Function of Sulfhydryl (–HS) Group During Microvia Filling by Copper Plating

Abstract

In this work, 3-mercapto-1-propanesulfonate (MPS) with one sulfhydryl (-HS) group and 2,3-dimercapto-1-propanesulfonate (DMPS) with two -HS groups were used as model additives to reveal the function of -HS group during copper plating. Chronopotentiometry was employed to characterize the different electrochemical behaviors of the two model additives. It indicated that DMPS showed stronger accelerating effect than MPS in the plating bath containing Cl − , which could be attributed to its enhanced adsorption caused by two -HS groups. The pre-adsorption and desorption experiments demonstrated the synergistic effects and competitive adsorption between Cl − and the model additives. Moreover, the accelerating mechanism was investigated by cyclic voltammetry combined with rotating ring-disk electrode (RRDE), demonstrating MPS could accelerate the ratedetermining step (RDS) of copper deposition only if Cl − was present, whereas DMPS could enhance the RDS whether Cl − existed or not. Finally, microvia filling experiments were carried out to evaluate the filling performance of the two model additives. The results indicated that in the plating bath containing PEG and Cl − , MPS showed good filling performance, while DMPS did poorly. However, after the introduction of JGB, the filling performance of DMPS was greatly improved, which was resulted from the competitive adsorption between DMPS and PEG being balanced by JGB.

The effect of quaternary ammonium salts with different chain lengths on copper filling behavior in blind holes of printed circuit board

“…In order to ensure that the micropores are filled with non-porous and are completely filled, copper needs to grow from the bottom of the blind hole step by step from the bottom to the top during the electrodeposition process, which is achieved through the coordination of several additives [5][6][7]. Currently, three types of additives including suppressor represented by macromolecular polyether compounds (such as polyethylene glycol (PEG) [8][9][10], polypropylene glycol [11,12]), accelerator represented by propane sulfonate derivatives (such as sodium 3-mercapto-1propane sulfonate [13,14] and bis (3-sulfopropyl) disulfide (SPS) [15][16][17]), levelers represented by heterocyclic or alkyl compounds (such as Janus Green B, Diazine Black and Alcian Blue [18][19][20]). Among them, suppressors with larger molecular chains combine with Cl − and are usually adsorbed on the surface of the circuit board to form a chelate with Cu 2+ or Cu + to inhibit the deposition rate of copper, thereby reducing the current density of the blind hole orifice [8].…”

Effect of Copper Sulfate and Sulfuric Acid on Blind Hole Filling of HDI Circuit Boards by Electroplating

“…A large number of studies have shown that there are many factors affecting the effect of blind hole filling, such as the formula of the electroplating solution (composition and concentration), electroplating process parameters (electroplating method, stirring mode, current density, and electroplating time), and the geometric size of blind hole (diameter and diameter depth ratio) [ 11 , 12 , 13 ]. However, there are not many reports about how to obtain a good blind hole filling effect for an HDI substrate by changing the content and proportion of copper sulfate and sulfuric acid in the plating solution formula, and the available references are very limited.…”