As part of the “Production of the Future” program, the Solaris project is supported by the FFG funding agency and the Ministry of Technology. The project management lies with the Wieselburg lighting systems manufacturer ZKW. Together with the Vienna University of Technology and the Materials Center Leoben, the ZKW team is researching self-healing, particularly resilient solders. The material will be used to connect high-power LEDs and other power semiconductors for the automotive industry.
ZKW develops and manufactures such electronic assemblies – such as control devices and light modules – at the Wiener Neustadt location of ZKW Elektronik GmbH. “The Solaris project helps us to develop new products tailored to the needs of automotive customers and to manufacture them as environmentally friendly and resource-saving as possible. With the more powerful connection technology, we want to optimize the reliability of our electronic products, ”explains Oliver Schubert, CEO of the ZKW Group.
Material of the future
Numerous electronic components are integrated in modern vehicles, which provide various safety and comfort functions and should also enable autonomous driving in the future. These components have to withstand different loads, such as large temperature fluctuations and strong vibrations. One of the weak points is often the solder alloy that fixes the components on the circuit board. Cracks in the solder cause malfunctions in the electronics. The aim of the Solaris (Solder and Reliability Improvements) project is to develop a solder material with self-healing properties. This can be achieved by partially melting the solder at operating temperature, which closes the beginning of cracks and relieves mechanical stresses. “So-called non-eutectic alloys could be the key to success thanks to their self-healing properties,” says Schubert.
The soft soldering process with tin-silver-copper solder is currently used for the connection between electronic components and circuit board. In the case of semiconductor components, however, the power density and operating temperature as well as the required service life increase. According to the new GMW3172 standard, cycles in the temperature range from -40 ° C to + 140 ° C must be passed. Conventional solders can only withstand an operating temperature of up to a maximum of 120 degrees Celsius, while current high-power LEDs or power transistors can withstand up to 140 degrees Celsius and more.
Soft solder materials that are subject to high thermal and mechanical loads reach their limits here. Creep processes, pore formation and crack formation ultimately lead to failure of the assembly. As a solution, expensive or difficult to process printed circuit board substrates and exotic package materials are currently used.
Simulations for more security
In addition, the lighting systems specialist is also researching computer-aided simulations together with its partners, which should enable a prediction of the service life of the new solder material. Test assemblies are simulated and manufactured for tests in order to load them under extreme conditions until failure. These tests can be used to check models and predict the expected service life. The Vienna University of Technology provides support not only with basic research, but also with thermodynamic calculations for solder alloys. It also provides laboratory and test equipment, such as a state-of-the-art scanning electronic microscope.
The Materials Center Leoben, in turn, contributes its expertise in modeling, simulation, service life prediction and damage analysis. One focus is the analysis of defective components using imaging processes such as X-ray tomography. ZKW uses this know-how, for example, to examine destroyed electronic components and to make a service life forecast.