Kapton Heaters: Polyimide Etched-Foil Heating Elements

A Kapton heater is an etched metal foil sealed between two thin layers of polyimide film, so the finished part is only 0.2 to 0.3 mm thick and weighs almost nothing. It sits flat against a battery cell, an optical mount, a wafer chuck or an instrument wall without adding bulk and without holding warmth once the power is off. The foil does the heating and the film stores hardly any energy, so the part heats up quickly and follows a controller closely. That response, together with the very low outgassing of polyimide, is why these heaters turn up so often in vacuum, semiconductor, medical and battery work.

The range on this page is our standard program, all running on 12 V DC: a rectangular Kapton heater in seven sizes from 25 × 50 to 75 × 100 mm, and a circular Kapton heater in Ø50 and Ø75 mm. Each size comes in two output levels, up to 45 W, and with self-adhesive or plain backing, and the stock parts are sold from 5 pieces per variant. When a standard part will not do, we build to drawing instead, with different shapes, higher surface loading, higher temperatures and mains voltage. If your part is in the range, order it. If it is not, the range is the place to start the conversation about the one you actually need.

What a Kapton heater actually is

The working part is an etched-foil resistive track laminated between sheets of polyimide film, the material most people know by DuPont's trade name, Kapton; the finished part is often called a polyimide film heater, a thin-film heater or simply a flexible heating element. That build is flexible but not elastic. The heater is happy wrapped around a cylinder or laid on a flat or single-curve surface, but it must never be forced onto a compound or spherical shape, or onto anything that grows and shrinks underneath it, because the foil circuit eventually cracks where it is stretched. Continuous immersion is a similar caution: water finds its way in at the laminated edges over time, so anything submerged is worth discussing as a custom build rather than treating as a stock use.

Kapton or silicone?

Flexible surface heaters come in two materials, and they are not really competitors. As a supplier of both, we have no reason to push one over the other. Kapton is thin, fast, light and silicone-free, but the foil circuit is fragile and will not take a compound curve. Silicone rubber is thicker and slower to react, yet it shrugs off the handling that a workshop or a drum wrap involves. The table compares them on the points that decide a job rather than the ones that fill a brochure.

Kapton (polyimide) Silicone, wire-wound Silicone, etched-foil
Continuous temperature −40 to +200 °C −60 to +250 °C −60 to +200 °C
Self-adhesive version −40 to +180 °C −30 to +180 °C On request
Thickness / build height 0.2 to 0.3 mm 1.1 to 3 mm 0.8 to 1.5 mm
Largest single sheet 285 × 550 mm 940 × 3000 mm 595 × 2500 mm
Max surface loading 0.8 W/cm² in open air about 0.8 W/cm² about 0.8 W/cm²
Thermal mass and response Lowest, fastest Higher, slower Medium
Mechanical handling Delicate, single curves only Rugged Rugged
Suited to volume production Yes Less suited Yes
Vacuum, low outgassing Yes, low CVCM No No
Silicone-free Yes No No
UL and VDE versions Not available Available Available

The figures shown are based on our heater specifications and typical values for the respective constructions.

If the heater has to disappear into an assembly, react quickly, work under vacuum or stay clear of a silicone-sensitive process such as paint preparation or optics, Kapton is the right call. For drums, IBCs, gas cylinders or anything that takes rough use, a silicone heater is the better tool, and plenty of builds use one of each: polyimide on the sensitive part, silicone on the bulk vessel.

How much heat it can take

Watt density, or surface loading, is the number that decides whether a polyimide heater lasts. The stock range here stops at 0.6 W/cm², and 0.8 W/cm² in open air is the recommended ceiling for any flexible heater, Kapton or silicone alike. You can go higher, but only when the heat has somewhere to escape. Bonded to a metal plate and run under a fast controller, a custom heater can reach 2 to 3 W/cm². The detail that catches people out is where the sensor sits. If it is mounted on the part being heated rather than on the heater, a poorly bonded heater can run far hotter than the controller shows, and the element quietly cooks itself. High surface loading without a heat path is the usual way these parts fail.

Mounting and temperature

The film itself runs from −40 to +200 °C, but how you hold the heater sets the real limit. The self-adhesive backing, a low-outgassing pressure-sensitive adhesive, is good to about 180 °C and covers most mounting jobs. The plain, non-adhesive version is used up to 200 °C, held against the surface by a clamp; for that, and for any higher-temperature custom build, the heater is clamped between metal plates with a thin silicone buffer, around half a millimetre, to spread the clamping load and keep the etched circuit from being crushed. Copper or aluminium plating, and adhesive-less all-polyimide construction, push the working temperature toward 260 °C, and both of those are custom territory.

