Impedance and Morphological Properties of Electroless Gold on Industrial Metal Coupons

Abstract

An approach for correlating the bath chemistry during electroless gold deposition with the overall plating quality on industrial wirebond samples is presented. Electrochemical impedance spectroscopy of the reducing agent dimethylamine borane (DMAB) on gold in alkaline solution was used to provide qualitative information on the interfacial adsorption/desorption processes occurring during deposition. Depending on hydroxide and DMAB concentration, impedance data obtained under hydrodynamic conditions at the gold oxide reduction potential (0.184 V vs Ag/AgCl) follow two different equivalent circuit models that do not exhibit contribution from diffusion. Gold deposit quality was assessed with scanning electron microscopy and energy-dispersive spectrometry under a variety of bath compositions. Finally, bath efficiency was evaluated in terms of plating rate obtained from X-ray fluorescence data. The substrate surface/solution interactions are linked to the final quality of the resulting gold layer. This work shows that substrate incompatibility and the ratio imbalance between gold and the reducing agent concentrations produce thin, dull deposits. Maintaining the optimum ratio of DMAB/KOH provides balance in the bath chemistry necessary for efficient plating.

Pd–P electroless deposition on carbon steel: An electrochemical impedance spectroscopy study

“…The final values for the capacitance are in the order of hundreds of micro-Faradays and they are coherent with those observed for copper electroless deposits [20].…”

“…However, an increase in value of i 0 corresponding to the total reaction is observed, due to the higher catalytic activity of the deposit towards the oxidation reaction. The charge transfer resistance for the partial and complete reactions ðR Ã ct Þ can be calculated from i 0 through the relation R Ã ct ¼ RT =i 0 nF , derived from the Tafel equation [20,24], where R is the gas constant, T the temperature, F the Faraday constant and n the number of the electrons for the reaction.…”

“…Several reaction paths, determined using different experimental techniques, have been proposed in the literature. These techniques include plating rate measurements, alloy composition dependency as a function of experimental parameters, d.c. polarization studies, chronoamperometric and chronopotentiometric investigations and electrochemical impedance spectroscopy (EIS) [13][14][15][16][17][18][19][20][21].…”

“…However, most of the studies were performed under potentiostatic or galvanostatic control [17][18][19][20][21]. Under these conditions, a displacement of the reaction path occurs and the mechanism can differ from that of the electroless process at its characteristic deposition potential.…”

Smart electrochemical biosensors: From advanced materials to ultrasensitive devices

“…The polymeric structures developed have been used for biochemical sensing, environmental monitoring, and microelectronic applications [41][42][43][44]. We have explored the feasibility of designing advanced conducting polymeric materials for sensing and remediation applications.…”