A thermal rollercoaster: Unraveling temperature dependence in CVS determinations
2023. 10. 30.
문서
Manufacturing printed circuit boards (PCBs) is a complex process. The PCB layout requires precisely controlling the organic additive concentrations during the copper plating step. Cyclic Voltammetric Stripping (CVS) analysis is used to measure and quantify the concentration of these additives. Temperature variations can affect the accuracy of CVS analysis. Therefore, it is important to monitor and control the temperature of the copper plating bath.
This article introduces the methodology to determine organic additives in copper plating baths and explains how temperature affects CVS measurements. In addition, a straightforward and effective way for groundbreaking improvement of precision in the analysis of organic additives is demonstrated.
Overview of PCBs, copper plating, and organic additives
Electronic devices continue to shrink in size while expanding in functionality and performance. For this reason, every millimeter of space on a printed circuit board is a precious commodity. Modern PCB layouts push the boundaries—increasing the number of connecting vias while simultaneously reducing interconnection distances [1]. This growing complexity places stringent requirements on the production process, where precision is paramount.
Among the crucial steps in PCB manufacturing, galvanic copper plating of drill holes and the board surface takes center stage. This process uses organic additives like suppressors, brighteners, and levelers to achieve precise control over the physical properties of plated copper. It is imperative to keep the concentration of these organic additives within a very narrow concentration range.
How to measure and quantify the concentration of organic additives
The complex interplay between the organic additives and the copper plating process itself is investigated using Cyclic Voltammetric Stripping. CVS utilizes one of the simplest principles in electrochemistry: the electroplating rate. This is the speed at which a copper layer is deposited onto a substrate surface.
To perform CVS analysis, an electrochemical cell equipped with a three-electrode system is employed. One of these is a rotating platinum disk electrode, precisely controlled by the instrument (Figure 1).