Study on the pre-tinned effect in the electroless tin plating process

Tin-plated copper structure was widely applied in the electronic products. With the development of the electronics industry, the integration degree increased and the component size reduced obviously. The conventional tin plating technology met the micro-structure challenge; it may not be used in advanced electronic packaging process. The electroless tin plating technology could solve this problem. In this paper, the pre-tinned method was studied. The Sn layer thickness was about 1.5 µm, and the surface morphology was silver-white, uniform and luster. The pre-tinned treating could make the tin coatings uniform and restrict the formation of copper-tin intermetallic compound. Compared with the electro-deposition tin, electroless tin layer surface got more uneven after aging 8 hours at 200 °C. And less intermetallic compound (IMC) can be found in the pre-tinned chemical tin plating layer interface. This may be due to the pre-tinned process could form more compact initial layer, and it decelerated the diffusion rate of copper and tin.