Material Considerations for Advanced Driver Assistance Systems Assembly

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For many years, the expanding scope of electronic systems in vehicles has been built on a very conservative design ethos, with a considerable focus on reliability. It is well known that automotive electronics was, by far, the largest electronics market segment to be exempted from 2006’s EU RoHS legislation, which included the removal of lead (Pb) from electronic assemblies.

The core argument during the successful lobbying of the EU, and subsequent exemption for the automotive electronics companies, was that there was insufficient reliability data of the Pb-free alternatives. Now these exemptions are coming to an end, and this growing segment is rapidly employing the most common alloy group which the majority of other segments had adopted before 2006. This solder alloy group is the standard Tin-Silver-Copper alloys, based close to the ternary eutectic point at Sn Ag3.8 Cu0.7.

Added complexity in material selection comes from the ever-increasing array of applications in automotive electronics, and one of the newer applications is the deployment of an array of vision and detection systems for driver assistance, collectively known as advanced driver assistance systems (ADAS).

The Evolution of Vision and Detection Systems

Parking sensors have become commonplace in the last 10 years, making the process of getting your car into a tight parking space a much less risky proposition. This is based on relatively simple radar technology and provides the driver with an increasingly audible alarm as the object to be avoided comes closer.

In more recent years, a number of vision and detection systems have started to play a much more critical role in the driving experience. One of these examples is lane departure warning system (LDWS). This system uses AOI vision technology to track the edge of the road or the lane markings, and provides the driver with a warning if the vehicle veers over the line without indicating.

The system interprets the absence of purposeful use of the indicators as a likely result of the driver losing concentration, or in its extreme form, falling asleep. The first generation of LDWS activated a significant vibration alert in the seat in order to alert the driver to imminent danger. The second generation took things closer to automatic intervention with a low-torque nudge of the steering wheel to put the vehicle back "on-course". The reliability of such a system is clearly more critical than the simple parking sensors, as the operation is designed to work at speed and prevent high-speed collision.

An increasingly common feature in vehicles is cruise control. This has been available for decades and like many features which enter the market on luxury vehicles, has become standard for any vehicles intended for distance driving. The new generation of cruise control is emerging, and is known as "active cruise control".

This technology not only regulates the speed, but also maintains a minimum distance between the vehicle in front, automatically reducing the throttle, and in some cases activating the brakes automatically, and then only returning to the set-speed when the distance to the vehicle in front allows. This radar based technology is integrated with the braking and throttle controls to achieve its function, and so its performance is absolutely critical to safety.

The fourth and final area we will consider is the new generation of parking aids. Supplementing the radar-based parking sensors is the integration of rear-view cameras with superimposed guidance lines to help the driver with reversing into a parking space. This passive parking technology is already being advanced with some active systems which will actually assess a parking space and automatically steer the vehicle into a parking space requiring the driver to only operate the throttle and the brake pedals. This technology uses a combination of radar and cameras to provide this advanced parking function.

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Editor's Note: This article originally appeared in the September 2015 issue of SMT Magazine.



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