As devices become more powerful and smaller, engineers across industries have been relentlessly working on thermal management for electronics. While many innovative solutions exist to dissipate heat using high-temperature heat-conducting devices such as fans, liquid coolers, and heat pipes, advancements in the devices themselves have fundamentally optimized thermal performance. To help you better understand how to optimize your devices and thermal management systems, this article outlines the key components responsible for thermal performance in electronics and highlights some key parameters you can manipulate on your devices to optimize the flexibility and performance of your cooling systems.
Operating ambient temperature
When designing end products such as IoT devices, medical tools, or industrial sensor devices, almost every device includes its maximum ambient operating temperature as a parameter. This maximum ambient temperature is set by the device manufacturer to ensure that the device's performance meets acceptable standards and its physical characteristics are not compromised. For example, some switching transistors can withstand very high power loads, but if exposed to excessively high ambient temperatures, their internal semiconductor junctions can melt. Furthermore, temperature directly affects the conductivity of materials, and exceeding the maximum operating temperature can alter the device's performance.
Remove heat at the source
Like most power conversion devices and ICs, devices with fixed internal power consumption and ambient temperature thresholds have a case surface temperature that depends on internal thermal resistance and the efficiency of heat transfer. Internal thermal resistance describes the efficiency of heat transfer from a heat source to the device surface. However, when most people think of thermal management, they think of the efficiency of heat transfer from the device to the environment, i.e., convection, conduction, or radiation. These methods are typically passive heat exchangers, fans, liquid cooling systems, heat pipes, and heat sinks, etc.
Figure 5.7: Heat dissipation path of cylindrical capacitors mounted on PCB
The best way to maintain a good casing temperature is to directly modify the device's internal thermal resistance and its efficiency in dissipating heat to the surrounding environment. A device with perfect thermal management has zero thermal resistance and virtually unlimited heat dissipation. However, because devices are made of real-world materials, each with its own unique thermal resistance characteristics, and because no system can perfectly transfer heat, system designers must strive to optimize the thermal performance of each critical component from the early stages of the design process.
Fixed variables
As many designers know, the various parameters of an application are often fixed, so a design needs to be developed to meet these requirements. In some cases, the device's efficiency, ambient temperature, and the system's heat transfer mechanism depend on the end application. In many situations, the only way for a device to achieve acceptable operating conditions and low case temperatures is to choose a device with improved internal thermal design and lower internal thermal resistance.
Optimized internal thermal resistance
Two key parameters are available for examination: the overall thermal resistance of the device and the thermal resistance between the junction temperature and ambient temperature – Ψjt and θja. Both Ψjt and θja are unique thermal resistance parameters for each device and vary depending on the package. Ψjt is a thermal characteristic parameter used to measure the multiple heat flow paths between the heat source and the package surface, while θja represents the linear thermal resistance between the heat source and ambient temperature. Ψjt is power-dependent; increasing Ψjt at higher power dissipation and case temperatures will ultimately degrade device performance. Even with optimized Ψjt, a high θja resistance value can lead to excessively high case temperatures and limited ambient operating temperatures.
Image source: Ricoh
There are many ways to reduce Ψjt and θja, such as material optimization, manufacturing techniques, and different junction-to-environment heat transfer methods. One of the latest advances in reducing thermal resistance is 3D Power Packaging®. Using 3D Power Packaging® (3DPP) technologies, such as FCOL, embedded ICs, and heat pipes, RECOM has successfully and significantly improved Ψjt and θja values. By reducing these values in 3DPP products, higher power performance can be achieved without limiting the ambient temperature of the device. High power density solutions such as 3DPP products are designed for high-performance and high-efficiency devices that do not require active cooling or large passive heat sinks.
For more information on the importance of RECOM's cutting-edge 3DPP technology and low thermal resistance in high-efficiency power supply design, please visit our 3DPP Applications page or contact [email protected] to order RECOM 3DPP evaluation boards.
