Material of the Future
A large number of electronic components are integrated into modern vehicles. These provide many different safety and comfort functions, and in the future will facilitate autonomous driving as well. These components need to withstand different loads, such as large temperature fluctuations and strong vibrations. The brazing alloy used to affix the components on the printed circuit board is often a weak point. Cracks in the solder cause electronic faults. The goal of the Solaris project (solder and reliability improvements) is to develop a solder material with self-healing properties. This can be achieved by partially melting the solder at operating temperature, causing any incipient cracks to close and reducing mechanical tension. “So-called non-eutectic alloys could be the key to success, thanks to their self-healing properties” Schubert states.

Increasing Requirements
Currently, tin-silver-copper solder is used to connect electronic components to the printed circuit board using soft soldering. However, the power density and usage temperature increase for semiconductor components, along with the required service life. In accordance with the new standard GMW3172, components must withstand cycles in a temperature range from -40°C to +140°C. Commonly available solders only withstand operating temperatures up to 120 degrees Celsius, while current high-power LEDs or power transistors cannot withstand 140 degrees Celsius. Soft solder materials are not able to handle the high thermal and mechanical loads. Creeping, pores and cracks ultimately cause the assembly to fail. Currently, expensive or difficult to process circuit board substrates and exotic package materials are used to solve the issue.

Simulation for Better Safety
In addition, the lighting system specialist is working with our partners to jointly research computer-supported simulations intended to predict the service life for the new solder material. Test assemblies are simulated and manufactured for testing in order to expose them to loads at extreme conditions until they fail. These tests can be used to test models and predict the expected service life. The Vienna University of Technology not only provides support through basic research, but also completes thermodynamic calculations. Furthermore, it provides laboratory and testing equipment, such as a scanning electronic microscope equipped with the newest features. The Materials Center Leoben, in turn, contributes its expertise in modeling, simulation, operational lifetime forecasting and damage analysis. One key area is analyzing defective components using accompanying products like X-ray tomography. ZKW uses this expertise to test destroyed electronic components, for instance, and prepare a program for service life.