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64 PCB007 MAGAZINE I JULY 2025 thousands of through-holes are needed to meet the escalating I/O requirements of GPUs and other high-performance processors. Pulse plating ensures reliable per- formance across both densely clustered and isolated areas, reducing process variation and enhancing downstream reliability. Meeting the Demands of AI Substrate Designs Traditional package substrates feature fewer than 300,000 through-holes on a 510 mm × 515 mm panel. In contrast, substrates engineered for AI applications often exceed 350,000 through- holes—reflecting the need for far greater I/O interconnectivity. These complex panels include regions of both high and low hole density, posing serious challenges for uniform copper deposition. MKS' Atotech's recent evaluations of three such AI-specific panel designs demonstrate the supe- rior performance of pulse plating in addressing these challenges. The tests highlight the technol- ogy's ability to ensure consistent copper thickness, reduce surface thickness gaps, and maintain high plating quality across complex geometries—fulfilling the stringent requirements of today's AI and HPC applications. High Hole-density Surface Factor (HHD-SF): A Key Metric for Copper Plating Performance One of the major advancements in the evaluation of copper plat- ing technology is the introduc- tion of the high hole-density sur- face factor (HHD-SF). This metric quantifies the complexity of plating designs with varying hole densities and the challenges they present for uniform copper depo- sition. A higher HHD-SF value indicates a more challenging plating process, with clustered through-holes and narrower pitch distances making it more difficult to achieve uniform copper distri- bution. Understanding and man- aging HHD-SF is critical for opti- mizing plating processes and ensuring consistent performance in advanced package substrates. Optimized Plating Electrolyte and Equipment Meeting the rigorous demands of AI-driven applications requires a holistic planning approach— one that tightly integrates special- ized electrolytic chemistry with advanced equipment platforms. E xa m p l e fo r C a l c u l at i n g t h e H i g h H o l e - d e n s i t y S u r fa c e Fa cto r ( H H D - S F ) ▼ F i g u re 2 : D ef i n i t i o n of g r i d s u r fa c e at h i g h h o l e d e n s i t y a re a s . ▼ Figure 3: D efinition of total grid sur fac e at high hole densit y areas.