Why Oxygen Sensor Gasket Is Suitable For High-Temperature Sealing and Insulation

Oxygen sensor gaskets are critical components in automotive exhaust and industrial combustion systems. Operating in harsh environments with high temperature, corrosive gases, and thermal shock, these gaskets must provide hermetic sealing and electrical insulation simultaneously. Proper material selection, structural design, and joining technology directly determine sensor lifetime and measurement stability.

Application Background and Challenges

Operating Environment:

• High-temperature exhaust gas with potential moisture, salt spray, and sulfides

• Frequent hot-cold cycling and vibration/shock loads

Design Objectives:

• Hermetic sealing

• Dimensional stability

• Electrical safety

• Corrosion resistance and assembly reliability

Common Risks:

• Thermal stress cracking

• Seal surface wear and leakage

• Insulation degradation over time

Material Selection Strategies

Lead-Free Low-Temperature Sealing Glass Options:

• Bismuth-based (Bi): 580–600 °C → Excellent wettability and hermetic strength; ideal for high vacuum and stable sealing.

• Phosphate-based (P): 520–550 °C → Eco-friendly, lower thermal stress, strong candidate for replacing leaded glasses.

Both are optimized for stainless steel/Kovar glass-to-metal or ceramic-to-metal seals.

Dimensions and Geometry (Customizable)

• Typical ID: 3–30 mm

• Typical OD: 8–45 mm

• Thickness: 0.5–4.0 mm

Tolerances:

• OD/ID ±0.10 mm

• Thickness ±0.05 mm (standard); tighter available on request

Design Notes:

• Chamfer and fine-grind sealing surfaces to prevent assembly damage

• Provide adequate creepage distance to avoid dielectric breakdown

• Prefer face or ring contact with metals; control surface roughness for reliable sealing

Manufacturing and Joining Processes

Ceramic Fabrication:

• Pressing / injection molding → Sintering → Grinding / chamfering

Optional Metallization:

• Mo-Mn metallization → Ni/Au plating for brazing or soldering

Joining Technologies:

• Active Brazing (Ag-Cu-Ti alloys): Reacts directly with metals

• Sealing Glass: Applied under Bi- or P-based process windows, with controlled heating/cooling cycles in vacuum or controlled atmospheres

Typical Performance Parameters (Reference)

Quality Validation and Reliability Testing

• Hermeticity: Helium leak test or pressure decay to specified leak rate

• Thermal Cycling: e.g., −40 °C ↔ 800 °C repeated cycles

• Corrosion Tests: Salt spray and chemical immersion (per OEM specs)

• Dimensional / Surface QC: Edge chipping, flatness, surface roughness

• Electrical QC: IR resistance, dielectric strength, partial discharge (if HV-related)

Failure Modes and Countermeasures

• Thermal Cracking / Leakage → Improve CTE matching; optimize cooling curve; select P-glass for reduced thermal stress

• Seal Surface Wear → Precision surface finish; control assembly force

• Insulation Degradation → Enhanced cleaning/drying; increase creepage distance; add edge chamfers

RFQ Checklist for Oxygen Sensor Gaskets

• Operating temperature range and cycling conditions

• Target hermetic leak rate & test method (helium, pressure decay)

• Material preference: Alumina / Steatite / Cordierite / Glass-ceramic

• Joining method: Metallization + brazing / Active brazing / Glass sealing (Bi 580–600 °C; P 520–550 °C)

• Drawing & tolerances, surface roughness, packaging needs, and annual volume

FAQs

Q: Why use sealing glass instead of purely mechanical compression?
A: Sealing glass provides long-term hermeticity and insulation at lower processing temperatures, reducing stress compared to mechanical preloading.

Q: Can it be sealed directly to stainless steel?
A: Yes. Both Bi-based and P-based lead-free glasses are engineered for stainless steel/Kovar, ensuring excellent wetting and bonding.

Q: How tight can tolerances be?
A: Standard OD/ID ±0.10 mm and thickness ±0.05 mm; tighter tolerances possible with precision grinding, depending on cost and volume.