Vacuum and low outgassing

Low outgassing is the property that sells a polyimide heater into the cleanest jobs, so it is worth stating in numbers rather than adjectives. Tested to ASTM E595, the self-adhesive construction returns collected volatile condensable material of 0.02 percent, a total mass loss of 1.54 percent and water vapour regained of 0.64 percent. The figure that governs whether a heater leaves a film on the surfaces around it is the condensable material, and 0.02 percent sits well inside the 0.10 percent limit used to judge that, which is what makes the standard part a sound choice for vacuum chambers, semiconductor tools and other clean processes. Total mass loss is the stricter screen: at 1.54 percent it is above the 1.0 percent line that flight-qualified space work asks for, so for satellite and space applications we specify a low-TML custom construction rather than the stock part.

What it takes to run one

These are 12 V DC component heaters, not appliances you plug into a wall. To put one to work you need a DC supply matched to the load, and a thermostat or controller with a sensor. The supply matters more than it first looks: the 45 W part pulls 3.75 A, and that current sets both the rating of the power supply and the gauge of the wiring. The control matters because a bare resistive heater regulates nothing on its own and will overshoot if it is left to itself. The trade-off is worth it, because 12 V is extra-low voltage, which keeps the shock risk far below that of a mains heater and is one reason polyimide heaters are used so widely in laboratory and medical equipment. If you need a mains-voltage version at 115 or 230 V, that is a custom build.

Custom Kapton heaters: when the standard range is not enough

The stock program covers 12 V up to 0.6 W/cm². Past that, we engineer the part to suit. That covers higher surface loading of 2 to 3 W/cm² with the heat path designed in, higher temperatures toward 260 °C using plated or all-polyimide construction, mains voltage, shapes with holes, cut-outs and slots, and sensors or thermostats built into the heater itself. If any of that describes your job, tell us what you need and we will quote a custom Kapton heater built to your drawing.

Where they are used

Typical work includes warming electric-vehicle and equipment batteries, semiconductor and wafer handling, medical devices and diagnostics, optics and display assemblies, laboratory instruments, telecom enclosures, anti-condensation and defrost duties, and aerospace, satellite and vacuum systems. The thread running through all of them is a sensitive component, a tight space or a process that cannot tolerate contamination, the cases where a thin, fast, clean foil heater beats a heavier one. For larger or more rugged heated surfaces, such as drums, IBCs and gas cylinders, our silicone heaters are the better starting point.

Kapton Heaters FAQ

What is a Kapton heater?
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It is a thin, flexible heater made from an etched metal foil sealed inside polyimide film, the material often called by the trade name Kapton. The whole part is only 0.2 to 0.3 mm thick, warms up quickly and gives off very little outgassing, which is why it suits batteries, vacuum chambers, medical and laboratory equipment and other places where a bulky heater would be in the way.
How much watt density can a polyimide heater handle?
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The standard range here goes up to 0.6 W/cm², and 0.8 W/cm² in open air is the sensible ceiling for any flexible heater. Higher figures, in the region of 2 to 3 W/cm², are only safe when the heater is bonded to a metal heat sink and run under a fast controller, which is a custom build rather than a stock part.
Can I run a Kapton heater from mains voltage?
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The standard parts are 12 V DC, so they need a DC supply and a controller and cannot be plugged straight into the mains. We do build mains-voltage versions at 115 or 230 V as a custom order, so ask if that is what your application needs.
Are Kapton heaters safe to use in a vacuum?
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They are widely used in vacuum, and the numbers say why. Tested to ASTM E595, the self-adhesive construction gives collected volatile condensable material of 0.02 percent, well within the 0.10 percent limit that governs how much a material contaminates nearby surfaces, which is what matters inside a chamber or a clean tool. Its total mass loss is 1.54 percent; for the strictest space-flight screening, which asks for total mass loss under 1 percent, we build a low-TML custom version.
What is the difference between a Kapton heater and a silicone heater?
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Kapton is much thinner, lighter and faster to respond, it is silicone-free and it works in a vacuum, but the foil is delicate and only takes flat or single-curve surfaces. Silicone is thicker and slower but far more rugged and better for drums, IBCs and large surfaces. Many builds use a Kapton heater on the sensitive component and a silicone heater on the bulk vessel.
Should I choose self-adhesive or plain backing?
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The self-adhesive version has a low-outgassing pressure-sensitive adhesive on the back and is good to about 180 °C, which suits most mounting jobs. Choose the plain, non-adhesive version when the surface runs hotter, up to 200 °C and clamped in place, or when you want to bond it with your own method.