Meaning
Obstruction to the flow of heat occurs at the physical boundary between a heat-generating component and a cooling surface. Within a battery pack, thermal interface resistance is found between the cell casing and the thermal paste or cooling plate. Minimizing this value is essential for keeping the cells at a uniform temperature during rapid charging.
Heat Dissipation
Efficient cooling depends on the ability of thermal energy to move quickly away from the active materials. High thermal interface resistance causes heat to build up inside the cell, even if the cooling system is running at full power. This temperature rise can lead to accelerated aging and an increased risk of localized hot spots that can trigger a thermal runaway event.
Contact Quality
Surface roughness and lack of flatness create microscopic air gaps that act as insulators. Using soft thermal interface materials or high clamping pressures can fill these gaps and reduce thermal interface resistance. The choice of material must balance the need for high thermal conductivity with the requirement for electrical insulation to prevent short circuits between the cells and the cooling plate.
Thermal Transfer
Measuring the temperature drop across the junction allows engineers to calculate the effectiveness of the assembly.
