Bubble-free encapsulation and casting of components in epoxy resin
Potting compounds such as epoxy resin play an important role in the electrical and electronics industries, where they serve the protection of sensitive components from moisture, dust and damage. Epoxy resin consists of two material components – the resin and a hardener with filler. When epoxy resin is being processed, the two components are filled into separate containers of a 2K metering system, metered and mixed according to a precisely set ratio. Potting resins often require processing in higher temperatures to reduce their viscosity and flow easier. Potting systems accommodate this requirement with heated storage tanks, hoses and pumps, among other things.
Often, the terms “potting”, “casting” and “encapsulation” are used interchangeably. This is simply because the process can be carried out in various ways. While the most common method involves potting a component in a case, which then becomes part of the finished unit, in the casting method, the case is removed once the compound has hardened, to produce more of a moulded unit. Lastly, components like printed circuit boards, require only a thin layer of protective film. Encapsulation or “dip coating” is a process where such components are dipped in a bath of low viscosity resin and taken out again. No matter the method, the prime purpose is always to protect against external influences and ensure the stability of the component.
As with any process, correct potting depends on getting a number of factors right. For example, the resin must have the right temperature to be of the viscosity needed for the specific application. Most importantly however, the formation of air bubbles in the potted material and in the cavities around the component must be avoided at all costs. This can be achieved with the correct configuration of the metering system.
Meter Mix® metering and mixing systems provide everything that is required for successful potting of electrical and electronic components. They are specifically designed to process low to high viscosity potting materials such as epoxies, polyurethanes or silicones in a consistent and bubble-free way. Our high quality standards are based on 30 years’ worth of experience in the engineering of metering systems for potting applications.
BONDING AND SEALING
Complex, yet strikingly effective applications
No matter which industry we look at – be it electronics, automotive or aviation – we will notice that bonding has replaced the established joining methods such as welding or screwing. For example, up to 18 kilograms of adhesive are used in the production of a single car. The electronics industry relies on adhesives for potting or sealing of components. In any case, bonding is a complex technique and requires significant specialist knowledge. Material manufacturers are constantly working on new adhesives and increasingly often they are also tailoring them to specific applications. In many cases, bonding is the only viable technique of binding modern materials.
ADHESIVE BONDING WITH EPOXY RESIN, POLYURETHANE AND SILICONE
Adhesive material can be based on epoxy resins, silicones, polyurethanes or methacrylates and it can be a one or a multi-part substance. Multi-component adhesives are metered and mixed by dispensing systems according to a fixed mixing ratio. Polyurethane adhesives often perform a sealing function, are easy to process and have a very good chemical resistance. Most commonly used are epoxy adhesives. They can be processed very well at room temperature and are highly resistant.
METERING METHACRYLATE ADHESIVES
Methacrylate adhesives usually have a very short pot life, which can complicate their processing. On the other hand, they offer the advantage of short curing times and particularly high strength. They are an excellent alternative for the joining of metal, glass and duromeric plastics.
PRE AND POST-TREATMENT OF COMPONENTS
Adhesives do not adhere easily to all components. Depending on the component properties, a pre-treatment such as by corona flame, corona primer or brushing, may be required. The subsequent application of the adhesive can be carried out in various ways, for example in a dot or bead form. After the components are joined, curing systems such as infrared light, ultraviolet light or continuous furnace can be used to accelerate the bonding reaction and speed up the time in which the components are available for the next production step.
In summary, the bonding and sealing process is a relatively complex one with many factors at play. The selected material must be a perfect fit for the application, the application parameters must be clearly and precisely defined and lastly, a metering solution capable of processing the selected material in the defined way needs to be identified. METER MIX® offers robust and proven metering systems which are continuously adapted to the evolving demands of adhesive technology. They present an accessible solution to process-reliable and high-quality processing of adhesive materials.