KF40 Flanged, 125 Volt, 15A Female-to-Female Socket Vacuum Feedthrough

BACKGROUND

A BCE customer needed to replace a bulky power system located within a chamber.  A custom KF40 three-slot single female receptacle feedthrough was the optimal solution to help reduce size and increase efficiency.

SCOPE

The KF40 Socket Feedthrough needed to satisfy the following criteria:

• 80°C continuous operating temperature 
• 125V and 15A
• Female to female connection
• Vacuum rating: 10-5
• ALL TESTS PERFORMED AT ROOM TEMPERATURE 

OUTCOME

BCE designed a simple yet effective unit using a custom elongated KF40 flange with two three-slot single female receptacles. The customer was able to relocate the power system to the outside chamber increasing the available space within the vacuum chamber while maintaining the desired vacuum rating.

BCE’s Epoxy chemical adhesion, the strongest mechanism of any adhesive bond, made the seal possible.  The viscoelastic nature of the epoxy absorbs vibrations and allows for a better performance by reducing fatigue.

Download the BCE Application Note here.

Here's to a Great 2019 from BCE!

Happy Holidays from BCE!

All of us at BCE (Belilove Company-Engineers) wish our customers, partners, vendors and friends a very Happy Holiday Season and a wonderful 2019!

Save Time and Money in the Long Run: Choose a Custom Electric Heater When It Comes to Heating Clean and Ultra-pure Fluids

Custom heater for clean and ultra-pure fluids (from BCE)

What do the fuel cell, bio-med, laboratory, food, pharmaceutical, medical, semiconductor, and electronics industries all have in common? Applications in their processes requiring a fast responding and accurate high purity fluid heater.

Each of these industries include manufacturing processes that require a small and efficient heating source as a component of their production. These heaters must be ruggedly designed, made from materials immune to process contamination, and be vacuum tight. The heaters will be subject to high temperatures, harsh solvents, and corrosive gases. Many times they must maintain a seal for full vacuum, demonstrate a unique heating profile, and maintain very close control.

Common requirements in these processes:

• Capable of handling high vacuum.
• High temperatures.
• Isolation the process media from heating element.
• Isolation from other area of contamination.
• Very accurate control, including internal sensors.
• Fast heat up and cool down.

Few manufacturers offer electric heaters with all of these features with an off-the-shelf product, so a custom (or semi-custom) heater is required. Heater customization allows for specific application requirement to be addressed. Examples are type of internal sensor (RTD or TC), the use of chemical inert glass liners, a profiled heating pattern, and specific wetted materials.

Using stock screw plug immersion heater for these applications should be avoided. This category of heater will not stand up to the rigors of the application, as they are designed for general industrial service. They are not intended for high purity, will not meet material compatibility requirements, have poor controllability and are bulky in size.

The answer is in a custom high purity fluid heater designed with the specific process in mind.

Benefits of developing a custom fluid heaters are:

• Available in a variety of voltages.
• Available in a wide range of watt densities.
• Temperatures up to 350°C.
• Effective heated area can be profiled to generate a liner temperature profile.
• Vacuum compatible up to 1.0 x 10-8  STD. CC/SEC Helium.
• Can be provided with internal sensors (RTD or thermocouples).
• Can be glass lined for ultra pure gas application.

Careful review of the application is important and the help of an experienced heater application engineer is required. Choose a vendor with a long, proven track record of success. The outcome of the test, process or product will be infinitely improved.

The Top Four Reasons Why Cartridge Heaters Fail

Cartridge heaters fail because either the heat generated in the internal resistance wire is not efficiently dissipated or moisture (or a foreign substance) seeps inside the protective sheath, creating a short circuit.

Inadequate heat dissipation results in an elevated internal temperature, which can rapidly breakdown the heating element. Inadequate heat dissipation occurs for several reasons: when machined tolerances are outside of an accepted range (improper fit); if the watt density is too high; or when powered by too high a supply voltage.

1) Loose Fit

Loose fit is the most common cause of premature cartridge heater failure. The bore hole within which they are inserted must be held to tight tolerances. High watt density cartridge heaters are even more sensitive as the internal temperature of the heater can rise rapidly and jeopardize the life of the heating element. To ensure adequate thermal dissipation, the recommended hole diameter is no more than 0.002 in. greater than the nominal diameter of the heater.

Typical allowable watt densities for swaged cartridge heaters are based on fit and operating temperature.

Max. allowable watt density vs. fit. Click image for larger view.
Graph courtesy of Backer Hotwatt.

2) Too High a Watt Density

The watt density of the heater is vital to its performance. This is a measure of thermal power density and the higher the watt density, the greater the needs are for thermal dissipation. High watt densities can lead to premature failure when thermal dissipation needs are not met, as the internal temperature of the heater will exceed the limits of the resistive heating element.

