How Through-Glass Via (TGV) Technology is Reshaping the AI-Driven Packaging Industry
1. What is TGV? — From “Through-Silicon” to “Through-Glass” Interconnects
In the era of rapidly evolving advanced packaging, Through-Glass Via (TGV) technology has emerged as a key foundational enabler connecting optics, electronics, and AI computing systems.
A decade ago, TSV (Through-Silicon Via) enabled vertical interconnects between chips. Today, TGV extends this concept further, integrating electrical, optical, and mechanical signals on a single, insulating, transparent, thermally stable, and low-dielectric glass substrate.
1.1 Core Principle of TGV
TGV involves creating micrometer-scale vias in a glass substrate using laser modification and chemical etching, followed by metallic filling (typically copper or tungsten) to establish vertical electrical connections. These vias allow sensors, optical modules, and AI accelerators to be integrated in extremely compact, short-path arrangements.
1.2 Key Advantages over Traditional Organic Substrates or Silicon Interposers
- Low dielectric constant and low loss – ideal for high-speed AI signal transmission and millimeter-wave packaging.
- Optical transparency – enables co-integration of optical and electrical signals, unlocking photonic-electronic hybrid designs.
- High thermal and dimensional stability – thermal expansion closer to silicon reduces mechanical stress, enhancing package reliability.
Summary: TGV enables seamless interconnection between AI compute units, edge sensors, and optical modules.
2. Why TGV is Crucial in the AI Era
2.1 Dual Drivers: AI Compute and Sensing
The rapid growth of AI chip compute power has made interconnect bandwidth and thermal management major bottlenecks. Traditional organic substrates (BT, ABF) experience significant signal loss at GHz frequencies, whereas TGV glass substrates—with low dielectric constant (Dk ≈ 5.5) and low dissipation factor (Df ≈ 0.005)—enable higher transmission rates with lower latency.
AI applications are migrating from central compute to edge intelligent sensing, including:
- Autonomous driving: LiDAR, cameras, and IR sensors
- Consumer electronics: 3D vision and gesture recognition modules
- Medical imaging and industrial inspection: high-precision optical modules
These systems require co-located optical and electrical integration, which the transparency and stability of glass TGV substrates naturally support.
2.2 Ecosystem-Driven Industrialization
From equipment providers (e.g., Germany’s Trumpf, Japan’s Hamamatsu) to specialty glass manufacturers (Corning, AGC, NEG), and packaging houses (ASE, Amkor, SPIL), industry players are accelerating TGV deployment.
In AI-driven packaging architectures, TGV + Glass Interposer is gradually becoming the second mainstream path alongside silicon interposers.
3. How TGV is Implemented — From Process to System-Level Integration
3.1 Microvia Formation: Laser-Modified Chemical Etching (LMCE)
Mechanical drilling or pure laser ablation often causes oversized vias, high stress, and cracking.
The LMCE process involves localized laser modification inside the glass, followed by selective wet etching to create vias with diameters of 20–80 µm and aspect ratios >10:1. This method offers high throughput, low stress, and excellent yield, making it the core approach for TGV mass production.
3.2 Metallization and Filling: Balancing Conductivity and Reliability
Vias are first coated with a seed layer (Ti/Cu) via sputtering, followed by chemical or electroplating.
To avoid voids and electromigration, industry practices optimize current density, additives, and flow control. Modern TGVs can achieve via resistances below 10 mΩ, meeting high-speed AI interconnect requirements.
3.3 Redistribution Layer (RDL) and Multi-Layer Interconnects
Fine metal traces are formed on the glass surface and connected via TGVs, enabling multi-chip and multi-module high-density interconnects.
Glass stability allows line width/spacing down to 2 µm, surpassing traditional organic substrates and supporting chiplet-scale packaging.
3.4 Inspection and Reliability Control
A combination of inline optical inspection, X-ray CT, and holographic stress monitoring detects voids, cracks, and delamination in real-time—ensuring industrial-scale reliability.
4. Challenges and Directions for Breakthroughs
4.1 Thermal Stress and Reliability
Glass and copper have different coefficients of thermal expansion (CTE mismatch), potentially causing cracks or delamination.
Solutions: CTE-matched glass (e.g., Corning Willow Glass), intermediate buffer layers, or optimized via geometries.
4.2 Micro-Cracks and Via Geometry Control
High-energy laser processing may induce subsurface cracks affecting long-term reliability.
Solutions: Multi-pulse laser optimization and post-etch polishing significantly improve yield.
4.3 Cost and Throughput
TGV is more complex and slower than ABF or BT substrates.
Solutions: Panel-level packaging (PLP) and automated inspection can reduce costs by 30–40% within 3–5 years.
4.4 Lack of Standardization
Via diameters, spacing, and thickness vary among manufacturers.
Solutions: SEMI, IEEE, and JEDEC are developing standards for metrics and testing, critical for global scale-up.
5. Future Trends and Industry Recommendations
5.1 Technology Integration
TGV will increasingly merge with:
- Co-packaged optics: transparent glass can host optical waveguides, enabling co-platform electrical-optical transmission
- Heterogeneous AI chip packaging: TGV supports high-density interconnects across diverse compute chips
- MEMS and sensor integration: glass substrates offer rigidity and transparency, ideal for next-generation smart modules
5.2 Industry Chain Layout
- Upstream materials: high-purity, low-CTE glass, plating chemicals
- Midstream equipment: laser-modification systems, chemical etching tools, precision plating machines
- Downstream applications: AI camera modules, AR/VR devices, automotive radar, AI accelerators
Japan and South Korea lead in materials and equipment, while China is rapidly advancing production lines and R&D capabilities. Some wafer-level packaging houses already operate TGV glass interposers + chiplet assembly lines, achieving tens of thousands of glass interposer units per month.
5.3 AI and Big Data in Yield Control
AI is not only an application endpoint but also a manufacturing optimization tool. Machine vision and AI algorithms predict via shape and fill quality, enabling yield rates exceeding 99%, forming a closed-loop AI-driven manufacturing ecosystem.
6. Conclusion: TGV as a Key Window into the AI Packaging Era
TGV does not replace TSVs or organic substrates—it is a critical component in multidimensional AI interconnect systems. It enables packaging to evolve from purely electrical connections to electrical-optical-thermal-structural co-optimization, supporting miniaturization, high speed, and high reliability for AI devices.
Over the next five years, as photonic-electronic integration, chiplet packaging, and panel-level packaging become widespread, TGV will emerge as a new competitive high ground in the AI industrial chain.
For equipment makers, material suppliers, or IDM packaging companies, the strategic window for TGV deployment is now, laying the groundwork for the next wave of AI-driven innovation.
📩 Contact SIMVACO
For inquiries about advanced vacuum PVD coating quipment for TGV, Anti-reflection, automotive displays, and high-end packaging:
Contact Person: Simon
Phone / WhatsApp: +86 15958205967
Email: simon@simvaco.com
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