What Is a Relay Alumina Ceramic Housing?
A relay alumina ceramic housing is the insulating ceramic envelope of a relay package. It surrounds the contact chamber, holds the terminal openings in position, and sets the creepage and clearance paths between those terminals and the surrounding metal parts. The ceramic body also forms the base that the contact or coil assembly sits inside and the face that joins to the cap or header.
Most relay housings are made in 95% or 96% alumina (AD-ALU-950 or AD-ALU-960), with higher-purity grades available for specific electrical or sealing requirements. The ceramic holds its shape and dielectric margin where molded plastics creep, outgas or track at high voltage and elevated temperature.
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 |
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Alumina Ceramic Relay Housing Properties
| Material property |
AD-ALU-950 · 95% Al₂O₃ |
AD-ALU-960 · 96% Al₂O₃ |
| Density |
3.75 g/cm³ · material value |
3.70 g/cm³ · material value |
| Thermal conductivity |
18–25 W/(m·K) at 25°C |
25 W/(m·K) at 20°C |
| Dielectric strength |
10 kV/mm · 5 mm material specimen |
8.3 kV/mm · 6.35 mm material specimen, AC |
| Volume resistivity at 20°C |
>10¹² Ω·cm · material value |
10¹⁴ Ω·cm · typical material value |
| Flexural strength |
260–280 MPa · material value |
330 MPa · material value |
| Application orientation |
Cost-balanced terminal insulation and moderate electrical duty |
Higher insulation resistance and tighter tolerance sealing faces |
These material properties guide initial design screening. Actual housing performance depends on geometry, wall thickness, surface condition and operating environment; the project drawing defines acceptance inspection and test requirements.
Select the Housing Stage for Your BOM
| Purchased stage |
What the drawing defines |
Acceptance at that stage |
| Fired ceramic body |
Grade, cavity, walls, openings, datums and sealing land |
Geometry, edge and surface condition, cleanliness and ceramic inspection |
| Metallized or plated body |
Ceramic form plus interface pattern, overlap, edge setback and specified layer finish |
Pattern location, layer specification and agreed interface checks |
| Joined housing assembly |
Ceramic and metal parts, terminal stack, joining materials and joint geometry |
Assembly drawing, joining process and project electrical or leak-test acceptance |
The selected stage aligns your BOM with the component definition and inspection scope.
Relay Alumina Ceramic Housing Design Variables
Each housing is made to the relay drawing. Four connected decisions define its geometry, insulation and joining requirements.
Terminal Geometry and Creepage Path
Specify hole count, pitch, diameter, depth and terminal seating. Check how these dimensions affect fit, creepage and clearance between terminals and chamber walls.
Contact-Chamber Form
Choose an open, partitioned or enclosed chamber to suit the contact or coil assembly. Include any vents or pressure-relief features on the drawing.
Sealing and Joining Route
Define a fired sealing land for glass or compression sealing, or a metallized and plated pattern for brazing or soldering. Specify overlap, edge setback, layer finish and inspection requirements.
Alumina Grade and Surface State
Select the grade for electrical duty, temperature and assembly conditions. Define as-fired, ground, lapped or polished faces, plus glazed or unglazed exterior surfaces, to suit the insulation and joining design.
Relay Alumina Ceramic Housing Packaging
- Protective packaging: Each housing or assembly is wrapped in anti-static film and packed in foam-cushioned cartons with moisture-barrier bags.
- Separation and ESD protection: Trays or dividers prevent part-to-part contact. Metallized or joined assemblies receive additional ESD protection.
- Agreed requirements: Packaging follows the inspection and handling instructions for the purchased stage.
Relay Alumina Ceramic Housing Applications
Relay alumina ceramic housings are specified by relay, contactor and instrument design teams, and the application decides which housing features carry the most weight: the insulation path in HVDC switching, the join interface in vacuum and gas-filled designs, stable geometry in instrument relays, and repeatable mating fit in a second-source program.
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HVDC Relays and EV Contactors
In battery disconnect and main contactor designs, the ceramic housing carries the insulation path around the terminals and contact chamber while the package itself gets smaller. What the design team fixes on the drawing is the terminal pitch and hole diameter, the wall thickness between terminals, the creepage and clearance to adjacent metal parts, and the alumina grade with its published dielectric data. Surface condition matters as much as grade: an as-fired surface and a ground sealing face behave differently under DC stress and surface contamination. Whether the chamber is gas-filled or evacuated belongs to the joined assembly, not to the fired body.
