The materials used for electrical potting compound are based on the conditions of their application. The most commonly used material for potting is Silicone because it has several desirable qualities that make it very suitable as a pottant. Materials such as Thermoplastics, Epoxy, Polyurethane, Polyester and Acrylic are also used. These materials vary in hardness and are designed to withstand many different types of environments. They each have their own strength and weaknesses. Determining which compound is best suited for your application will be based on the operation and environmental conditions, the physical properties of materials and their processing needs. Always remember, if potting compounds are not properly selected, they may not be able to meet our standards. They could also cause damage due to unwanted stress and heat.
Encapsulants can be classified into three different types:
1. Potting Compounds - Potting compounds are poured into potted circuit boards. They have many important features:
- Low viscosity and longer pot life.
- Moderate cure temperatures.
- Filler settling resistance
- Good adhesion for all surfaces of substrates.
- Thermal stability and insulating properties.
2. Glob Tops - Encapsulants of this type directly applied to microelectronic components mounted on a PCB. Glob tops have higher viscosity, compatibility to adhesion, shorter curing time, mechanical strength and are good electrical insulators.
3. Molding Compounds - Molding compounds are granulated powder tablets that must be mixed with fluid. It is then heated afterwards until it can be formed into soft dough. Then it is used to fill electrical packages by using a molding press. It is a one-component formula consisting of finely grounded resins.
An important factor to consider in potting compounds is their curing or hardening process. Encapsulants begin at a liquid form. Then it is poured into a circuit of a solid protective substance. Electrical potting compounds may cure in different ways. Exposure to UV light can cure encapsulants like the way it does when it is exposed to air temperature. Condensation is also applicable as long as the moisture is present in the atmosphere. There are also those encapsulants that need an additive in order to cure. They are known as two-component system which uses the resin and a catalyst. Most people that focus on cost assembly normally use potting compounds that have a faster cure schedule. Unfortunately, they could also raise potential thermal damage and has a higher potential for entrapped bubbles that can reduce their mechanical properties. You should also know the difference between one and two component systems. If you want to keep things simple, then you should consider one-component potting compounds. Just remember that they require a heat cure that might push heat sensitive components to their limits and they have limited range of properties. For excellent performance, choose two-component potting compounds.