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Hermetic Sealing Technology
Read about news, technical breakthroughs and design best practices related to hermetically sealed wire feedthroughs and hermetic connectors.
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.
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.
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/
Engineers who work with pressure and vacuum chambers usually reach for off-the-shelf sealed bulkhead connectors when they need to pass power and signal wires through the chamber wall. And while these connectors may seem like the best or only way to breach the chamber walls, they can actually drive cost, impose unnecessary mechanical design constraints and trigger electrical problems. So what’s the alternative? Wire feedthroughs hermetically sealed with epoxy.
If your application doesn’t need frequent disconnects on one or both sides of the sealed chamber, it pays to consider continuous wire feedthroughs before ordering an off-the-shelf connector. If you do, you can benefit from:
- Design flexibility. Even a large offering of standard bulkhead connectors may accommodate just four wire gauges, each typically with 10 pin configurations per wire gauge. Additionally, mixed wire gauge connectors are often unavailable or special order. Bottom line is that it’s often difficult to find an off-the-shelf connector that’s exactly right for the job at hand, which leads to compromises and over-engineering as engineers try to adapt the application requirements to available connectors rather than the other way around. Continuous wire feedthroughs, by contrast, can literally contain thousands of conductors—or just a handful if that’s all the application requires. Equally important, continuous wire feedthroughs give you the ability to mix and match conductors in ways that off-the-shelf connectors do not.
- Increased connector density. Wire feedthroughs have a huge conductor density advantage. Compared to connectors, well-designed feedthroughs can easily double the number of conductors that can squeeze through a given opening. This density advantage often allows a single wire feedthrough that combines all the application’s power and signal wires to take the place of multiple bulkhead connectors.
- Performance enhancements. Even the best electrical connectors have more losses that a continuous wire harness. For instance, connectors typical voltage greater than 1 mV per crimp and another 1 mV or more across the mated pin and socket. Contact resistance for the same connector would typically be as 100 mΩ. That’s enough to make a difference in thermocouple and other sensing applications that benefit from signal integrity. Wire feedthroughs also can also provide an edge in mechanical performance. Unlike bulkhead connectors, a wire feedthrough is not a wear item whose lifecycle depends on a finite number of mating and un-mating cycles. In non-flex applications, the lifecycle of a wire feedthrough equals that of the wire harness itself. There’s no extra failure mode as there would be with a connectorized feedthrough.
- Reduced Cost. It’s tempting to think that bulkhead connectors from a catalog or website will cost less than a custom engineered wire feedthrough. Yet nothing could be further from the truth if you consider the total installed cost of the two feedthrough technologies. Remember that a single continuous wire feedthrough can often replace multiple bulkhead multiple connectors. The resulting reduction in the number of wire harnesses that need to be engineered and manufactured produces a significant cost savings relative to connectors. In many cases, the feedthrough costs just half as much as a comparable connector-based designs.
For more information on best practices for wire feedthrough design, download our latest white paper, When Wire Feedthroughs Make Sense.
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