The atomistic state and desorption behavior of hydrogen in electrolessly deposited pure Pd and Pd-P alloy films employed for the surface finishing of printed circuit boards were examined by thermal desorption spectroscopy, X-ray diffraction and transmission electron microscopy. For the pure Pd films, a broad desorption peak of hydrogen were observed at 400 ~ 700 K. The lattice contraction decreased and the grain size increased with temperature of heat treatment up to 700 K. In a

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... region above 700 K, a lot of desorption peaks were observed and the grain growth proceeded. The total amount of hydrogen desorbed from pure Pd film between 300 ~ 1100 K was x = 7.3×10 -3 in atomic ratio (x = H/Pd). For the Pd-P alloy films, a broad desorption peak was observed in the amorphous state at 350 ~ 500 K and a sharp desorption peak was observed in the vicinity of 570 K with the formation of intermetallic compounds such as Pd 3 P and Pd 6 P. The grain size of these intermetallic compounds increased and a few broad desorption peaks were observed at 700 ~ 1100 K. The total amount of desorbed hydrogen of Pd-P alloy film was x = 3.2×10 -3 .