Glass to Metal Seal
Custom manufactured glass to metal seals from Tekna Seal are used in a variety of applications requiring hermeticity, including aerospace, automotive, batteries, electronic packages, high vacuum, medical, military and sensor packages. Tekna Seal also offers a limited selection of standard products.
Advantages of Tekna Seal Oxide Free Glass to Metal Hermetic Seals
The Tekna Seal proprietary oxide-free process eliminates the need for pre-oxidizing of the metal components prior to glass sealing. This lack of heavy oxide interface between glass and metal allows for:
- Increased pressure withstanding
- Higher levels of hermeticity
- Repeatable, reliable processing
Eliminates the need for post oxide removal:
- Glass and metal are clean, free of etching residue
- Hazardous waste stream eliminated
Traditional Glass to Metal Sealing Process
Traditional glass to metal seals rely on a visible oxide layer formed on the metal components to allow glass flow and adhesion. This oxide layer limits the strength and hermeticity of a conventional glass-to-metal seal. This process also requires an additional operation to remove the oxide from other surfaces of the assembly. This cleanup process is usually a chemical etch, which will result in deterioration of dimensional tolerances and potentially contaminate the materials.
Material Selection for Glass to Metal Seals
The Tekna Seal oxide-free process allows us to use a multitude of glass to metal seal materials. This list is typical, yet not comprehensive. Many other materials are available upon request for your specific design.
| Compression | Housings | Glass | Pins |
|---|---|---|---|
| High | 3xx Stainless Steel, 1010 Cold Roll Steel, Hastelloy, Inconel, Nitronic, Duplex Stainless Steel | Barium Alkali Soda Lime Low Silica | 52 Ni/Fe Alloy, 446 Stainless Steel, Copper cored 52 Ni/Fe alloy, Copper clad 52 Ni/Fe alloy, Molybdenum |
| Medium | Titanium | Cabal 12 | Molybdenum Kovar Niobium, Tantalum |
| Low- Medium | Stainless Steel or Superalloy | Ceramic-Glass | Hastelloy, Nickel, Copper |
| Matched | Kovar 42 Ni/Fe Alloy | Borosilicate Borosilicate | Kovar 42 Ni/Fe Alloy |
| Metal Injection Alloys | Barium Alkali Borosilicate | 52 Ni/Fe alloy Kovar |
Plating and Pin Finishes
Entire assemblies or pins selectively can be plated for improved corrosion resistance, solderability and ultrasonic wire bonding.
| Plating | Solderability |
|---|---|
| Gold | Excellent |
| Tin | Excellent |
| Electrolytic Nickel | Good |
| Electroless Nickel | Good |
Various Conductor Configurations
In addition to glass to metal seals, tubes and pins can be brazed metal-to-metal, or metal-to-ceramic. Hybrid assemblies containing both glass-to-metal and brazed components may also be produced. Typical applications include brazing ground leads or evacuation tubes to housing, often made of dissimilar metals.
- Straight
- Bent
- Radiused
- Flattened and Pierced
- Headed
- Tubes
- Custom
Electrical Properties
- Insulation Resistance
- Typical values exceed 1 Gigaohm at 100 VDC
- Volume resistance is always higher than surface resistance
- Dielectric Properties
- Dielectric withstand voltage dependent upon joint geometry and dimensions of the seal
- Dielectric constant is dependent on the glass material selected
Below are typical values for some glasses:
| Glass Material | Dielectric Constant 20° C 1 MHz | Loss Factor |
|---|---|---|
| Borosilicate | 4.9-5.7 | 1.3-1.6 |
| Barium Alkali | 6.3-6.7 | 0.17-0.25 |
| Soda Lime | 7.2-7.3 | 0.90-1.00 |
Mechanical Properties
- Operating Temperature Range: -65° to 200° C, tested by thermal shock from +200° to -65° air-to-air, with traditional sealing glasses. Up to 600° C with Ceramic-Glass.
- Mechanical Strength: It is possible to achieve seals capable of withstanding pressures in excess of 20,000 psi with proper design and appropriate qualification testing.
- Hermeticity: Tekna Seal can test seals to 1×10-10 ATM• cc/sec Helium using a mass spectrometer. Actual leak rates are typically less than 1×10-10.
- Corrosion Resistance: A compression seal can be fabricated with stainless steel or other corrosion resistant metal body, the limiting factor for corrosion resistance is often the nickel iron alloy used for pin material. Our glass/ceramic material will allow the use of corrosion resistant pin materials such as Hastelloy or 3xx Stainless Steel.