What is an alumina ceramic insulation frame used for?

It separates conductive parts, supports mechanical alignment and maintains electrical insulation in high-voltage, vacuum, laser, gas-filled and industrial equipment assemblies. What separates it from a plain ceramic plate is the opening: a window or aperture keeps a path clear for an optical path, gas flow or a feedthrough, while the surrounding sections carry the support and the electrical separation. The frame is therefore judged by its opening, its support sections and its mounting contacts together, not by outer size alone.

Which alumina grade should I choose for an insulation frame?

Choose from AD-ALU-990, 995, 997 and 999 (99.00 to 99.90 wt% Al2O3). The 990 and 995 grades are the common starting points for general insulation frames. Move to 997 or 999 when the project needs the lower water absorption shown in the properties table, or when the process is sensitive to the sintering additives in the lower grades. Purity should not be selected by number alone: frame size, mounting force, aperture shape, surface finish and cleaning method often have a stronger effect on service reliability than a step in purity.

What electrical values apply, and how is a finished frame accepted?

The four grades on this page show volume resistivity above 10^14 Ohm-cm at 20 C and a dielectric strength of 10 kV/mm on a 5 mm specimen; relative permittivity is 9.6 to 9.8 and dissipation factor is 0.0006 or lower at 1 MHz and 25 C. These are material values. Acceptance for a finished frame is agreed on the actual part or assembly: AC or DC voltage and waveform, electrode positions, test medium, ramp and hold conditions, leakage and acceptance criteria. The 5 mm specimen value is not converted into a withstand voltage for the frame, because the finished part has its own geometry and electrical path.

Can ADCERAX machine custom windows, holes and slots?

Yes. Drawing-based frames are reviewed with single or multiple windows, rectangular or stepped openings, slot-type apertures, clearance or threaded holes, feedthrough holes, countersinks, counterbores, grooves, chamfers, rounded corners and controlled datum surfaces. State which faces are functional, whether sealing, contact or datum, so the flatness and finish requirements land on the right surfaces.

Why do alumina frames crack, and how can it be prevented?

Cracks usually start at corners, holes and window edges, and most start before the equipment runs. Common causes are a forced fit into a misaligned housing, an over-tightened fastener bearing directly on the ceramic, sharp internal corners that concentrate stress, and burrs or debris on the mating metal face. Prevention is design and procedure together: generous internal radii, protected edges, torque-controlled fastening, load-spreading washers or plates, and clean, flat mating surfaces checked before the frame is located. Alumina is strong in compression and much more sensitive to bending, so the load path should run into a section designed to carry it.

Can alumina ceramic replace polymer, mica or glass insulation parts?

It can be considered when polymer, mica or composite insulators cannot meet the required temperature resistance, dimensional stability, vacuum cleanliness or electrical margin. Alumina holds its shape and its electrical behavior at temperatures where polymer parts soften or degrade, and it insulates and carries load in one part. The mounting design must be adjusted, because ceramic behaves differently from polymer and metal under bending and impact, and a press fit or clamping force copied from the original part can crack it.

What information is needed for a quote?

Send what you have: a 2D or 3D drawing, an old-part photograph or a sample, plus the intended use and quantity. A drawing with outer dimensions, window size, hole layout, alumina grade, surface finish, operating voltage, temperature and atmosphere is ideal. Where information is missing, ADCERAX can develop the remaining geometry and acceptance details with you during drawing review.

High Purity Alumina Ceramic Insulation Frames for HV Equipment

What Is a High Purity Alumina Ceramic Insulation Frame?

A high purity alumina ceramic insulation frame is a machined Al₂O₃ structural insulator used to separate conductive parts, support assemblies and maintain electrical isolation in high-voltage, vacuum, laser and industrial equipment. It is selected when polymer, glass or metal-supported insulation parts cannot meet the required temperature resistance, dielectric stability, dimensional accuracy or cleanliness level.

What sets this frame apart from a plain ceramic plate is the opening. A window or aperture has to stay open for an optical path, gas flow, a feedthrough or an assembly clearance, while the sections around it carry the support and keep the electrical path separated. The frame is therefore judged by its opening, its support sections and its mounting contacts together — not by outer size alone.

