标签：led light fittings

LED light fittings need technological upgrade and support

Currently, LED light fittings are still in the early stage of development. Although LED lighting products have entered the industrial area, commercial area and residential area, the immature technologies still need further development, like output power, luminous flux, secondary optical design, cooling and other problems. Among them, cooling problem is the biggest difficulty for LED manufacturers. Limited by LED working principles, all structure accessories of LED lamps should have good cooling effects (good thermal conductivity) on the basis of safety. If using plastic materials, LED light fittings will soften and begin to melt within a few hours. Therefore, LED makers have restricted requirements on the LED light source structure designs and materials selection.

 

Currently, LED light fittings are still in the early stage of development.

 

The commonly used cooling material in the market is aluminum/aluminum alloy. As a result of high costs (selling prices), some makers stated to find cheaper replacements with good thermal conductivity as well. Then PC covered LED lamps started to appear in the market. PC raw materials were firstly used as fixtures during the design for kitchen lights committed by Bayer Germany. They are durable and also have good thermal conductivity. The most important thing is that they are cheap.

 

Compared with traditional lamps, LED light fittings distinguish in many aspects: different deterioration speed in lamp bead (in high temperature, under high/low voltage); Electrical control. LED lights need to work under direct current; structure design, material selection, appearance design need corresponding variations. Insolated circuits/protections should be applied to guarantee the independent operation of LED light source and lamp body.

 

Many insiders indicated that, the main reason for LED light fittings hardly to be accepted by ordinary families is their expensive selling prices, which is caused by their high production costs. The light-emitting principle determines the cost of the product. The production cost of LED lamps is two times higher than traditional lights. Specifically: the over-expensive production costs of light source; restricted requirements to package structures and materials increase the production cost by nearly 50%. Semiconductor light emitting components are generally more expensive than traditional light emitting components. Due to lacking of core technology, the majority of our LED chips need to import from foreign companies. However, the production cost of LED chips occupied more than 60% total cost of the entire lighting fixture. The profit that China’s LED manufacturers obtained is rather limited.

Analysis of LED light fittings failure

In terms of the package, there is an important factor to affect the LED life is corrosion. In the use of LED lights, the general corrosion caused mainly due to water vapor infiltrated within the packaging material, resulting in lead deterioration, PCB copper corrosion; sometimes movable ions introduced with the water vapor resides in the chip surface, resulting in leakage. In addition, the package poor quality of the devices, encapsulated within a large number of residual bubbles, these residual bubbles would also cause corrosion of the device.

Analysis of LED light fittings failure

(3) thermal stress failure of led light fittings

The temperature has been an important factor of the LED optical properties, LED failure modes of the research scholars to consider the working environment temperature accelerated stress to the LED accelerated life test. This is because the LED spot lights system thermal resistance of the same premise. The welding point of the package pin temperature, junction temperature will also increase, leading to early failure of LED.

Hsu test samples provided by different vendors LED, the LED samples in the experiment were placed 80、100、120℃, 3.2V voltage drive, and provisions when the optical power of the sample decreased to the stating value of 50%, which is determined to be invalid. High power led light fittings with the accelerated life test temperature and the accelerated and the acceleration time increases and decreases.  In the accelerated life test, the LED junction temperature rise will make the epoxy material mutation, thereby increasing the thermal resistance of the system between the chip and package thermal surface degradation, eventually leading to package failure.

(4) electrical overstress failure of led light fittings

If LED tunnel used under the current circumstances or electrostatic impact damage of the chip, the chip will result in open circuit, the formation of electrical overstress failures. For example, GaN is a wide band gap materials, high resistivity. If you use such chips, the induced charge due to static electricity generated in the production process which is not easy to disappear when its accumulated to considerable extent. It can produce very high electrostatic voltage, this voltage exceeds the bearing capacity of the material occurs of the material, it will occurs breakdown phenomena and discharge, and making the device failure.