Description

Electrical and electronic resins are used in electrical, electronic, and semiconductor applications and include:

• Adhesives
• Greases
• Pads
• Stock shapes
• Tapes
• Encapsulants
• Potting compounds
• Thermal interface materials
• Electrically conductive substances

Applications

Electrical and electronic resins are used in many industries and applications. Some products are used in the manufacture of printed circuit boards (PCBs). Others are designed for electrical power and high voltage products such as generators, transformers, circuit breakers, and motor assemblies.

Specialized electrical and electronic resins meet military specifications (MIL-SPEC) and are suitable for many aerospace applications. Products for automotive and optoelectronic applications are also available.

Flame retardant materials resist ignition or reduce the spread of flames when exposed to high temperatures. Flexible or dampening materials form layers that can bend without cracking or delaminating.

Types

Dielectric or electrically insulating electrical and electronic resins are the most prevalent types.

Electrically conductive products provide low resistivity and are often used to prevent electrostatic discharge (ESD), electromagnetic interference (EMI), and radio frequency interference (RFI). They are also used in thick film metallization and to provide electrical interconnections at both the device and circuit board level.

Thermally conductive electrical and electronic resins are applied between a heat-generating electrical device and a heat sink in order to improve heat dissipation. These products form a thermally conductive layer, either between components or within a finished product. Thermal interface materials that use a phase change are also available. 

Materials

Chemical Systems

Chemical systems may contain:

• Acrylics
• Elastomers
• Natural or synthetic rubbers
• Epoxy resins
• Water-based resins
• Silicone compounds
• Volatile organic compounds (VOCs)
• Bismaleimide (BMI) resins
• Phenolics
• Formaldehyde resins
• Cellulosic thermoplastics
• Liquid crystal polymers (LCPs)
• Vinyl compounds
• Polyamide
• Polybutadiene
• Polycarbonate (PC)
• Polyolefin
• Polypropylene (PP)
• Polysulfide
• Polyurethane (PUR)

Filler Materials

In terms of filler materials, some electrical resins and electronic compounds include:

• Aramid fiber
• Chopped fiber
• Carbon powder
• Graphite powder
• Glass fillers
• Metal fillers
• Inorganic compounds

Unfilled electrical and electronic resins are also available.

Curing Technologies

Typically, thermoplastics and hot melt adhesives are cured using heat or heat and pressure. Vulcanization, a thermosetting reaction, uses heat and/or pressure in conjunction with a vulcanizing agent to produce materials with greatly increased strength, stability, and elasticity. Some products cure or vulcanize at room temperature. Others cure with radiation, electron beam irradiation, visible light, or ultraviolet (UV) light.

Single component curing systems consist of a resin that hardens through the application of heat or a reaction with surface moisture. Two-component and multi-component curing systems consist of two or more resins and a hardener, crosslinker, activator or catalyst. 

Specifications

Selecting electrical and electronic resins requires an analysis of physical, mechanical, thermal, electrical, and optical properties.

Physical Properties

Melt flow index (MFI) is the output flow occurring in a 10-minute period through a standard die while a fixed pressure is applied via a piston to a 190° C melt. Other physical properties include:

• Viscosity
• Gap fill
• Water absorption

Mechanical Properties

• Tensile strength
• Tensile modulus
• Elongation

Thermal Properties

• Temperature range
• Deflection temperature
• Thermal conductivity
• Coefficient of thermal expansion (CTE)

Electrical Properties

• Resistivity
• Dielectric strength
• Dielectric constant

Optical Properties

Optical properties include index of refraction, a measure of the speed of light in a material, and transmission.  

Standards

ASTM D2902 - This specification applies to flexible heat-shrinkable extruded tubing made from tetrafluoroethylene resin, copolymer of tetrafluoroethylene and hexafluoropropylene, and from perfluoroalkoxy resin for use as electrical insulation.

BS 3816 - Specification for epoxy resin casting systems used for electrical insulating applications.

BS 5664 P1 - Applies to resinous or elastomeric compounds, with or without fillers, furnished as solids, semi-solids or liquid materials, either as separate constituents or mixed together, capable of being applied in a liquid, paste or powder form.

References

Image Credits:

Ellsworth Adhesives | Thermon Manufacturing Co. | Quist Electronics