40 The dispensing process can be manual through a pressure-driven gun or with meter-mix equipment for largevolume production. For two-component systems, dynamic and static mixing heads may be used, with static mixing the most common for thermal potting due to the abrasive qualities of the filler. The most common dispensing methods for potting of batteries include static, static-dynamic or fully dynamic mixing in preparation for lowpressure injection or filling. The latter are typically accomplished with gear pump, progressive cavity pump or piston-pump systems, says ViscoTec’s Paintmayer. In contrast, high-pressure mixing and injection systems are used with foaming materials. For potting highpower electronics, mixing units based on progressive cavity or piston-pump technology are mainly used. ViscoTec makes dosing and filling systems, along with dosing components based on the progressive cavity pump technology for semi-automatic and fully automatic production plants and assembly processes. “We have been able to dispense a wide variety of materials, but in the area of potting and encapsulation we have gained most experience with silicones and polyurethane,” says Paintmayer. “For thermally conductive and thus typically abrasive fluid types, we have optimised our pump technology to combine high precision with long equipment life.” After dispensing, the material needs to be cured, which can often be done at room temperature, but may be accelerated at an elevated temperature, Brown at Henkel adds. New materials and methods Axalta is working on a new epoxy material that meets the Class H temperature specification of 180 C and offers thermal conductivity in the range of 1.5-1.6 watts per metre kelvin (W/mK). This, says Koschmieder, enables good heat transfer from encapsulated motor windings. “It’s the same resin base that showed excellent resistance to some ATF oils. Of course, we can’t test every ATF oil in advance, so we would recommend that customers do some of their own tests with particular ATF oils.” C-Therm tests all kinds of potting and encapsulation materials, says Brown, including cured and uncured products used in r&d and manufacturing. It has introduced sensing technology that can thermally map the composite material formed by the resin and filler, assessing the distribution of the filler as it relates to thermal conductivity. “We are starting to deploy the sensors in manufacturing, monitoring in real time the process of dispensing potting compounds and two-part adhesives to check for sedimentation,” he adds. In terms of process, incorporating thermal property sensors in the dispensing equipment will significantly improve manufacturing confidence in the application of these materials, says Brown. For the automotive industry, this will give assurance of greater consistency in the performance of potting materials and two-part adhesives. “The immediate benefit will be less downtime on dispensing equipment, less scrap or rework, and much improved traceability at a critical step of the manufacturing process,” he adds. Henkel notes the surge in demand for EVs has brought a significant increase in volume, plus a drive to lower cost while maintaining performance in critical applications. This pushes the development of new and improved materials, and addresses unmet needs, which the company seeks to pursue though collaboration with customers and partners. For potting compounds, White says the goals are to expand their operating temperature range, reduce density, and improve their overall mechanical and electrical protection characteristics. At the same time, the company’s engineers work to maintain thermal conductivity and a cost structure suitable for large volumes. “From a process perspective, the goal is always to have a product that can integrate seamlessly into customer process flows, which means ensuring excellent coverage and wet-out without requiring vacuum or other post-dispensing treatment, and carefully March/April 2024 | E-Mobility Engineering In potting the container remains part of the component; in encapsulation it is removed before the component is installed into another assembly (Image courtesy of C-Therm) Thermal potting compounds can transfer heat away from embedded electronic components, and provide resilience against vibration/shock, corrosion and harsh chemicals (Image courtesy of Henkel)
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