37 Potting & encapsulation | Insight E-Mobility Engineering | March/April 2024 the resins are likely to be exposed. In electric-motor windings, this might include exposure to oils such as automatic transmission fluid (ATF) used as a coolant, notes Ulf Koschmieder at Axalta, a company with a background in coatings for transport applications has a range of high-performance epoxies. Often, these factors are affected by the location of the components to be protected, Epic Resins’ Staller notes. A sensor in a vehicle cabin will face very different conditions from one under the bonnet, requiring greater protection from thermal cycling, while a sensor immersed in a fluid would need protection with specific chemical resistance properties. “Each application is unique and requires unique polymer property considerations.” “Potting is the process best suited to fully cover a large number of electronic components with small features, particularly inductors,” says White at Henkel. “For components not contained in a housing, such as an isolated chip on a PCB, encapsulation or a coating may be more appropriate and would consume less volume of material.” “It is up to our customer to evaluate how much stress is placed on their component and to decide how they want to protect it, particularly when they are concerned about its geometry and power density, which demand different handling of thermal and safety management,” says Manuel Paintmayer at ViscoTec. Materials and dispensing Potting and encapsulation materials are typically epoxy, polyurethane or silicone resins. Epoxy provides excellent adhesion, mechanical strength and chemical resistance. Polyurethane exhibits good electrical insulation and mechanical protection, and can be flexible. Silicone is best for flexibility, thermal stability and resistance to extreme temperatures. The higher the application temperature, the more likely that epoxy and silicone will be chosen, says Paintmayer. Silicones are favoured if higher flexibility is needed to minimise stress transfer to electronics. Low glass transition temperature (Tg) is a critical temperature at which an amorphous material will transition from a rigid, glassy state to a softer, more flexible one. Epic Resins reports rising demand for two principal properties in potting and encapsulation materials for EV applications: soft elastomers with a low glass transition temperature (Tg) and rigid polymers with a very high Tg. Low Tg materials put significantly less stress on sensitive components and offer vibrational dampening, while hard, high Tg materials tend to have lower coefficients of thermal expansion (CTE) and better chemical resistance, he adds. Epic Resins can provide products with high or low Tg to satisfy a wide range of EV applications with temperature ranges from -50 C to over 150 C. the current collector/busbar assembly, says White at Henkel. “The potting product can assist in the protection of the electrical connections, and act as a vibration dampener to protect the delicate wire bonds or other types of connection between the cells and the busbar assembly.” Today, additional functionalities are added to encapsulating and potting materials, but mainly the latter. These include thermal conductivity, flame retardance, and even thermal insulation to combine the mechanical protection with safety management and protection of parts from fire, especially in batteries. To pot or encapsulate? The choice of which type of protection to apply to a component or assembly is affected by many factors. These can include the operating and environmental conditions, the properties and processing requirements of the resins, the shape and size of the components, how serviceable they are intended to be, and the cost and production volume. Potting is generally better for more extreme conditions, but it makes assemblies more difficult to repair, notes Brandon Brown, vice-president of engineering at C-Therm. Besides shock and vibration, operating and environmental conditions that must be considered include heatrelated factors such as the anticipated maximum temperature, total thermal load and the chemical stresses to which Soft PU potting- compound protecting, surface-mounted components in an electronic control module (Image courtesy of Epic Resins) SikaBiresin RE is a family of flexible PU resins, designed to protect electronics from vibration and water, including underwater. Radio waves can pass through, making them suitable for protecting connected devices (Image courtesy of Sika)
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