Effects of electroless nickel plating process on the microstructure and properties of complex shape ceramic capacitors

Surface metallization is crucial for capacitors. Screen printed method is usually adopted in the ceramic capacitors with regular structure. However, core-piercing capacitor not only exhibits complex shapes with double-layer step, deep hole, but also requires to meet further welding. It is a challenge to achieve the high-quality electrode. In this work, Y5V-type core-piercing ceramics capacitor has been adopted as the research objects through to electroless nickel plating process achieve high-quality electrode. The effects of pre-treatment and plating process such as etching, sensitization, and activation and reducing agent concentration, pH value, plating temperature and plating time have been systemically investigated on the microstructure evolution and performance. The optimal pre-treatment is etching in 30 wt% H 2 SO 4 solution at 70 °C for 1.5 hours, sensitization in 15 g L -1 SnCl 2 solution and activated in 200 mg L -1 PdCl 2 solution for 3 minutes, respectively. The best process parameters are NaH 2 PO 2 concentration of 25 g L -1 , C 12 H 25 SO 3 Na concentration of 20 mg L -1 and pH value of 6.0, temperature of 70 °C, time of 10 minutes. After plating, the bright electrode is achieved for the core-piercing ceramics capacitor, which exhibits the microhardness of 590 HV, excellent stability of dielectric properties. The low variation of capacitance is less than 9% and the dielectric loss is still below 0.01 after two times thermal shock, from room temperature to 300 °C to room temperature, corrosion of 10 wt% HCl, 10 wt% NaOH, 3.5 wt% NaCl solution. This work provides an effective approach for surface metallization of complex shape capacitors.