Effect of Cupric Methanesulfonate on through-Hole Filling by Copper Electroplating

Through-hole (TH) filling of a printed circuit board (PCB) by copper electroplating was performed using copper sulfate (CuSO₄) in recent years. However, the process might cause crystallization issue of CuSO₄ because of extremely high CuSO₄ concentration (i.e., 220g/L). In the other words, CuSO4 concentration cannot be increase anymore, if someone wants to enhance the copper filling rate inside the TH by increasing plating current density.

The anions of cupric methanesulfonate ( Cu(CH₃SO₃)₂ ) is CH₃SO₃^-, which is different from copper sulfate (CuSO₄). The solubility of cupric methanesulfonate is much higher than CuSO₄, so that we can increase the current density and decrease plating time for TH filling by means of increasing cupric methanesulfonate concentration.

In this work, we employed the butterfly filling formula^[1] to perform the TH filling. The copper source was changed from CuSO₄ to Cu(CH₃SO₃)₂ in order to increase copper ion concentration. The result show that with the high concentration of copper ion, we can enhance the copper filling rate inside the TH by increasing plating current density. Moreover, the copper thickness deposited on the board surface is not increased and the filled TH is void-free when the plating current density is increased.

Keywords: Through-hole filling, Printed circuit board, Leveler, Cupric methanesulfonate

References

1. J. J. Yan, L. C. Chang, C. W. Lu, and W. P. Dow, “Effects of organic acids on through-hole filling by copper electroplating

”, Electrochim. Acta. 2013, 109, 1– 12.