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22 PCB007 MAGAZINE I OCTOBER 2023 these controls, and shown rapid ROI through both yield improvement and overall de-risking of the process. Copper Foil and Seed Layers In the case of copper foil and copper-plated surface layers, the overall goal is to be able to etch through this layer as fast as possible, thereby achieving the least possible under- cut/lateral-etching of the masked features and thereby achieving higher resolutions. e per- formance can be pushed in this direction by the utilization of low Rz/thin foils, modifying the grain structure to be more columnar for rapid etching, as well as through the utilization of 3D measurement of the average Cu height prior to etching/next-level plating for recipe set-ups. microscopy inspections, weight gains/losses, and SIR readings associated with laser drill and the metallization of microvias, best practice has recently found that three different inspec- tion steps for copper structural assessment to assure high-reliability results are also valuable to de-risking the process (Table 1). e opportunity from these QC steps is to optimize the process recipes, and the field experience is that this can oen yield large improvements in microvia reliability. e capability gains from the addition of this con- trol scheme can then be leveraged to demand higher willingness to pay from clients, as well as improving capabilities to produce higher margin products. Multiple new greenfield fabs that we have engaged with have implemented