Glass PCBs

Sentak provides custom glass PCB solutions featuring excellent thermal stability, dimensional accuracy and optical transparency for high-performance electronics, optoelectronics, displays and semiconductor applications.

Ultra-Low Dielectric Loss(Df<0.001)

Near-Zero Coefficient of Thermal Expansion

Hermetic Sealing&Optical Transparency Options

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A Paradigm Shift in Substrate Technology

What Is a Glass PCB?

Glass PCB is a printed circuit board that uses glass as the substrate material instead of traditional FR-4 materials. Due to its excellent dimensional stability, low thermal expansion coefficient and optical transparency, glass substrate PCBs are suitable for advanced electronic applications requiring high precision and reliability.

Moving beyond conventional organic laminates (FR-4) and ceramic substrates, Glass Core PCBs represent a transformative approach for applications demanding the utmost in precision, signal integrity, and reliability. Utilizing a pure glass core (often borosilicate or specialty formulations) as the foundational substrate, this technology enables performance characteristics unattainable with standard materials.

Why Glass as a Core Material?

Near-Zero Coefficient of Thermal Expansion(CTE)

Matches silicon and other semiconductor materials,eliminating stress in packaged systems and during temperature cycling.

Ultra-Smooth Surface

Enables fabrication of extremely fine lines and spaces and reduces conductor loss at millimeter-wave frequencies.

Inherently Low Dielectric Loss

Excellent and stable electrical properties(Dk,Df)from RF through THz frequencies.

Thermal&Mechanical Rigidity

High thermal conductivity for a dielectric and exceptional flatness for large-panel processing.

Key Properties & Comparison to Conventional Materials

Performance Comparison Table:

Property	Standard FR-4	High-Frequency Laminate	Glass Core Substrate	Advantage for Design
Dimensional Stability (CTE)	14-17 ppm/°C	10-15 ppm/°C	~3.2 ppm/°C (matches Si)	Eliminates warpage, enables reliable large-size packages and chiplet interposers.
Dielectric Constant (Dk)	4.2-4.5 (varies)	2.2-3.5 (stable)	~5.3 (very stable with freq./temp)	Enables compact RF designs with predictable performance.
Dissipation Factor (Df) @ 10 GHz	~0.020	0.001-0.005	< 0.004	Ultra-low signal loss for millimeter-wave and high-speed digital.
Thermal Conductivity	0.3 W/mK	0.4-0.6 W/mK	~1.1 W/mK	Better heat spreading than polymers, improving device reliability.
Surface Roughness (Ra)	> 2 µm	~0.5 µm	< 0.1 µm	Minimizes skin effect losses, critical for >30 GHz frequencies.
Moisture Absorption	~0.1%	< 0.02%	~0%	Eliminates performance drift due to humidity, ideal for hermetic packages.

Primary Applications & Industries Served

Glass Core PCB technology is enabling innovation in several high-growth sectors:

RF&Millimeter-Wave Communications

● 5G/6G Infrastructure: Antenna-in-Package(AiP), beamforming modules, and mmWave front-end modules.

● Automotive Radar: 77/79 GHz radar sensors for ADAS, where stable performance across temperature is critical.

● Satellite&Defense: Phased array antennas, secure comms, and radar systems.

Advanced Semiconductor Packaging & Heterogeneous Integration

● Silicon/Glass Interposers: Providing ultra-fine RDL(Redistribution Layer)routing with superior electrical and thermal performance compared to organic interposers.

● Chiplet Integration: The ideal substrate for 2.5D/3D chiplet architectures due to CTE matching and high planarity.

● MEMS&Sensor Packaging: Provides a hermetic seal and stable platform for sensitive MEMS devices.

High-Performance Computing&Photonics

● Co-packaged Optics(CPO): Excellent substrate for integrating optical waveguides and electrical traces.

● Data Center Switches/Routers: Interposers and substrates for next-gen ASICs and FPGAs requiring massive I/O density.

"Design for Glass" Guide: Critical Rules for Success

Designing with glass substrates requires a paradigm shift from traditional PCB design, focusing on the material's brittleness and unique properties.

Our Recommended Glass PCB Design Practices:

Design Parameter	Recommended Practice(For High Reliability)	Common Pitfall to Avoid
Mechanical Layout&Corners	Use rounded corners and avoid sharp angles in the substrate outline to prevent stress concentration and cracking.	Designing with 90-degree corners, creating fracture initiation points.
Trace-to-Edge Clearance	Maintain a generous clearance(e. g. , >1. 0 mm)between any copper feature and the glass edge.	Routing traces too close to the edge, making the board susceptible to edge chipping.
Via Design&Pitch	For Through-Glass Vias(TGVs), use a conservative pitch≥3x the via diameter. Follow manufacturer guidelines for aspect ratios.	Overpopulating TGVs, compromising the mechanical integrity of the glass.
Thermal Management	Actively manage heat dissipation. While glass is thermally stable, it is a thermal insulator. Use thermal vias(if applicable)or direct thermal paths to a heatsink.	Assuming the glass substrate itself will effectively dissipate heat from power components.
Handling&Mounting	Design for uniform mechanical support. Specify mounting points that apply even pressure and avoid point loads.	Using point-to-point mounting or clips that induce bending stress.
Impedance Control	The highly stable Dk of glass allows for extremely precise impedance control. Provide clear targets for our thin-film process engineers.	Applying design rules meant for fibrous, anisotropic materials like FR-4.

Pro Tip: Engage Early in the Design Phase!Glass PCB fabrication is highly specialized. Contact our engineering team during the conceptual stage for guidance on material selection, stack-up feasibility, and design rule optimization tailored to our manufacturing processes.

Our Glass PCB Manufacturing Capabilities

We possess the specialized equipment and cleanroom environment required for high-precision glass substrate processing.

