Backer Hotwatt offers the largest product line available of micro-cartridge heaters to solve difficult engineering and performance challenges. Our rugged, reliable small form factor heaters are used in a wide range of applications—from semiconductor test sockets to medical devices, gas detection equipment to opto-electronics—any application where precision heating and reliability are paramount!


What Are Micro-cartridge Heaters?

A micro-cartridge heater is a miniature tube-shaped heating element designed for insertion into a small-diameter borehole. The cartridge consists of an outer metal shell, called a sheath, which contains a coil of heating wire surrounded by insulating material. When powered up, the coil begins to heat up, which in turn, heats up the sheath, which then heats up the surrounding metal.

This discussion provides an overview of micro-cartridge heaters. If a particular section interests you, we have provided links to take you directly to that portion of the page.


Solving Small-Space Heating Challenges

Cartridge heaters provide localized heat to restricted work areas that require precise thermal control. Part of Backer Hotwatt’s extensive cartridge heater family, our revolutionary micro-cartridge heaters help you solve small-space heating challenges

To function efficiently, a micro-cartridge heater must be able to maintain a stable, uniform temperature. Closely controlled work temperatures of up to 1200°F (648.9°C) can be obtained by a combination of heater location and proper wattage output.

Starting at just 1/2-inch in length, Backer Hotwatt’s SunRod mini-cartridge heater is the smallest element available. Its unique split-sheath design, steady temperature, and long life are ideal for highly miniaturized applications.

Our revolutionary micro-cartridge heaters help you solve small-space heating challenges.

How Micro-cartridge Heaters Work

Cartridge heaters consist of a heated wire packed with inorganic powder, packed tightly into a metal sheath. The size, sheath allow, leads, terminals, wattage, and voltage can be customer specified or customized to meet your heating requirement needs.

Micro-cartridge heaters are used to heat the metal surfaces of dies, platens, and other types of processing equipment. They play an important part in a wide range of engineering and manufacturing applications.


Backer Hotwatt’s extensive line of micro-cartridge heaters help to solve difficult engineering and performance challenges for a wide range of applications, including:

  • Industrial 3D print heads
  • Diagnostic equipment
  • Gas monitoring equipment
  • Ink printing and labeling
  • Instrumentation
  • Laminating presses
  • Mass spectrometry
  • Medical devices
  • Stabilizing laser crystals
  • Balloon catheter manufacturing
  • Semiconductor test equipment
  • Valve actuators

Available in lengths as small as 1/2-inch, our micro-cartridge heaters give you a durable, reliable heat supply with low wattage requirements and exceptional performance that work in diverse environments and applications. With three product lines to choose from—Low-Watt Density Micro-Cartridge Heaters, High-Watt Density Superwatt Heaters, and SunRod heaters—we have your heating needs covered.

Our team can help you determine the precise wattage requirements for your application, taking into consideration a few basic thermodynamic heat transfer questions:

  • What is the material you are heating?
  • What is the environment?
  • What is the weight of the material?
  • How does the material react to certain heat?


  • How quickly does it heats up?
  • What temperature are you starting at and what temperature do you want to hit, and in what length of time?

Test Socket Heaters

Computer-designed and built in the USA, Backer Hotwatt’s micro-cartridge heaters are engineered to meet the precise standards for burn-in test socket applications. The exclusive split-sheath design eliminates the failure points of conventional mini heaters.

Properties and benefits that set the SunRod mini-cartridge socket heaters apart from others in the industry include:

  • Unique hot tip
  • Rapid and uniform heating
  • Highest watt densities available
  • Split-sheath design maximizes heat transfer and uniform heating for lower operating temperatures and extended heater life—25,000 hours or more
  • De-energized split-sheath contracts for easy cartridge slide-out removal, guaranteed never to seize in the bore
  • Simplified wire management within the test socket due to high flexibility lead wires that allow free motion of floating spring-loaded heater assemblies
  • Customizable size, sheath, leads, terminals, and wattage to meet your heating requirements
  • Stringent in-process and multi-point quality assurance testing


When energized, the split sheath expands into contact with the surrounding borehole. This allows for a rapid heat-up of the heat sink and DUT, resulting in maximum heat transfer, longer heater life (25,000 hours or more), and lower operating temperatures. When de-energized, the split sheath contracts for easy slide-out removal and is guaranteed to never seize in the bore.

Unlike other cartridge heaters, Backer Hotwatt micro heaters generate heat rapidly and continuously for the full length of the heater—including the tip—for uniform heating without any cold or hot spots. Uniform heating is critical to many applications and helps to ensure longer heater life, optimal performance, and consistent, repeatable quality.

Because our heaters are designed with reduced watt density, heater life expectancies can be extended to 5-10 years for mission-critical applications.


Backer Hotwatt micro-cartdridge heaters (left) generate heat rapidly and continuously for the full length of the heater—including the tip—for uniform heating without any cold or hot spots.

Other Micro-cartridge Heater Applications

Opto-Electronics/Metrology/Test & Measurement

  • FTIR analysis—crystal stabilizers
  • Vaporizing samples in gas chromatography
  • Crystal ovens
  • Sample heating in thermogravimetric analysis (TGA)
  • Gas & explosives detection

Medical Diagnostic Equipment & Devices:

  • Pleating & sealing ballons for catheters
  • Sample conditioning in molecular diagnostic testing
  • Blood/gas analyzers

Other Industrial/Commercial Applications for Cold-Weather Environments

  • Pitot tubes for avionics
  • Atmospheric sensors
  • Microfluidic valves


Catheter Baloon

Micro-Cartridge Heater Product Lines

Backer Hotwatt’s micro-cartridge heater product line comes in three styles to meet different output and design requirements. Our Low-Watt heaters are a cost-friendly solution when less heat is required. When more power is required, our Superwatt heaters offer maximum temperature ranges and great performance. Low-Watt and Superwatt heaters are highly customizable, allowing for value-added features such as bushings and flanges.

