Bonding of low temperature co-fired ceramics to copper and to ceramic blocks by reactive aluminum/nickel multilayers

Reactive multilayers of nickel and aluminum were deposited by magnetron sputtering directly onto low temperature co-fired ceramics (LTCCs) and copper plate for an easy bonding process. The morphology, interface structure, and exact composition of the nanolaminate films were investigated before and after reaction. It was possible to ignite the reaction for all deposited films by electrical spark discharge or by a laser pulse. It was found that the high roughness of the LTCCs enhances the adhesive force of the multilayers to the ceramic. Apart from the directly deposited multilayers, commercially available Nanofoils® covered with 5 µm tin on each side were used for comparison to join two ceramic carriers and also to join LTCCs to copper. In some cases, acceptable resulting bond strengths of the joint were found, a problem being the still poor reproducibility. The tests with the commercial Nanofoils® also showed a mixing of the tin coatings with the used silver based thick film metallization. The latter was printed on the LTCCs. Thus, the experiments confirm that directly deposited reactive multilayers are a promising possibility for joining ceramic devices, either to other ceramics or also to thermally mismatched metallic devices. A careful preparation of the multilayers in composition and total thickness is necessary to adjust the maximal temperature and the heat load to the bonding task in order to achieve best results.