3) Too High a Supply Voltage

In a resistive circuit, since the resistance is fixed, when the voltage is doubled, the current doubles as well as quadrupling the wattage output. Incorrectly specifying the supply voltage can lead to premature heater failure, as voltage has a dramatic effect on the wattage and the amount of heat generated as can be seen in the following formula.

Voltage calculation. Courtesy of Backer Hotwatt.

4) Moisture or Contaminant Ingress

Even when cartridge heaters feature heliarc-welded end caps, they are prone to failure when the air surrounding the heater contains impurities or has a high moisture content and the heater’s leads are not adequately sealed. This is due to the nature of MgO insulation: it is a highly hydroscopic white powdered mineral, and when the heater undergoes thermal cycling a vacuum is created, drawing in moisture or other contaminants such as oil, which can result in internal shorting.

Watt Density Selection and Thermal Cycling

Suggested watt density is based on several factors including the fluid medium to be heated, the desired operating temperature and process variables such as flow rate. In general, operating temperature is inversely related to the suggested watt density. Additional considerations are taken when heating a fluid to a point near its boiling point, as phase changes drastically reduce its heat transfer capabilities. Highly viscous fluids or fluids that tend to coke or carbonize also require a low watt density. Highly corrosive solutions also need a low watt density, as the increased watt density increases the potential for corrosion, drastically reducing the life of the heater’s sheath.

Selecting an incorrect watt density can have adverse effects to the response of a thermal system, but it is not the only factor to consider. There are four basic elements to any thermal system, including the thermal load, the heat source, the heat transfer device and the temperature controller.

Thermal power delivered by a heating element is a function of wattage, and a correctly sized heating element will provide an ideal thermal response without rapid cycling of the element. The optimal wattage results in a 50/50 off/on cycle, which prevents or minimizes hunting or temperature overshooting. For more precise thermal control, variable voltage devices or solid-state controllers may be used.

For more information on properly applying cartridge heaters, contact BCE by calling 510-274-1990 or by visiting the cartridge heater section of the BCE website.

Electric In-line Clean Fluid Heater Provides On-demand Heat in a Small Package

Clean fluid, flow-through heating system.

Many original equipment manufacturers require precise temperature control and a very compact package to heat clean fluids. Equipment examples are semiconductor gas processing equipment, kidney dialysis (hemodialysis) machines, process gas analyzers, ink preheating systems, photoresist coating equipment, and parts cleaning equipment.

Electric heaters used in these applications must be compact, lightweight, and made of materials that won't contaminate samples. They also must be fast responding and provide large amounts of power when required.

BCE, a Northern California manufacturer of custom electric heating elements, developed their "Mini Clean Flow" heater for these types of applications. The Mini Clean Flow is a very compact, fast responding electric heating element designed for applications where the heating of clean fluids is required, most often in the semiconductor, medical, and laboratory equipment industries. Designed with high power ratings wrapped in a small package, these specialized heaters offer ultra-fast heat-up and precise, accurate temperature control.

Mini Clean Flow heaters combine inlet and outlet connections along with a baffled stainless steel enclosure, creating a turbulent flow pattern for efficient heat transfer. Sealed resistance heaters are used to isolate process fluids from having contact with the elements directly. Internal thermocouples provide for outlet temperature regulation as well as for maximum sheath temperature control.  The Mini Clean Flow's advanced mechanical design, along with its high power density and overall low mass, provides the end-user with a very efficient and precise heating solution.

For more information, contact BCE.
Phone: 510-274-1990
Web: https://bcemfg.com/minicleanflow

Consistent, Repeatable and Efficient Results from a 300mm Semiconductor Chuck Heater with Mirror Finish

300mm Hot Chuck Heater with Mirror Finish

Semiconductor fabrication involves numerous processes, materials, and specialized equipment. The base semiconductor material from which integrated circuits and microchips are manufactured comes in the form of round, thin crystalline disks referred to as wafers. During semiconductor production, wafer temperature uniformity is one of the most critical factors affecting product quality and consistency.

To increase the speed at which a physical or chemical reaction takes place, heat is applied at various stages of the process. Heat is applied through the use of heated chucks which provide precise thermal uniformity which, as mentioned above, is critical for production.

Click image for larger view.

To summarize, the goal of the heated chuck is to provide a very high level of temperature uniformity across the entire wafer surface so that processing output is highly consistent, repeatable and efficient.

BCE, a manufacturer of custom electric heaters and thermal systems was asked by a customer

to replace a cast aluminum heater plagued with surface finish problems. Poor surface finish equates to poor thermal uniformity and heat transfer. To add insult to injury, the vendor was quoting extremely long lead-times for replacements.

Using their broad experience in semiconductor chuck heater design, BCE knew immediately the best solution would be a vacuum brazed-in 6061 T6 aluminum heater with a 2-3 Ra μin surface.

