Flex cracks cause a significant drop off in internal resistance, which undermines the capacitors performance. In a worst-case scenario, the capacitor short circuits completely. For this reason, some capacitors are designed to fail open.
The features of antivibration capacitors
There are a few different approaches to resolving vibration effects on capacitors.
- One solution focuses on the connection between the capacitor and the PC board. By improving the way in which the terminations and the capacitor itself are joined, a barrier can be formed that limits the vibration experienced by the capacitor.
- Polymer capacitors are an alternative to material to ceramic capacitors. They offer lower ESR than MLCCs and better performance over a wide range of operating conditions.
- Hybrid capacitors have a liquid and conductive polymer as the anode and an aluminium cathode. The large surface area of the liquid allows for higher capacitance ratings in a smaller footprint. This is important in the automotive industry where space is at a premium.
Vibration proof capacitors can cope with more severe forces of acceleration. Their specifications fall in the range of 30G as opposed to the 10G of standard components. They are also rated for a vibration frequency of 5 to 2000 Hz and an amplitude of 5 mm peak to peak.
Some leading antivibration solutions
KEMET offers a Flexible Termination (FT-CAP) multilayer ceramic capacitor as a solution to high vibration applications. It has a flexible termination system that reduces the transfer of stress from the board to the capacitor. The flexibility is provided by a conductive silver epoxy layer that steers a potential flex crack away from the ceramic body. These capacitors offer a 5mm flex rating versus 2mm of standard ceramic capacitors.
AVX also offers a flexible termination solution to high vibration applications. Their MLCC with Flexiterm range of capacitors carry the ability to improve flex performance from 2 mm to 5 mm. They also have a soft termination option which offers improved performance in applications with high temperature variations and cycling - like the automotive industry. MLCC with Flexiterm have a temperature cycle of 0% failure up to 3,000 cycles compared to only 1,000 cycles for standard capacitors.
Panasonic have a range of conductive polymer hybrid aluminium catalytic capacitors. Their auxiliary side terminals make the installation more stable and less vulnerable to flex. It offers a superior vibration performance and minimises the dependence of manufacturers on antivibration re-enforcement.
The technological advances in EVs and HEVs are generating a demand for higher performance electronic components. They must offer consistent electrical characteristics in widely changing and adverse operating conditions - especially in terms of vibration and temperature cycling. At the same time, manufacturers of ECUs are under pressure to reduce the footprint so that they fit into the more compact spaces that integrated electromechanical systems require.
Electronic component manufacturers are finding new ways to improve the reliability of capacitors for these harsh conditions. Their solutions offer ECU manufacturers the capability to meet the quality and space demands of the auto industry.
The authoring team is employed at international component distributor TME