Article Abstracts | April 2007
The complete article appears in the April 2007 issue of Photonics Spectra. If you do not have a copy of this issue,
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How Temperature Affects Silicone Encapsulants in
High-Brightness LED Applications
Several factors must be considered, but an appropriate packaging material likely exists for your hot application.
by Randall Elgin, Bill Riegler and Rob Thomaier, NuSil Technology LLC
Historically, high temperatures have negatively affected the function of LED chips; however, recent designs from companies such as Philips Lumileds Lighting Co. reportedly perform at temperatures as high as 185 °C without compromising output. The transition from low- and midpower LED chips to high-power devices has challenged packaging engineers to seek materials that function at higher temperatures.
As part of ongoing research into the effects that high temperatures have on silicone packaging materials — which range from the impairment of physical properties to the degradation of optical quality — NuSil has evaluated several of its optically clear materials. In general, our results have revealed that exposure to high temperature permits chemical reactions between the silicone being tested and the gasket material used to form the sample preparation. Some of the materials tested maintained optical transmission after exposure to high temperatures but, in others, these reactions led to optical transmission degradation...
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