Advanced electronic systems powering today's vehicles require robust solutions to resolve a growing array of performance-hindering issues. Deploying effective thermal management is one challenge and issues involving excess heat can arise from the drivetrain to the dashboard. Increased demands for heat-generating electrical energy are everywhere. Heat is emitted by system complexity itself. In this paper, Laird probes each of these design hurdles and explores automotive thermal management in depth.
Deploying Thermal Interface Solutions in Automotive Electronic Systems
Today’s vehicles contain some of the most complex integrated electronic systems. To ensure proper operation under these challenging conditions, the latest thermal management technologies and materials must be implemented.
The continued growth in the amount of advanced electronic systems in vehicles has placed pressure on automotive systems designers to develop and deploy robust solutions. The higher power required by these systems, also means that they will generate more heat that needs to be effectively managed to ensure proper operation. From the drivetrain to the dashboard, the growth in powered solutions presents a challenge in thermal management.
The increased electrical energy demands in automotive systems come from a variety of industry trends that have significantly increased the amount of power used by vehicles. One power-sensitive aspect of modern vehicles includes the ever-increasing motor requirements for powered subsystems, not to mention drivetrain modules and motors in EVs. Another is the growing complexity and functionality of operator interface, vehicle infotainment, communication, and performance management systems.
These and other aspects underscore the growth in both power requirements and the number of systems using it. This is further exacerbated by the high levels of system integration from technology advances as well as form-factor pressures. This means more and more powered systems in a crowded, harsh environment. From the battery management circuitry in the vehicle charging subsystem to the power electronics in the drivetrain to the increased functionality in ADAS and driver interface systems, the need for proper thermal management is greater than before.
Thermal Challenges
Every powered system in a vehicle needs proper thermal management, for a variety of reasons. The first consideration is to protect the electronics themselves from the heat generated during operation. The first echelon in any powered system is the power conversion electronics needed to drive it. Even the most efficient power supplies still generate heat, and that heat must be managed. This includes optimizing any cabling or bus bars carrying high current.
The second echelon is the device being utilized and how efficient it is at that task. This is a critical consideration to ensure the desired performance and protection of the device. Those devices have their own power conversion inefficiencies, and excess heat that must also be addressed. Subsystems like braking and stability control must also have thermal management solutions for their active circuitry.
The center stack with its infotainment and driver interface content has a plethora of power-consuming devices, and any thermal management solution must address the high levels of system integration involved. Functionalities like ADAS also involve a high level of increasing system integration, with each subsystem having varied thermal needs. Illumination systems range from dashboard instrument illumination to a vehicle’s headlights, and each of the lighting drivers involved has thermal management needs as well.
The vehicle itself presents a harsh environment to the electronics contained within it, and any thermal management solution must address any issues presented. For example, an underbody electronic package may need to be made waterproof, forcing designers to use a convection-cooled design instead of an air-breathing one. Active vs. passive cooling thermal management decisions can dictate the options available to the design team.
Where a system is deployed can present additional design challenges in thermal management. Engineers can’t always predict every use case, but as broad a leeway for users and user errors should also be considered. Using the appropriate thermal solution for the operational environment increases reliability and effectiveness of the system. Even solar heat and regional environmental issues must be addressed, or there could be problems with thermal management in impacted systems.
Once your systems have been optimized for efficiency, and vehicle deployment issues have been considered, any remaining thermal management falls to a variety of heat-transfer methodologies. These solutions move the heat out and away from the electronics to where it can be dissipated, using a variety of technologies, often leveraged in concert with one another.
Filling the Gap
Thermal gap fillers can be used to bridge the interface between hot components and a chassis or heat sink assembly to increase the overall heat transfer from the system. The thermal conductivity properties of gap fillers help keep components within desirable temperature ranges. Gap fillers need to be relatively compliant to achieve high deflections without generating excess pressure within an application. The unique combination of thermal conductivity and softness reduces mechanical stress while maintaining thermal performance. Other optimal properties of gap filler materials include low total thermal resistance, high thermal conductivity, thermal reliability and low outgassing and ease of use.
