How Electrical Components are protected by Electrical Potting Compound

An electrical potting compound is designed to protect and insulate electrical components from application and environmental stresses. With their good electrical properties, mould flow characteristics and affordable costs, thermosets such as epoxies, phenolics and thermoset polyesters used to be the only materials used for the encapsulation of electrical components until recently when the direction of electrical potting compounds shifted to thermoplastics. Why did this shift in direction occur? The reasons for the shift to thermoplastics are:

-        Productivity and component integration

-        Thermoplastics have better physical properties in thin sections when compared to thermosets

-        Thermoplastics have been widely recognized for the encapsulation of motors, solenoids and transformers

-        Electrical potting compound using thermoplastics eliminate the emissions of volatile organic compounds (VOC) making it an eco-friendly material.

Environmental considerations in electrical potting compound

Thermoplastic encapsulation processes only use solid materials that melt when heated. Whatever VOCs used in varnish impregnation is not present so whatever harmful solvent emissions are virtually eliminated. When thermoplastics are used for electrical potting compound they come out direct from ready-to-assemble moulds that do not require dirty de-flashing and trimming operations that are associated with thermosets. This contributes to the lower costs of thermoplastics since these operations are eliminated and breakage of parts is minimized. In instances when breakage of parts is not avoided for some reason or another, the broken parts can be recycled for another molding process.

The technique of molding and tooling

Molding

When thermoplastic is used for electrical potting compound, the wound coil or electrical component is inserted into a mould and the thermoplastic material is injected while lead wires and terminals are clamped off the resin flow. The object being encapsulated is usually held by stationary pins or hydraulic pins that are withdrawn before the melt freezes. This technique was previously used on golf balls but is now being used extensively for the encapsulation of sensors and transformers.

Encapsulation

Encapsulation is typically done using vertical clamping machines that use gravity to hold the coil and insert in place during the molding process. However, this does not prevent others from using horizontal molding equipment. In each case, an operator or a robotic device can remove the finished parts and insert the coils at the loading/unloading stations.

Tooling

Tooling for the encapsulated coils and components may be done in two different ways: coil forms are used in many encapsulated applications or it is used in the encapsulation process itself. In the design and molding of coil forms, care must be taken to produce fully crystallized products with uniform flanges that taper slightly for ease of removal. Uniform flanges are critical to safeguard against voids and distortions caused by the shrinkage of coil forms during the encapsulation process. In order to minimize coil distortion, it is important to ensure equal pressure on windings by filling the mould cavity through two or more gates.

Electrical potting compounds using thermoplastic are used in various applications that include solenoid, sensors, self-supporting coils, transformers, motors and electrical components of various types.