ELECTRIC ENGINE AND POWER ELECTRONICS RELIABILITY
Reducing production costs with extremely precise control over the lifespan of the most innovative subgroups in electric and hybrid vehicles. Warranties are becoming longer and longer, with some car makers offering up to eight years’ warranty from the time a model goes to market—a requirement from the international automotive sector.
Power components implement technologies in a context of continuous innovation to cut costs, reduce maintenance and retain control over failure modes, which impact vehicle performance and safety (self-driving vehicles).
Precise knowledge of the failure indicator and modes of these new technologies is of structural importance when the choice of topology is made, to enable the design of a high-performance vehicle with its production costs kept under control.
French industry does not produce power semi-conductors for traction equipment: the market leaders are currently German and Japanese. However, French industry can put forward innovative integration concepts; an experimental assessment of the lifespan under real conditions of use is a crucial step prior to industrialisation.
- Assessing and predicting the lifespan of new power electronics integration technologies (semi-conductor type and assembly technology) in conditions of actual vehicle use (vehicle integration, environment, mission profile, etc.)
- Comparing technologies on the basis of benchmark tests (PCT, TC),
- Putting forward new protocols and test benches (e.g. combined PCT-TCT tests), training in the required skills at European level
- Identifying and understanding the failure mechanisms to enable new, safe and enduring system design
- Putting forward new failure diagnosis and prediction tools for use in real-life conditions.
The approach usually taken when assessing automotive reliability applies the Automotive Electronics Council quality standards (AEC Q100, Q200). They define the test conditions to be applied to electronic components and printed circuit boards. This method is based on a statistical compliance criteria and requires test results from a large quantity of components. The approach selected by all the high-power, high-integration component specialists is experimental and involves identification of the parameters that indicate ageing and failure. Yet when new technology is developed in the current context of ongoing, competitive innovation, it is important to know under which conditions the faults appear and to conduct tests until failures occur in order to control the lifespan of the system.
The ‘Power Electronics Reliability’ project runs tests on technological demonstrators based on mature manufacturing processes, to which constraint cycles are applied to generate thermo-mechanical fatigue due to the stacking of the various materials that make up the power module (e.g. semi-conductors, conductors, insulators), thus corresponding to real conditions of use (environmental or vehicle driving):
- Thermal cycles generated via the thermal interface, the power module is passive: Thermal Cycling Tests (TCT),
- Thermal cycles generated by the semi-conductors, the power module is active: Power Cycling Tests (PCT),
- Combined cycles, which are highly representative of the specific mission profiles of the vehicles; these profiles may be configured according to the kind of use, type of vehicle and a specific climatic environment.
The levels and number of constraint cycles are representative of the conditions of use considered, the test conditions are accelerated by the amplitude of constraints in the planned range of use, and by the frequency of cycles maintained 24 hours a day. The duration of a TCT, PCT or combined type test is expected to be several months.
All the data acquired are used i) for a comparison of the performance of the various technologies under comparable test conditions, and ii) for an in-depth analysis to establish a behaviour law for a more or less restricted range of use, based on simulations using models reaching 3D complexity, in liaison with VEDECOM’s academic partners. This modelling work can be used to extrapolate and even predict behaviour over the lifespan in configurable conditions of use. The work can also be used to validate original assembly technologies for innovative design integration adapted to automotive mass production.
- Establishing an experimental platform recognised at least at European level for tests and failure analysis, paired with a digital calculation platform to optimise the lifespan of system design and integration technologies, benefiting from the skills and services of the VEDECOM network of partners.
- Establishing a database of experiment results on the lifespan and failure mode of the various power integration technologies for tractions and rapid vehicle charging, representing real conditions of use.
- Taking into account the behaviour of passive components in high-integration mechatronic systems.
- Putting forward a predictive maintenance solution based on the evolution of the failure indicator parameters.