Hermetic Sealing Technology


Read about news, technical breakthroughs and design best practices related to hermetically sealed wire feedthroughs and hermetic connectors.

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.

Sealed Sensor Assembly Gets A Reliability Boost

What’s the best way to incorporate sensors and sensing electronics into a pressure or vacuum chamber? Traditionally, the answer would have involved a hermetically sealed wire feedthrough. And in applications with complex or numerous electrical connections, well-designed hermetic feedthroughs are still the way to go.

However, there is another lesser-known way to bring sensors and similar electronics into a pressure chamber. Rather than pass sealed wires through through the pressure wall as with a feedthrough, you can instead hermetically seal circuit board assemblies that interface with a sensor. These sealed circuit board assemblies can then protrude directly into the pressure or vacuum chamber.

In the right applications, sealed circuit board assemblies have some persuasive performance and cost benefits. This white paper will examine how Lumasense, a leading provider of condition monitoring systems for power generation and distribution equipment, reaped those benefits.

 


Hermetic Assemblies Add Value

We’ve shipped our share of standalone hermetic feedthroughs over the years. Increasingly, however, sealed hermetic penetrations leave our plant as a part of a value-added assembly.

These turnkey assemblies typically combine our hermetic feedthrough technologies with non-hermetic connectors, printed circuit boards, flex circuits and wire harnesses. Assemblies can also incorporate strain relief, water-blocking overmolds, jacketing, shrink tubing, breakouts, mechanical subassemblies and patch panel wiring.

The growing popularity of value-added assemblies makes perfect sense because they:

  • Reduce Cost. Outsourcing value-added cable harness assemblies to the right supplier can save a substantial amount of money compared to internally-manufactured assemblies. On a typical assembly consisting of a back-potted connector and wire harness, we can typically reduce the cost by 25% or more. In more complex assemblies, the cost reduction can approach 50%. These savings result, in no small part, from specialization. We produce value-added assemblies every day, so we’ve invested in technician training, automated assembly systems, specialty tooling and testing equipment. These investments are not easily matched by non-specialists.
  • Save Time. Value-added cable harness assemblies can speed time to market. The finished assemblies arrive at your door as a single bill-of-materials item in a fraction of the time it would take for you to source and assemble individual components. We ship many assemblies on a just-in-time (JIT) basis, which helps you keep inventory costs low.
  • Improve Quality. Our value-added assemblies undergo an extensive testing regimen before they leave our plant. That regimen obviously includes leak testing of the hermetic connector assembly itself, but it also extends mechanical and dimensional evaluation.  Additionally, we offer full electrical testing of the entire assembly. Our line-up of electrical tests includes continuity, hi-pot and insulation resistance testing. By fully-testing the assemblies, we can provide a level of quality assurance that’s difficult and expensive to achieve if you’re not working with hermetic connector assemblies every day. What’s more, many of our QC tests are automated, which eliminates any potential for human error.

Standards-Based Assemblies

Value-added connector assemblies have mostly gained traction in automotive, semiconductor, aerospace and military applications. So compliance with a wide range of quality standards is essential. For example, we produce hermetic connector assemblies in accordance with a wide range of UL, SAE and DoD standards. And for wire harness quality assurance, our assembly technicians have earned the IPC 620 certification.

For more information on our value-added assemblies, visit www.douglaselectrical.com/products/cable-harnesses.