High Purity Alumina Ceramic Insulation Frame Specifications

This frame is made to drawing, so the specification table lists what you define rather than fixed stock sizes. Each line — outer size, aperture, thickness, hole and slot design, and surface finish — is confirmed from your drawing or sample before production.

Custom Alumina Ceramic Insulation Frame Specifications
Item No.	Outer Size	Aperture / Window	Thickness	Hole / Slot Design	Surface Finish
AT-HP-K01	Custom	Custom	Custom	Custom	As-sintered, ground or polished

Download the Product Catalogue

High Purity Alumina Ceramic Insulation Frame Properties

This frame is made in one of four dense sintered alumina grades. The values below are typical material values measured on test samples. Use them to compare grades; they are not ratings for a finished frame.

Property	Unit / condition	AD-ALU-990	AD-ALU-995	AD-ALU-997	AD-ALU-999
Al₂O₃ content	wt%	99.00	99.50	99.70	99.90
Density	g/cm³	3.80–3.91	3.90–3.92	3.94	3.94
Water absorption	%	≤0.10	≤0.10	≤0.05	≤0.01
Volume resistivity	Ω·cm at 20 °C	>10¹⁴	>10¹⁴	>10¹⁴	>10¹⁴
Dielectric strength	kV/mm, 5 mm specimen	10	10	10	10
Relative permittivity	1 MHz, 25 °C	9.6	9.7	9.8	9.8
Dissipation factor tan δ	1 MHz, 25 °C	0.0006	<0.0001	<0.0001	<0.0001
Flexural strength	MPa	300–320	320–350	330	315–340
Elastic modulus	GPa	355	365	370	359–375
Fracture toughness KIC	MPa·m⁰·⁵	3.3	3.5	3.6	3.8–4.2
Thermal conductivity	W/(m·K) at 25 °C	24	30–38	35–40	35–42
Coefficient of thermal expansion	10⁻⁶/K	7.2 (range not specified)	7.6 (range not specified)	7.6 (range not specified)	7.6 (25–800 °

How to Choose an Alumina Insulation Frame

Five questions decide most frames. Work through them before you fix the drawing.

1. Define the opening

Choose a single window, multiple windows, a stepped opening or a slot to suit the optical path, gas flow, feedthrough or assembly clearance.

Check the opening size together with the surrounding wall or rib width. A larger opening leaves less ceramic to support the load.

2. Check the span and support points

Review the unsupported span, minimum wall thickness, ribs and support locations against the expected load.

Long spans and thin walls are more sensitive to bending. Direct loads through supported sections and avoid concentrated loads on thin edges.

3. Plan the mounting and clamping

Specify the mounting holes or slots, edge distances and datum faces. Use load-spreading washers or plates on the designated mounting faces, with controlled clamping torque.

Do not copy a metal part’s press fit or clamping force without review; it can crack the ceramic.

4. Select the alumina grade

AD-ALU-990 and AD-ALU-995 are common starting points for general insulation frames. Consider AD-ALU-997 or AD-ALU-999 when lower water absorption or fewer sintering additives matter to the process.

Confirm the grade against operating temperature, voltage and atmosphere—not purity alone.

5. Check the insulation path

Locate conductors and grounded parts, then check clearance and creepage distances around the openings. Include aperture spacing, edge condition and surface finish in the review.

Agree a voltage acceptance test for the actual frame or assembly. The table’s dielectric strength is measured on a 5 mm specimen and does not establish the finished frame’s voltage rating.

Include these five points on your drawing to help speed up the quotation review.

Common Failure Modes of Alumina Insulation Frames

1. Cracks at Corners, Holes or Window Edges

Common causes include forced fits, overtightened fasteners, sharp internal corners and debris on mating surfaces.

Use suitable corner radii, load-spreading washers or plates, and controlled fastening torque. Check that mating surfaces are clean, flat and aligned before installation.

2. Edge Chipping During Handling

Prying, dropping or levering against the frame can chip ceramic edges.

