From pitch to package, the new stage of small pitch LED technology PK

ISLE is known as the world's most prestigious LED show industry event. 2017 ISLE, "COB small spacing LED" debut appearance, bringing fresh and refreshing to visitors, breaking through the previous various types of LED exhibition vendors, more in the space "smaller and smaller" on the competition. This also means that, for the entire LED industry, people are no longer only different spacing to separate LED products, different packaging technology has become another key to differentiate and select LED products.

Into the indoor market, the advantages of small spacing LED

LED products are available at the beginning, because of its high brightness, bright colors and other characteristics in the outdoor market, but seldom in the indoor field ". But with the development of technology, the emergence of small space LED (below P3.0) makes LED indoor applications become a reality.

The small spacing of LED products

From the technical point of view, although there are still some problems such as long time, continuous observation and easy vertigo in the indoor application of small spacing LED, it is undeniable that it has its inherent advantages. The first is "seamless", from the visual effects, the small distance LED can do the whole screen seamless display, the picture is more complete. In addition, for indoor large screen project, the space, the area often limits, and small spacing LED frivolous, screen thickness less than 100mm, relatively provincial space. In addition, the small spacing LED has high brightness, and the brightness can be adjusted arbitrarily between 350~2000cd/m2, and the adaptability to the environmental light is stronger. Finally, the small distance LED color gamut is wide, the color gamut reaches 114%NTSC, and the color is more brilliant, and is especially suitable for indoor scenes such as auditorium, demonstration hall and television studio.

From SMD to COB, the leap of LED technology development

Previously, for users, the choice of small spacing LED is more in the choice of different spacing, and spacing for small spacing LED, the main impact on the unit area resolution. At present, compared with different packaging technologies, both the technical innovation and the display effect, the COB small spacing LED is a great promotion to the SMD small spacing LED. This also shows that in use, can be used to solve the indoor Humphreys problems based on the small spacing LED development has entered a higher reliability and effect of visual experience stage, COB packaging is one of the most important technical direction.

SMD products, the lack of traditional packaging methods

The SMD (surface mount technology) package of LED products, the upstream manufacturers will package lamp bracket, lamp cup, wafer, lead, epoxy resin and other materials into different specifications of beads. The lower screen factory commercial high-speed SMT machine, reflow welding with high temperature will be led on the circuit board, a display unit made of different spacing.

The SMD LED PCB small spacing plate cross section diagram

As the first generation of small spacing LED products, SMD small spacing LED can be said to have been widely used, and now also occupy a larger share of the LED application market. However, due to the inherent luminescence principle of LED products and the unavoidable defects of SMD packaging technology, SMD small spacing LED also shows obvious deficiencies in the long-term market applications.

Dead lights and bad lights. LED dead lights directly affect the display of the screen, and the use of SMD packaging technology small spacing LED, it is easy to use in the process of producing "dead lights" and "bad lights" phenomenon. This is because the first SMD small spacing of LED in the production process, will need to light high temperature reflow (240-270 degrees Celsius) way of welding on the circuit board, and in high temperature reflow due to expansion coefficient in the lamp bracket, substrate, epoxy resin and other materials, easy to produce cracks, resulting in beads the sub healthy state in the factory. Secondly, using SMD encapsulation technology, LED lamp foot pads exposed is easily oxidized, resulting in water vapor intrusion LED chip, running in the water under the action of oxygen caused by long-term internal wick electrochemical reaction, dead lights, "Caterpillar" phenomenon. In addition, the electrostatic damage to the LED lamp can not be ignored. The small spacing SMD products are electrostatically sensitive, and bare lamp pads are susceptible to static electricity resulting in dead lights.

Analysis of the causes of bad light SMD

Generally speaking, the factory will be dead manufacturers rate control within the standard value; but as time goes on, Huaidian will continue to accumulate, the general use of half a year after the dead is obvious. How to reduce the dead light rate has become the primary problem of small spacing LED to solve.

Poor viewing comfort. In view of comfort, the human eye will feel uncomfortable because of the frequent refresh of the LED screen, the periodic reception of the light signal stimulation, long time watching and close viewing. In addition, there is the "blue harm" effect, because blue LED wavelength is short, high frequency, the human eye directly and chronically accept blue light influence, easily lead to retinopathy.

Low brightness gray scale is not good. In outdoor applications, the brightness of LED displays naturally has advantages. But in normal indoor applications, large screen screen brightness is generally around 200nits, long time to see the human eye comfortable. But under this brightness, the LED display will appear gray scale deletion, affecting the picture quality.

COB products, innovations in small space LED

In terms of technological innovation, the COB small spacing LED is the second generation product of small spacing LED.

COB (Chip On Board) is a kind of packaging technology, the circuit board of RGB packaging, mainly through the silicon wafer, the resin will lead directly packaged on the circuit board, eliminating the beads package SMD package, placement, reflow process, greatly enhance the stability of small spacing of LED products and viewing comfort.

From pitch to package, the new stage of small pitch LED technology PK

The COB LED PCB in cross section and small spacing