Glass Substrate Series · 06

Thermal Management —
Overcoming Glass's Achilles Heel

Glass conducts heat 100x worse than silicon. In a world where AI accelerators dissipate over 1,000 watts, that's a serious problem. Here's how the industry is solving it.

Glass Substrate Thermal Management Intermediate ~9 min read

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Glass substrates' signal loss advantage over silicon and ABF is now well established. But every strength comes with a trade-off. Glass has roughly 1/100th the thermal conductivity of silicon and about half that of ABF. In an era where a single AI accelerator dissipates hundreds of watts, this weakness could be fatal — unless engineered around. Here's how.

Thermal management is one of the last major hurdles to glass substrate commercialization. If TGV yield is the "can we make it?" problem, thermal management is the "can we use it?" problem. No matter how clean the signal, an overheating chip throttles performance and shortens lifetime.

Why Glass Can't Conduct Heat — The Material Physics

Thermal conductivity measures how quickly a material transfers heat. Higher is better for heat dissipation.

Thermal Conductivity (W/mK) — Higher is Better

Copper (traces)

400

Silicon

148

ABF Substrate

0.3–0.5

Glass Substrate

1–2

Glass thermal conductivity: 1–2 W/mK. About 1/100th of silicon. On paper, a disqualifying weakness. But there's a critical reframe: the substrate doesn't need to conduct heat.

💡 The Key Reframe

A chip's heat doesn't primarily travel down through the substrate to the PCB. It travels up through the heat spreader and cooling system attached above the chip. The substrate's thermal conductivity matters far less than the chip-to-heat-spreader interface design. Glass's low conductivity is a real weakness — but an engineerable one, not a fundamental disqualifier.

AI Accelerator Package — Heat Flow Paths

Four Thermal Solutions — How the Industry Is Solving It

🔶

Heat Spreader Optimization

High-conductivity material (copper, diamond composite) bonded above the chip to rapidly spread and dissipate heat. The primary thermal management tool in glass substrate packages.

Effect: 50–60% reduction in thermal resistance

🟢

Thermal Vias

Copper-filled vertical channels through the glass substrate create a secondary downward heat path. Formed using a similar process to TGVs.

Effect: 10–20x improvement in vertical conductivity

🔵

TIM (Thermal Interface Material)

High-conductivity material filling the microscopic air gaps between chip and heat spreader. Indium, silver sintering, and thermal pastes all under active development.

Effect: 80%+ reduction in interface thermal resistance

🟣

Microchannel Cooling

Microfluidic channels etched into the substrate allow coolant to circulate directly. Most powerful solution but highest structural complexity and cost. Targeting next-gen data centers.

Effect: 5–10x higher heat density capacity

Heat Spreader Materials — What's Being Used

Material	Thermal Conductivity	Cost	Deployment
Copper (Cu)	400 W/mK	Low	Current mainstream
Diamond Composite	500–800 W/mK	Very high	High-end servers, defense
Graphene Composite	700–1,000 W/mK	High (declining)	R&D / early commercialization
AlN (Aluminum Nitride)	170–200 W/mK	Medium	Ceramic packaging
Indium (TIM)	82 W/mK	Medium	High-performance CPU/GPU standard

⚠ The Reality of AI Chip Heat

Nvidia H100 TDP: 700W. The B200 exceeds 1,000W. Over one kilowatt of heat from a package the size of two palms. Dissipating this reliably in a glass substrate package is a mandatory engineering requirement for 2027–2028 production targets.

The Thermal Management Ecosystem — Who's Solving It

Glass substrate thermal management can't be solved by substrate manufacturers alone. TIM materials, heat spreaders, cooling systems, and simulation tools all need to align.

Glass Substrate Thermal Management Value Chain

TIM Materials

Indium Corp · Henkel · Duksan

»

Heat Spreaders

Sumitomo · Materion · AMC

»

Thermal Via Equip.

Philoptics · LPKF

»

Thermal Simulation

Ansys · FloTHERM

»

AI Chip Customers

Nvidia · Intel · AMD

🧪 TIM and Heat Spreader Materials

Indium Corporation USA

TIM and solder materials

Industry standard

World leader in indium-based high-conductivity TIM materials. Supplies indium foil and solder for GPU packages. Developing next-generation TIM materials for glass substrate packages.

»Higher-power AI chips directly drive TIM demand growth

Duksan Hi-Metal Korea

Solder balls and TIM materials

Growing

Korea's #1 solder ball supplier for semiconductor packaging. Developing low-temperature solder and TIM materials for glass substrate packages. Supply chain links to Samsung Electro-Mechanics.

»Key domestic materials player in glass substrate transition

Sumitomo Electric Japan

Diamond composite heat spreaders

Premium market

Developing diamond-copper composite heat spreaders with 500+ W/mK conductivity targeting extreme-TDP AI chip packages. High cost limits to premium applications.

»B200-class and above ultra-high-TDP package market

🌊 Cooling Systems and Data Centers

Vertiv USA

Immersion cooling and DLC

Market leader

Leads AI data center immersion cooling and direct liquid cooling (DLC) systems. The system-level partner for handling heat that glass substrate packages generate. AI chip TDP increases directly drive Vertiv demand.

»AI chip heat density growth = cooling infrastructure demand surge

Aavid (Boyd) USA

Heatsinks and thermal solutions

Partner

High-performance heatsink and vapor chamber design and manufacturing. Developing integrated heat spreader-heatsink solutions optimized for glass substrate package geometry.

»Package-level thermal design integration capability

Nvidia USA

Customer and thermal spec setter

Key customer

Managing 1kW+ heat dissipation is a defining design constraint for B200 and Rubin series. Nvidia's thermal requirements for glass substrate adoption define the standards the entire supply chain must meet.

»Nvidia's specs set the thermal bar for the whole industry

📌 Key Takeaways

Glass substrate thermal conductivity is 1/100th of silicon — but the primary heat path in chip packages runs upward through the heat spreader, not downward through the substrate. Heat spreader optimization, thermal vias, high-performance TIM, and microchannel cooling combine to make this weakness manageable. The ecosystem is already forming: TIM (Indium Corp, Duksan), heat spreaders (Sumitomo), cooling systems (Vertiv), and thermal simulation tools (Ansys). The thermal problem is glass's Achilles heel, but it is an engineering challenge, not a fundamental disqualifier.

Glass Substrate Thermal Management Heat Spreader Thermal Via TIM Immersion Cooling AI Accelerator Nvidia

← Previous · 05

AI Accelerators and Signal Loss — How Glass Keeps the Signal Intact

Dielectric loss advantage and the signal integrity ecosystem

Next · 07 »

Flatness and Yield — The Final Barrier to Glass Substrate Mass Production

Why sub-micron flatness matters and how manufacturers are improving yield