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64 DESIGN007 MAGAZINE I OCTOBER 2024 remove more copper, resulting in higher resis- tance. However, we discovered that circuit resis- tance precision was affected by dwell time with mSAP etching, increasing the standard deviation with increasing etch time. e pro- cess for this circuit needed to be optimized to determine the optimum window for the break- point. Several DOEs were performed, and they revealed the great effect of slight changes with etching on meeting the tight electrical requirements. rough ANOVA we deter- mined a specific range of etch exposure to con- trol this part of mSAP processing to provide an optimum resistance distri- bution while retaining robust etching conditions. We also concluded that we should not use etching process to adjust net resistance. Summary e project was successful due in part to clear communication between the customer and our product engi- neering about all requirements, including functionality, and feedback with initial prototypes, especially with the unique resistance require- ments. Our engineering knowledge and manufacturing capabilities were employed to refine processing to meet unusual requirements. e hurdles with electrical testing were overcome with creativity to adapt existing core competency to new testing require- ments. e project led to an increased understanding of wet processing factors affecting the nuances of net dimensions, which consequentially affects reliably attaining the custom- er's requirements. e mean of the range was more incidental, insofar as the main challenge was control of range. With the range under such good control, the target mean may be easily adjusted to reliably meet the customer's electrical requirements for new versions and possibly additional future applications. DESIGN007 Dean Neuburger is a process engineer with Sheldahl Flexible Technologies. Figure 5: mSAP copper plating before and after optimization. Figure 6: mSAP etching results with adjustment of multiple factors. Best precision with Adjustment D, Condition 1.