With the current high price of fuels, the mind-set of most people regarding ownership of large inefficient vehicles has changed quite a bit. The request for fuel-saving cars, including hybrid cars and even completely electric cars, is getting louder.
These types of vehicles need a number of electronic control units (ECUs) for more efficient engine management, fuel-saving operation, battery operation, and the like. Not only will power management require increased electronics in the car; so will safety features (ABS, airbags, distance control, etc.) and “luxury features” such as Internet access.
Additionally, hydraulic units (such as those for steering) in past automotive design will be done electrically. Vehicles are now evolving into computers on wheels, which can be used to travel from A to B with high speed, high comfort, and, of course, high safety. The electronic parts of this “driving” computer are getting smaller and smaller and more sensitive to electrostatic effects—but their reliability must be maintained.
Protection against electrostatic discharge (ESD) can be realized to a certain extent on the semiconductor itself. This on-chip protection is guaranteeing safe handling at the ECU manufacturer in an ESD protected area having basic ESD protective measures. Manufacturers are following international standards such as ANSI/ESD S20.20 or IEC 61340-5-1 so that even very sensitive parts can safely be handled.
The ECU will then be implemented in the vehicle, or certain parts of it (such as door modules), at the car manufacturer or its direct suppliers. These assembly lines often have no or very limited ESD handling measures. Therefore, the ECU must possess a much higher robustness against ESD.
There is always a debate as to what the right (voltage) level of protection is and what the right test to guarantee this robustness is. Is it more efficient to make the semiconductor devices themselves more robust or to increase the protection on board? Resistors and capacitors that are needed for performance or electromagnetic compatibility (EMC) are common measures. Extra-protective elements such as transient voltage suppression diodes are, of course, an excellent choice but could affect the performance. They are considered additional elements to be placed on board for assembly, which is a source of failure the manufacturer wants to avoid, and they add extra cost to the ECU and therefore the car.
All of these possibilities have advantages and disadvantages depending on the specific application, cost pressure, and expertise of the board designer. In the past, automotive suppliers and original equipment manufacturers did not discuss this topic in an effective way.
The challenge for the creators of the next generation of cars will be to develop the right ESD protection needed at the best price, the most efficient way, and with the highest reliability. Therefore, the dialogue between the car manufacturer, the ECU designer, and the semiconductor manufacturer (who has started the discussion of the ESD topic) must be expanded to avoid ESD problems in the field.
Reinhold Gaertner, EOS/ESD Association Board of Directors, wrote this article in celebration SAE's centennial.