Meaning
Highly conformable thermal interface material applied between battery cells and cooling plates maximizes heat transfer by eliminating insulating air pockets. This material is known as a thermal gap filler, and it is usually formulated as a two-part liquid silicone or polyurethane resin loaded with conductive ceramic particles. Liquid application allows the material to flow into irregular spaces before curing, accommodating the dimensional variations of the battery cells.
This process is essential for keeping cell temperatures low and uniform across the entire module.
Thermal Conductivity
Heat transfer through the interface material is governed by the volume of conductive filler particles suspended in the polymer resin. These particles, typically alumina or aluminum nitride, create a conductive pathway that bypasses the low conductivity of the polymer. The material must maintain this pathway even when subjected to the thermal expansion and contraction of the cells.
Sourcing teams must verify both the bulk conductivity and the contact resistance of the filler to ensure performance.
Mechanical Compliance
The material must remain soft and flexible after curing to absorb the mechanical stresses generated by the battery cells. Lithium cells expand and contract during charge and discharge cycles, exerting continuous pressure on the surrounding structure. A rigid interface material would transfer these forces to the cooling plate, potentially causing structural failure or leakages.
The flexibility of the cured filler protects the delicate cooling plate from mechanical fatigue.
Dispensing Automation
High volume battery assembly lines utilize robotic dispensing systems to apply the liquid filler in precise patterns. The material viscosity must be controlled to allow for rapid dispensing without causing tool wear or clogging. Automated systems use volumetric pumps to mix and dispense the two-part resins directly onto the cold plates before the cells are pressed into place.
This automation is critical for achieving consistent assembly cycle times and joint quality.