For applications where high wattage is needed in a very small design space, our patented split-sheath SunRod heaters offer outstanding performance. These heaters can be made in lengths as small as 1/2-inch and offer an uninterrupted hot zone for unmatched heat distribution with no cold spots. Easy to install, SunRod heaters offer maximum heat transfer, uniform temperatures, and longer life.

  • Low-Watt Density (Standard) Micro-Cartridge Heaters

These provide an economical solution when smaller amounts of heat are required in a small envelope. Their construction allows for value-added features, such as the addition of bushings and flanges, as well as sealing the lead end for moisture protection. These heaters are available in 1/8-inch, 5/32-inch, and 3/16-inch diameters, and lengths up to 12 inches. This technology will support maximum wattages of 10 to 12 watts per inch, as well as minimum wattages down to .5 watts. The max current-carrying capacity is 2 amps.

  • High-Watt Density Superwatt Heaters

These provide a powerful solution where higher power requirements are necessary. These heaters are designed for maximum temperature, watt density, heat transfer, and heater life. Available in 1/8-inch diameter and in lengths up to 8 inches, these heaters can be produced in watt densities up to 60 watts per square inch and can carry up to 3.5 amps of current.

  • SunRod Heaters

These provide an ultimate solution to challenging applications where high relative wattages are required in the smallest design envelope. These heaters can be made as small as .4 inch in length and come in both 1/8-inch and 4-mm diameters. The split-sheath design provides the maximum heat transfer when inserted into a bore.

Other cartridge heater technologies need non-heated sections at both ends of the heater to protect the leads and provide adequate electrical insulation. The SunRod heater only has one cold section near the leads. The unique hot tip section of the SunRod means a larger heated section for any given length.

SunRod 1” Inch

SunRod 3.5” Inch

X-Ray of SunRod 2” Inch

Advantages include:

  • When energized, the patented split-sheath expands into contact with the surrounding bore for maximum heat transfer, fast response.
  • When de-energized, the split-sheath contracts for easy, slide-out removal. SunRods are guaranteed never to sieze in the bore.
  • Uninterruped hot zone and fully heated tip provide unmatched heat distribution without cold spots.
  • Slender continuous leads simplify wire management. High flexibility allows free motion when heating “floating” components.
  • The result is a miniature cartridge heater offering longer life, uniform temperatures, and easy installation in the smallest devices



Backer Hotwatt Micro-Cartridge Heater Design Envelope

The versatile design envelopes of Backer Hotwatt’s family of micro-cartridge heaters meet many heating requirements, allowing for a variety of applications across industries.

Available Stock Sizes And Custom Orders

Cartridge heaters are our most popular product. Backer Hotwatt’s revolutionary micro heater is the smallest heater cartridge you can buy, offering the highest wattage and most uniform heating capability. Our micro-cartridge heater can be designed in lengths as small as 1/2-inch!

Micro-cartridge heaters are available in 1/8-inch and 4mm diameters. Our miniature cartridge heaters are available in 5/32-inch and 3/16-inch options and in densities up to 60 watts per square inch. Depending on your application, we can supply a higher watt density 1/8-inch cartridge heater that offers quicker heat transfer. Heater lengths run from just 1/2-inch to 4 inches long.

Our extensive line of cartridge heaters are produced to our customers’ specifications to meet varying size, leads, terminals, wattage, and voltage requirements for small-space heating challenges. As a leading electric heating manufacture, Backer Hotwatt can provide heating solutions to your specifications to accommodate your application and heating needs. We stock all material for the different diameter units listed in the catalog. For your order, upon specifying the wattage, voltage, diameter, length, and lead type, we can readily and quickly fabricate it from our inventory. In addition, many standard sizes are available from our in-stock cartridge heaters for immediate delivery.

Backer Hotwatt micro-cartridge heaters offer many installation and maintenance advantages, including:

  • Mounting method does not inhibit heat flow from the DUT to the heat sink during the cooling phase
  • Installation and servicing occur at your factory or test site
  • No complicated bonding or clamping required
  • Durable design not susceptible to damage during installation
  • Can be serviced at your location; no need to return to us for heater removal or replacement
  • Higher wattages
  • Longer life

Learn More

There is much more to know about how our miniature cartridge heaters can help you solve tough engineering challenges. Our patented high-temperature heaters give you the longer life and uniform temperatures you need. When you need a lot of heat in a small space, our extensive eBook shows you how. To learn more, download our micro-cartridge heater eBook.

You can check out our product catalog here.


Established in 1952, Backer Hotwatt, Inc. has been a trusted source of superior quality heating elements for OEMs in the medical, industrial, semiconductor, commercial, packaging, instrumentation, aviation, transportation, refrigeration/air conditioning, and military fields for almost 70 years. We’re here to help you design and manufacture the best heater for your crucial heat control requirements.

How can we help you with your next heating project? Contact an engineer today to set up an exploration consultation. We look forward to helping you soon.