Evaluating Interfacial Foam Compression Set Effects on Module Stress Distribution Profiles
Foam compression set collapses baseline clamping force, shifting planar pressure to rigid edges, elevating thermal impedance, and risking tab fatigue.
Thermal Interface Impedance
Meaning
Resistance to heat flow at the junction between the battery cell and the cooling plate limits the efficiency of the thermal management system. This thermal bottleneck, known as thermal interface impedance, depends on the thickness and thermal conductivity of the filler material. It must be minimized to prevent local overheating and extend the cycle life of the cells.
Heat Transfer
Microscopic surface roughness on metal and plastic surfaces creates tiny air gaps that act as thermal insulators. Thermal interface materials are applied to fill these gaps and lower the thermal interface impedance of the joint. By ensuring a continuous path for heat to flow, this treatment allows the cooling system to maintain stable cell temperatures during fast-charging cycles.
Pressure Dependence
Compressive force applied to the interface compresses the thermal pad and reduces the gap thickness. This action lowers the thermal interface impedance, but the pressure must be controlled to prevent squeezing out liquid thermal compounds or damaging the cell. Engineers use stress-relaxation curves to select the right compression level for the module.
Sourcing Metric
Sourcing teams utilize this thermal impedance value to evaluate different gap filler manufacturers. Choosing a material that achieves low thermal interface impedance under low assembly pressure allows the team to design lighter and cheaper module brackets. This selection process directly lowers both the material cost and the total weight of the battery pack, while ensuring that the thermal management system can prevent dangerous heat accumulation during high-rate charging.