Relay alumina ceramic housing is a shaped alumina (Al₂O₃) ceramic body used as the insulating and structural shell of a relay, especially in high-voltage DC (HVDC), EV contactors, vacuum relays and other high-energy switching devices.
Relay Alumina Ceramic Housing Benefits
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High insulation margin for compact HV designs: 95–96% alumina with dielectric strength around 8–9 kV/mm enables shorter creepage paths and compact relay envelopes while maintaining insulation safety margins.
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Hermetic, gas-tight ceramic body for vacuum or gas-filled relays: Dense, non-porous alumina combined with metallized and brazed joints supports helium leak testing down to 10⁻⁹–10⁻¹² Pa·m³/s, meeting typical vacuum relay and HVDC contactor requirements.
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Metallization compatible with common braze alloys: Mo–Mn metallization and nickel plating thickness in the 25 ±10 μm / 2–10 μm range aligns with standard Ag-Cu and Ag-Cu-Ti brazing systems used in high-voltage packages.
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Dimensional precision for automated relay assembly: Dry-pressed and precision-ground alumina relay housings can achieve dimensional tolerances down to ±0.02–0.05 mm on critical features, supporting automated insertion and welding processes in relay factories.
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Thermal and mechanical stability under DC switching stress: Alumina maintains high hardness, compressive strength and thermal shock resistance, enabling the housing to withstand contact arcing, temperature cycling and mechanical shock encountered in EV and HVDC service.
Alumina Ceramic Relay Housing Properties
| Property | Unit | 99.5% Al₂O₃ | 99.6% Al₂O₃ | 99.7% Al₂O₃ | 99.8% Al₂O₃ | 99.9% Al₂O₃ | 99.99% Al₂O₃ |
| Alumina content | % | 99.5 | 99.6 | 99.7 | 99.8 | 99.9 | 99.99 |
| Density | g/cm³ | 3.89 | 3.91 | 3.92 | 3.93 | 3.94 | 3.98 |
| Open porosity | % | 0 | – | – | – | – | – |
| Color | – | Ivory | Ivory | Ivory | Ivory | Ivory | Ivory |
| Water absorption | % | – | 0 | 0 | 0 | 0 | 0 |
| Young’s modulus (Elastic modulus) | GPa | 375 | 356 | 357 | 358 | 359 | 362 |
| Shear modulus | GPa | 152 | – | – | – | – | – |
| Bulk modulus | GPa | 228 | – | – | – | – | – |
| Poisson’s ratio | – | 0.22 | – | – | – | – | – |
| Compressive strength | MPa | 2600 | 2552 | 2554 | 2556 | 2558 | 2570 |
| Flexural strength | MPa | 379 | 312 | 313 | 314 | 315 | 320 |
| Fracture toughness | MPa·m¹ᐟ² | 4 | – | – | – | – | – |
| Hardness | GPa | 14.1 (≈1440 kg/mm²) | 23 | 24 | 25 | 26 | 30 |
| Thermal conductivity | W/m·K | 35 | 32–37 | 33–38 | 34–39 | 35–40 | 36–42 |
| Thermal shock resistance ΔT | °C | – | 222 | 223 | 224 | 225 | 228 |
| Maximum use temperature (no load) | °C | ≤1750 | 1755 | 1760 | 1765 | 1770 | 1800 |
| Coefficient of thermal expansion | 10⁻⁶/°C | 8.4 | – | – | – | – | – |
| Specific heat | J/kg·K | 880 | – | – | – | – | – |
| Volume resistivity | Ω·cm | >1×10¹⁴ | >1×10¹⁴ | >1×10¹⁴ | >1×10¹⁴ | >1×10¹⁴ | >1×10¹⁴ |
| Dielectric constant (relative permittivity) | – | 9.8 | 9.83 | 9.84 | 9.85 | 9.86 | 9.92 |
| Dielectric strength | kV/mm | 16.9 | 23.2 | 23.4 | 23.6 | 23.8 | 24 |
| Dissipation factor (loss factor @ 1 kHz) | – | 0.0002 | – | – | – | – | – |
Relay Alumina Ceramic Housing Specifications
| Model | AT-AO-JD1001 |
| Product Name | 35*15mm Automotive Relay Ceramic Metallized Ceramic |
| Material | Alumina, 96% |
| Silicon Dioxide, 1.6% | |
| Strontium Carbonate, 1.0% | |
| Kaolin, 0.5% | |
| Others, 0.4% | |
| Thermal Conductivity | 0.4 Cal/(cm·s·°C) |
| Volume Resistivity | 10^13 Ω·cm |
| Metallization Material | Molybdenum-Manganese |
| Surface | Nickel Plating |
| Molybdenum Wire Furnace Temperature | 850°C |
| Metallization Layer to Ceramic Bonding Strength | > 350 Mpa |
| Metallization Layer to Metal Part Bonding Strength | > 6000N |
| Metallized Ceramic Insulation Resistance | > 1x10^13 ohm·cm |
Relay Alumina Ceramic Housing Packaging
- Each relay alumina ceramic housing batch is separated in partitioned trays or blister plates to avoid edge chipping.
