Low temperature curable epoxy siloxane hybrid materials for LED encapsulant

Abstract

A thermally cured epoxy-siloxane hybrid material that is curable at low temperature (L-expoxy hybrimer) was investigated for use as an LED encapsulant. This new hybrimer was fabricated using thermally initiated, cationic polymerization of cycloaliphatic epoxy oligosiloxane (CAEO) resin, derived from non-hydrolytic sol-gel, mixed with oxetane hardener in the presence of a hexafluoroantimonate-type thermo-cationic initiator. The L-epoxy hybrimer was cured at a lower temperature (below 120 C) than previously reported for an epoxy hybrimer with anhydride hardener (above 180 C). The L-epoxy hybrimer showed high thermal resistance to yellowing under long-term high temperature condition, and maintained good optical transmittance. Also, it had a high refractive index (up to 1.57), as well as the hardness (Shore D 80), and low water-vapor permeability, when the new hybrimer was used to encapsulate an LED, it showed good adhesion without cracks or delamination and maintained their initial performance after the long-term aging tests (120 and 85 C at 85% humidity).

Improvement in thermal conductivity and mechanical properties of ethylene‐propylene–diene monomer rubber by expanded graphite

“…One of the most practical ways to improve heat transfer in rubber materials is to add into the rubber matrix with thermally conductive fillers , such as aluminum oxide, magnesium oxide, zinc oxide, aluminum nitride, boron nitride, and silicon nitride. Carbon‐based fillers including carbon fiber, carbon nanotube, and graphene are also promising fillers for thermally conductive composites due to their high thermal conductivity . However, these materials are currently too expensive to be applied in industrial scale.…”

Fast Curable Polysiloxane-Silphenylene Hybrimer with High Transparency and Refractive Index for Optical Applications

“…Epoxy-and siloxane-based polymers, which are common commercial products, are generally used for LED encapsulation, but 3. Cross-linker units such as phenyl [9], epoxy [8], zirconium [10], and silphenyl (this work) for the fabrication of polysiloxane hybrimers.…”

“…The increase in hardness is due to the rigid structure of the phenyl group of the PSH. Cross-linker units such as phenyl [9], epoxy [8], zirconium [10], and silphenyl (this work) for the fabrication of polysiloxane hybrimers. The mismatch of the refractive index values between the semiconductor (n = 2.50-3.50) and the polymer encapsulants (n = 1.40-1.60) often causes low light extraction efficiency of the device in high-brightness LED fabrications due to total internal reflection when light travels from the semiconductor into the encapsulant at certain incident angles.…”

“…To overcome this issue, silicon-based resins and elastomers are investigated in the industry as encapsulants [ 5 , 6 ]. Polyphenylsiloxane [ 7 ] and epoxy-based polyphenylsiloxane materials have also been reported for their good transparency and deformation resistance at high temperatures [ 8 ]. Other various cross-linking agents, such as phenyl- and zirconium-based polysiloxane hybrid materials have shown good optophysical properties [ 9 , 10 ].…”

Crosslink network and phenyl content on the optical, hardness, and thermal aging of PDMS LED encapsulant

“…[1][2][3][4] However, epoxy encapsulation induced yellowing during use, poor thermal stability leading to crack, and reduced transparency after prolong thermal and UV exposure. [1][2][3][4] However, epoxy encapsulation induced yellowing during use, poor thermal stability leading to crack, and reduced transparency after prolong thermal and UV exposure.…”