Remove obstructing metal parts first, then support the frame from below and lift it clear. Do not use the ceramic as a lever point.

3. Surface Flashover or Reduced Insulation

Conductive dust, metal particles, oil and handling residue can reduce surface insulation. Sharp edges and narrow aperture gaps can increase local electric-field concentration.

Keep surfaces clean and review creepage distance, aperture spacing and edge geometry. During maintenance, inspect corners and high-field areas for contamination or discoloration.

4. Loosening or Misalignment After Thermal Cycling

Different thermal expansion rates between the ceramic and mating metal can change contact stress, alignment and clamping preload.

Allow for relative movement and review the support and clamping arrangement across the full heating and cooling cycle.

5. Deposits or Discoloration in Vacuum or Gas Service

Check for residue from handling, cleaning and nearby assembly materials.

Specify material purity and surface cleanliness separately. Agree the cleaning, drying or bake-out procedure and acceptance criteria for the actual assembly.

Before reusing a frame under different voltage, pulse or temperature conditions, review its insulation distances, material limits and mounting arrangement.

For replacement inquiries, send photos of the damaged part and its mounting arrangement, together with the operating conditions.

High Purity Alumina Insulation Frame Packaging

Each alumina ceramic insulation frame is individually separated using foam or soft interlayers to avoid ceramic-to-ceramic contact.
Parts are packed in clean PE bags and then located in custom cut foam or honeycomb cartons to minimize movement during transport.

Where Alumina Insulation Frames Are Used

Alumina ceramic insulation frames are used where a rigid part has to hold electrical separation around a passage. Match the frame design to the assembly it sits in.

High-Voltage, Vacuum and Pulsed Power Modules

Used in power modules, vacuum assemblies and pulsed systems where conductive parts must stay separated under electrical stress. The frame can support connectors, electrodes or feedthrough areas while keeping the clearance and the alignment stable. Confirm the voltage level, the creepage distance, the aperture spacing, the edge radius and the mounting pressure, and review the surface condition for the vacuum requirement.
Industrial Laser and Gas-Filled Equipment

Used to support discharge electrodes, optics mounts or structural reference points in laser and gas-filled systems, where the open window keeps the optical or gas path clear. Review gas cleanliness, thermal cycling, the surface finish on faces that meet seals or housings, hole position and the cleaning method. Where the frame contacts a seal or a precision alignment part, specify the faces that need grinding or lapping.
Electronics and Semiconductor Equipment Hardware

Used in non-wafer-contact structural or insulation positions in electronics and semiconductor equipment, where polymer insulation parts may not hold the required flatness or cleanliness. Review the cleanliness requirement, flatness, particle control, voltage insulation, mounting force and the inspection method. State clearly whether the part is a wafer-contact item, because that changes the cleanliness and the acceptance requirements.
Industrial Hot-Zone Supports and Equipment Replacement

Used to carry support around an opening in industrial heating equipment, and to reproduce a worn or broken frame from an existing machine. For a replacement, compare the original geometry, the drawing revision and the first-article acceptance baseline before production. Send photographs or the worn part if the original drawing is not available.

Use Guide – High Purity Alumina Ceramic Insulation Frame

Handling

1. Wear clean gloves and support the frame from underneath. Do not lift it by a window edge or a thin wall.
2. Keep the frame in its packaging until it is needed, and set it down on a soft, clean surface.
Installation

1. Check that all mating metal surfaces are clean, flat and free from burrs or loose debris before the frame is located.
2. Locate the frame on its datum faces first, then align the mounting holes or slots. Do not force a misaligned frame into place.
3. Use torque-controlled tools and load-spreading washers or metal plates so the clamping force is applied evenly across the approved mounting faces.
4. Follow the tightening sequence for the actual fixture. Do not let a fastener bear directly on a thin ceramic section.
Operation

1. Keep the applied voltage, the pulse shape and the creepage distances inside the design envelope agreed during engineering.
2. Follow the approved heating and cooling profile for the equipment. Avoid sudden temperature changes beyond the reviewed design condition.
3. Check high-field regions, corners and contact faces for contamination, microcracks, chipping or discoloration during scheduled maintenance.
4. If the operating voltage, pulse mode or temperature profile changes significantly, review the creepage distances, the material limits and the mounting arrangement before the frame is reused.
Storage

