Ultraviolet radiation curable epoxy resin encapsulant for light emitting diodes

• Published in: Journal of applied polymer science 2006-04, Vol.100 (2), p.1048-1056
• Main Authors: Kumar, R. N., Keem, Lim Yoke, Mang, Ng Chee, Abubakar, Abusamah
• Format: Article
• Language: English
• Subjects: Applied sciences; cationic photoinitiators; Electronics; epoxy resins; Exact sciences and technology; light emitting diodes; Optoelectronic devices; Physicochemistry of polymers; Polymerization; Polymers and radiations; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; ultraviolet radiation curing
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.23189

Light‐emitting diodes are currently encapsulated by thermally curable epoxy resins. Thermal curing systems require long curing cycles at high temperatures. Further, because of viscoelastic behavior of the resin, the resin tends to “creep” along the connecting wires (Weisenberg effect), which causes solderability problem. The cured resin should be removed manually, which is time consuming and labor intensive. These problems are solved by the ultraviolet radiation curable systems. UV curing is an ultrafast reaction and takes place at room temperature. No creep behavior occurs due to the rapidity of the curing. The UV curing technique can result in higher productivity and energy saving than the thermal process. This article presents results on the development of UV curable formulations based on cycloaliphatic diepoxide, diglycidyl ether of bisphenol A, and epoxidized novolac induced by cationic photoinitiators. “Mixture experimental design” was employed to arrive at the optimum composition, which meets the stringent demands of performance characteristics and durability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1048–1056, 2006