Specification to be met:

• Temperature uniformity +/- 1%
• 350°C - 450°C Temperature range
• Surface finish of 2-3 Ra μin
• Hard coat Anodize
• 6061 T6 Aluminum
• Be able to heat ceramic top plate
•  20 Meg-ohm isolation at 1000 VDC
• Hi-pot 2E + 1K at 3mA

Results

BCE designed a chuck heater using their own proprietary internal element patterns, notches, and thermocouple holes, as well as adding additional manufacturing processes to provide the 2-3 Ra μin finish. Vacuum integrity for the customer has been greatly increased as well as contact with the ceramic workpiece and temperature uniformity.

For more information, contact BCE by calling 510-274-1990 or through visiting their website at https://bcemfg.com.

BCE Remembers, Thanks, and Salutes Our Veterans. Never Forget.

Important Safety and Performance Precautions When Using Electric Heating Elements

The safety and performance of electric heating elements is dependent upon the user's proper handling, installation, control, application, and maintenance. While it is impossible to anticipate all the operating conditions for electric heaters, the following items are universal precautions that must be considered in every situation.

Electric heater element handling, installation, application, and maintenance precautions:

1. Always have a qualified person install the heating element in accordance with the National Electrical Code and/or local codes.
2. Always use extension wire rated for the current, voltage, and exposure temperatures suitable for the application.
3. Always use the proper environmentally rated electrical connection and housing for the type of  service the heater will see.
4. Use temperature controlling and/or limiting devices with electric heaters.
5. Use ground fault protection where required.
6. Do not apply higher voltages than the marking on the heater indicates.
7. Do not operate heaters in thermally insulated conditions where sheath temperatures may exceed the recommended maximum.
8. Do not expose heaters to conditions, substances or contaminants that can damage, change, or destroy the integrity of the heater's sheath or electrical insulation.
9. Heaters by their nature can absorb moisture which can cause high leakage current. A megohm test to the manufacturers specification should be performed to ensure moisture levels are within acceptable standards.
10. Do not apply heaters with operating sheath temperatures that exceed the safe exposure temperature of the process media.

Understanding Vacuum

At sea level, the earth's atmosphere exerts a standard pressure upon us of 14.7 pounds per square inch absolute (PSIA), or 29.92" of mercury (Hg), or 760 mm of mercury (Torr). All of these values refer to "standard atmosphere" which is measured at sea level.

Vacuum is a term used to describe an area, zone, or compartment containing less pressure than atmospheric pressure.

Vacuum is measured in inches of mercury (Hg) in the United States. There are two different scales to measure vacuum.

One scale is referred to as "inches of mercury gauge vacuum" ("HgV), where the measuring range starts at 0 inches of mercury (atmospheric pressure) and goes up to 29.92 inches of mercury, known as perfect vacuum (not achievable on Earth).

The alternative scale is "inches of mercury absolute vacuum" ("HgA), which reverses the "HgV scale, having it instead read 29.92 inches of mercury at atmospheric pressure and 0 inches of mercury at perfect vacuum.

Here's an example of the relationship between inches of mercury gauge and inches of mercury absolute:

24 inches of Hg gauge = 5.92 inches of mercury absolute.
Calculation: 29.92 - 24 = 5.92

It is very important to  determine what scale you are using, meaning gauge or absolute. A misunderstanding can result in large errors.

The unit "Torr" is used when working in higher vacuum ranges (low absolute pressure). 1 Torr equals 1 millimeter (mm) of mercury in absolute pressure.

Considering one linear inch equals 25.4 mm, and atmospheric pressure (at sea level) is 29.92 inches of mercury, then using the equation 29.92 inches x 25.4 mm = 760 Torr. 760 Torr is 0 vacuum, while 0 Torr is perfect vacuum.

BCE is a leading manufacturer of electrical, fiber optic, and tubing feedthroughs for use in vacuum applications. Visit https://bcemfg.com or call (510) 274-1990 to learn more.

BCE In-house Heater and Feedthrough Machining Capabilities

BCE, a California manufacturer of electric heating elements and vacuum feedthroughs, has extensive in-house machining capabilities providing BCE a competitive advantage with customized products and quick prototype turnaround.

BCE produces machined components for their specialized cartridge heaters, vacuum feedthroughs, and custom thermal assemblies. A good example of their in-house capabilities is their complete machining process for wafer chuck heaters used in the semiconductor industry. BCE machines the complete assembly, with grooved patterns to accommodate interference fit, vacuum brazed, or welded-in heaters and / or cooling tubes. BCE can both deliver fast prototypes as well as handle production manufacturing in both standard and exotic materials.

https://bcemfg.com
(510) 274-1990

MEGA CLEAN FLOW Heater: Minimizing Toxic Emissions for Cogeneration

BACKGROUND

Using a small (~25HP) lean burn natural gas motor for cogeneration, our customer wanted to mitigate toxic emissions on the exhaust. The challenge is reducing Formaldehyde and Benzine output levels as well as reducing all other toxins without air-flow exposure to ni-chrome resistors.

