曝气气氛对镀铜电化学行为及填盲孔性能的影响

Effect of aeration atmosphere on electrochemical behavior during copper electroplating and blind-via filling effectiveness

通过计时电位法、循环伏安联合旋转环盘电极技术和印制电路板(PCB)盲孔电镀实验,对比分析了氮气、空气和氧气3种不同的曝气气氛对盲孔电镀过程中铜沉积电化学行为及填孔能力的影响。结果表明,氮气气氛下的填盲孔效果最好,氧气会参与铜沉积的反应过程,并抑制铜沉积。曝气气氛会影响镀铜层的晶粒尺寸,进而影响其微观形貌、拉伸强度及硬度。氧气气氛下所得镀铜层最平整细致,具有最高的拉伸强度、延伸率和显微硬度,综合性能最佳。采用先曝氮气1.0 h、再曝氧气0.5 h的阶梯曝气方式在1.5 A/dm^(2)的电流密度下电镀时,能够在保证盲孔填孔率合格的前提下最大限度地减薄面铜。

The electrochemical behavior of copper deposition during blind via electroplating and the filling capacity under aeration with three kinds of atmosphere including nitrogen,air,and oxygen were compared by chronopotentiometry,cyclic voltammetry combined with rotating ring-disk electrode technique,and electroplating experiment on printed circuit board(PCB).The results showed that the filling effectiveness of blind-via in nitrogen atmosphere was the best.Oxygen inhibits the electrodeposition of copper due to the fact that it takes part in the reactions relevant to copper electrodeposition.The aeration atmosphere had great effect on the grain size of copper coating,thus affecting the micromorphology,tensile strength,and microhardness of copper coating.The copper coating electroplated under aeration with oxygen atmosphere had the best comprehensive performance as shown by the smoothest and most compact surface,as well as the highest tensile strength,elongation,and microhardness.When the electroplating of blind-vias on PCB was conducted at a current density of 1.5 A/dm^(2) with a two-step aeration process(in nitrogen initially for 1.0 h and then in oxygen for 0.5 h),the thickness of surface copper coating can be reduced mostly under the premise of a qualified filling rate.