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Vacuum and Gas-Filled Relay Development
Here the alumina relay housing is the ceramic member of a designed ceramic-to-metal package. The metallized band, overlap, edge setback and layer finish define the braze joint, and the sealing land defines the glass or compression seal. Leak acceptance is set for the finished assembly against the project's test method and pressure basis. Naming the intended atmosphere and joining route on the drawing lets the ceramic and metal parts be matched from the first revision instead of after the first build.
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Industrial Relays and High-Voltage Test Equipment
Instrument, analyzer and test relays need contact alignment and creepage distance to hold through repeated cleaning, inspection and thermal cycling. That puts the weight on stable geometry, flat sealing faces and a surface that tolerates the cleaning route actually used in the lab or on the line. Solvent or ultrasonic cleaning is checked against the metallization and nickel layer before it is written into the process.
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Second-Source Programs for an Existing Relay
Replacing an existing housing starts from the original drawing revision. The work is repeatable mating geometry — terminal alignment, locating features, sealing land and datums — confirmed by a first-article trial fit before volume. Material grade and purchased stage are matched to the existing part, and any deviation is agreed in writing rather than absorbed during production.
In each of these cases the housing is quoted at the purchased stage the drawing defines, so the inspection scope and the supplied part stay aligned.
Relay Alumina Ceramic Housing Usage Instructions
The steps below apply to the purchased stage. Handling, cleaning and storage apply to any ceramic body; brazing and leak acceptance apply to a metallized or joined housing. Where a value is not stated, the project joining specification and the drawing govern, not a default.
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Incoming Inspection and Handling
Inspect before assembly. Check edges, rims and metallized bands for chips or cracks under adequate light. A chip on a sealing land or through a metallized band is a reject; a chip on a non-functional outer edge is dispositioned against the drawing.
Keep the sealing areas clean. Use clean gloves or finger cots. Oils and particles on a sealing land or metallized band are the most common source of later joint defects, and they are far cheaper to prevent here than to recover after brazing.
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Fixture Support and Alignment
Support the base, not the walls. Seat the housing in a fixture that supports the base and distributes contact, particularly on thin-wall sections. Point loading on a wall or a single corner constraint shows up as a crack after the thermal cycle, not at the moment of clamping.
Align to the drawing. Center caps, terminals and braze rings on the metallized bands before loading. Off-center placement thins the joint on one side and thickens it on the other, which changes fillet geometry on both.
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Furnace Brazing
Control ring and paste thickness. Keep braze rings and paste within the thickness range set for the metallized band so that fillet geometry forms as designed. Verify ring dimensions before the run rather than adjusting after inspection.
Follow the approved profile. Use the heating and cooling ramp approved for the actual ceramic, metal and braze alloy, and keep the thermal gradient through the part within that profile. Where the profile needs to change, change it through the project procedure so the change is recorded against the drawing revision.
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Leak and Electrical Verification
Test the joined assembly. Perform helium leak testing or the agreed equivalent method at the joined-component stage, against the project's leak-rate threshold, pressure basis and units. Leak acceptance applies to the finished assembly; it is not inferred from the ceramic body.
Apply electrical checks to the relevant state. Insulation resistance and dielectric withstand are measured on the assembly state the project defines, with the conditions recorded alongside the result.
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Storage Between Stages
Keep parts closed and dry. Store finished and semi-finished housings in closed trays or boxes at the temperature range specified for the ceramic and layer state. Separate parts with cushioned dividers and do not place heavy loads directly on trays holding thin-wall housings.
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Cleaning Unassembled Housings
Start dry. Remove loose particles with dry compressed air or filtered nitrogen before assembly.
Check solvents against the layer. Where deeper cleaning is required, use a solvent or ultrasonic route assessed as compatible with the metallization and nickel layer. Dry completely before brazing or leak testing; trapped moisture in a cavity or blind hole distorts both results.
ADCERAX supplies handling and inspection guidance with the drawing review, and the agreed points are written into the project inspection plan rather than left to operator judgment.
