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deSign CHAllengeS in HARSH Automotive ConditionS It seems self-evident that cutting-edge features will continue to "drive" the use of electronics in automobiles —and that a growing number of electronic devices will need to be able to withstand the harsh conditions that can be encountered in the vehicle environment. This article will review some of the key challenges to the design of these systems and some approaches that can be used to mitigate these challenges. The items covered in this article only scratch the surface of the wide range of challenges confronting the developer—they have been selected to illustrate some of the most common—and interesting—examples. The high temperature areas vehicle electronics may be required to operate in varies by the type of vehicle and where the electronics are located. 20 Figure 1: Traditional automotive temperature ranges. CYLINDER PRESSURE: 200° TO 300° C ON ENGINE, IN TRANSMISSION: 150° TO 200° C ON WHEEL SENSORS: UP TO 150° C TO 250° C ExHAUST SENSING: UP TO 850° C, AMBIENT 300° C Exhaust sensing electronics can face temperatures up to 850°C and cylinder pressure sensors can face up to 300°C, while "on engine" temperatures can range from 150°C to 200°C. Cooling can be used to mitigate high temperatures, but cooling system failures can lead to electronics failures, so most cooling approaches are limited to the placement of electronics on parts of the vehicle that offer natural heat-sinking capabilities—such as the metal vehicle body. Vehicles can also be exposed to extremely low temperatures as well, so the possible range of temperatures can impact the choices developers make regarding mechanical connections and adhesives. High temperatures are typically considered the main issue when developing electronics for automotive applications—and under-the-hood temperatures can be a challenge—but other aspects of the automotive environment such as vibration, corrosion, loose particulates and moisture can't be overlooked. For example, temperature cycling from hot to cold can cause mechanical stresses that cause gaps. These gaps can then allow moisture or particulates to get in and further expand the gaps. Over time this can cause mechanical or electrical failures – a rugged design must consider all of these environmental challenges and their interactions. A successful design must start with component selection. There are two common approaches developers usually take: the first is to is to use existing devices with specifications close to that of the target environment and do additional testing and qualification to see how the devices

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