添加剂对印制线路板微盲孔填铜效果的影响

Effects of additives on microvia copper-filling efficiency of printed circuit board

在电流密度1.94 A/dm^2、温度25°C和空气搅拌的条件下,采用由220 g/L CuSO_4·5H_2O、0.54 mol/L H_2SO_4和4种添加剂组成的酸性镀铜液对PCB(印制线路板)微盲孔进行填充。所用添加剂包含Cl-、加速剂(聚二硫二丙烷磺酸钠,SPS)、抑制剂(聚乙二醇-8000,PEG-8000)和整平剂(4,6-二甲基-2-巯基嘧啶,DMP)。通过电化学阻抗谱和阴极极化曲线分析了上述4种添加剂的用量对微盲孔填充效果的影响。结果表明:当Cl-为30~60 mg/L、SPS为0.5~1.0 mg/L,PEG-8000为100~300 mg/L、DMP为1~7 mg/L时,填孔效率最佳,所得镀层表面结构均匀、致密,耐浸锡热冲击和抗高低温循环的性能良好,满足PCB的可靠性要求。

Microvia of PCB （print circuit board） was filled by electroplating in an acid bath composed of 220 g/L CuSO4· 5H2O, 0.54 mol/L H2SO4 and four kinds of additives at temperature 25 ℃ and current density 1.94 A/dm2 under air agitation. The employed additives are Cl-, sodium 3,3＇-dithiodipropane sulfonate （SPS, as accelerator）, polyethylene glycol （PEG-8000, as inhibitor） and 4,6-dimethyl-2-mercaptopyrimidine （DMP, as leveler）. The effects of the dosages of the above mentioned additives on microvia-filling efficiency were analyzed by electrochemical impedance spectroscopy and cathodic polarization measurement. The results showed that the microvia-filling efficiency is the best when the mass concentrations of Cl-, accelerator, inhibitor and leveler are 30-60 mg/L, 0.5-1.0 mg/L, 100-300 mg/L and 1-7 mg/L respectively. The obtained coating is uniform and compact, and has good resistance to thermal shock in tin immersion and temperature cycling tests, meeting the requirement of reliability for PCB application.