The MEGA CLEAN FLOW HEATER needed to satisfy the following criteria:

• Exhaust air flow rates from 15cfm to 30cfm
• Inlet 2” NPT, outlet 2” NPT
• Engine loads for 25% to 100%
• Insulation of all inlet & outlet entries as well as process chamber
• Air-flow exposure to 304 or 316 stainless steel only
• Outlet temperature must be <288°C at ALL flow rates
• BCE Controllers needed for operating temp and
• 50 Meg-ohm isolation at 500 VDC
• Hi-pot 2E + 1K at 3mAmp
• ALL TESTS PERFORMED AT ROOM TEMPERATURE 

OUTCOME

The Mega Clean Flow Heater proved to be the most optimal design for Cogeneration. The temperature, watt density, and variable flow rates assured success when operating the instrument. BCE’s proprietary design was essential in the application.

Download the PDF version of the MEGA CLEAN FLOW Heater: Minimizing Toxic Emissions for Cogeneration case study here. For more information, visit https://bcemfg.com or call 510-274-1990.

Vacuum Feedthroughs the Way You Want Them

Equipment manufacturers and scientific researchers are continually challenged with supplying power, fiber-optic, control, and monitoring cables into sealed vacuum vessels. Whether due to space restrictions, special geometries, or number and type of conductors, standard glass-to-metal or ceramic feedthroughs never quite fit the bill. Unfortunately, because of limited options, many designers are forced to compromise and go for an off-the-shelf solution.

Until now. 

BCE designs, engineers, and manufacturers feedthroughs that can handle custom shapes, tight angles, curves, shielded wire and still provide a tight seal.

Why You Need to Consider BCE:

• Feedthroughs Designed to Your Specifications
• 24 Hour Turnaround on Custom Drawings & Quotations
• Custom Feedthroughs Ship in 2 Weeks

Call today. 510-274-1990

Basic Wattage Requirement Calculations for Metals, Non-metals, and Gases

Accurately heating various materials such as metals, non-metals, liquids and gases is complex. There are many variables to consider. Material properties such as density, thermal conductivity, specific heat and time all must be known to calculate a correct wattage value. Phase change (solid to liquid, liquid to gas) requires additional calculations to account for latent heat of vaporization and latent heat of fusion.

BCE, a manufacturer of custom heating elements and thermal systems, has a page on their website providing basic wattage requirement calculations for your reference. These calculations will assist you in determining the amount of power your heater will require, but it is strongly suggested you consult with a heater application expert before designing, specifying, or purchasing. Their expertise and knowledge will assure a safe, efficient, and economical heating solution.

Visit the BCE Basic Wattage Calculation page.

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

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. 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 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. 

Clean Gas and Liquid Stream Heating

Clean gas and liquid heater
(BCE Mini Clean Flow)

As demand for purity increases throughout the medical, analytical, and semiconductor industries, equipment manufacturers continuously require new tools to reach the next technology threshold. In these industries electric heating applications for clean gases and liquids abound. Just a few examples are; clean air circulation, nitrogen heating, product drying, dehumidification, analytical instrument sample prep, incubation, DI water heating, solvent removal, wafer drying and processing.

High purity gas and liquid heating is challenging. Heater designs have to address problems and concerns involving contamination, thermal efficiency, electrical isolation, controllability, size, and packaging. Gas and liquid heating applications can vary dramatically. Some applications are very difficult to control and size is always a concern. One of the toughest issues to overcome is the seemingly mutually exclusive requirement for smaller size and higher power.

General diagram of "clean flow" heater.

Driven by innovation and competition, the need for hotter, cleaner, smaller and more efficient electric heaters is unceasing. One type of heater known as the "clean flow" has broad adaptability to many clean gas and liquid heating needs. It utilizes an internal heating element isolated from the process flow chamber, both electrically and physically. Best described as a "mini circulation heater", the heater's flow chamber, with inlet and outlet connections, completely protects the clean gas or liquid from external exposure and contamination.  The internal heating element can run at fairly high watt densities to accommodate fast changing flow rates, while still maintaining a compact and efficient package.  Internal RTDs or thermocouples can be incorporated to monitor temperature closely, or to protect the heater from over-temperature.

If you have questions about electrically heating clean gases or liquids, contact BCE by either visiting https://bcemfg.com or by calling (510) 274-1990.

BCE ISO 9001: 2015 Update

BCE is very pleased to announce the company has been awarded ISO 9001: 2015 approval.

July 23, 2018 - BCE, Inc., a California based designer and manufacturer of electric thermal systems and vacuum feedthrough devices, announced today that it has been recognized for its commitment to quality and excellence by being certified in accordance with ISO 9001:2015.