More of a paste than a fluid, liquid gap-filling materials perform thermal transfer between electronics generating heat such as GPUs or power semi’s, and a mechanical component carrying the heat to the exterior like a heat pipe or heatsink. Liquid gap fillers are also beneficial when elimination of mechanical stress or bulk automated dispensing are critical design considerations. These materials can be dispensed to fill large and uneven gaps in assemblies and due to their super compliant nature; little to no pressure is transferred between interfaces.
In addition to being used for heat management, a thermally conductive insulator is also electrically insulating. Made up of a thin electrically-insulating PI film coated on both sides with a thermally conductive polymer composite material, such a solution can be used to permanently attach ICs or other electronic packages to a heatsink. This not only can eliminate mechanical fasteners, it also prevents dielectric failures in screw-mounted assemblies.
Some electrically-insulative dielectric materials offer good thermal performance using polymer films coated with ceramic-filled materials such as high-temperature silicone rubber. These thermal solutions address applications that need a consistent temperature across the interface with a high dielectric strength. Some high-performance insulator pads also include thermal phase-change compounds to significantly reduce contact thermal resistance.
Thermal interface phase-change materials enhance thermal transfer between a hot component and a thermal solution like a heatsink, lowering temperatures to increase speed and extend component life. Phase-change materials soften to a near-liquid state at higher temperatures, allowing them to thoroughly wet the mating surfaces to provide the lowest possible thermal resistance and best performance with long-term reliability. Available in silicone-based and silicone-free versions, thermal grease thoroughly wets contact surfaces to create a low thermal resistance, and can be used in pneumatic dispensing and screen printing systems.
Additional Considerations
Once you have considered the thermal requirements of a given system, you should consider the aspects to address other parts of the design. For example, the mechanical properties of the thermal materials used can also serve other needs of the system. Adhesive thermal pads and tapes can replace mounting hardware, reducing the BoM and simplifying the design for more reliability, among other benefits. This is especially important in automotive systems, which must be as safe and reliable as possible.
Another aspect to thermal interface materials is the potential for vibration and noise mitigation. Compliant pads and putties can also absorb vibration, protecting the electronics further. Every aspect of your thermal solution should be leveraged for the maximum system benefit. Manufacturing needs must also be considered, as various means of material deployment, like liquid dispensing, pick and place, or tape dispensers, should be integrated into the manufacturing flow to minimize any assembly complication.
One often overlooked issue in developing solutions for thermal management is having the right development partner. A good thermal management solutions provider will not only be able to provide you with the products you want, but can also help you determine the products you need. In addition, a good supplier will have the experience needed to understand your application and the potential solutions available to address it. They can also help you address supply-chain issues, by ensuring the solutions they provide are in good supply.
Looking Forward
Developing and deploying electronic thermal management solutions in an automotive environment can be challenging. Needs and solutions must be balanced against each other, to ensure the right products are used in the right places. Knowing what the advantages are in each solution can go a long way to a successful deployment. Having a good development partner can also help you address these issues in a painless manner.
About Laird Performance Materials (Laird)
Laird Performance Materials, integrated into DuPont Electronics & Industrial’s Interconnect Solutions (ICS) business, solves signal integrity and power transmission issues. We enable high-performance electronics by creating protection solutions for advanced interconnects and systems. World-leading technology brands rely on Laird for improved protection and helping accelerate their products’ time-to-market. A global brand, Laird solves design issues by providing Laird™ branded innovative products such as EMI suppression or absorption materials, thermal interface materials, structural and precision metals, magnetic ceramic products, and multi-functional solutions (MFS). The Laird™ MFS product family solves multiple EMI, thermal and structural design issues simultaneously using a single process design. Visit Laird at https://www.laird.com.
Copyright © 2022, Laird Technologies, Inc. DuPont™, Laird™, Laird Performance Materials™, and corresponding logos, are trademarks owned by Laird Technologies, Inc., DuPont de Nemours, Inc., or their subsidiaries. All rights reserved.