Polyimide Thermofoil Heaters Used for Space Applications

Thermofoil heaters of an all polyimide (adhesive-less) construction are used for high reliability space applications. They are ideal for extreme temperature fluctuations and have high tear and tensile strength. The specifications for the design and manufacture of these heaters are rigidly controlled, and rightly so. These heaters often perform critical heating application on satellites and other space craft.

Construction

A polyimide (Kapton) is used as the heater base material, also known as the substrate or mounting surface. A second polyimide layer over the heating element provides a protective enclosure.

Heater Element

The heating element is made of a Ni-600 Inconel (nickel-chromium-iron) alloy. Single or dual resistive elements may be used in the design, but the element must be must be of a single layer in cross-section. The element are normally an etched foil design with uniform in cross-section, and they have a minimum trace width of 0.010 in. (0.0254 cm) by design. Spacing between foil traces is tightly controlled and must not be less than 0.010 in. (0.0254 cm). The spacing between the outer foil trace and the heater edge (border trim) also cannot be less than 0.010 in. (0.0254 cm).

Lead Wires

Lead wires must be a minimum of 26 gauge when using high strength copper alloy conductors, and 24 gauge for all other copper conductors. Lead wire insulation must consist of polyimide (Kapton), polytetrafluoroethylene (PTFE/Teflon), or ethylene-tetrafluoroethylene (ETFE) materials.

Lead Termination

The termination of the lead wire has to be welded and contain a minimum of two weld points between the lead wire and landing bond pad. Lead wire terminations also need to be enclosed in a hardened Hysol epoxy potting, in order to secure lead wires to the heater so that lead pull stresses are not transmitted to the weld joint.

Power Rating

Polyimide thermofoil heaters used for space have a maximum power rating of 4.5 W/in2 (0.7 W/cm2) when suspended in still air at 25°C, although this specification is for test purposes only and is not indicative of the maximum power rating in application (with heater mounted to a heat sink). Actual rated power (or voltage) are specified in each application.

Visit this web page to view or download the entire NASA General Specification for Thermofoil Heater, All- Polyimide, Space Applications.

Rapid Response Electric Heaters Designed for Clean Gases and Liquids

Mini Clean Flow Heater

In advanced technologies such as analytical, biomedical, pharmaceutical, aerospace, electronics and laboratory applications, special purpose electric heating elements are required for heating high purity fluids and gases. These applications require rugged design, fast heat-up, tight control, high temperatures and the ability to withstand exposure to harsh solvents and corrosive gases. They also must be constructed in a way to prevent contamination of the process media.

The use of standard screw plug immersions heaters, screwed into a stainless steel welded vessels (known as circulation heaters) are almost always a misapplication for these unique requirements. Circulation heaters create more problems due to leaks, material compatibility, poor controllability, and bulky size.

BCE, a northern Californian manufacturer of custom heating elements offers it's Mini Clean Flow Heater specifically for these applications. These heaters are designed for heating "clean" liquids and gases normally found in fuel cell, bio-med, laboratory, food, semiconductor and pharmaceutical applications.

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

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

Summary:

• Designed for heating of clean gases or liquids
• Gas flow passes over an enclosed heated body; not exposed to resistive elements (Nichrome)
• All parts exposed to gas flow are constructed of 304 stainless (other material available)
• High temperatures
• Custom wattages, voltages, inlet and outlet fittings (NPT, SAE, BSP &VCR) are available.
• Made in U.S.A.

For more information, visit http://heater.belilove.com

Custom Electrical, Pneumatic, and Optical Feedthroughs

Equipment manufacturers and scientific researchers are continually challenged with supplying power, fiber-optic, control, and monitoring cables into (and out of) 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.

You don't have to fit a square peg in a round hole anymore. Choose BCE custom feedthroughs for your next design.

http://www.belilove.com/feedthrough

(510) 274-1990

Kapton (Polyimide) Etched Foil Heating Elements

Kapton (Polyimide) Etched Foil Heating Element.

According to Wikipedia, "Polyimides have been in mass production since 1955. With their high heat-resistance, polyimides enjoy diverse applications in roles demanding rugged organic materials, e.g. high temperature fuel cells, displays, and various military roles. A classic polyimide is Kapton ..."

Kapton etched foil heating assemblies are constructed from a very thin etched foil circuit embedded between two layers of Kapton, or one layer of Kapton and some other material (such as alumina.) The result is a heater with features perfect for a wide variety of industries - from aerospace, to medical and scientific equipment, to research & development applications. 

Kapton heaters provide excellent heat transfer to adjoining surfaces with the release of minimal contaminants through the use of this very low mass, low outgassing, high dielectric material.  They provide very even heat distribution extremely fast heat-up and cool-down rates. Additionally, they can be constructed in just about any shape, size, wattage or voltage. They are also ideal for applications where distributed wattage (heating profile) is required. 

