36 March/April 2024 | E-Mobility Engineering Peter Donaldson examines the finer points of potting and encapsulation Potted parts Many electrical and electronic components last longer, perform better and stand up to the stresses and strains of hard use with fewer complaints if they are potted or encapsulated in a polymer. While the two terms are often used interchangeably, they don’t quite mean the same thing. Potting is a process by which a form or ‘pot’ containing the parts to be protected is filled with a polymer resin and becomes part of the finished component. Encapsulation differs in that the parts and the hardened resin around them are removed from the pot to be placed in an assembly. Which method is chosen depends on various factors, such as the design of the component, the manufacturing and assembly process, and the demands of the application. The resin can be formulated to provide the components with benefits such as protection from moisture, tailored thermal conductivity, electrical insulation, and isolation from shock and vibration. It can also help to make the components more resistant to tampering and conceal them from prying eyes if there is sensitive intellectual property. While the same polymer type may serve in either role in different applications, this is not always the case. Defining a specific polymer as a potting compound or an encapsulant is generally a marketing technique, and is based on a component used in a specific industry, says Joe Staller at Epic Resins. A polymer used as a potting compound could act as an encapsulant, and vice versa. Equally, a material that makes a good encapsulant in one application may not work at all in another, he says. As one application may be more demanding than another in a variety of ways, the polymers may need different properties. “We feel it is important to have this conversation with customers so that we have a thorough understanding of their application. This allows us to provide recommendations and support beyond the generalised use of a polymer.” The two processes can place different demands on the material. For example, encapsulation may involve applying the polymer directly to a component within a housing, effectively forming a shell around it. This requires high form stability, unlike a potting compound, which must sufficiently self-level to fill the entire housing without residual voids, notes Dr Kevin White at Henkel. Potting and encapsulation are referred to as embedding processes, alongside a third major process of this kind, called impregnation. Here, the part to be protected is immersed in a liquid and then pressure or a vacuum is applied to ensure complete wet-out of the component. This causes all air to be eliminated and all of the component’s surfaces are covered by the polymer. Varied applications The list of components protected by these methods is long and includes onboard chargers, battery packs, power electronics, electric motor stators and rotors, electronic control units (ECUs), battery management systems (BMS) and sensors. In EVs, thermal-potting compounds are important for any heat-generating element, and they find widespread use in power electronics and e-drive components; a key example is power conversion devices such as inverters. Low-density, thermally insulating potting compounds can also be used in battery modules or packs to encapsulate the cells to help prevent a thermal runaway event from one cell to another. “Another possible application would be the encapsulation and protection of Axalta’s Voltacast 3310 is a two-component epoxy casting resin that can be used to protect motor windings. It cures at up to 80 C, self-extinguishes and has high thermal conductivity (Image courtesy of Axalta)
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