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Trouble in Your Tank: Case Study: Plating Nodules— Where Did These Come From?

Introduction

Sometimes the problems can really get pretty ugly. One would assume these uglies would be easy to correct. But most often, solving such a problem requires a much deeper dig into the process. In this column this principle will be illustrated with a real-life case study. In this real-life troubleshooting exercise, plating anomalies were detected on the PWBs plated in two different plating cells. This study points out that the root of the defects is rooted in two different causes. One is related to addition agent control, the other to solution filtration and anode maintenance. The study digs into plating roughness and multiple causes and corrective actions.

Severe Plating Roughness/Nodules

In previous columns, this author has presented many possibilities for copper plating nodules. However, what occurred with one PWB fabricator was on the extreme (Figure 1).

In Figure 2, a somewhat different type of nodule appeared on circuits at the same fabricator. Only this defect occurred on circuit boards plated in a different cell.

Basically this fabricator was seeing two different types of nodules/roughness. The nodules depicted in Figure 1 clearly show “normal” copper grain structure (fine-grained equiaxed). However, in Figure 2, the grain is quite large. In addition, the nodule/roughness shown in Figure 1 can be traced to what looks like debris that has been essentially plated up and around.

Editor's Note: This column originally appeared in the October 2016 issue of The PCB Magazine.