The content dilemma
The never-ending development of new technologies and their addition to modern vehicles leads to a phenomenon that can be labelled as the ‘content dilemma’. The content dilemma epitomises the conflict between the technology content that vehicle manufacturers try to integrate into their vehicles and the weight, cost and packaging space required for wiring harnesses.
Weight, in particular, is emerging as a key concern for carmakers as more electronic circuitry is added into vehicles that are either fully or partially powered by batteries. As a result, automotive manufacturers are exploring alternative substrate materials, different types of sensor fusion, less complex architecture to reduce the number and length of wires and neoteric wiring harness methods. Adding pounds reduces the driving range for electric or hybrid vehicles. The automotive industry needs to shed weight and still perform its juggling act to hit all functional safety, reliability and longevity targets.
Since the E/E system content of automobiles is growing almost exponentially, the weight and space requirements for these traditional system components will no longer be manageable. It’s easy to point to the wiring and circuit board side and challenge them to find weight savings. Traditional wiring harnesses are exceptionally heavy and bulky due to heavy copper cores and thick insulators. Some modern vehicles contain close to 40 different harnesses, comprised of roughly 700 connectors and over 3000 wires. If taken apart and put into a continuous line, these wires would exceed a length of 2.5mi (4km) and weigh approximately 132lbs (60kg). Five years ago, vehicles had 25% less circuits than today’s cars. Five years from now, that number will increase by more than 30%. For instance, The BMW 5 Series has increased total vehicle weight by 50% over roughly 40 years. In another case, in only one generation of evolution of the Golf the cost of the E/E system increased by 70% and the weight 32%.
Vehicle electrification creates a power challenge, too, which has a direct bearing on weight. As we move to vehicle electrification, we are now talking watts and kilowatts instead of talking small amounts of currents. That’s a massive change for the automotive industry.
More power is needed to run the EV if it weighs more. Electrified vehicles are critically impacted by weight, which is rapidly becoming ever more critical and thus a major KPI of increasing importance to vehicle engineers. In fact, weight takes on a new meaning in the age of EV as it is the equivalent of fuel efficiency, and it has a linear impact on battery range, and every OEM is chasing the ultimate ‘extended’ range vehicle, except for the performance-minded.
Flexible circuits and printed wiring have the potential to replace these components and reduce system weight significantly and at the same time make the integration of electronics with the physical structure of the automobile much more seamless. Photocurable thermoplastics expand the range of polymeric materials that are available for making flexible circuit substrates, and they have the unique ability to be stabilised in a desired shape after they are moulded or formed. That creates new possibilities for producing E/E systems that conform to the surfaces within the automobile. In addition, a digital twin of the E/E system allows an optimised architectural platform to be created, correct-by-construction, reducing the cost and weight of the vehicle.
While the automotive industry works to lower the weight and cost of E/E systems, those systems also must be reliable enough to use in safety-critical systems. This has created an enigma for automakers since the best way to ensure reliability is through redundancy. This approach has been proven in extreme environments, such as in satellites where tin whisker growth has been known to cause short circuits, as well as in automotive E/E systems today using far less sophisticated technology. But redundancy also adds weight to the vehicle, so just duplicating components everywhere is far from feasible. In future data-driven business models, some functions may only be temporarily enabled via OTA software updates. In the case of electric vehicles, this can also include the motor performance. For car manufacturers to be able to implement such functions, the cabling must be designed for the maximum possible performance, even if this is rarely required at all. This will also make cable harnesses even more expensive.
Autonomous driving requires the addition of a multitude of hardware redundancies and fail-safe mechanisms to prevent single points of failure that could disable the autonomous system unexpectedly. System redundancies are critical because unexpected failures may cause the vehicle to crash if the driver isn’t paying attention or actively involved in the driving and steering process. However, these safety redundancies will add further significant weight and cost to the wiring harness.