Back-potting Standard Connectors

Can you use standard off-the-shelf electrical connectors in hermetically sealed feedthroughs? Thanks to an epoxy backpotting process that we’ve pioneered, the answer is yes.

Our proprietary backpotting process works with nearly any standard non-hermetic connector—including MIL-spec, D-Sub, circular, coaxial and more. Once back-potted, these connectors can offer hermetic performance at pressures up to 15,000 psi or vacuum to 1x10–10 Torr.

The technology used to seal third-party connectors borrows from our proven line of Potcon® hermetic feedthroughs, which also support a wide variety of connector types. But there are many good engineering reasons to stick with off-the-shelf connectors that do not offer hermetic performance. These reasons include:

  • Freedom of choice. Starting with a non-hermetic connector may allow you to use plastic or plated steel connectors if they meet the application requirements, saving cost and potentially weight. Standard connectors also give you many insert configurations to choose from, so you can pick exactly the right one for the job.

  • Function integration. Non-hermetic connectors can allow you to incorporate signal conditioning elements such as fuses or filters. You may also be able to integrate some of the wire harnessing elements.

  • Reduced lead times. Non-hermetic connectors usually ship from stock, eliminating lead time delays that can occur with some custom hermetic connectors.

Take all these engineering benefits into account, and you will often find that an off-the-shelf connector can save money, even after you’ve factored in our backpotting process.

Backpotted Assemblies

From cost and design standpoints, backpotting often makes the most sense when the off-the-shelf connector is part of a more complex feedthrough that has functional requirements beyond sealing.

In one recent job, for example, we combined a standard 32-pin round connector with a PCB that processes signals for a battery management system. We make feedthroughs like this every day using our CircuitSeal™ technology, but this particular design did require some extra attention because it operates in an inert gas environment. Because the dielectric constant of the inert gas environment is about three times lower than air, the potential for electrical arcing rises dramatically.

So we created a design that uses different layers of epoxy potting to address sealing and electrical isolation requirements. One layer hermetically seals the 32-pin connector. And the other layer provides electrical isolation between adjacent pins as well as between the pins and surface mounted components.

Delivering both the electrical and hermetic performance required careful formulation of the epoxy—which had to strike a delicate balance between electrical, mechanical and flow properties. And the complexity of this electrically-isolating feedthrough design involved the development of a new manufacturing process. But the results paid off. This feedthrough assembly meets the hermetic performance requirements of 1x10-8 cm3 He/sec while readily withstanding voltages as high as 2700 Vdc.

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