed in the present study is a powerful tool to determine the optimum bonding conditions. 8) the applicability of this algorithm is verified by the experiments.