SURFACE INVESTIGATION OF COPPER IN THE PRINTED-CIRCUIT BOARD

The aim of the study was to determine both the oxidation rate of copper in the printed circuit board and the degradation of an organic compound (ENTEK) present on its surface during the different phases of circuit assembling. A large number of samples stripped from electronic cards have been measured by XPS and Auger techniques ‘as received’ in order to have a statistical indication of surface composition. Other samples were heated at 220°C in a vapour‐phase atmosphere. A very thin layer (∼20 Å) is present on the copper of the printed circuit board. This layer comprises carbon, oxygen and nitrogen. After vapour‐phase treatment at 220°C, the layer on the copper surface increases up to ∼100 Å and its composition changes: carbon decreases, oxygen appears more in the ‘lattice form’ than as hydroxide and nitrogen is present in two valence states. Copyright © 1990 John Wiley & Sons Ltd.