The adhesion of electroless plated Ni layers on Al/Si substrates has been investigated. The zincating treatment was conducted with both a conventional method and a modified method. In the modified method, an ultrasonic agitation was applied during zincating. Adhesion strength was evaluated by a pull-off test and scratch test. The ultrasonic agitation during zincating increased the nucleation density of Zn particles and refined Zn particle size. The adhesion strength of the electroless Ni layer deposited on the modified zincated surface was higher than that on the conventionally zincated surface. The improvement of adhesion was attributed to the fine and dense Zn particles. (C) 2004 Elsevier B.V. All rights reserved.