Abstract

The brazing adhesion properties of Ag coated W-Ag electric contact on the Cu substrate have been investigated in therms of microstructure, phase equilibrium and adhesion strength. Precoating of Ag layer (3µm in thickness) on the W-40%Ag contact material was done by electro-plating method. Subsequently the brazing treatment was conducted by inserting BCuP-5 filler metal (Ag-Cu-P alloy) layer between Ag coated W-Ag and Cu substrate and annealing at 710°C in H_2 atmosphere. The optimum brazing temperature of 710°C was semi-empirically calculated on the basis of the Cu atomic diffusion profile in Ag layer of commercial electric contact produced by the same brazing process. As a mechanical test of the electric contact after brazing treatment the adhesion strength between the electric contact and Cu substrate was measured using Instron. The microstructure and phase equilibrium study revealed that the sound interlayer structure was formed by relatively low brazing treatment at 710°C. Thin Ag electro-plated layer precoated on the electric contact (3µm in thickness) is thought to be enough for high adhesion strength arid sound microstructure in interface layer.

• Keywords: W-Ag electric contact;BCuP-5;Filler-metal;Brazing;Adhesion test;;