Thermal solutions for color consistency and maximum lifecycles for LEDs
Light Emitting Diodes (LEDs) have been around for years, primary concentrated in such markets as cell phones, PDAs and other consumer electronics. Since most of these products have relatively short lifecycles, protecting LEDs wasn't a primary concern because the product would fail Or become obsolete long before the LED failed.
Today, as technological advancements in LED design and processes are continually boosting light output to rival incandescent, fluorescent, and even halogen light sources, the need to protect the LEDs against heat build-up is greater than ever before.
Three and five-watt LEDs are now commonplace, and industry experts are predicting 10-watt LED availability in the next few years. Power LEDs of greater than one-watt are almost always surface mounted devices.
Is because the axial leads to the die in a leaded package do not conduct enough heat away from the LED. Chip-on-board (COB), flip chips and remote efficient packages are emerging as the standard thermal management packaging solution for Power LEDs.
The Effect of Temperature The LEDs color, or wavelength, will change with temperature. As the die temperature increases, the wavelength of the color increases. This is particularly important with white light. The human eye can differentiate small color changes in white light. Power LEDs are populated in an array, consistent thermal resistance from one die to the next assures consistent color.
Because of the comparatively low thermal resistance Thermal Clad offers versus FR-4, die temperature is less affected by slight variances in the junction-to-case thermal resistance that occurs with tin eutectic or epoxydie mounting techniques. It is also possible to pack the die More closely in an assembly that utilizes good thermal management techniques, such reducing the effects of temperature.
Generally, a 50 percent drop in light output for a constant-forward current indicating end-of-life for Power LEDs. With proper thermal management, Power LED lifetimes can exceed 100,000 hours.
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Today, as technological advancements in LED design and processes are continually boosting light output to rival incandescent, fluorescent, and even halogen light sources, the need to protect the LEDs against heat build-up is greater than ever before.
Three and five-watt LEDs are now commonplace, and industry experts are predicting 10-watt LED availability in the next few years. Power LEDs of greater than one-watt are almost always surface mounted devices.
Is because the axial leads to the die in a leaded package do not conduct enough heat away from the LED. Chip-on-board (COB), flip chips and remote efficient packages are emerging as the standard thermal management packaging solution for Power LEDs.
The Effect of Temperature The LEDs color, or wavelength, will change with temperature. As the die temperature increases, the wavelength of the color increases. This is particularly important with white light. The human eye can differentiate small color changes in white light. Power LEDs are populated in an array, consistent thermal resistance from one die to the next assures consistent color.
Because of the comparatively low thermal resistance Thermal Clad offers versus FR-4, die temperature is less affected by slight variances in the junction-to-case thermal resistance that occurs with tin eutectic or epoxydie mounting techniques. It is also possible to pack the die More closely in an assembly that utilizes good thermal management techniques, such reducing the effects of temperature.
Generally, a 50 percent drop in light output for a constant-forward current indicating end-of-life for Power LEDs. With proper thermal management, Power LED lifetimes can exceed 100,000 hours.
For details, click http://
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