For more information, contact BCE by calling 510-274-1990 or visiting https://bcemfg.com.

The SMARTFLOW Circulation Heater - Highly Efficient Electric Heater Design for Heating Liquids

The SMARTFLOW liquid heater is designed for applications where fast heating of liquids is required. All parts exposed to liquid flow are constructed of 304/316SS (other materials available). All units have built-in Type J or K TC with potential of added adapter for outlet flow.

• Wetted parts constructed of 316 stainless steel (other material available) 
• Liquid flow passes over an enclosed heated body.
• All threaded fittings are available as NPT, SAE, BSP & VCR
• Internal heater provides uniform heating.
• Made in U.S.A.

https://bcemfg.com
510-274-1990

Get Hot! with BCE's Mini Clean Flow Heater

A very compact, fast responding electric heating element for liquids and gases for all clean, fuel cell, bio-med, laboratory, food, and pharmaceutical applications.

The heating elements inside the Mini Clean Flow Heater are isolated electrically from the process media, protecting them from contaminants and providing long life.

The Mini Clean Flow Heater operates in a liquid or gas stream providing very fast response times and accurate control capability.

Epoxy Feedthroughs: Fast, Flexible, Affordable

During the past decade, new epoxy compounds have been developed that rival glass and ceramic in performance. BCE is at the forefront of this development.

With modern epoxy feedthroughs, any kind of standard or custom connector is sealed in a completely potted, high-performance, clear epoxy compound. Epoxy seals offer countless design options, and most amazingly, performance equal to or better than glass or ceramic. Better yet, pricing is very competitive and quick turn-around for prototypes and short production runs are not a problem.

FAST PROTOTYPES
BCE can provide custom prototypes for your design with high vacuum performance for today's fast moving markets.

PRINTED CIRCUIT BOARD, FLANGED OR THREADED CONNECTIONS
Wide variety of standard and custom mounting options for epoxy vacuum feedthroughs.

FEWER COMPONENTS, INCREASED RELIABILITY
Fewer components and connectors, often reducing 5 components to 1, BCE epoxy feedthroughs also eliminate multiple potential failure points.

CERTIFIED LOW OUTGASSING
BCE feedthroughs meet NASA outgassing requirements. BCE vacuum leak checks 100% of feedthroughs.

Electric Heating Element Design: Nichrome Wire

Nichrome wire heating element inside a quartz tube.
(Image courtesy of Wikipedia)

When an electric current passes through a conductive material (a resistor) energy in the form of heat is released. The greater the resistance to electron flow, the greater the heat energy created. The terms resistance and conductance apply to the nature of the conductive material, and it's ability to pass current.

Resistance (measured in ohms and using symbol "R") is defined as the electrical voltage (in volts using symbols "V") divided by the current (in amps, using symbol "I"), or R=V/I. This formula is one variant of Ohm's Law.

The heat, or power, released from the resistor (measured in watts, using the symbol "P") is a function of the supply voltage squared, divided by the conductor resistance. This version of Ohm's Law looks like this: Watts = Voltage squared / Resistance, or P=V²/R.

You can see if the resistance is too high, voltage does not flow, and no heat is produced. For the benefit of simplicity, we'll forego a discussion into superconductors, like those used on MRI machines and mass spectrometers, because their behavior includes complicated magnetic field discussions. Instead, we'll stick to common conductors often used to pass electrical current.

Selecting the right resistive material for a heating element is crucial in order to maximize heat output, heater longevity and energy usage - a conductive material with high resistance that is also easy to work with.

Nichrome alloy, made up of 80% nickel and 20% chromium is by far the most popular resistance heater wire, and is a available in a wide variety of wire gauges and ribbon shapes. It's popularity is performance based - it has high resistance, is easy to apply to many heater configurations, does not oxidize, has a low expansion coefficient and a high melting point. In the design and development of electric heating elements, if you grant that nichrome wire is at the heart of most electric heaters, everything else comes down to packaging and performance.

While there are other materials such as Kanthal (iron / chromium / aluminum) and Cupronickel (copper / nickel), and newer exotic ceramics, the vast majority of electric heaters used in industrial, commercial, OEM, and consumer goods all still rely on the ubiquitous and time proven nichrome alloy.

For more information on electric heating elements, contact BCE by visiting https://bcemfg.com or by calling (510) 274-1990.

Happy Independence Day from BCE!

"America was built on courage, on imagination and an unbeatable determination." Harry S. Truman

Happy Independence Day from all of us at BCE.

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.

OEM and Replacement Heaters for Mass Spectrometers

Mini Clean Flow Heater

MINI CLEAN FLOW HEATER

A very compact, fast responding electric heating element for liquids and gases for all clean, bio-med, laboratory, food, and pharmaceutical applications.

