关键词: 通孔, 电镀铜, 甲基红, 表面形貌

Abstract:

Electroplating copper within through-holes serves as a crucial technique for interconnecting high-performance printed circuit boards (PCBs). Improving the throwing power (TP) of copper plating through these holes is essential for advancing PCB technology. This article explored the influence of methyl red (MR) on three key aspects: the electrochemical behavior of the plating solution, the surface morphology of the electrodeposited copper layer and the uniformity of through-hole copper plating. Firstly, electrochemical assessments were conducted to examine how methyl red and flow velocity affect the performance of acidic copper electroplating systems. Subsequently, copper layers were electrodeposited within through-holes, and the effects of methyl red on the surface morphology of these copper layers were investigated through roughness measurements and X-ray diffraction analysis. Finally, to evaluate the effect on plating uniformity, cross-sections of the through-holes were prepared and analyzed by using a metallographic microscope. Within the range of 0—1600r/min, increasing convective velocity accelerated the copper deposition rate. Additionally, as the concentration of methyl red increases from 0 to 9mg/L, the deposition rate initially increased and then slowed down. Under the condition of a current density of 2A/dm², the addition of 6mg/L MR could enhance the brightness of the copper layer surface, reduce the roughness to 0.287μm, and improve the TP of the plated through hole to 0.978. To summarize, methyl red was a special copper electroplating leveler with a depolarization effect.

Key words: through hole, copper electroplating, methyl red, surface topography