The production of high-power white LED

Currently, the market power white led tens of watts from 1 watt to have, but 1 ~ 3W white LED chip LED package into a single point source, while the majority of more than 5W white LED is a high-power blue LED chip integration, in particular, 10W high-power white LED is generally more directly integrated in the aluminum plate or copper plate, strip or disc-shaped and made of the surface light.

W-class power white LED package has its particularity: First, W-class power white LED phosphor in the package must be used; Second, W-class power white LED in the package when the power, heat large. Therefore, in the W-class power white LED package, the three channels must be considered:

* Current channel. W-class power white LED by the current relatively large, typically tens of milliamps to several hundred mA or more, so this current channels to be considered good.

* The optical channel. Light from the blue LED chip emitting layer issue, how to make part of the Blu-ray excited phosphors, which issued a yellow and blue to another part of the synthesis of white light, which is needed careful study.

* Hot channel. The W-class power white LED emitted heat, the heat conduction out how to reduce the W-class power white LED in the pn junction temperature, which is to be considered.

These three channels can design a good, for the W-class power white LED is critical. The best of these three channels are independent, do not share, especially in the current channel and thermal channels do not share. Figure 1 is the W-class power white LED's that light, power and thermal diagram.



Figure 1 W-class power white LED light, electricity, heat to diagram

Current channel

W-class power white LED of the current channels through the current very large, so use should consider the use of conductive gold relatively thick, the diameter of each gold and allow the maximum current has a corresponding reference system, according to The reference coefficients are selected.

On the other hand the current, the on and off the power fluctuations, there is great rush current, thus requiring electrical channel impact resistance. White LED device has a larger temperature difference, so for the package coefficient of thermal expansion and contraction of various materials to be a good option, especially to consider the gold in the case of thermal expansion can withstand the impact of high current.

The optical channel

The W-class power white LED heat, high temperature epoxy resin at high temperatures will change the yellow dirt, thus reducing the transmission rate, hindering the optical channel, and ultimately affect the light. The optical channel in the selection of materials, taking into account the long-term use as ultraviolet light, will produce plastic "glass", the W-class power white LED plastic package should be chosen in the present case silicone gel (silicone or .)

The other factors to take into account the refractive index, W-class power white LED chip index generally about 3.0, the refractive index of plastic packaging should be selected as the transition value. LED light from the refractive index of about 3.0 to 1 chip fired into the air refractive index, then the middle layer of the refractive index of how much it should be used? In general, the refractive index should be greater than 1.5, so that the optical efficiency will be high.

W-class power white LED from half-intensity angle of light plastic and covered by the shell closure decision, the half-intensity angle light according to the characteristics of the LED chip to design, general design point of view is 30 °, 60 °, 90,120 °, and so on. LED chip according to the optical position, light intensity should "focus" point of injection up to the light, in order to obtain greater intensity.

Hot channel

W-class power white LED in the hot channel is also very important, it is directly related to the W-class life and power white LED light failure problems. LED chips in the pn junction temperature increases, prompting the chip temperature, and then the temperature of the chip will be transmitted to the heat sink. This center should be equipped with better thermal conductivity material, the chip temperature can be reached quickly on the heat sink. Now, this thermal plastic there are many, to be selected according to actual use.

At present, the connection between the chip and heat sink, there are two ways: First, the solid crystal chip and heat sink adhesive connection, and second, tin and gold eutectic alloy solder. Both methods achieve very well if you'll get a good thermal conductivity effect. Thermal contact area of ​​the chip also has a relationship, so the chip and heat sink contact area, the area has a large thermal conductivity, thermal conductivity is also fast.

Evaluation of W-class power white LED

For W-class power white LED, the LED chip and package materials and processes used are different, the resulting performance is not the same tube. How to judge a W-class white LED tube pros and cons of it? Can generally be evaluated by the following indicators:

* After a period of continuous light, its luminous flux decay curve like? Reverse leakage changing? Color temperature changing?

· W-class power white LED color temperature distribution of what? The distribution of intensity is like?

* Resistance size?

These indicators is to determine W-class tube power white LED important indicator of good or bad.