CAPILLARY SOURCE HEATER

Capillary Source Heater

The APCI (Atmospheric pressure chemical ionization) heater has a Resistance Temperature Detector (RTD) built into it.  The heater assembly has a .016” ID capillary tube in the center of the heater axis.  The maximum operating temperature is up to 400°C.  This assembly comes complete with the connector plug.

The APCI sample is typically dissolved in a solvent and pumped through a heated capillary.  Nitrogen gas is introduced, the gaseous solvent is heated up to 400°C and the sample is then ionized by corona discharge.

FLANGED GASLINE HEATER

Flanged Gasline Heater

This heater assembly is used in the electron ionization in gas chromatography and mass spectrometry to ionize and fragment analyte molecules before mass spectrometric analysis and detection.

A typical electron ionization source exposes the analyte, under vacuum to a stream of thermionic electrons produced from a resistively heated-gas weldment assembly. Gas heated up to 450°C. Built-in thermocouple for precise temperature control is incorporated in the gas body assembly.

CERAMIC HEATER

CeraWatt Ceramic Heater

CeraWatt ceramic heating elements are composed of high temperature materials such as tungsten and alumina ceramic substrates. The metal heating resistance element is thick film technology. CeraWatt heaters provide excellent corrosion resistance, high operating temperature, long life, energy efficiency, uniform surface temperatures, and outstanding thermal conductivity.

Inline Gas Heaters: Precise Heat and Control without Contamination

Inline gas heaters are designed to heat clean gases or liquids without contaminating the stream. They provide exceptionally fast thermal response and high power densities in a compact package. The process fluid never comes in contact with the heating element directly, but instead, is shielded by a 316 stainless steel barrier. These heaters, often customized to suit a particular requirement, are available in a wide range of wattages and voltages. They are capable of high temperatures and heat and cool very rapidly due to their low mass.

Inline Electric Gas Heater for Clean Fluids
(BCE)

The heating elements are isolated electrically and physically from the process media, protecting them from contaminants and providing long life. The gas flow passes through the heater housing and over an enclosed heated body. The process media is never exposed to the resistive heating element. Inlet and outlet connections also come in a variety of sizes and types including NPT, SAE, BSP and VCR.

Applications:

• Mass Spectrometers
• Medical Devices
• Pharma Analyzers
• Lab Equipment
• Semiconductor process

FAQ: Custom Heater Assemblies

Custom heater assembly that includes a sealed cartridge
heater, thermowell, and thermocouples (multiple).

What is a custom heater assembly?

In general terms, a custom heater assembly is a device that transforms electrical current to heat energy, is designed in a way that accommodates the needs of a unique heating requirement, and is used for the heating of gases, liquids, plastics, or metals.

What is a thermowell?

A thermowell is machined metallic tube used to house and protect sensors or heating elements. Thermowells not only protect heaters and sensors from erosive or corrosive media, they also allow for easy removal and replacement without exposing the process media.

What is a cartridge heater?

A cartridge heater is a cylindrically shaped electric heating element intended to be inserted in holes in metal platens or immersed in flowing media. The design incorporates a ceramic bobbin wound with nichrome resistance wire, carefully centered inside a metallic tube, and then backfilled with magnesium oxide (MgO), which provides electrical insulation. Cartridge heaters can be either swaged (compacted MgO) or un-swaged (loosely filled MgO). Swaging allows for maximum heat transfer to outside surfaces while keeping internal heater temperatures as low as possible, and preserving dielectric qualities.

What is a sealed cartridge heater?

A sealed cartridge heater incorporates all of the characteristics of a standard cartridge heater but is additionally sealed with BCE’s proprietary epoxy seal making it vacuum compatible. The seal additionally elongates heater life, especially in high humidity and moisture environments.

What electrical tests are performed on heaters?

Heaters undergo 3 main electrical tests: Resistance, MegOhm and Hipot.

A resistance test is performed using a fluke meter to ensure that the heater is manufactured within the correct tolerances of the electrical specifications. Heater leads are connected directly to the fluke meter leads to perform the test.

A MegOhm or Insulation Resistance test is performed using a megohmmeter. As its name implies it tests for any breakdown in a heater’s insulating material. The test is performed by supplying low to medium voltage to the insulating material for a small period of time.

A Hipot test is also used to assess the dielectric strength of the heater’s insulating material. In addition to performing a Dielectric Withstand Test like the Megohm, it can also perform a Dielectric Breakdown Test. This means that the heater insulating material is shocked at very high voltages until failure is achieved. This is more commonly performed on samples as it destroys the heater.

What is a thermocouple?

A thermocouple is a thermoelectric device that measures temperature. When the wire junction of its two dissimilar metals changes in temperature, a small voltage is created. The voltage is then used to calculate the temperature using the thermocouple’s reference table.

What is an RTD?

RTD stands for "resistance temperature detector". It is generally constructed of a fine and pure metallic wire wound around a ceramic or glass core. The relationship between wire resistance and temperature is used to sense the temperature of other devices.

