Intelligent thermal management in the battery joining process for electric vehicles

Electromobility must constantly evolve to meet increasing market demands regarding operational safety, performance, range, charging times, and costs. As the heart of the vehicle, the battery can only deliver its maximum performance within a specific temperature range. Every battery generates heat during charging and discharging, which must be controlled and dissipated for safety and to maintain long-term battery capacity. A thermal paste is applied in the battery tray to prevent overheating due to the heat generated by the operation of the cells.

These highly viscous material enriched with special fillers, also known as gap fillers or thermal interface materials (TIM), enable active thermal management of large battery packs by dissipating the heat generated during charging and discharging of the cells into appropriate cooling structures.

In the joining process, a thermal compound like TIM is applied after sealing the battery tray and assembling the cooling system and compartments. Precise application without air pockets is essential. Advanced tightening technology ensures optimal contact between the housing and battery module by considering the behavior of the conductive paste at the joint.

Applying the liquid material in large quantities and with a high flow is challenging. A high-performance application system is critical, with components that can withstand the abrasive material. Various application patterns, such as parallel lines, meanders, or so-called bone application, can be used to promote the bubble-free pressing of the modules onto the conductive paste. Extensive material tests are necessary to develop the appropriate application pattern.  At our global Innovation Centers, we bring battery and equipment manufacturers, and material suppliers together with our joining experts to find the optimal application for each specific case.

When applying the material, tolerances in the fit between the battery compartment and the cell module as the counterpart must be considered. The respective tolerance chains of the components result in gaps of 0.5 to 3 mm.
If too little material is applied, this can lead to insufficient filling and air pockets, which negatively affects the quality of thermal management.
Manufacturers usually apply too much material to ensure the gap is adequately filled even at maximum tolerances leading to wasted material, increased battery weight, and increased costs. Squeezing out of material when the modules are tightened together can also lead to technical defects. The goal: To apply the material volume in a precisely minimized manner.

Atlas Copco relies on an upstream industrial image processing system in combination with an intelligent algorithm, which enables the metering system to apply the thermal interface material accurately.  Smart.Adjust calculates and controls the optimal amount of material.
In the first step, 3D sensors measure the underside of the battery module and the surface of the battery compartment. The scan data are merged into the software. This allows the tolerances and the volume of the column to be calculated precisely. The intelligent algorithm determines the required material volume from the scan data and sends the information directly to the line control of the application system, which adjusts the parameters accordingly for each individual application, and the optimum material volume is applied. The precise adjustment of the volume is directly carried out via the metering system.

To improve thermal management, attention should be given to material supply in addition to application. Challenges arise due to the unique properties of thermal management materials. The high density often leaves drums only half full, necessitating frequent drum changes. Manual venting and purging are required after each change, resulting in the loss of 1.5 to 6 liters of material as pump-on waste. Additionally, conventional pumps struggle to completely empty a drum, leaving up to 6 liters of material behind in a 200-liter barrel.
This complex process consumes time, wastes expensive thermal paste, and requires costly disposal of material residues. Ensuring consistent quality throughout the dispensing process is also challenging due to manual operations.

To answer these challenges, Atlas Copco invented a new material pump generation, called Plus.Supply. With half-automated barrel change, a newly designed Flat Follower Plate, and vacuum technology, SCA ENSO Plus.Supply is our “carbon footprint hero” with 99,4% of material usage per barrel. A vacuum pump automatically pumps out the air trapped between the Flat Follower Plate and the material, allowing a half-automated barrel change. Manual processes such as venting and rinsing are eliminated. This reduces the complexity of barrel changing and the amount of training required avoids air pockets in the material that can lead to application errors and increases operator safety. Offering three different base plates for the Plus.Supply, we meet nearly every manufacturer's logistic needs.

Measurable benefits are achieved by an innovative application system that can take component tolerances into account and apply the material optimally.  The role of material supply is often underestimated in thermal management. Innovative material supply concepts offer great leverage for material savings and process improvements during barrel changes, also helping to significantly reduce CO2 emissions in the EV batteries assembly process.