Investigation of benzoquinone as a new type of Cu electroplating additive

It is becoming more and more difficult to achieve the conformal electroplating of through-holes (THs) and superfilling of micro-vias with the increasing number of layers of high-density interconnect (HDI) printed circuit board (PCB). Therefore, organic additives as the one of the most convenient methods to accomplish uniform plating, obviously play an important role in electroplating Cu. In this paper, benzoquinone as a new type of additive was investigated in order to reduce the copper thickness of the surface. According to the cyclic voltammetry (CV) test and galvanostatic measurements (GMs), it is confirmed that the principle was competitive reduction reaction of benzoquinone and Cu ²⁺ when benzoquinone injected into the electroplating solution. Besides, the results of GMs and cyclic voltammetry stripping (CVS) also indicated that the effect of benzoquinone on the surface and the center of THs is different due to the difference in mass transfer between the surface and center. Furthermore, the Haring cell tests was conducted in order to figure out the thickness of surface THs. Through calculation, compared to none of benzoquinone, the thickness of surface reduced 4.3 μm. Thus, it can be concluded that the benzoquinone was a new type of additive which aimed to reduce the Cu thickness of surface and it can achieve conformal electroplating together with brightener, inhibitors, levelers in further application.