Electrical Feedthroughs: Types and Applications

With over twenty years of experience in manufacturing and supplying a wide variety of feedthroughs for customers worldwide, Allectra is an experienced electrical feedthrough specialist.

2 X 50-way Sub-miniature D type feedthrough on a 100 CF flange.

2 X 50-way Sub-miniature D type feedthrough on a 100 CF flange. Image Credit: Allectra Limited

The Sub-miniature D Type feedthrough is available as 9, 15, 25, 37, and 50 way as it is based on the electronics industry standard, MIL-C-24308. These feedthroughs come as multiple and custom feedthrough flanges with several accessories, including PEEK, UHV, ceramic and air side sockets.

Allectra provides weldable versions suitable for TIG welding. Special versions, e.g., 9 pins on a 25KF flange or 25 pins on a 50KF flange, can facilitate vacuum side connectors without the need for mounting screws while standard air side connectors are compatible.

Several feedthrough flanges can be acquired as standard, CF, and ISO-K, or custom, with Allectra offering in-house manufacturing to ensure rapid delivery times. Allectra can both produce drawings for a customer’s approval or work with a customer’s own drawings. This is the company’s standard procedure for customized fabrications. Additionally, Titanium feedthroughs welded to Titanium flanges are also available on special order.

Combination feedthroughs in one shell are offered with a mixture of Power pins, Coaxial pins, and Standard pins: the Power pins are ideal for heater applications.

High Density Sub-D feedthroughs offer an increased amount of pins on the same shell size: rather than 15 pins, it is possible to fit 26 pins or, in the case of 50 pins, 78 pins. This is accomplished by reducing pin diameter and positioning them at a closer pitch – PEEK connectors are also available for the vacuum side.

Allectra can provide 12 and 19 pin Circular Miniature feedthroughs and 6 pin High Current versions. The conventional air side connectors used in industry are shielded and EMC compliant, and all air side connectors are metric threads. Used in conjunction with vacuum side housing, a fully shielded connection from air to vacuum is made possible.

For an immediate connection to Printed Circuit Boards on either air or vacuum side, dual in-line feedthroughs are utilized. Generally, the electronic board is connected to the air side to generate the smallest signal path. Up to 3 feedthroughs providing 120 signals will fit onto a 63CF flange.

Where high voltage and defined impedance are not required, conventional BNC feedthroughs are an economical, versatile coaxial solution. Up to 4 feedthroughs will fit on a single 40CF or 40KF flange; both single or double-sided and in-vacuum cables for both types are readily available.

The 50 Ohm BNC feedthroughs are suitable for high-frequencies. The double-sided version can be applied in applications up to 4GHz. Air-side sockets are included, and in-vacuum cables are available for both versions.

Allectra also offers an SMA 50 Ohm miniature Co-axial feedthrough for applications up to 18GHz. Thus, due to the extremely small-scale, up to 4 feedthroughs can be fitted onto a 40CF or 40KF flange, with DC (direct current) to 6.5GHz or 18GHz. This feedthrough can be acquired double-sided with both internal and external 50 Ohm plugs.

Allectra provides a microwave feedthrough, SMA-K type (2.92mm), for up to 40GHz, if 18GHz is not enough. MHV (Miniature High Voltage) and MHV 50 Ohm feedthroughs are better suited for high-voltage applications than BNC, with an enhanced voltage rating. Both versions are available double-sided, single-sided, and floating shield.

Due to a lack of in-vacuum connectors, no impedance matching, and greater cost, the SMB feedthrough was not always a first-choice for customers. However, the new Allectra SMB feedthrough surmounted these issues as the company produced an alternative to the well-established SMA types. With this newer feedthrough, small dimensions are combined with a frequency range up to 1GHz, and in-vacuum connectors and cables are accessible at more cost-effective prices.

Safe High Voltage (SHV) feedthroughs are Coaxial feedthroughs developed to offer a secure high voltage connection on the air side. They come in two versions on the vacuum side: exposed ceramic and recessed ceramic. The feedthroughs are available as standard (5KV) and a specialized version is available (6KV) with 50 Ohm impedance.

SHV10 are Safe High Voltage feedthroughs rated for 10KV and SHV20 rated for up to 20KV. The inclusion of air-side connectors is standard for both types.

Allectra also provides 50 Ohm Type N feedthroughs for high-frequency signals up to 200MHz. 7/16 feedthroughs are available only as High Vacuum versions and are appropriate for applications where high frequency and high power are required.

Between Series feedthroughs are available with BNC on the air side and Microdot on the vacuum side. Cable combinations are also available with Microdot to Microdot, BNC or SMA connectors.

Allectra provides a wide range of Power feedthroughs: low voltage types are 500V and 1KV. 500V feedthroughs are extremely small and thus perfect for applications where space is limited. 1KV feedthroughs are typically reserved for general purpose instrumentation use.

Feedthroughs rated at up to 5KV, and up to 20A are available as single pin weldables with up to 4 pins on a 16CF or 16KF flange. Custom arrangements are available with a choice of flange upon request. Additionally, 5KV and 10KV feedthroughs are available up to 30A: these hold up to 12 pins on a 40CF or 40KF flange.

High Current feedthroughs up to 1000A are appropriate for furnaces, heaters, and Electron Beam Evaporation Sources. A range of types can be provided as weld adaptors or on KF or CF flanges. For an exceptionally high current, a 1000A water cooled feedthrough is available.

Allectra also provides Multi-way feedthroughs with MS Circular Sockets, with 10, 23 or 40A per pin. The sockets are compliant with MIL-C-5015 requirements. Furthermore, High Voltage 12KV Multi-way feedthroughs can be obtained with 7.5A per pin.

Power Glove feedthroughs are a design of High Voltage 5KV, 10KV, 20KV to 40KV feedthroughs and are offered with sockets and air side cables 2.4m in length. There are choices for 1, 2 or 4 pins on a 40CF flange or alternatively, the feedthrough can be provided on CF, KF, ISO or custom flange designs.

High Voltage feedthroughs are available in ratings up to 60KV, but they are not manufactured for high currents, as high voltage and high current are generally not used together. However, Tube feedthroughs are appropriate for liquid cooling applications where higher currents and high voltage are used together.

Baseplate feedthroughs have been developed to fit through a 1" (25.4mm) hole and sealed by compressing an O-Ring between 2 nuts. Suitable applications for these feedthroughs include High Vacuum Coaters. Many of Allectra’s feedthroughs can be offered as Baseplate types.

Thermocouple feedthroughs have pins made from the relative thermocouple pair materials and on the vacuum side, termination of the pins is achieved with a screw connector (included): the (+) pole is 25mm shorter than the (-) pole. Miniature Thermocouple connectors are included for the air side.

In addition to the popular K, N, and C Thermocouples, Allectra provides the special purpose R, S, and T types. Types R and S are constructed using the same feedthrough pin material (R- extension grade). Type T is especially well-suited for cryogenic applications. Types E and J are available to order.

The intended use for Combination Power/Thermocouple feedthroughs is in heaters where both power leads and temperature measurement are necessary. These feedthroughs are provided with either Copper or Nickel conductors and either K or C type Thermocouple connectors, available up to 150A.

This information has been sourced, reviewed and adapted from materials provided by Allectra Limited.

For more information on this source, please visit Allectra Limited.


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