IPC International Community magazine an association member publication
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www.atotech.com Glass is transitioning from pilot programs to commercial manu facturing because it offers dimensional stability, low warpage, smooth surfaces, and a coefficient of thermal expansion (CTE) similar to silicon's. These properties make glass highly attrac tive for heterogeneous integration, largepanel processing, and increasingly demanding AI/HPC package architectures. How ever, these properties also make metallization more challenging because glass is chemically inert and mechanically brittle. Trends and manufacturing context Glass is becoming an increasingly relevant option for advanced packaging applications that require low loss, tight overlay, and through-substrate interconnects. For PCB and substrate man ufacturers, the key question is no longer whether glass will play a role, but how plating on glass can be translated into a stable, manufacturable panellevel process that meets both technical and economic requirements. The solution – A three-step process MKS' Atotech has developed a three-step wet metallization process for plating on glass. This process is designed to address three main challenges of the material: reliable adhesion, con formal seed coverage, and void-free TGV filling. The strength of this process lies in its sequential nature, with each step prepar ing the foundation for the next and creating a coupled process flow that supports downstream fine-line manufacturing. 1. Vitrocoat ® GI – Adhesion promotion. A nanometer-thin metal oxide layer forms a chemical bond to the glass which is then able to support wet metallization. This improves adhesion to inert glass surfaces, eliminating the need for a sputtered adhesion layer. 2. Cupratech ® GI M – Electroless copper seed. An autocatalytic copper seed layer is deposited onto the pre-existing vitrocoat layer. This provides uniform depo sition across the glass surface, with unrivalled coverage into high-aspect-ratio TGVs, which can't be achieved with traditional PVD or "sputtered" methods. 3. InPro ® Pulse TGV – TGV filling. Reverse pulse plating guides copper growth toward the via center. This enables void-free filling with low overburden. It addresses one of the main challenges in TGV metallization and helps ensure electrical, thermal, mechanical, and sur face planarity for downstream processes. Outlook Manufacturers that establish glass metallization capabilities during the current qualification phase will be better positioned for the next production increase. With panel sizes up to 515 × 510 mm already demonstrated, the focus is shifting towards industrialization, glass handling discipline, and process integration rather than basic feasibility. Conclusion As the use of glass substrates becomes more widespread, wet-chemical metallization provides a practical solution to the material's three main challenges: adhesion, conformal coverage, and void-free TGV filling. The above-described process creates a manufacturable path for plating on glass by combining adhesion promotion, electroless copper seeding, and reverse-pulse TGV fill in one coupled sequence. This sequence supports the fine-line downstream requirements of next-generation package substrates. Roger Massey Senior Manager Technical Marketing Manager and Global Product Manager PTH/ STT at MKS' Atotech roger.massey@mks.com +44 7881 26 56 92 Wet metallization for glass substrates – From market trend to manufacturable flow