HERMETIC SEALS
Hermetic seals are airtight seals that prevent the invasion of moisture, humidity, and chemical contaminants from entering a sealed chamber. Typically the sealing process is performed in a furnace under controlled atmospheres such as nitrogen, vacuum, etc.
Seals are typically formed by glass-to-metal or ceramic-to-metal feedthroughs to provide a leak-proof electrical or vacuum/pressure connections.
Glass-to-Metal Seals (GTMS) are leak-tight joints of glass and metal fused together to form electrical or vacuum connections.
Ceramic-to-Metal Seals (CTMS) are joined or bonded assemblies of ceramic and metal by brazing.
AlKaLi Barium (Corning 9010) for compression seals.
AlKaLi Borosilicate (Corning 7056) for matched seals.
Al2O3 (Aluminum Oxide) 96% purity and up
Helium leaking rate < 1X10-8 He cc/sec. Approximate bubble equivalence of 1cc/3years.
Strength can be up to 4000 PSI.
Glass Feedthroughs are popular. For applications subject to extreme conditions such as high operating temperature (800°C and more), cryogenic or high current ceramic feedthroughs are the ultimate solution.
Complete Hermetics inspects and tests the parts before delivery. Many parts are 100% visually inspected and 100% leak tested. Other tests include strength and dimensional inspection, etc.
Plastic and rubber materials, sometimes even metals and glass, give off gaseous molecules, heat and vacuum increase the rate of diffusion. In hermetic sealing processing the gases can contaminate parts and the sealed chamber. In spacecraft, the gases coming off polymers can contaminate optical surfaces and other instruments.
HERMETIC CONNECTORS
Hermetic connectors have the quality of airtight seals. Hermetically sealed connectors therefore provide gas tightness resulting in a much higher level of sealing over time than connectors made for traditional environments.
Complete Hermetics uses glass as insulation for most of its hermetic connectors. Sometimes due to extreme temperature and harsh operating conditions, ceramics are used as insulators as well.
In general, Complete Hermetics only provides custom made hermetic connectors.
Hermetic connectors are typically used to maintain enclosure integrity in harsh and critical environments; commonly in electrical, vacuum, and higher pressure applications.
Yes! Complete Hermetics does provide Titanium and Aluminum hermetic connectors which significantly reduce the weight while maintaining the connector’s strength.
All finished products from Complete Hermetics are subject to inspection before delivery. Certificate of Compliance will be enclosed as well. Most parts are 100% leak tested and 100% visual inspected. Other inspections include dimensions, strength, etc.
CERAMIC METALLIZATION
Ceramic is a non conductive electrically insulated material. Ceramic Metallization is a metal conductive coating process. The coating can be applied by hand for small quantities and automatically for large quantities. Often the parts are then dried and fired at high temperatures in a special furnace and form an adhesive conductive layer for different applications.
If the metalized ceramic will be brazed into other components, usually nickel plating will help to protect the ceramic metallization adhesion layer and form an intermediate layer for the brazing process. Electrolytic Nickel per QQ-N-290 is a very common process. Electroless Nickel per AMS 2433 is another option as well.
The typical thickness of the film, such as but not restricted to Mo/Mg is 0.0005 inches.
Nickel Plating is 100-200 micro inches.
Al2O3 (Aluminum Oxide) 96% purity.
0.005”/in is typical.
This depends on the brazing alloy applications. For example, Nickel plating is good for CuAg (CuSil) brazing, thin gold plating is good for Au wire bonding, etc.
All finished products at Complete Hermetics are subject to inspection before delivery. Certificate of Compliance will be enclosed with the product. Most parts are 100% leak tested and 100% visually inspected. Other inspections include dimensional, strength testing, etc.
BRAZING
Brazing is a process for joining similar or dissimilar metals using a filler metal known as brazing alloy. The process basically involves the brazed alloy melting and flowing between the two piece of material. This is commonly referred to as ‘wetting’ and is absolutely critical – particularly when brazing ceramics. Today there are many materials that can be fused to produce joints between materials – those that melt in a temperature range of 1200 C to 450°C are classed as brazes and melting temperature bellow are called solders.
If a braze alloy is melted between two ceramics, a poor joint is likely to result because of poor wetting. Wetting is measured in terms of the contact angle between brazing alloy and the substrate after melting. For good wetting, the contact angle is less than 90°; for poor wetting the angle is greater than 90°.
In addition to controlled atmosphere utilizing Nitrogen or Argon and vacuum environment, two methods are generally used to increase wetting. The first method is to apply something to the surface of the ceramic in order for brazing alloy to wet; common surface treatments are metallization, metal coating, metal hydride treatment. The second method is to apply something to brazing alloy to induce wetting.
Brazing alloys are alloys utilized for brazing. Currently, high temperature (approx. 1200°C) brazing of SiC and low temperature (420°C) active brazes, capable of joining ceramics in air versus a controlled atmosphere, are the most prospective alloys in the market.
High-Temperature Active Metal Brazing process involves coating the ceramic with reactive or refractory metal (W, Ta, Cr, Mo) then brazing using high temperature alloys, such as palladium or platinum based systems. Although, high temperature alloys are not readily available commercially and the majority of active brazes are developed for moderate temperature use, high temperature braze alloys have the potential for higher strength, oxidation resistance, and ductility at a larger range of temperatures.
RAB is a novel brazing process that reactively modifies one of both ceramic surfaces with an oxide compound dissolved in a molten noble metal alloy such as the newly formed surface is readily wetted by the remaining liquid filler material. This technique forms a predominantly metallic joint directly in air without need of vacuum chamber/inert gas or the use of surface reactive fluxes.