Hermetic glass-to-metal seals are used in demanding applications where it is necessary to transfer electricity from one component to another. The qualities of a good glass-to-metal seal include:
- gas tight (hermeticity)
- high electrical resistance
- high breakdown voltage
- good chemical corrosion resistance
- good thermal shock
- high mechanical strength
- low weight
Glass-to-metal hermetic seals can typically be separated into two types
Matched Seals
In a matched seal, the thermal expansion of the glass and metal are close – normally within 10%. Stress in the glass is generally small. The oxide layer formed on the metal bonds with the glass and metal, forming the seal.
Mismatched or Compression Seals
Compression seals are formed using glass and metal materials with differing thermal expansions. The contraction of the metal exceeds that of the glass and exerts compressive forces on the glass.
Glass-to-Metal seals are used in a wide variety of applications. Below are just a few examples:
Automotive
- Power Train Testing
- Air Bag Testing
- Anti-Lock Braking Systems
- Fuel System Testing
- Exhaust Gas Measurement
- Fuel Injection Pressure Measurement
- Automatic Transmission Worm Channel Pressures
- Lubrication System Testing
- In Cylinder Pressure Measurement
- Crash Sensors
- Airbag Initiators
- Seatbelt Pretensioners
- Catalytic Converters
- Rollover Sensors
- Yaw Rate Sensors
- Alternative Fuel (LPG, CNG and Hydrogen) Pressure Sensors
- Tire Inflation Monitoring
- Steering Controls
- Fuel Control Valves
- Infrared Vision Systems
Aviation
- Sensors
- Brake
- Flap
- Rudder
- Torque
- Oil
- Fuel
- Hydraulics
- Speed
- Temperature
- Altimeters
- Engine Control and Monitoring
- Turbine and piston ignition
- Flight data recorders
- Pressure switches
- Transducers for Rotocraft:
Marine
• Engine Control Systems
 • Firemains
• Air guns
• Depth Sensors
• Rudder Control Systems
• Desalination Systems
• Towed Seismic Arrays
• Subsea Wellhead Controls
• Refrigeration Systems
• Equipment Health Monitoring and
Predictive Maintenance Systems
• Shipboard High and Low Pressure Air Compressors
• Membrane Dehydrators for shipboard pneumatic
systems and wave guide radar systems
Medical
- Feed throughs
- Various implantable devices
- Various Sterilized electronics
- Cardiac pacemakers
- Defibrillators
- Cochlear implants
- Implantable drug pumps
- Implantable heart pumps
- Diagnostic imaging
- UV lasers for surgical drilling, cutting and “cold marking” bone
- Surgical drills / saws
Lighting
- Compact Florescent
- Halogen (PAR, HIR)
PAR: Parabolic Aluminized Reflector
HIR: Special coating reflects infrared heat back onto element consuming less energy
- Miniature automotive lighting (signals, cabin lighting)
Resource Exploration and Recovery
- Wire line tools
- MWD (Monitor While Drilling) Tools
- LWD (Logging While Drilling) Tools
- Drill Guidance Systems
- Geophones and Hydrophones
- Down hole pressure and temperature monitoring
Industrial and Communications
- Pressure and Temperature Sensors
- Transmitters
- High Vacuum Gauge sensors
- Radiation Detectors
- Commercial Power Generation
- Test and Measurement Equipment (RF Frequency)
- Satellites
- Optical Networking Components
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