This article is adapted from a contribution by “Electronic Chief Intelligence Officer (E-CIO)” and originally published in the 2nd issue of HKPCA Journal 2025. For more journal highlights, visit: https://www.hkpca.org/journal/.
Recently, Mr. Albert Tseng, Product Manager of MacDermid Alpha Electronics Solutions, delivered a keynote speech titled “Optimization Research on Direct Metallization and Acid Copper Plating Processes” at the International Electronic Circuits (Shenzhen) Exhibition Forum. He delved into MacDermid Alpha’s latest research achievements in Direct Metallization (DM) and plating processes, pointing out that direct metallization, as an environmentally friendly, efficient and reliable alternative, is gradually replacing the traditional electroless copper plating process and becoming a
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Mr. Tseng reviewed the development history of direct metallization processes. From the first-generation carbon powder technology (Carbon PTH) launched by MacDermid Alpha in 1984, to the first-generation graphite technology (Graphite Gen 1) based on more conductive graphite in 1993, and then to its application in HDI board production in the 2000s, direct metallization processes have continuously improved their performance and reliability to meet the growing demand for higher circuit density and refined production.
In 2017, as smartphone motherboards evolved from single-piece to two-piece designs to expand battery capacity, the line width and spacing reduced from 40μm to 30~35μm, making high-end mSAP processes a necessity. The core of the mSAP process lies in the application of ultra-thin copper foil, which requires strict control of the total etching amount. To address this, MacDermid Alpha launched the second-generation graphite technology (Graphite Gen 2). By optimizing formulas and processes, graphite particles were ground to below 350nm, reducing the etching amount from the traditional 0.8~1μm to less than 0.5μm, perfectly adapting to high-end fine-line processes. In addition, the introduction of Wet Etch technology further simplified the production process, improved efficiency and reduced production costs.
Addressing board manufacturers’ concerns about the differences between carbon-based chemicals, graphite Shadow and second-generation graphite Shadow Plus chemicals, as well as precautions for circuit matching, Mr. Tseng focused on interpreting the latest wet etching process. Compared with the traditional dry etch process of “coating, drying, etching”, wet etching omits the drying step and can be directly etched after coating. This improvement not only significantly reduces electricity costs (customer feedback: two drying tanks cost at least 2,000 RMB per day, and up to 3,000-4,000 RMB for larger production lines) but also simplifies the process and improves production efficiency.
The core advantage of the new chemical formula is its strong adsorption on resin in a wet state—similar to modern waterproof tape that can adhere firmly even when soaked in water. Thus, it can directly enter the etching tank to remove graphite particles on the copper surface. During etching, the wet gaps between particles allow the chemical to quickly penetrate to the bottom copper surface and react, efficiently removing graphite particles while reducing the total etching amount. In contrast, traditional processes require penetration and diffusion to reach the copper surface, resulting in higher total etching amount. The combination of second-generation graphite chemicals and wet etching process, with the advantages of no drying step, low cost, high efficiency and low etching amount, marks an important innovation in circuit board micro-etching processes.
Mr. Tseng clearly identified four significant advantages of direct metallization processes over traditional electroless copper plating processes through detailed comparisons. Firstly, it is more environmentally friendly. Traditional electroless copper plating requires the use of harmful substances such as formaldehyde, while direct metallization processes completely avoid these substances, complying with increasingly strict global environmental regulations. Mr. Tseng shared a distressing industry case: his predecessor developed leukemia due to long-term formaldehyde exposure, highlighting the core value of direct metallization processes in protecting employee health and fulfilling environmental responsibilities.
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Secondly, it is more efficient. Direct metallization processes have shorter workflows, requiring fewer equipment and chemicals. For example, traditional electroless copper plating requires multiple water washing tanks and chemical tanks, while the latest Shadow Plus direct metallization process only needs 3 water washing tanks and 3 chemical tanks, greatly simplifying the production process. Thirdly, it has higher reliability. The metal layer formed by direct metallization processes bonds more closely with the substrate. MacDermid Alpha’s IST test results show that both 22-layer PTH thick boards and 6-layer microvia boards using the second-generation graphite direct metallization process can pass 1,000, 2,000 or even 3,000 thermal cycle tests, demonstrating significant reliability advantages. Fourthly, it has better economy. Equipment investment and operating costs are lower: electroless copper plating consumes at least 700ml of chemicals per square meter, while the Shadow Plus direct metallization process consumes a maximum of 70ml per square meter, only 1/10 of the former, and the amount of waste liquid is also reduced by 1/10. In terms of equipment space, for production lines with the same 2m/min speed limit, the Shadow Plus process only needs 22 meters in length, while traditional electroless copper plating requires at least 44 meters, saving half the space and doubling the production capacity in the same space.
