If you're designing an EV onboard charger, a solar microinverter, or a high-power-density server power supply, you've probably run into a common frustration: standard enameled litz wire needs extra insulation layers, tape, or margin winding to meet reinforced insulation requirements — eating up window space and adding cost.

ETFE extruded litz wire solves this problem elegantly. By extruding a continuous ETFE (ethylene tetrafluoroethylene) jacket directly over a stranded litz core, you get a single wire that combines high-frequency performance, reinforced insulation, and solderable termination — all in one product.

In this guide, we explain what ETFE extruded litz wire is, how it's built, and why it may be the right winding solution for your next design.

What is Extruded Litz Wire with ETFE?

Three layers of Extruded ETFE . Litz wire with ETFE : In the world of high frequency, certain materials and designs are sparked that take advantage of certain physical phenomena to reduce losses or energy dissipation across the conductors. For use where this could be an important consideration at power levels of DC in the center frequency up to 10's of GHz, the conductor core is a here litz construction. Fine strands of copper to reduce the skin effect as well as proximity effect losses at high frequency are twisted together to form the core.

Extruded ETFE insulation: A seamless fluoropolymer jacket extruded over the strand bundle
Other external layers or serving as depends on the application.

Extruded construction => reinforced insulation: Uniform void free wall - A uniform, void-free wall is why extruded constructions universally under-perform reinforced insulation testing with some margin, due to their consistent dielectric strengths.

Key Features

1.Why choose the Extruded Construction in Your Applications?

The Extruded Construction.Works because it provides a uniform insulation and good reinforced isolation. Tape wrapped or even served wrappers can have small gaps between two layers at the area of overlap in between. In this case, extrusion provides a single, continuous, and air-free wall around the litz bundle:

Uniform dielectric strength along the entire wire length

No weak points at bends or corners from overlaps

Consistent compliance to hipot and partial discharge testing

2. No Margin Winding, No Layer Tape

Because each wire carries its own reinforced insulation, you can wind full-width across the bobbin. The benefits compound quickly:

• Smaller cores and bobbins → smaller transformers
• Faster winding with fewer process steps
• Better thermal contact between windings and the core

3. Hot-Melt Solderability

ETFE insulation is solderable at approximately 420°C using solder pots or hot-bar tooling. No mechanical or chemical stripping is required, which:

• Eliminates a whole process step (and its scrap risk)
• Enables high-throughput automated termination
• Produces clean, consistent solder joints

Pro tip: work with your wire supplier to dial in solder temperature and dwell time — ETFE melts cleanly when process parameters are properly tuned.

4. High-Frequency Performance from the Litz Core

Above roughly 50–100 kHz, solid wire suffers severe AC losses from skin and proximity effects. The litz core keeps AC resistance close to DC resistance, which means:

• Lower winding losses and cooler transformers
• Higher power density within the same thermal budget
• Better efficiency at GaN/SiC-friendly switching frequencies

5. Excellent Environmental Resistance

As a fluoropolymer, ETFE offers:

• Outstanding abrasion resistance — survives high-speed automated winding without nicking
• Excellent chemical and moisture resistance for outdoor and industrial environments
• Good flexibility for tight bobbin winding

Typical Applications

Design Tips for Engineers

Match strand diameter to frequency. As a rule of thumb, keep strand diameter below roughly twice the skin depth at your switching frequency. For 100kHz+, strand diameters of 0.05–0.1 mm are typical.

Verify thermal headroom. Class F means the wire is rated to 155°C — check your hotspot temperature, not just ambient.

Plan your termination process. Design solder pots or hot-bar tooling around the ~420°C hot-melt temperature.

Confirm certification early. Request your supplier's UL file and insulation system data when starting a safety-certified design.

Ask about custom builds. Strand count, lay length, and insulation wall thickness can all be customized to optimize your window fill and loss targets.

Conclusion

ETFE extruded litz wire brings together what high-frequency magnetics designers need most:

Low AC losses from a true litz core

Seamless extruded ETFE insulation for reliable reinforced isolation

Solderable termination — no stripping, no scrap

Class F (155°C) rating for the majority of power applications

As a manufacturer of ETFE extruded litz wire with custom strand counts, insulation walls, and certified builds, we support designs from prototype quantities to mass production.

Contact us for samples and datasheets — let's find the right wire for your next transformer design.