The contact thermal resistance between the charging pile copper substrate and the heat sink fins is a core factor affecting overall heat dissipation efficiency. Optimization requires a comprehensive approach encompassing material properties, contact surface treatment, pressure control, interface material selection, and structural innovation. As a critical heat-conducting component in high-power-density applications, the charging pile copper substrate has a much higher thermal conductivity than aluminum substrates. However, improper treatment of the contact interface with the heat sink fins can still lead to heat accumulation due to contact thermal resistance, affecting equipment stability and lifespan. Therefore, reducing contact thermal resistance requires focusing on two core principles: "increasing the actual contact area" and "reducing interface gaps."
First, the surface flatness of the copper substrate and heat sink fins directly affects the contact area. Even seemingly smooth metal surfaces have micron-level uneven structures at the microscopic level. These gaps are filled with air (which has extremely low thermal conductivity), forming a thermal resistance barrier. Through chemical etching or laser micro/nano processing techniques, regular microgrooves or micropore structures can be formed on the copper substrate surface. This increases the actual contact area and fills the gaps with thermally conductive material through capillary action, significantly reducing contact thermal resistance. For example, after adopting laser etching technology, a charging module experienced a decrease in contact thermal resistance and an improvement in heat dissipation efficiency.
Secondly, precise control of contact pressure is crucial for reducing thermal resistance. Insufficient pressure leads to residual gaps at the contact surface, while excessive pressure can cause material deformation or damage. In engineering practice, elastic clamps or thermo-pressing systems are often used to achieve dynamic pressure adjustment. For example, in the assembly of IGBT modules and heat sink fins, a preload is applied using spring clamps, significantly increasing the actual contact area. For high power density scenarios, pressure sensors can be integrated to automatically trigger a pressure compensation mechanism when the temperature at the detection point exceeds a threshold, ensuring contact stability.
The selection and application of interface materials are core aspects of reducing contact thermal resistance. While traditional thermal grease can fill gaps, long-term use can lead to a pumping effect (material flow causing increased thickness), affecting long-term stability. Phase change materials (PCMs), through their softening upon heating and solidification upon cooling, can maintain a tight fit with the contact surface. In a charging module case, replacing silicone grease with a paraffin-based PCM significantly reduced contact thermal resistance. For ultra-high temperature applications, liquid metals (such as gallium-based alloys) can further reduce contact thermal resistance to extremely low levels due to their excellent fluidity and thermal conductivity.
Structural innovation can overcome the limitations of traditional designs. Thermoelectric separation copper substrates, by creating windows in the insulating layer, allow device pins to directly contact the highly thermally conductive copper substrate, bypassing the inefficient insulating layer and significantly reducing thermal resistance. In charging pile design, heat sinks and copper substrates can be integrated into a single structure, achieving seamless connection through diffusion bonding or friction stir welding. One electric vehicle charging module uses a copper-graphene composite substrate, combined with a micro-hole array heat dissipation structure, resulting in a significant reduction in overall thermal resistance compared to traditional designs.
Optimizing heat dissipation paths is equally important. Adding copper-filled vias under high-power components enhances heat conduction paths; reducing the dielectric layer thickness in critical heat dissipation areas, or even directly exposing the metal substrate, improves heat exchange efficiency. In a charging pile case, the adoption of a locally ultra-thin dielectric design reduced contact thermal resistance and improved heat dissipation efficiency.
Maintenance and reliability management must be implemented throughout the entire product lifecycle. Regularly inspecting the oxide layer thickness on the contact surface and promptly replacing aging interface materials can prevent the contact thermal resistance from deteriorating over time. A data center UPS system, by implementing a regular maintenance strategy, maintains the contact thermal resistance within a certain percentage of its initial value, ensuring long-term heat dissipation stability.
