BASF’s flame retardant PBT chosen for major power electronics application

A flame retardant polybutylene terephthalate (PBT) from BASF has been selected for use in the mass production of a range of semiconductor modules.

Ultradur B4450 G5 is now being used for the production of MiniSKiiP Dual power semiconductor modules from Semikron, one of the world's leading manufacturers of power modules and systems, mainly in the medium output range of approx. 2 kW up to 10 MW.

BASF says the flame retardant system used in the PBT contains no halogen and complies with the Restriction of Hazardous Substances Directive (RoHS). Application examples of power semiconductor modules (or DC/AC converters) are in industrial drive technology, solar inverters, or in the powertrain of electric vehicles. Developing heat is dissipated from the modules by metallic heat sinks. This prevents any rise in temperature and helps to ensure an optimum operating temperature. The power semiconductors are protected from external influences such as moisture, dirt, and fluctuations in temperature by a housing made from thermoplastic Ultradur.

The material is classified as V-0 under UL 94 from a wall thickness of 1.5 millimetres and, BASF says that, in combination with an excellent temperature performance (RTI = 140 °C), makes it particularly well suited to applications in electric power modules that are subject to a high amount of heat generation.

The thermoplastic also reportedly has good mechanical properties and can be light-coloured. With a CTI value of 600, the material has good electrical insulation capacity, which BASF says offers great freedom of design even for small and detailed components, such as the MiniSKiiP Dual. Ultradur B4450 G5 is reinforced with 25 percent glass fibres, which gives the components additional stability.

“Thanks to the positive cooperation and the professional support we have received from BASF in respect of application development and simulation, we have managed to manufacture components which are not just extremely stable, but also display a very low level of wear for a material that is reinforced with glass fibres,” commented Dr.-Ing. Jörn Grossmann, New Technologies Material Expert at Semikron, in explaining the approach adopted in the trial phase. The company is now examining other possible uses for Ultradur B4450 G5.