Study of Electroless Plating Technology for Copper Hohlraum

Electroless plating was performed to fabricate integral copper hohlraum on the surface of pretreated core axis made of polymethyl methacrylate (PMMA) used for a laser device. The effects of the content of formaldehyde as the reducing agent and pH value and temperature of the plating bath on the deposition rate and bath stability were studied. The optimization of the bath formulation and plating parameters was established. As the results, the optimized bath was suggested to be composed of 10 g/L CuSO_ 4, 20 g/L Na_ 2EDTA, 40 g/L potassium and sodium tartarate, 0.1 g/L stabilizing agent, 10~20 mL/L formaldehyde; while the optimal pH value and temperature of the plating bath were suggested to be 12.0~13.0 and 40~70 ℃, respectively. The copper coating prepared under the optimized conditions had a wall thickness as much as 25 μm and was free of cavities and cracks. After removal of the core axis by chemical etching, the remaining copper hohlraum was able to keep its shape in the absence of external load.