Leaking Cars Lead to Sunken Reputations

How wireless sensing can drive moisture out of vehicle assemblies

Moisture ingress related quality issues can be a hard-to-detect, slow-burn problem for automakers—one that does not usually present a clear, immediate failure. This problem can loom large on the assembly line, where it is routine for vehicles to go through an end-of-line spray test to detect any water leaks that could represent a potential problem over the life of the vehicle.

Visual inspection methods can reveal significant leaks, but smaller leaks, often in inaccessible areas, are at best difficult, and at worst, almost impossible to find. Modern vehicle assembly methods and increasing electronic content in today’s vehicles accentuate the potential for moisture ingress and its impact on reliability.

ON Semiconductor and RFMicron have sought to address this increasingly important issue by jointly developing a unique, hands-free production turnkey leak detection system. The system employs tiny, low-cost, battery-free wireless moisture sensors placed strategically around the vehicle early in the assembly process. These sensors, read after the spray test, can support an effective way to not only detect moisture ingress problems, but also drive process improvements to eradicate the issue completely.

This article looks at the growing leak problem, its implications, and how this innovative approach looks set to solve the problem, minimize field failures, and protect automakers’ reputations.

Water Leaks are Costly
Water leaks are a costly problem for automakers in more ways than one. Modern vehicles have become more complex and incorporate new materials including aluminum, composites, and glues.  Today’s cars and trucks feature hundreds of electronic sub-assemblies, which make them more susceptible to water damage than ever before.

Large leaks are usually quite easy to find and address, although the thicker sound-deadening foam being incorporated in vehicles can easily mask significant problems. Smaller leaks are much harder to detect and over time can lead to mold growth that has a potential negative impact on the on-board electronics as well as on the health of vehicle occupants.

Water ingress will always lead to expensive warranty claims for automakers; consumer surveys indicate that around 150,000 vehicles are recalled each year for water leak issues. With an average repair cost per vehicle as high as $5000, this equates to a hidden leak cost of $100 for every vehicle sold—not counting the value of a damaged brand reputation and the potential loss of future sales.

Spray and Seek
While vehicle design has moved on significantly and leaks are far less prevalent than in the past, it is estimated that up to two percent of vehicles leave the factory with hidden water leaks. In order to identify these vehicles before they reach the consumer, many automakers implement a two-to-five-minute soak test at the end of the assembly line.

These soak tests generally involve the vehicle being sprayed with high-pressure water jets from multiple angles to probe all of the vehicle openings and accelerate any water ingress. The magnitude of water intrusion during a test can range from large puddles accumulating in low lying areas of the vehicle, to just a few drops in the more obscure places. The former are relatively easy to spot through traditional visual inspection methods. But the latter—especially if in out-of-sight areas such as between the inner and outer skins of the vehicle or soaked into sound-deadening material—are not.

Figure 1: Automakers turn up the pressure to find leaks with water jets in the 2,000 psi range.

Currently, there are several manual methods employed to detect water ingress after the spray process has finished. Some automakers use differential probes to electrically identify leaks or water contact indicator tapes that change color when damp. These methods may increase the chance of detecting a leak. However, they still struggle with penetrating the thicker foams and small interior spaces present in today’s vehicles. The most common method remains physical inspection by assembly line workers.

This manual method of inspection is prone to error, not least because the worker is also carrying out a plethora of other (unrelated) checks and inspections at the same time. Even when performed well, this method can only verify water that can be seen or felt by the worker’s hands. Any water that is hidden from view in inaccessible areas, such as behind interior trim or underneath carpet, is inevitably missed, setting up a future warranty claim.

Not only is the current method of ‘spray and seek’ unreliable, it also takes time and therefore imposes significant additional costs on the automaker.

Non-invasive Leak Detection that is Cost Effective and Accurate
Given the costs associated with unreliable test and inspection as well as the high costs of repairing every leak that reaches a consumer, it is no surprise that semiconductor manufacturers and automakers have been looking at alternative solutions. One innovative and dependable approach that has been developed to address water ingress in vehicles is the RFM5126 Moisture Intrusion Detection System. This turnkey solution allows automakers to determine if water has penetrated a vehicle. In addition, it shows the exact time and location of any leak. Furthermore, through storing and analyzing data from the system, statistics and trends can be developed for vehicle models and factories, allowing for effective design through process improvement.


Figure 2: RFM5126 Moisture Intrusion Detection System

At the heart of the integrated system, multiple tiny, battery-free, wireless water leak sensors are placed underneath the carpet, behind trim panels, and in other small hidden areas within the vehicle.

These sensors, sold under the Smart Passive Sensing™ and SPS™ brands, have an adhesive backing that allows them to be installed on the vehicle chassis, in locations prone to water leaks, at the bare metal stage of assembly. The sensors come with an option to include a water wicking tail during install that adheres to both the top of the sensor and bare metal chassis, thereby extending the range of leak detection in a specific vehicle location.

Figure 3: Sensors are adhered directly to the vehicle’s metal chassis at the pre-trim stage and have an optional wicking tail.

After completing all assembly, vehicles move through the high-pressure spray test, where the system flags any leaks including the small, hard-to-find ones. Drive-through portals receive data from the sensors, and sophisticated sensor monitoring software within the portals can accurately report leak locations to pinpoint and speed up any necessary rework.

Water ingress is a significant problem for automakers costing them time on the assembly line as well as significant warranty claims and, ultimately, loss of brand reputation. Current testing methods are unreliable, as many leaks are hidden and assembly line workers making checks are often performing other tasks at the same time.

New Smart Passive Sensors form the heart of sophisticated leak detection systems that eliminate manual inspection and improve inspection accuracy.

The data collected provides the information needed to drive process improvement efforts that help the automaker identify systemic issues with the ultimate aim of eliminating the problem completely and permanently.

Jeremy Correale is Automotive Marketing Manager, ON Semiconductor. He  leads the automotive segment of ON Semiconductor’s Protection and Signal Division based in Phoenix, Arizona. He is responsible for the definition and execution of the business unit’s automotive strategy revolving around a portfolio of ESD Protection and Small Signal Discretes, electronic fuses (eFuse), and Smart Passive Sensors (SPS). Correale joined ON Semiconductor in 2010 after completion of his BSE in Electrical Engineering from Arizona State University. In his free time, Correale is an active member of the Arizona-Nevada section of Society of Automotive Engineers (SAE) and enjoys racing in the occasional track day under the National Auto Sport Association.


Alan Hansford is currently the Vice President of Marketing and Business Development at RFMicron, Inc. in Austin Texas. Mr. Hansford has workedwith numerous startups and corporations to deploy IoT technologies to industrial and consumer segments. Mr. Hansford has deep experience in with embedded and system products processing at the edge.





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