Furthermore, when the heater and ceramic insulator is bound in such a way to meet NASA’s low outgassing specification, Kapton heater assemblies are ideal for use in vacuum applications.

For more information, visit http://heater.belilove.com. Also, take a fast look at the video below.

9 Pin Vacuum Feedthrough: UHV Compatible Technology Serving the Semiconductor Industry

Some of the most stringent tolerances and vacuum requirements exist in the ever-expanding semiconductor industry. Tight restrictions in vacuum ports, high temperature applications and exposure to high stress environments further add to the challenge of designing an electrical feedthrough that can be manufactured quickly and installed with ease. An American multinational manufacturer of chips and microprocessors approached BCE with these exact requirements in order to replace their existing vacuum feedthroughs incapable of providing an adequate performance in ultra-high vacuum environments. Furthermore, their existing supplier had long lead times and the procured feedthroughs needed to be replaced often as their contacts would fail due to oxidation formation on the conductive layer.

SCOPE

• The feedthrough needed to satisfy the following requirements: 
• Ultra-High Vacuum (UHV) compatibility up to 1 X 10-10 atm.cc/sec 
• Remain operable at temperatures exceeding 250°C 
• Pins preventing oxidation of conductive layer for longevity 
• 9 pin feedthrough configuration 
• Voltage requirement: 750 AC RMS 
• Current requirement: 7 AMPS 
• Quick-turnaround on feedthrough manufacturing 
• Robust seal withstanding high stress environments 
• Ease in installation, simple design 
• Low cost for application 

OUTCOME

All customer requirements were exceeded by BCE’s 9 pin vacuum feedthrough. Not only did it meet all electrical and configuration specifications, it provided a vacuum compatibility twice as much as that required by the customer allowing them to expand their capabilities to higher vacuum thresholds. It also remained operable at higher temperatures, nearing maximums of 300°C. Furthermore, the gold plated pins proved to be ideal in the prevention of oxidative layers inhibiting current flow. Moreover, BCE’s proprietary ceramic seal achieved the desired robustness and allowed the feedthrough to remain operable under high stress conditions. Finally, the client was equally impressed by BCE’s quick-turnaround time and competitive pricing.

Download the PDF for this application note from the Belilove site here.

Video: Flanged, Replaceable, Multi-Thermocouple Electrical Feedthrough

With most vacuum feedthroughs, troubleshooting can be difficult as well when multiple fixed elements are involved. If one element fails, generally the entire vacuum feedthrough is rendered useless. With BCE’s Multi-TC, Flanged Feedthrough, arduous troubleshooting procedures are a thing of the past. In fact, this feedthrough’s thermocouples are replaceable as they can be extracted from the compression fittings with great ease. This means that if thermocouples fail, they can be removed, tested and replaced within minutes. Thus, this no-hassle design allows for faster, more accurate and more cost-effective thermal data collection. Trust BCE’s Multi-TC, Flanged Feedthrough for your most complicated thermal detection needs. Contact BCE for more information.

Replaceable, Flanged, Multi-Thermocouple Vacuum Feedthroughs

(Click for larger view)

One of the biggest challenges facing the vacuum industry is to collect multiple readings from complex assemblies while being limited by the number of existing feedthrough ports in a vacuum chamber. With BCE’s Multi-TC, Flanged Feedthrough, companies no longer need to invest in adding more ports for a greater collection of temperatures from a vacuum environment as multiple thermocouples are embedded in just one feedthrough. The number, type and lengths of the thermocouples can be altered to match specific application requirements meeting each customers’ unique needs. As the thermocouples can be adapted to meet unique design constraints, so can this feedthrough’s flange. All sizes used are standard and are easily mountable with readily available hardware. No complicated assemblies are required for the most complicated of vacuum setups.

With most vacuum feedthroughs, troubleshooting can be difficult as well when multiple fixed elements are involved. If one element fails, generally the entire vacuum feedthrough is rendered useless. With BCE’s Multi-TC, Flanged Feedthrough, arduous troubleshooting procedures are a thing of the past. In fact, this feedthrough’s thermocouples are replaceable as they can be extracted from the compression fittings with great ease. This means that if thermocouples fail, they can be removed, tested and replaced within minutes. Thus, this no-hassle design allows for faster, more accurate and more cost-effective thermal data collection. Trust BCE’s Multi-TC, Flanged Feedthrough for your most complicated thermal detection needs.

Specifications

• Replaceable thermocouple(s) design 
• Vacuum Integrity: 10-8 atm.cc/sec 
• Multiple types and lengths available for thermocouple(s) 
• Multiple types and sizes available for flange(s) 
• Multiple types and sizes available for lead wires (KAPTON available for minimal contaminant release) 
• Compatible O-rings available for flange(s) 
• Can be adapted to virtually any temperature range

For more information, visit http://www.belilove.com/feedthrough.