Two catalytic systems for electroless metal deposition have been investigated by means of Rutherford backscattering spectrometry (RBS). The well-known tin sensitizer, palladium activator, two-step catalyst had the main emphasis, but also a commercial one based on evaporated palladium was examined. The behavior of the two-step catalyst was largely dependent on the substrates used. On A12O3, the Sn:Pd ratio was 1:1 with 1.3 x 1016 atoms/cm2 each. On carbon substrates, the Sn:Pd ratio was 1:4 with 6 × 1015 tin atoms/cm2 and 24 x 1015 palladium atoms/cm2. Both these results violate the simple reaction mechanism described by the equation Sn2+ + Pd2+→ Sn4+ + Pdo. The commercial catalyst on polyimide containing 2.5 × 1015 palladium atoms/cm2 on the surface behaved differently compared to the two-step catalyst by diffusing into the deposited layer and thereby influencing its deposition rate.
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