Adhesion of electrolessly-deposited copper to photosensitive epoxy

The adhesion between electrolessly-deposited copper and photosensitive epoxy was measured with a pull test designed in this work. The test pads were fabricated on the epoxy substrate using a semi-additive plating process. The pull strength was measured with a mechanical tester. A chemical treatment was used to roughen the epoxy surface; two sets of specimens were tested with different swelling and etching times to obtain the optimal adhesion strength. Another set of specimens was tested as reference without swelling. The effects of the chemical treatment on surface topography and adhesion were studied. The surface topography of the epoxy was examined by optical microscopy, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The ranges of swelling and etching times, which resulted in good adhesion, were presented. It was confirmed that the procedure of swelling and etching processes had to be optimized for achieving the desired epoxy surface properties without altering the bulk properties.