PTC -3D: Lead-Free PTC Heaters from 3D Printing

PTC heaters are electrical heating elements with a ceramic core that regulate their own temperature to prevent overheating. They are mainly used as air and liquid heaters in electric vehicles, but they can also heat batteries, provide overcurrent protection or serve as temperature sensors. Fraunhofer IKTS has developed high-voltage heaters and lead-free PTC ceramics with transition temperatures of 180 °C. Both electrical contacting and electrical insulation were taken into account for operating voltages up to 1000 V DC.

Up to now, the geometries and potential applications of PTCs have been limited by the manufacturing process (pressing, extrusion). In addition, aluminum heat exchangers are typically attached to them. In the PTC-3D project, additive manufacturing of lead-free PTC heaters was developed using high-resolution vat photopolymerization. The 3D printing technology enables the production of high-precision, complex ceramic components for medical and industrial applications, with scalability up to industrial-scale mass production. This shortens development cycles and accelerates market introduction, since the process does not require expensive tooling and offers a high degree of flexibility. PTC structures based on barium titanate were printed (Fig. 1), and both simple and complex multichannel angled tubes were produced. In addition to 3D printing, key expertise lies in the debinding and sintering processes.

The increased binder content required for additive manufacturing must be completely removed, while the complex geometry limits mass transport. At the same time, the high-performance ceramic component must sinter to full density at 1300 °C in order to achieve the desired electrical properties.

The 3D-printed PTC heaters exhibit excellent heating properties (Fig. 2). Electrical resistance is low at room temperature but rises sharply above 100 °C in operation, reaching levels more than 10,000 times higher. This prevents thermal runaway under applied voltage. The angled tubes can be operated up to at least 200 V and heat to 150 °C under passive convection. The next development step is to implement active cooling of the tubes with possible cooling media to include liquids and gases.

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Fraunhofer IKTS is currently working to further improve these ceramics. This includes the use of lead-free materials for temperatures of 180 °C, new component designs, and the contacting and integration of these components in devices and systems. We are seeking partners from industry and research to jointly advance the commercialization of additively manufactured PTC heaters.