The adhesion between the electroless seed layer and the buildup film substrates was studied. After the buildup film was laminated, the buildup film surface was modified by a desmear treatment from 0 to 30 mm, and electroless Cu or electroless Ni-P was plated as the seed layer on the buildup film. The Cu was then electroplated, and the post curing was carried out at 180 degrees C for 2 h before or after Cu electroplating. The adhesion strength between the electroless seed layers and the buildup film substrates was measured by the 90 degrees peel test. Increasing the desmear treatment time made the buildup film surface rougher, and consequently enhanced the adhesion strength of the electroless Cu and electroless Ni-P to the film. Under the same conditions, the electroless Ni-P specimen showed a higher peel strength than the electroless Cu specimens. Post curing significantly increased the adhesion strength due to the increased ductility of the metal layer after heat-treatment. In addition, the peel strength decreased as the thickness of the seed layer increased, which was also related to the mechanical properties of each metal layer. (C) 2013 The Electrochemical Society. [DOI: 10.1149/2.049303jes] All rights reserved.