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JULY 2023 I PCB007 MAGAZINE 71 to scribe the traces and pads into the surface material (Figure 4). Aer metallization of the substrate and specialized electroplating 2 (dam- ascene fill), the metallization is flash-etched off, resulting in flush circuitry (Figure 5). Electrolytic Copper Filling Processes Filling an embedded trench but not the sur- face requires the new generation of copper plating chemistry. Vertical and Horizontal Methodologies One of the new critical process steps which must be mastered in this process is electro- chemical deposition (ECD) or electroplating of the trench. Some of the key process speci- fications, which were transferred from plating wafers to plating panels, include deposition uniformity, substrate throughput, and flexibil- ity for depositing multiple metal layers. Bulk plating, which is used in traditional PCB man- ufacturing, is not well suited to meeting these specifications. A new panel-plating tool (racking) was designed to address the needs of advanced packaging on a panel substrate. In place of bulk processing, the tool was designed with a com- pact series of cells which process a single panel at a time. Using a vertical orientation in the plating cell allows high throughput in a small footprint and enables the inclusion of a set of features which are required for advanced pack- aging plating applications. e large number of cells and an optimized overhead transport system allow flexible processing with different metals, and a throughput of up to 60 panels per hour. e panels are gripped in a rigid holder during transport and processing, minimizing any issues arising from panel warpage. Getting to a perfect copper surface required more than just replacing soluble anodes with IrO anodes. It required: 3 • New membrane technology to isolate the insoluble anode • Testing and implementing advanced equipment designs • Understanding the root causes for defects • Understanding the impact of basic cell design Shear Plate Agitation Deposition of metal from a bulk solution involves the transport of metal ions across a hydrodynamic boundary layer at the active sur- face 4 . e effective thickness and uniformity of this boundary layer is a critical factor in the deposition rate and the quality of the deposit. e vertical cell architecture of the panel plat- ing tool allows the direct application of shear Figure 4: Traces, vias, and pads (near landless) after ablation into the surface of the board 2 . Figure 5: Traces, vias, and pads from Figure 4 now metallized and plated 2 .