Influence of Metal Foil Width on Bonding Strength in Capacitor Discharge Ceramics Joining

A capacitor discharge joining technique used to fabricate an alumina-(Al₂O₃) tile-titanium-foil-Al₂O ₃-tile joint was investigated to clarify the influence of titanium foil width on bonding strength. A several-kiloampere pulse current was supplied from an 8.28-muF storage capacitor to the titanium foil while simultaneously applying a pressure of 8.3 MPa to the joint. The temperature of the foil rapidly increases owing to ohmic heating with a large current. As a result, the titanium foil melts and vaporizes in a short time. The Al₂O₃ tiles were successfully bonded when the charged voltage in the capacitor was almost the same value as the energy required for vaporization of the titanium foils. The bonding strength increases with the energy input to the foil. The attainable bonding also increases with increasing shear strength from 150 to 300 kg, which in turn increases with increasing foil width from 1 to 7.5 mm for a 50-mum-thick foil. The main reason of the shear-strength improvement was the increase of the joined area that was measured with image analysis of the joint surface