Study of microvia filling process based on multi-physical coupling

Abstract

ABSTRACTThe microvia filling process used in the high-density interconnect printed circuit board manufacturing industry was investigated by multi-physical coupling technology. To achieve a perfect filling, SPS (bis-(sodium-sulphopropyl)-disulphide), EO/PO (ethylene oxide and propylene oxide block co-polymers) and PEOPI (polyethylene oxide-polyimide) were used. Furthermore, electrochemical behaviours of electrodeposition were investigated by cyclic voltammetry, galvanostatic potential transient measurement and dynamic potential polarisation technology. Through numerical simulation, the relationship between coverage of additive, concentration of additive, rotating speed of rotating disc electrode, exchange current density and curve slope was fitted. Based on multi-physical coupling to copper electrodeposition, a mathematical model of microvia filling was built to simulate the filling process by a finite element method, and a systematic analysis of the whole filling process was carried out. The void-free microvia filling and filling process with different shapes were finally achieved in acid copper electroplating solutions consisting of 0.3 M CuSO4·5H2O, 0.2 M H2SO4 and 80 mg L−1 Cl− (virgin make-up solution) plus additives SPS, EO/PO and PEOPI. Subsequently, from images of the microvia filling experiment at different times, shape evolution of the microvia filling and variation of electrodeposition rate at the bottom of the microvia and surface were analysed. The modelling result was compared with the measured data and showed good agreement with the experiment. The results showed that a process model was an excellent tool for quickly and cheaply studying the process behaviour greatly reduced need to execute time-consuming and costly experiments.