From green to mature: LED packaging indicators to consider

China LED package powers, with the world's top packaging technology is gradually narrowing, and local products in the forefront of the world. In the SSL advanced packaging and module technology branch, the delegates on their latest research results and the latest products to do a detailed introduction, and share the latest trends and information LED packaging industry.

Compared with the past, now the most significant trend no longer focus on a single parameter, but a comprehensive consideration of the luminous efficiency, color index, service life and cost index. Currently on the market mainstream LED is used to produce white light blue LED yellow phosphor excited, warm white but the resulting color index is relatively low, China Academy of Sciences assistant researcher Lu Pengzhi pointed out, adding red phosphor in the yellow phosphor, can improve the color index, but the luminous efficiency will reduce.

In order to solve the contradiction display color index and luminous efficiency, Professor He Guoxing Applied Physics Department of Donghua University believes that by adding red phosphor powder to improve the white LED color light effect will be greatly reduced, should use the red LED or chip to replace the red fluorescent powder can achieve high luminous efficiency and high color LED white. He also suggested that in the design of high color LED, can not only consider the general color rendering index Ra, more attention should be paid to the special color index R9 of saturated red, the average value of R index and the special color of red, yellow, green, blue and other 4 kinds of color saturation (9-12). Because the study found that the general color rendering index Ra for the evaluation of the color rendering of LED is inconsistent with visual evaluation. The general color rendering index (Ra) of the lower LED white light in the visual color may be a certain and poor, on the contrary, the higher the LED white light in the visual color may be better and better. Only when Ra and R9 have higher values, can the high color rendering of LED white light be ensured. In addition, Professor Ho proposed the LED spectrum model under different current, and successfully developed LED color simulation software, to achieve high efficiency high color adjustable color temperature white light LED.

For phosphor link, Intel executive vice president and chief technology officer Yi-Qun Li photoelectric America to do a detailed analysis, he believes that the TV backlight phosphors is green and red phosphors, lighting is mainly YAG phosphor, silicate phosphor, aluminate green fluorescent powder, and mixed nitride red fluorescent powder with yellow and green fluorescent powder. He will Beta-SiAlON green phosphor, silicate green fluorescent powder, new green aluminate phosphor, respectively with nitride red phosphor R650 combination for LCD TV backlight, and compare their temperature characteristics. Finally, aluminate green light fluorescent powder and nitride red phosphor R630 combination can be realized for warm white LED general lighting; YAG, OG450, Portland yellow fluorescent powder phosphor can be realized for the cold white LED general lighting.

Wuhan National Laboratory for optoelectronics, Huazhong University of Science and Technology, director of the micro system research center Liu Sheng to discuss with you the key is the key technology of LED encapsulation - pressure welding technology (wire, bonding) in the LED packaging process mainly through the pressure welding process for LED chip is connected with the bracket of electric package. LED packaging enterprises generally use gold wire pressure welding, but the gold price is expensive, resulting in increased LED costs. On the contrary, copper prices are low and have great potential for cost reduction. In the report, Professor Liu Sheng through the finite element method to establish the model, the high power LED packaging in the gold and copper wire pressure welding process analysis and comparison, the copper wire pressure welding process parameters to provide a theoretical basis for optimization.