Tuesday, September 11, 2018

Epoxy-based Feedthroughs Provide Design Flexibility, Rapid Prototyping and Cost Savings

Multi-conductor, flanged feedthrough
Multi-conductor, flanged feedthrough.
The point of view that epoxy-based feedthroughs are inferior to glass-to-metal feedthroughs in terms of sealing and outgassing may have once been true, but modern manufacturing techniques and new epoxy compounds have all but eliminated those concerns. Modern epoxy formulations are more capable of enduring greater mechanical stresses, operating under wider temperature ranges, and sustaining exposure to harsher chemicals than ever before. Today's epoxy-based feedthroughs are excellent choices for even the most challenging feedthrough applications.

Take BCE's proprietary epoxy compound for instance. It seals to 1 X 10E-9 cc/sec of Helium under high vacuum and high pressure and can operate at 150°C continuous operating temperature (with a maximum exposure temperate of 200°C.)

Concerns of outgassing have been erased with the formulation meeting NASA’s ASTM E-595 low-outgassing specification, the industry standard test for measuring outgassing in adhesives and other materials. Developed to screen for low outgassing materials for use in deep space, the test determines the volatile content of material samples placed in a heated vacuum chamber under tightly controlled humidity, temperature, and vacuum conditions.

PCB feedthrough with clean epoxy feedthrough
PCB feedthrough with clear epoxy feedthrough.
Epoxy feedthroughs allow designers and engineers to procure a feedthrough built for the specific task, rather than to accommodate off-the-shelf connectors that are rarely ideal for the specific requirement. Off-the-shelf connectors and feedthroughs impose restrictions on the number and gauge of conductors, as well as the geometry of the device. The use of epoxy-based feedthroughs opens the door for virtually any combination of conductors, tubes, fiber optic cables, sizes and geometries.

It’s important to use the right feedthrough for a given application. Epoxy feedthroughs are not always the right choice, and consultation with an applications expert is always recommended.  But from the viewpoint of engineers and designers, epoxy-based feedthroughs usher in design freedom, prototyping, and cost advantages that once didn't exist.