1. Store frames in cushioned trays or on dedicated racks with dividers. Do not stack heavy components on top.
2. Keep storage areas dry and free from corrosive vapors or dust that could contaminate the ceramic surface.
Cleaning

1. Remove loose particles with dry, oil-free compressed air or a soft antistatic brush.
2. For deeper cleaning, review a neutral-pH detergent in deionized water for the required process, then rinse thoroughly and dry at a temperature suitable for alumina ceramic.
3. Do not use metal scrapers, abrasive pads or impact tools on the ceramic surface.
During Maintenance

Design the maintenance sequence so that metal parts are removed first, and the frame is then supported from below and lifted out. Do not lever or pry against a ceramic edge to free a part — this is a common cause of chipped corners. Agree project-specific inspection points and acceptance criteria separately from these handling practices.

Alumina Insulation Frame FAQ

What is an alumina ceramic insulation frame used for?
It supports and electrically separates components while keeping an opening clear for optics, gas flow or feedthroughs. Applications include high-voltage, vacuum, laser and industrial equipment.
Select the opening, surrounding support sections and mounting contacts together—not just the outer dimensions.
Which alumina grade should I choose?
AD-ALU-990 and AD-ALU-995 are common starting points for general insulation frames. Consider AD-ALU-997 or AD-ALU-999 when lower water absorption or reduced sintering additives matter to the process.
Review the grade alongside operating conditions, frame geometry, mounting loads, surface finish and cleaning requirements.
What electrical values apply to a finished frame?
The listed grades have these typical material values:
a. Volume resistivity: >10¹⁴ Ω·cm at 20 °C.
b. Dielectric strength: 10 kV/mm on a 5 mm specimen.
c. Relative permittivity: 9.6–9.8 at 1 MHz and 25 °C.
d. Dissipation factor: ≤0.0006 at 1 MHz and 25 °C.
These values do not establish the finished frame’s voltage rating. Agree the test voltage, waveform, electrode positions, medium, ramp, hold time and leakage limits for the actual part or assembly.
Can ADCERAX machine custom windows, holes and slots?
Yes. We review drawing-based designs with single or multiple windows, stepped openings, slots, mounting and feedthrough holes, grooves, chamfers and rounded corners. Threaded holes, countersinks and counterbores are assessed during drawing review.
Identify sealing, contact and datum faces so flatness and finish requirements apply to the correct surfaces.
Why do alumina frames crack, and how can this be prevented?
Common causes include forced fits, overtightened fasteners, sharp internal corners and debris on mating surfaces. Cracks can start during installation.
Use suitable corner radii, protected edges, load-spreading washers or plates, and controlled fastening torque. Keep mating surfaces clean and flat, and direct loads through supported sections rather than thin walls.
Can alumina replace polymer, mica or glass insulation parts?
Alumina may be suitable when an existing insulator cannot meet temperature, dimensional stability, vacuum cleanliness or electrical requirements.
Review the mounting design before substitution. Ceramic responds differently to bending and impact, so the original part’s press fit or clamping force should not be carried over without assessment.
What information is needed for a quote?
Send a drawing, sketch, old-part photos or a sample, together with the intended use and quantity.
Include available outer dimensions, window sizes, hole positions, material grade, surface finish, operating voltage, temperature and atmosphere. Missing dimensions and acceptance requirements can be clarified during drawing review.

Catalogue No.	AT-HP-K01
Material	Al₂O₃
Purity	AD-ALU-990 / 995 / 997 / 999 (99.00–99.90 wt%)
Openings and mounting	Drawing-defined windows, ribs, walls, holes and slots
Dimensions/Sizes	Download PDF

High Purity Alumina Ceramic Insulation Frames

What Is a High Purity Alumina Ceramic Insulation Frame?

High Purity Alumina Ceramic Insulation Frame Specifications

High Purity Alumina Ceramic Insulation Frame Properties