Enhanced Backlight Solutions (EBS) from Future  Electronics

Thermal Control

Why do LUXEON® LEDs Require Heat Sinking?

The LUXEON® LEDs in your EBS™ system generates about 1 Watt of power through a heat slug no greater than 8mm in diameter. In addition, because there is no IR or UV in the light source, all of that power gets converted into visible light and heat. Therefore, it is crucial to dissipate the heat and in turn maximize your system efficiency. When designing with a LUXEON® LED you will need to ensure that you keep the junction temperature (temperature of the LED die, Tj) as low as possible. There are four major effects that heat has on the LED:

1. Light output (LOP) decreases
2. Wavelength shifts
3. Forward voltage decreases
4. Decrease in lumen maintenance (lifetime)

In a backlighting application each one of these variables plays a crucial role to the overall performance of your system. Using heat sinks, heat spreaders, fans etc. can help keep the junction temperature low and manageable.

To help you understand how to design a thermal solution for the LUXEON® LED please reference the application briefs available at www.lumileds.com.
www.lumileds.com/pdfs/AB05.pdf
www.lumileds.com/pdfs/AB12.pdf

Managing the System

EBS™ uses a built-in metal core board which acts as a heat sink. Depending upon the EBS™ selected and how hard you drive the LUXEON® LEDs, you may require additional heat sinks for heat dissipation. Future Electronics can help you select the appropriate thermal management system.

The heat emitted from the LED system must be controlled either by using a heat sink or attaching the system directly to a portion of a metal enclosure used to house the LCD solution. Typically the LCD only increases by 0.25” - 0.35” in the area where the CCFL was housed, in order to make room for the LEDs and metal core board.

The type of heat sink selected will determine the temperature of the light source (see Figure 6), and will impact how hard you can drive the LUXEON® LEDs, and therefore how much brightness can be achieved.

Figure 6 - The influence of the thickness and height of a heat sink on the temperature of the light source

Available Thermal Management Products

There are a number of standard heat sinks available from Aavid Thermalloy. See Figure 7 for details of these standard heat sinks.

Figure 7 - Standard heat sinks from Aavid Thermalloy

Profile	Part Number	Thermal Resistance °C/W at 12" in 90°C max	Width 1.25-1.5 in	Height 0.25-0.5 in	Surface Area inches
	79200 [033532]	4.03	1.3	0.49	8.7
	82440 [039530]	3.93	1.25	0.5	8.9
	75440 [028128]	5.26	1.38	0.28	6.7
	76810 [031011]	5.76	1.4	0.45	6.1
	79940 [035060]	4.31	1.5	0.4	8.1

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