Understanding the Role of Powder Glass in Ceramic-to-Metal Sealing Systems

Release time：2025-05-07

Creating robust hermetic seals between ceramic and metal components is essential in sectors such as aerospace, defense, and medical electronics. The different thermal and mechanical behaviors of these materials make bonding a challenge. Powder glass offers a scientifically engineered solution, enabling strong, stable, and vacuum-tight joints through sintering and thermal matching.

Why Ceramic-to-Metal Sealing is Challenging

Ceramics like alumina and zirconia have low thermal expansion and high stiffness, while metals expand more and have higher ductility. Direct bonding often results in stress and cracking. Powder glass works as a compliant interlayer that balances these differences through viscous flow sealing at moderate temperatures.

Why Use Powder Glass?

Customizable CTE to match ceramics and metals
Excellent adhesion to oxide surfaces
Proven hermeticity (leak rates < 10⁻⁸ atm·cc/sec)
Works with precision geometries in feedthroughs and implants

Powder Glass Composition Types

Type	Base System	Softening Temp (°C)	Strengths	Limitations	Applications
Borosilicate	SiO₂–B₂O₃–Al₂O₃	750–850	High strength, dielectric, chemical resistance	Requires high-temp processing	Aerospace, vacuum packaging
ZnO–Bi₂O₃	Zinc-Bismuth Oxide	500–600	Low-temp sintering, strong flow, good wetting	Moderate acid resistance	Sensors, microelectronics
Phosphate Glass	P₂O₅–SnO–ZnO	450–550	Eco-friendly, RoHS compliant, low stress	Needs devitrification control	Medical devices, low-temp circuits

Matching Guidelines

Ceramic Type	Recommended Glass Systems	Compatible Metals
96% Alumina	ZnO–Bi₂O₃, Borosilicate	Kovar, Nickel, 304/316 Steel
Zirconia (ZrO₂)	Phosphate glass with dopants	Titanium, Ni-alloys
AlN	Bi₂O₃-based, low-alkali glass	Fe–Cr–Al, Nickel

Conclusion

Powder glass enables long-lasting, vacuum-tight seals between ceramics and metals where traditional bonding fails. Its adaptability to different thermal environments and compliance with environmental standards make it an essential material in advanced sealing applications.

Design Takeaways for Engineers

Match CTE values within ±1 × 10⁻⁶/K
Use low-softening formulations for temperature-sensitive components
Sinter in dry, controlled environments and cool slowly
Pre-treat surfaces for better wetting and adhesion
Validate seals with helium leak and thermal cycling tests