Custom Heating Elements and Thermal System Design

The design and manufacture of custom heating elements and thermal systems are a specialty of BCE Inc. (Belilove Company-Engineers), a Hayward, California-based company that has served the aerospace, semiconductor, analytical and medical equipment industries for more than 25 years.

As both a manufacturer and integrator of components, BCE offers custom electrical heaters, sensors, and controls as discrete components, or as part of a larger, value added thermal system.

Visit https://bcemfg.com or call 510-274-199 for more information.

Vacuum Feedthrough FAQ

What is a vacuum chamber?

It is an enclosure in which a low pressure or vacuum environment is created through the removal of air and gases.

What is a feedthrough?

Feedthroughs are electro-mechanical devices that provide leak-proof electrical and pressure connections into a vacuum chamber.

What is a hermetic seal on a feedthrough?

It provides an airtight seal against contaminants entering a vacuum chamber. Contaminants can include gases and fluids like moisture, humidity, and chemicals.

What processes are used to provide a hermetic seal?

Hermetic seals are generally processed in furnaces under regulated temperatures and pressures. They can be glass-to metal, ceramic-to-metal or epoxy based.

What metric is used to assess the hermeticity of a feedthrough?

Feedthroughs generally undergo helium leak checks to establish the helium leak rate, an indicator of the feedthroughs’ vacuum compatibility. Prior to a helium leak check, feedthroughs are visually inspected for cracks, damage and porosity in the seal.

What is the NASA ASTM E595 standard?

This standard pertains to epoxies that exhibit low Total Mass Loss and Collected Volatile Condensable Materials during Outgassing in a vacuum environment.

For information on vacuum feedthroughs, contact BCE by calling 510-274-1990 or by visiting the BCE website - https://bcemfg.com

New Electric Heater Design Maintains High Flow Rate of Cold Propellants and Optimizes Flow in Space Launches

Ideally a rocket engine would capitalize on internal heat dissipations to create a self-regulating thermal environment. However, in the majority of instances, maintaining a high flow rate of cold propellants can obstruct the flow path. Thus, it becomes essential to integrate resistive heaters inside the flow path’s valves and manifolds. Surface-mounted patch heaters are generally used for this application. These are polyimide/silicone sheathed resistive elements with one side adhered directly to the valves and manifolds. Although patch heaters may present a viable solution, the BCE HEM Sealed Heater™ outperforms as heat flows uniformly from inside the cartridge directly to the heated bodies.

This is because they are secured directly to components by the means of an integrated flange. In essence, the BCE HEM Sealed Heater™ incorporates both the cartridge heaters’ wire wound resistive element encased in a metal sheath and the vacuum compatibility of a feedthrough. Furthermore, the BCE proprietary epoxy seal allows the heater to pass strict electrical tests ensuring the purity of the dielectric materials and hence, preventing shorting.

SCOPE

• Easy mounting of heaters into manifolds and valve bodies
• Mounting to be compatible with standard hardware
• 6 to 36V electrical specifications
• Resistance tolerance to be +/-5%
• < 1,500 VDC or greater on the Hi-pot test
• < 4,000 Megohm at 500 to 1000 VDC on the Megohm test
• < .010 sheath thickness
• Sheath can be Inconel or 300 series stainless material
• Sealing Epoxy to meet NASA ASTM E595 Low Outgassing Standard
• Maximum operating temperature of heater <200°C

OUTCOME

The BCE HEM Sealed Heater™ proved to be the most optimal design for the heating of fast-flowing liquid propellants. The heater incorporated all engineering requirements and was mounted into the manifold through an integrated flange using custom hardware. In addition, the heater’s vacuum compatibility was ensured through BCE’s proprietary black epoxy meeting NASA ASTM E595. Furthermore, successful rocket launches into lower to high earth orbit validate that the BCE HEM Sealed Heater™ is rocket ready and capable of high vacuum applications. BCE, the ultimate partner for resistive vacuum applications.

For more information on the HEM Sealed Heater visit this link.

Everything You Wanted to Know About Cartridge Heaters ...

Cartridge Heater (Hotwatt Backer)

Reprinted with permission of Backer Hotwatt

WHAT ARE CARTRIDGE HEATERS?
Cartridge heaters originally consisted of a ceramic-supported heating wire inserted into round metal tube, making them look like cartridges (the likely source of their name). They provide localized heat to restricted working areas requiring close thermal control. Their power density is less than 60 W/in2 and they generate temperatures up to 1,200°F. They range in diameter from 1/8 to 2 in. and vary in length from less than an inch to over four feet. Although they are usually round, they can have square or rectangular cross sections. Standard cartridge heaters account for an estimated 20% of all electric heaters made.