Technical Specifications of Glass PCB:

● Substrate Materials: Borosilicate Glass, Fused Silica/Quartz.

● Standard Thickness: 100µm to 1.1 mm.

● Metallization: Thin-Film(Ti/Cu, Cr/Cu seed layers)with Electrolytic/Electroless Plating.

● Minimum Trace/Space: 8µm/8µm(standard), down to 5µm(advanced).

● Through-Glass Via(TGV)Diameter: 30µm-100µm.

● Surface Finishes: ENIG, Electrolytic Gold, Immersion Silver.

Quality&Assurance:

● Standards: Fabricated and inspected to relevant MIL-PRF and IPC standards for hybrid circuits.

● Testing: 100%Electrical Testing.High-Frequency Network Analysis for RF performance.Microscopic inspection for trace integrity.

● Inspection: White Light Interferometry for surface planarity measurement.Cross-sectioning for TGV and metallization quality.

Design Considerations for Glass PCBs

Glass is dimensionally stable but more brittle than conventional organic PCB laminates. The mechanical design must therefore be considered from the beginning.

Recommended practices include:

Use rounded substrate corners
Avoid sharp internal cutouts
Maintain sufficient copper-to-edge clearance
Control TGV diameter, pitch and aspect ratio
Avoid excessive via density in one area
Provide uniform mechanical support
Avoid concentrated mounting pressure
Define thermal paths for heat-generating devices
Specify impedance requirements before circuit patterning
Coordinate optical windows with the metallization layout

Early collaboration with the Glass PCB Manufacturer helps align the design rules with the selected material and fabrication process.

Glass PCB vs FR-4 PCB

Glass PCB and FR-4 PCB use different substrate materials, resulting in differences in thermal performance, dimensional stability and application fields. Glass PCBs are mainly used for high-precision and advanced electronic applications, while FR-4 PCBs are widely used in general electronic products.

Feature	Glass PCB	FR-4 PCB
Substrate Material	Glass substrate	Fiberglass reinforced epoxy resin
Thermal Stability	Excellent thermal stability with low thermal expansion	Good thermal performance for general applications
Dimensional Stability	Higher dimensional accuracy and less deformation	Suitable for standard electronic applications
Electrical Performance	Suitable for high-precision and high-frequency applications	Widely used for conventional electronic circuits
Transparency	Available with transparent or optical glass substrates	Not transparent
Application	Optoelectronics, sensors, displays, semiconductor equipment	Consumer electronics, industrial control, power electronics
Cost	Higher due to advanced material and processing requirements	More cost-effective for mass production

Glass PCBs are ideal for applications requiring high precision, excellent stability and special optical properties, while FR-4 PCBs remain the preferred choice for general-purpose electronic devices due to their mature technology and cost advantages.

Custom Glass PCB Manufacturer

SENTAK provides custom Glass PCB manufacturing for applications requiring high dimensional stability, precise circuit geometry, low moisture absorption and stable electrical characteristics.

Unlike conventional FR-4 PCB production, glass substrate processing requires specialized via formation, metallization, thin-film patterning and handling controls. Our engineering team reviews the substrate material, thickness, circuit layout, through-glass vias and final assembly requirements before production.

Our custom Glass PCB services include:

Borosilicate glass substrates
Fused silica and quartz substrates
Through-glass via substrates
Fine-line copper circuit patterns
Thin-film metallization
Controlled impedance structures
Optical window integration
Glass interposers
Prototype and low-volume production
Surface finishing and electrical testing
Design-for-manufacturing review

As a China PCB Manufacturer, SENTAK supports projects from early design evaluation through prototype validation and repeat production.

Why Choose Sentak as Glass PCB Manufacturer

● Advanced PCB manufacturing capability
● Customized glass substrate solutions
● Strict quality control system
● Prototype to mass production support
● Engineering support for PCB design optimization
● Reliable delivery for global customers

Glass PCB FAQ

What is a Glass PCB?

A Glass PCB uses glass as the primary circuit substrate instead of an organic laminate such as FR-4. Conductive traces and vias are formed on or through the glass to create electrical interconnections.

What is a glass core PCB?

A glass core PCB uses a glass layer as the structural and dielectric core. It may include surface redistribution layers, metallized through-glass vias and additional conductive structures.

What are through-glass vias?

Through-glass vias are metallized holes that pass through a glass substrate and provide electrical connections between opposite surfaces or circuit layers.

Can SENTAK produce Glass PCB prototypes?

Yes. Prototype feasibility is evaluated according to the glass material, substrate thickness, circuit dimensions, TGV structure, metallization and order quantity.

Are Glass PCBs suitable for high-frequency applications?

Glass substrates can provide stable dielectric properties and smooth surfaces that are useful for selected RF and millimeter-wave applications. Performance depends on the specific glass formulation, circuit structure and operating frequency.

Can Glass PCBs include optical windows?

Yes. Transparent areas or optical windows can be incorporated when the material, metallization pattern and assembly structure are properly coordinated.

What affects Glass PCB cost?

The main cost factors include glass material, substrate size, thickness, TGV quantity, via dimensions, circuit density, metallization, surface finish, testing requirements and production quantity.

Can components be assembled directly onto a Glass PCB?

Component attachment may be possible using soldering, conductive adhesives, wire bonding, flip-chip bonding or other packaging methods. The appropriate process depends on the pad finish, component type and thermal requirements.

Looking for a Glass PCB Manufacturer for an RF, photonics, sensor or advanced packaging project?

Send SENTAK your substrate drawing, circuit files, TGV requirements and production quantities. Our engineering team will evaluate the design and provide recommendations for material selection, metallization, via construction and manufacturing feasibility.

Get a Glass PCB Quote