Mass Balance and Deposition Mechanism of Electroless Palladium Plating Using Trimethylamine Borane as a Reducing Agent

Abstract

The deposition mechanism in palladium electroless plating from ethylenediamine complex solutions containing trimethylamine borane (TMAB) as a reducing agent was investigated.
The TMAB utilization factor was found to be 68% to 86% for palladium deposition and 25% to 32% for boron deposition. The deposition mechanism can be explained by the electrochemical mechanism, based on the following reactions.
Local anodic reaction
(CH₃₎₃NBH₃+2H₂O→(CH₃₎₃N+BO₂^-+7H⁺6e^-
Local cathodic reaction
Pd²⁺+2e^-→Pd
mPd²⁺+(CH₃₎₃NBH₃+(2m-3)e^-→Pd_mB+(CH₃₎₃N+3H⁺