Compacted cartridge heaters were developed about 60 years ago and feature inorganic powder tightly compacted onto the heater wire. This increases their power density to nearly 500 W/in2 and maximum temperatures approach 1,800°F. The need for higher quality tubing and precision-fired crushable ceramics makes compacted heaters cost 1.5 to 3 times the cost of a standard cartridge. They are available in diameters from 1/8 to 1 in. and lengths from 1 inch to over 3 feet.

HOW ARE CARTRIDGE HEATERS MADE?

Cartridge Heater Internal View

For standard cartridge heaters, nickel / chromium heating coils are inserted in a ceramic tube inside a metal housing or sheath. Magnesium oxide filler is then vibrated into the hole to fill any voids. This increases heat transfer to the metal exterior. An end cap is welded on the bottom and insulated leads are installed at the opposite end. For swaged cartridge heaters, the nickel / chromium wire is wound around a ceramic core, placing the wire closer to the metal housing. Magnesium oxide is vibrated in and the heater swaged to a specific diameter. This compresses the MgO so it becomes a better conductor of heat while maintaining its dielectric properties. This improves heat transfer and allows for higher watt densities. Swaging also lets the heaters operate at higher temperatures and better withstand vibrations.

HOW CAN YOU GET THE MOST EFFICIENT HEAT TRANSFER AND LONGEST OPERATIONAL LIFE OUT OF A CARTRIDGE HEATER?
There are several steps users can take. On installation, for example, cartridge heaters should be installed in holes drilled and reamed to no more than 0.002 inches larger than needed. The heaters are routinely sized to never be 0.005 less than the nominal diameter and always at least .001 under the nominal diameter for a slide fit. These close fits ensure rapid heat transfer from the heater to the housing and helps keep the heater as cool as possible, which contributes to a long life. Heaters should not be cycled from low to high temperatures as it shortens their life considerably. Instead, designers should calculate the proper wattage for their applications. The best wattage results in a 50/50 off/on cycle. For temperatures over 750°F, off/on control can be replaced by input voltage regulation through variable transformers or proportioning controllers to minimize temperature fluctuations. If a heater is going to be turned off routinely, the air around it should be kept dry and no impurities (oil, gas,) should be in contact with the heater. That’s because the ceramic material used in cartridge heaters is hygroscopic. Every time power to the heater is switched off, it creates a vacuum inside the cooling housing which draws in air and any nearby impurities from the surrounding area. The moisture or impurities, once inside the housing, can cause a short circuit and result in heater failure.

If a thermostat is used to control the temperature, it should be no more than 0.5-in. from the heater. Mounting it any farther away could let the unit run hot and thereby shorten its life. Another cause of failures is too high a watt density. If the heater was incorrectly specified for an application and provides too much heat, the heater will not be able to dissipate the heat and will fail. Similarly, if the heater is designed for 120 V but is being powered by 240 V, the output wattage will be four times greater than it should be, which can, again, lead to failure.

WHAT OPTIONS ARE AVAILABLE ON CARTRIDGE HEATERS?
There are several options and variations available. Heaters may be three-phase or multiple wattage in a single unit. For instance, an application might need quick heat ups and then a standby circuit to maintain a relatively low temperature using different wattages based on changing thermal loads. Heaters can have wattage outputs that vary over their lengths in order to even out temperatures over a platen or a large surface. Heaters can also have built-in thermocouples, usually at the bottom of the heater and type J or K grounded or ungrounded. If a precision fit is needed, companies can supply centerless ground diameters. They can also supply certain heaters at higher voltages (300 to 600 V).
Heaters used in corrosive environments can be Teflon coated or electro-polished. Heaters that need hermetic sealing or will be used in a vacuum application can be ordered with ceramic-to-metal seals that withstand temperatures to 1,000°F.

CAN CARTRIDGE HEATERS BE USED IN LIQUIDS AS IMMERSION HEATERS?
Yes, when applied with a mount- ing fitting. Not all cartridge heaters made as immersion heaters are completely moisture sealed. The heater and bushing are submersible but the termination end is not necessarily sealed. If an application is in a high humidity area, however, the termination area should be sealed. Seals can be silicone rubber or Teflon which are good to 400°F, or epoxy potting which can handle temperatures to 265°F.

WHAT ARE SOME OF THE TERMINATION OPTIONS OFFERED ON CARTRIDGE HEATERS?
There are multiple options for cartridge heaters, almost too many to list. Standard options start with straight internally connected leads. External connections are optional on larger sizes, recommended when repairable leads are required. There are also post terminals available on cartridges 15⁄16-in. and larger. For applications with limited space, manufacturers can supply right-angle leads.

There are also several options for protecting leads. Fiberglass or silicone rubber sleeving, as well as ceramic bead insulation, protect against temperatures up to 1,000°F. Additional protection can be provided using flexible conduit or stainless steel braid.

Have a requirement for cartridge heaters? Call BCE now at 510-274-1990 or visit https://belilove.com