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Top Ten Myths of LEDs: #5 – “LEDs color-shift with time”

Tue, 07/02/2013 - 8:31am
Mike Krames, CTO, Soraa

In the early days of white-emitting LEDs, the available chip packaging materials were ones developed decades earlier for use with red- and green-emitting devices. Unfortunately, when using those materials for blue-based white LEDs (blue LED + phosphors), unexpected problems arose. The epoxy resins typically used as the lens encapsulation for the LED chip were photosensitive to the new blue emission. They absorbed small amounts of blue light and reacted chemically in a way that increased the light absorption further, leading to a runaway effect that ultimately resulted in the epoxy turning yellow and then brown. The first observation wasn’t so much a decrease in light output, but rather a change in color, which is fairly unacceptable when it comes to general lighting applications requiring white light.

Eventually, the packaging materials were improved (the industry moved away from epoxies, towards more robust silicones) and solutions for these color shifts became available. Nevertheless, concern over color stability with LEDs remained – consequently, color maintenance became an important requirement for many critical lighting standards, such as the EPA’s Energy Star program.

The good news is that state-of-art LEDs provide extremely tight color maintenance capability. At Soraa (and other top-tier LED companies), we spend considerable time and effort to test our LEDs with the packaging materials needed for our lighting products, ensuring that any color shifts are well below the required limits throughout the warrantied life of our products which, unlike traditional light sources, can be as long as 25,000 hours or more.

 

See Myth #6: “LEDs can't run hot”: http://www.ecnmag.com/blogs/2013/07/top-ten-myths-leds-6-%E2%80%93-%E2%80%9Cleds-cant-run-hot%E2%80%9D

See Myth #7: "LEDs have high glare": http://www.ecnmag.com/blogs/2013/06/top-ten-myths-leds-7-%E2%80%93-%E2%80%9Cleds-have-high-glare%E2%80%9D

See Myth #8: "LEDs are best left to China": http://www.ecnmag.com/blogs/2013/06/top-ten-myths-leds-8-%E2%80%93-%E2%80%9Cleds-are-best-left-china%E2%80%9D

See Myth #9: "LEDs are expensive": http://www.ecnmag.com/blogs/2013/06/top-ten-myths-leds-9-%E2%80%93-%E2%80%9Cleds-are-expensive%E2%80%9D

See Myth #10: "LEDs are dangerous": http://www.ecnmag.com/blogs/2013/06/top-ten-myths-leds-10-%E2%80%93-%E2%80%9Cleds-are-dangerous%E2%80%9D

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