One bus, one central electrical system and 420,000 km

The central electrics made by Würth Elektronik ICS were installed in a bus and from 2001 to 2008 it covered a distance of 420,000 kilometers. That equals about nine trips around the world!

We tested the thermic behavior of this component group in our thermography laboratory. First we observed the heat build-up of the central electrics at a constant and then later at an increasing current load over a period of 30 minutes.

The result

The result was unequivocal: There were no bottlenecks in the press-fit zone. It was the printed circuit board paths that posed the limitations. During additional testing we examined the micrographs of press-fit connections in a transverse direction. We paid close attention to the deformation of the sleeves, residual thickness and cracks in the metalization.

The micrographs showed that the press-fit connection was in pefect condition. No signs of corrosion or other deteriorations in the press-fit connection were found. The deformation of the sleeves was far below the critical value of 70 μm specified in the standard EN60352-5:2001. The residual thickness in the metalization was partly under the recommended 8 μm, but as we know, the electrical conductivity of the press-fit zone is very insensitive in its response to deformation and metalization thickness of the sleeves. This means that as long as the connection of the circuit paths to the sleeves is intact, the press-fit zone will also be in perfect condition. The thermographic images of the component group confirmed this as well.