They must offer very high reliability so that they work correctly for a vehicle’s multiyear lifetime, across extreme temperature ranges, from polar winters to desert summers. And they have to do all this while surviving mechanical shocks and complex vibrations; frequent thermal cycling; electrical, electrostatic and electromagnetic interference; constant exposure to moisture, humidity and solvents; and possible mechanical stresses due to flexing PCBs.
The automotive electronics industry has responded to this laundry list of challenges by defining a component stress-test standard for passive components known as AEC-Q200. The standard covers all the issues mentioned above, as well as production issues such as solder-ability and resistance to soldering heat. Although AEC-Q200 appears comprehensive, some manufacturers apply further statistical tests to their manufacturing lots in order to be able to claim greater levels of component reliability.
For example, Panasonic has developed the EEH-ZE series hybrid aluminium electrolytic capacitors for use in filtering the inputs and outputs of power converters and voltage regulators, and for power and battery decoupling. The AEC-Q200 compliant parts are designed to operate from –55 to 145°C, have a thermal endurance of 2,000 hours at 145°C, can sustain high ripple currents, and have low equivalent series resistances. Nichicon offers UBY aluminium electrolytic capacitors for use in electric power steering and direct- injection engine drive systems. The parts offer higher capacitances and withstand much higher ripple currents than other electrolytic capacitors. The UBY parts are available with capacitances from 160 to 12,000µF, at operating voltages from 25 to 100V, and with a rated temperature range from –40 to +135°C.
The reliability challenge is likely to become bigger once vehicle makers move from 12V DC to 48V DC power systems, so they can offload engines by powering subsystems such as the steering, brakes, water pumps, radiator
cooling, and air conditioning electrically. When this happens, automotive electronics designers will have to spec and source passives that can sustain relatively high voltages, high currents, and high operating temperatures, reliably over the long term. This may have profound consequences for their manufacturing processes if, for example, it requires a shift from the use of surface-mounted to radial-leaded components that have to be wave soldered.
This challenge will continue as the automotive industry shifts to e-mobility. Passives manufacturer TDK has responded by creating a range of CeraLink capacitors in low-profile packages, which can act as ripple- current suppressors, DC link capacitors, and snubbers. The parts have been designed for use in fast-switching automotive power supplies and inverters, made possible by the availability of new IGBTs and MOSFETs, where low equivalent series resistances and inductances are important.
These are just some examples
of the ways in which the passive component industry is adapting to the multiple challenges that its automotive customers are facing as their industry evolves. Automotive electronics designers can be reassured that, despite cars becoming more complex, their suppliers are working hard to ensure that they have the parts they need to succeed in this increasingly challenging design environment.
Dashboards have become infotainment systems, like this one used in a Tesla. (Source: Tesla)
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