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Take it All Through the Wall with Epoxy Vacuum Feedthroughs

Glass-to-metal feedthrough

Advances in analytical processes, medical research, and semiconductor processing continually refine the manufacturing capabilities for vacuum systems and components. The need to monitor and control processes is increasing, and getting the required power and control signals into vacuum chambers is increasingly difficult. Devices known as vacuum feedthroughs are used to pass electrical signals, light beams, or pure gases inside a vacuum chamber. Leakage through or around the vacuum feedthrough cannot be tolerated as the vacuum seal is critical to preventing contamination and insuring process integrity.

Glass-to-metal and ceramic-to-metal seals, traditionally the preferred technology, are increasingly problematic - not because of their performance, but because they are constrained by size, geometry, flexibility, and electro-magnetic shielding options. Engineers worked within this reality simply because there were no viable alternatives. Fortunately though, new, advanced sealing epoxy compounds were developed that provided exciting opportunities for vacuum feedthrough manufacturers.

Faster, Less Expensive, More Customizable Feedthroughs

Epoxy vacuum feedthrough.

Today's epoxy vacuum feedthroughs provide the virtually the same performance as their glass and ceramic cousins in low to medium temperatures. Epoxy vacuum feedthroughs offer designers and engineers an excellent alternative in terms of customization and specialization. Shapes, angles and curves are not a problem. Virtually any kind of shielded wire or cable can be used. Custom epoxy vacuum feedthroughs can be quickly provided in very small quantities for prototyping and R&D. Modern epoxy feedthroughs maintain a vacuum up to 10-8 Torr, with temperatures up to 200°C continuous (300°C intermittent), and also meet NASA's outgassing requirement of <1.0% Total Mass Loss (TML). Liquid epoxy's ability to flow and fill spaces thoroughly provides it's advantage, and in most applications, an epoxy feedthrough can be used where a glass-to-metal or ceramic feedthrough is used - the only notable exceptions are in very high temperature applications or where organic compounds are not allowed.

Designers and engineers no longer have to think within the constrained world of glass-to-metal and ceramic-to-metal feedthroughs. Epoxy feedthroughs are a new, exciting player in town, and their lower cost, easy prototyping and more flexible design capability make them a very attractive alternative.

For more information, visit https://BCEmfg.com or call BCE at (510) 274-1990

Custom Electric Heating Elements Provide OEM Designers Freedom and Flexibility

Custom heater for vacuum
applications with thermowell
and multiple RTD sensors.

Technology advances rapidly and new discoveries in material science, medicine, pharmacology, biology and semiconductors are being made every day. Along with these advancements in  technology comes new treatments, medicines, materials, and processes.

Original equipment manufacturers (OEM's) of analytical, semiconductor, biomedical, life-science, and aerospace equipment continually design new equipment to apply and leverage these discoveries. Pressure to produce new machines offering greater efficiencies, compactness, and greater production is always present. Each item in the precedent design undergoes scrutiny and very often has be modified to a new fit, form, or function.  New components are needed to meet the new design requirements.

The application of localized electric heating elements is one area that OEM design engineers find themselves navigating in unchartered waters. Very logically, they often attempt to use an off-the-shelf cartridge, silicone rubber, or mica heaters for their specialized heating requirement. Unfortunately this approach leads to compromises in layout, packaging, and performance. A much better alternative is considering a custom heating element, developed in consultation with an experienced custom heater manufacturer.

Custom semiconductor wafer
chuck heater. Highly uniform heat
with no brazing or casting. 

Experienced custom electric heater designers provide many important benefits throughout the entire product development cycle. For instance:

• Front-end, practical design review to optimize manufacturability.
• Timely prototype development.
• Partnerships and alliances with platers, brazers, casters and heating element manufacturers.
• Single source responsibility.
• Testing, calibration, and QC.
• Inventory management.
• Value-added assembly.

APCI Heater/Capillary Source Heater
400 deg. C, connector
plug, and internal RTD sensor.

The heater manufacturer partner provides critical guidance in areas such as material selection, power requirements under load, temperature vs. time data, watt density and packaging. With their help, high performance, precise fit, and long heater life are better ensured.

By choosing a custom electric heating element design, the OEM gets exactly what they need in terms of form, fit, and function plus scores of other benefits derived from the heater vendor's tacit knowledge and past experiences.

What is a Vacuum Feedthrough?

Electrical Vacuum Feedthrough
(Epoxy)

A vacuum feedthrough is designed to pass matter or energy, without leakage, from the outside of a vacuum chamber to the inside. The term vacuum feedthrough is often used interchangeably with electrical feedthrough, glass feedthrough, ceramic feedthrough, epoxy feedthrough and hermetic feedthrough. There are of course differences, but they all provide the same function - provide a leak-tight seal between the inside and outside of a vacuum chamber.

Epoxy, glass or ceramic feedthroughs refer to the materials used to seal the conductor, tube, or fiber optic cable from the vacuum/process connection. Hermetic feedthrough refers to the device's nature of being airtight or vacuum tight, such as "hermetically sealed".

Fiber Optic Vacuum Feedthrough

Vacuum feedthroughs are used for 2 primary functions: delivering energy (usually in the form of electricity or light pulse); and for delivering matter in the form of liquids and gases.

Electrical feedthroughs use electrical conductors such as wires to deliver electricity inside the vacuum chamber.

Liquid and gas feedthroughs use metal tubes or fiber optic cables to introduce fluids or light beams.

Liquid & Gas Vacuum Feedthrough

There is debate over what sealing material provides the best over-all performance-to-cost benefit.  Glass to metal seals and ceramic seals are ubiquitous and provide very good sealing properties, but they are expensive and difficult to customize, making prototyping and small production runs challenging. Early epoxy seals were limited in temperature range and were known to outgas, but new, modern epoxy compounds have been developed to perform as well as glass to metal and ceramic.

Modern epoxy feedthroughs can now achieve vacuum up to 10^-8 Torr, temperatures up to 200°C continuous (300°C intermittent), and meet NASA's outgassing requirement of <1.0% Total Mass Loss (TML).

For more information, contact BCE by visiting http://bcemfg.com or call (510) 274-1990.