Plating through Hole with High Throwing Power Using Dual Levelers

In recent year, the technology evolution of wireless networks promoted the development of multifunctional pad, computers and mobile phones. The circuit density of density electron product increased as function increased. As a result, the reliability of electron products was more and more important for high density interconnect (HDI) tendency. The copper electroplating process for high throwing power of plating through holes and the thin surface layer with filling via technology were key process for HID. In this paper, copper electroplating formulas that were composed of dual levelers were studied for plating through holes with high throwing power (TP). The base plating solution contained CuSO₄, H₂SO₄, chloride ions, polyethylene glycol (PEG), bis (3-sulfopropyl) disulfide (SPS). When leveler A was added in the base plating solution, it resulted in a smooth surface, which looked like a mirror, but its TP was not good. When leveler B was added to the base plating solution, it enhanced the TP of the plated through hole. However, the board surface was rougher than that adding leveler A. Both leveler A and leveler B could not lead to smooth surface and good TP simultaneously. Interestingly, when both leveler A and leveler B were simultaneously added in the base plating solution, they not only enhanced the TP of the plated through hole but also made the board surface smooth and bright. These results show that chemical interaction can achieve unexpected functional plating.

Key words： High throwing power, high density interconnection, plating through hole and dual levelers.