Comparison of epoxy resins for applications in light-emitting diodes

Epoxy resin is a material commonly used for the encapsulation of light-emitting diodes (LED). Three epoxy resins were chosen in this study: D.E.R.-331 was a bisphenol A type epoxy resin, Eporite-5630 was a bisphenol A type epoxy resin modified with a UV stabilizer, and ERL-4221 was a cyclo-aliphatic epoxy resin. The curing agent was methyl hexahydrophthalic anhydride (MHHPA), and the catalyst was tetra-butyl ammonium bromide (TBAB). Thermal, environmental, and optical properties of the cured epoxy resins were studied. It was found that cured ERL-4221 had better UV resistance, but other properties of ERL-4221 were lower because of the internal stress generated during the curing process. D.E.R.-331 showed better thermal stability, but the aromatic groups in the main chains caused sensitivity to photodegradation. Eporite-5630 had the advantages of D.E.R.-331 and better UV resistance than D.E.R.-331 because of the addition of UV stabilizer. Among the three materials, Eporite-5630 was the best choice of the balance properties for LED applications. This finding may assist in the selection of epoxy resins used in LED technology.