“High-reliability components supporting automobile”
Tough environment surrounding electronic components for in-vehicle use
Assurance of long-term reliability and durability is essential

Requirements for in-vehicle use of electronic components are strict. High reliability in hard usage conditions and durability that enables long-term use are a must. Moreover, these components must be equipped with safety features to protect human bodies in an accident. In designing electronic equipments to meet such requirements, electronic components with excellent reliability and durability are indispensable.

Fig-1. Hard environmental conditions of electronic equipments and components for the in-vehicle use.

As electrification of automobiles advances, various electronic equipments, such as Electronic Control Unit (ECU) ,have been installed in various areas such as a dashboard and around the seats. But it cannot be said that the in-vehicle environment is good for electronic equipment. For example, when we look at just temperature, it can become an adverse condition for electronic parts and equipments as shown in Fig-1.

Temperature inside the engine room reaches to 100°C~120°C. Temperature around the passenger seats may exceed 65°C because of insulation. Temperature on the surface of the dashboard directly exposed to the sun can reach as high as 100°C. Recently even the engine and the gearbox are starting to be embedded with electronic components. In such areas, the ambient temperature may rise to 150°C. So, the reliability of bonding a part with conventional solder on a printed circuit board decreases rapidly. In addition, it must stand against the continuous vibration from running. Furthermore, acceleration around 3G to 4G is also applied to electronic equipments during running.

Long-time durability is essential

There are many adverse conditions related to water to which electronic components are vulnerable. Driving in rain increase the possibility that in-vehicle electronic equipment gets wet. Humidity can reach up to 98% around the door or inside the trunk room. Rapid temperature change from driving can cause condensation. Not only running, but also washing can lead the electronic component exposure to water. Washing the vehicle body with water can cause condensation as well by a sharp temperature change. Not only heat and water, but also fats and oils can affect electronic components depending on the place of installment. Therefore, some components require oil resistance. Since a vehicle can be used around the ocean, damage from salt water on electronic equipments must also be considered.

Electrical environment is also strict. Since a single battery is shared by many types of electrical equipment, a voltage change is easily generated. As many electronic devices are installed into the restricted space in a vehicle, the problem of noise interference generated by each electronic device occurs. Electrostatic discharge that takes place in every nook and cranny in a vehicle also affects badly to reliability of electronic devices.

As the environment can be strict, we have to consider one more points to boost the reliability of electronic devices used in a vehicle. More specifically, durability for long time use is important. Compared with digital consumer electronic equipments of which the product life cycle is short, in-vehicle electric devices have longer period of usage ranging from some years to 10 years or longer. Reliability of systems in a vehicle must be met for such a long period of usage.

The key is securing reliability of individual parts and components

To realize high durability in an electronic equipment that can withstand hard usage in an extreme environment, each electronic part and component of the equipment must have high reliability and durability. So, the Automotive Electronics Council (AEC), that was set up by major automobile manufacturers and parts suppliers in US, has established a standard to evaluate reliability and durability of electronic parts and components for in-vehicle use, which has become the de-facto industry standard. In this standard, specifications by product category are available. For example, “AEC-Q100” is for semiconductor devices, “AEC-A101” for discrete semiconductor devices, and “AEC-Q200” for passive components. Actually many automobile manufacturers have even stricter evaluation criteria based on this standard.

Most semiconductor and electronic component manufacturers that are aiming their business expansion in the market for in-vehicle products are preparing products with higher reliability than products for other application fields based on the standards. Many manufacturers are reinforcing their systems for reliability evaluation and quality control to grow their share of the market for in-vehicle use products.