Thermal Interface Selection Criteria for Prismatic Battery Modules
Optimal prismatic module thermal interface selection balances bulk conductivity against rheology and compliance to accommodate swelling without dielectric rupture.
Thermal Pad Compression
Meaning
Deformation of soft elastomeric sheets occurs when they are squeezed between a heat-generating component and a cooling structure. The process of thermal pad compression determines how well the pad conforms to irregular surfaces and fills microscopic air gaps. It is a critical factor in optimizing the heat transfer pathway in electronic modules.
This behavior must be balanced to avoid damaging sensitive silicon dies.
Load Response
Compressive force must be controlled to achieve the desired deformation without overloading the assembly. Thermal pads are designed to be soft, but their resistance to deformation increases as they are compressed further. This non-linear relationship means that higher strain requires disproportionately more force.
Designers use force-deflection curves provided by material suppliers to calculate the required clamping pressure.
Thermal Resistance
Reduction in thermal resistance is achieved as the pad is compressed, which increases the contact area and reduces the interface thickness. A compressed pad has fewer air voids at the boundary, which enhances the rate of heat conduction. However, compressing the material beyond its recommended limit does not yield further thermal benefits and can damage the internal structure of the elastomer.
This limit is typically between twenty and fifty percent of the initial thickness.
Assembly Stress
High assembly forces can bend printed circuit boards or crack delicate solder joints. Managing this stress requires choosing highly compliant pads that achieve low thermal resistance at low pressures.