Cast resins for electronics applications
A casting resin is a two-component synthetic resin that is mixed from resin and hardener in a liquid state. When cured, the end product is a thermoset. Potting is used to protect components from moisture, wetness, dust, foreign bodies, corrosion, manipulation, temperature or vibrations.
Casting resins are mainly used in electrical engineering and electronics. For example, for potting electronic components such as transformers, insulators, capacitors and printed circuit boards. Here, dielectric strength, dielectricity, flammability (UL94) or self-extinguishing, thermal conductivity and glass transition temperature are important parameters.
ISO-ELEKTRA offers casting resins for electronics and electrical engineering based on polyurethanes, epoxy resins, liquid rubbers and silicones. Below you will find our different casting resins sorted according to their chemistry.
- Good flexibility
- Though over a wide temperature range
- Adjustable flame retardant (UL94)
- Wide curing characteristics
- Hydrophobic
- Soft over a very wide temperature range
- Very diffusion-tight
- Non-labelled systems available
- Hydrophobic
- Hard
- High temperature stability
- Good flame retardancy
- Good curing characteristics
- Diffunsion-tight
- Soft over a very wide temperature range
- Very good temperature stability
- Good flame retardancy
- Filled 1:1 systems
- Remeltable
- Hydrophobic
- Non-labelling
Casting resins electronics
The solidification of cast resins occurs through chemical cross-linking reactions between resin and hardener and is irreversible; depending on the degree of cross-linking, they are referred to as elastomers or duromers. Thermoplastics, which are processed / poured in hot and can be re-melted, are an exception.
Polyurethane-based casting resins are characterized above all by their toughness and versatility, which is why they are suitable not only for potting small but also large electronic components or cable fittings (cable sleeves) in electrical engineering. Both soft and hard potting solutions can be formulated, which are additive UL94 V0 and at the same time allow operating temperatures of over 120°C. Based on partially native oils, particularly moisture-resistant potting solutions with low moisture permeability can be offered, which even allow a slight variability in the final strength by varying the hardener content. Additive polyurethanes allow the production of transformers, microswitches and the potting of almost all electronic components at up to 120°C.
Epoxy resins are particularly strong casting resins with very good adhesion, very good insulating properties, very low moisture permeability and low flammability (UL 94 V0). The high glass transition and service temperature also allow use above 120°C. In the case of very sensitive components, attention must be paid to mechanical stresses, as the high strength of the epoxy resins transmits higher forces locally than the supposedly low thermal expansion would suggest.
Silicones are ideal for particularly soft potting and temperature-stable applications in electronics. They can even be used at temperatures below -30°C without any problems. However, the low moisture absorption should not obscure the fact that these resins have a comparatively high moisture permeability. Corrosion protection must therefore be ensured by additional measures and the absolute exclusion of cavities. Despite their high temperature stability, silicone gels are flammable and degradation with the associated formation of quartz cannot be ruled out.
If low-temperature flexibility, a low glass transition temperature (< – 30°C), low moisture permeability and low moisture absorption are required, liquid rubbers are an excellent alternative to silicones. Isocyanate-cured systems (a special form of polyurethane) are particularly impressive due to their hydrolysis resistance, hydrophobicity and toughness – properties that are often problematic with silicones.