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In the unyielding vastness of space, rugged and reliable equipment isn’t just helpful – it’s essential. Space-bound equipment must withstand numerous obstacles, including extreme temperatures, shock, and vibration. The technology used within spacecraft equipment carries a lot of responsibility and can threaten the equipment’s lifespan and performance, so it must undergo rigorous testing on earth before it can be launched into space. This is where hermetic connectors come into play.

To recreate the space environment on earth, researchers and manufacturers use thermal vacuum chambers. However, the testing instruments are rarely compatible with the space environment, so all connections must pass through the pressure differential walls separating the distinct environments. Hermetic connectors play an important role in this process, linking the testing instruments with the equipment being tested inside the thermal vacuum chambers. With its decades of experience and engineering expertise, Positronic understands how to design, develop, and manufacture the perfect hermetic connectors for testing space-bound technology.

Why Hermetic Connectors?

When space-bound equipment is tested in thermal vacuum chambers, which simulate environmental conditions in space, it must meet certain requirements. Two of the most important requirements are temperature cycling under vacuum (-100°C to 100°C is generally required for most electronics) and outgassing in vacuum at elevated temperatures (usually meeting a total mass loss, or TML, of less than 1 percent and a collected volatile condensable materials measurement, or CVCM, of less than 0.1 percent for most connectors). Because the test instruments are not vacuum compatible, hermetic feedthrough connectors must link the test instruments to the electronic devices inside the vacuum chamber. In years past, the only way to accomplish this was to employ a circular connector filled with glass. Positronic aimed to create thinner hermetic connectors that would provide the same secure, dependable connections.

The Construction of Hermetic Connectors

Our hermetic feedthrough connectors are formed of a solid aluminum body and one-piece machined contacts. The aluminum body is filled with layers of resin, which is economical and easy to work with. Each type of contact (power, high-voltage, shielded, or signal) has a specific design of grooves to ensure no hermeticism issues. To establish a hermetic connection that won’t leak, there are also small grooves on the aluminum body. Fixed jackscrews on either side of the connector provide flexibility, allowing the customer to mount either side toward the vacuum.

Performance and Testing

Our hermetic connectors are tested to ensure they meet these parameters:

• Helium Leak Rate less than 5 x 10^-9 mbar x l/s under a vacuum of 0.015 mbar
• Operation from -40°C to +85°C
• Proof voltage of 1kV rms
• Insulation resistance greater than 5G Ohms

The connectors are tested for leakage using a helium detector machine, which identifies how many helium atoms pass through the detector. Helium atoms are used for this purpose because they’re smaller than oxygen atoms, which are found in air. In addition, helium is economical, nonexplosive, and readily available in the industry.

The resin in Positronic’s hermetic feedthrough connectors is Stycast, which offers the following benefits:

• Approved by NASA and the European Space Agency (ESA)
• Allows for the use of various contact alloys

Stycast doesn’t cure to be rock-solid. It retains a measure of viscosity throughout its lifetime, unlike glass (a common alternative insulator), which becomes rigidly crystalized and may fissure or crack, causing premature failure. In addition, glass melts at 1600°C, and not all copper alloys will resist that high temperature. With a glass insulator feedthrough, it’s very difficult to employ a hard contact that offers high conductivity. While there are instances in which glass is mandatory (namely, applications that require extreme temperatures, like jet propulsion), resin has replaced glass in many connectivity solutions.

Positronic’s Hermetic Feedthrough Connectors

XAVAC Series

Designed for space and industrial vacuum applications, the XAVAC series of hermetic feedthrough connectors is composed of D-subminiature connectors. Both sides contain four threaded mounting holes, an o-ring groove, and fixed female jackscrews. The redundant features allow the customer to mount either side of the connector toward the vacuum, providing flexibility. The idea is to mount the feedthrough against the flange from the high-pressure side so that the vacuum on the inside will suck the connector toward the wall.

All XAVAC series connectors are 100-percent leak tested after fabrication. They use precision-machined contacts for strength and durability, and various types of contacts are available so that customers can request the ideal type for their specific application. In addition to the standard options available, Positronic can supply XAVAC series connectors on board mount varieties or with flying leads.

The materials and finishes used in the XAVAC series, as well as the technical characteristics, conform to MIL-DTL-24308, Goddard, and SPACE-D32 specifications.

SAVAC Series

Smaller than the XAVAC series, the SAVAC series is another family of D-subminiature feedthrough hermetic connectors for space or industrial vacuum applications. Both sides contain two threaded mounting holes (female jackscrews) and an o-ring groove. The redundant features provide flexibility, allowing the customer to mount either side of the connector toward the vacuum.

All SAVAC series connectors are 100-percent leak tested after fabrication. They use precision-machined contacts for strength and durability, and various types of contacts are available so that customers can request the ideal type for their specific application. In addition to the standard options available, Positronic can supply SAVAC series connectors on board mount varieties or with flying leads.

The materials and finishes used in the SAVAC series, as well as the technical characteristics, conform to MIL-DTL-24308, Goddard, and SPACE-D32 specifications.

HIVAC Series

The HIVAC series is composed of feedthroughs equipped with D-subminiature adapter connectors for space or industrial vacuum applications. The connector configuration requires three separate units to function properly: the center unit (the feedthrough) and its two adapter units (one for the atmospheric side, one for the vacuum side). Both sides of the feedthrough contain four threaded mounting holes and an o-ring groove. The redundant features provide flexibility and allow the customer to mount either side of the connector toward the vacuum.

The HIVAC series feedthrough always has female/female contacts, and the adapter connector is male. The contact types on the other sides may be chosen by the customer (male/male or male/female for normal density, male/female for high density). The feedthrough has five types of insulators: 37 or 50 contacts for normal density; 44, 62, or 104 contacts for high density. Like the other two series, the HIVAC series uses precision-machined contacts for strength and durability.

The materials and finishes used in the SAVAC series, as well as the technical characteristics, conform to MIL-DTL-24308, Goddard, and SPACE-D32 specifications.

The great advantage of the HIVAC series is its versatility. Its adapter connector allows for several combinations with a feedthrough, so users are able to purchase a single feedthrough and use it with a variety of adapters.

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To learn more about the design challenges and engineering requirements of hermetic connectors for space-bound equipment, please check out our webinar, Hermetic Connectors Are Essential in the Development of Space Bound Equipment. 

At Positronic, we believe in crafting versatile, high-quality connectors. Our design and manufacturing processes meet and often exceed our customers’ needs for quality and reliability. And to suit the needs of our varied customers, we have a plethora of options available. If you would like to request product recommendations, locate a sales agent, ask a technical question, or simply request a quote, please contact Positronic today.