Adhesion strength and microstructural evaluation in electroless Ni-P metallized AlN substrate

The adhesion strength of the electroless Ni (EN)-plated AlN substrates is studied through investigation of the microstructural morphologies at the AlN-EN interfaces. Etching sites around the Al-Y-O compounds on the etched AlN substrate provide the anchor acceptors for interlocking the EN film to achieve a high adhesion strength. Separation of the EN film from the AlN substrate under the action of force leaves the fracture cracks propagating along the AlN/EN interface, cutting through the anchors and making the fragmental EN films around the etching sites reside on the AlN fracture surface. However, the polished AlN substrate lacks the interlocking sites and fails to obstruct the cracks propagating along the AlN/EN interface, and thus results in a poor adhesion strength. An appropriate adhesion strength of 13.7 MPa with a small standard deviation (/spl plusmn/2.3 MPa) can be obtained for the previously etched and 10 /spl mu/m thick EN-plated AlN substrate.