A Study of the Impacts of Current Density on High Aspect Ratio Through Holes Using a Novel Modular Vertical Electrolytic Copper Plating Tool

The increasing prominence of high aspect ratio (HAR) through holes in printed circuit board (PCB) and integrated circuit (IC) substrate manufacturing is driven by the ongoing evolution of high-performance electronics, including the growing influence of artificial intelligence (AI) and machine learning. These technologies demand unprecedented levels of data throughput, signal integrity, and power efficiency. As devices shrink and component density rises, HAR through holes enable the vertical interconnection of increasingly complex circuit architectures. This is especially critical in high-density interconnect (HDI) structures, where space savings and electrical performance are key.In AI-driven applications, from cloud data centers to edge computing devices, substrates must support high I/O counts, low-latency communication, and reliable signal transmission across multilayer interconnect stacks. HAR vias are defined by their narrow diameter and deep penetration through thick panels this help meet these requirements by minimizing signal path lengths and reducing parasitic inductance and capacitance. These performance enhancements are essential for AI processors, accelerators, and advanced memory interfaces operating at high frequencies.In addition to electrical benefits, HAR through holes also contribute to mechanical integrity and thermal reliability. As substrates continue to become thinner and more layered, maintaining structural stability during thermal cycling, such as reflow soldering or operational heating, becomes increasingly important. HAR structures provide mechanical anchoring and consistent connectivity between layers, improving overall reliability in advanced electronic packages.The increasing complexity of heterogeneous integration which includes the stacking or side-by-side placement of logic, memory, and AI-specific SIC, has further fueled the demand for vertical interconnect solutions. Technologies such as 2.5D and 3D IC packaging rely heavily on precise, high aspect ratio via structures for routing signals between multiple functional components within compact footprints.To explore fabrication capabilities and process optimization for HAR through holes, this paper presents an evaluation using a novel modular vertical electroplating system developed by GreenSource Engineering (GSE). This electroplating cell is designed to merge the advantages of horizontal and vertical conveyorized plating lines while offering unmatched process flexibility and modular control. The study focuses on 16:1 aspect ratio through holes; specifically, 0.2 mm diameter vias in 3.2 mm thick PCB panels.Three different current density settings will be applied in a controlled plating sequence to assess process uniformity, via quality, and repeatability. The objective is to determine optimal operating conditions for reliable metallization of HAR vias in a high-throughput, production-relevant environment. By leveraging this advanced vertical plating platform, the study aims to highlight scalable approaches for manufacturing next-generation substrates that meet the performance demands of AI and advanced electronics.The plating tools uniquely designed compatibility with GSE’s patented closed loop water recycling system will also be touched upon.