HD LED Display Brought The Challenges to the LED Chip (Part 1)

LED display compared to other display technology, with self-luminous, excellent color reproduction, high refresh rate, power save, easy maintenance and other advantages. High brightness, large size can be achieved through the mosaic of these two characteristics, that is the LED display in the past two decades decisive factor in high-speed growth. In the field of large-screen outdoor display, no other technology can compete with the LED display technology so far.

But LED display also has its shortcomings in the past, such as lamp packaging between the large spacing, that make in lower resolution, not suitable for indoor and close viewing. In order to improve the resolution, it is necessary to reduce the distance between the lamp, but reduce the size of the lamp, although it improve the screen resolution, and the cost will rise rapidly

In recent years, with efforts of the chip manufacturing and packaging manufacturers, IC circuit manufacturers and screen manufacturers and others, single-package device cost is getting lower and lower, LED packaging devices smaller and smaller, smaller screen pixel spacing, Resolution is getting higher and higher, making small-pitch LED display in the indoor large-screen display of the advantages more and more obvious.

At present, the small pitch LED is mainly used in advertising media, sports venue, stage background, municipal engineering and other fields, and also in the transportation, broadcasting, military and other fields continue to open the new market. Expected to 2018, the market size were close to 10 billion. Can be predicted in the next few years, small pitch LED display will continue to expand market share, and squeeze the DLP rear projection market space. Everbright Securities Research Institute, according to forecasts, by 2020, small pitch LED display with DLP rear projection of the replacement rate will reach 70% to 80%.

The following we start from the product design, technology point of view to discuss the development of small pitch LED display on the blue and green LED chip demand, as well as chip-side may take the response program.

Small pitch LED display with the demand on LED chip

As the core of the LED display, LED chip played a crucial role in the small pitch display developing process. The current achievements and future development of small pitch LED display are depends on the tireless efforts of the chip side.

On the one hand, The pitch of indoor LED display from the early P4 gradually reduced to P1.5, P1.0, there is the developing of P0.8. Corresponding to the size of led lamp from 3535,2121 reduced to 1010, and some manufacturers to develop the size of 0808,0606, and even some manufacturers are developing size 0404.

As all we know, encapsulation lamp to reduce the size, will inevitably require the chip size reduction. At present, the common small pitch led display use the blue green chip surface area of about 30mil2, part of the chip factory has been in production 25mil2, or even 20mil2 chip.

On the other hand, the smaller the surface area of the chip, the lower brightness of the single chip, a series of problems affecting the display quality become prominent.

One of the difficulties of the small pixel pitch LED display is the “low brightness and low  gray, That is the gray level is not enough in the low brightness, in order to realize the low brightness and high gray, at present the package is used black bracket ,due to weak support to the chip reflective of black bracket, so requires the LED chip t have enough brightness.

The second is the display uniformity problem, compared with the common display, small pixel pitch will appear afterglow, first sweep of the dark, low bright red and low gray, uneven and other issues, At present, for the afterglow, the first scan of the dark and low gray and other issues, Package side and IC control side have made the effort. effective mitigation of these problems, the brightness of the low gray level of the problem is also through point by point correction technology to ease. However, as one of the root causes of the problem, the chip needs to pay more effort, specifically, the small current brightness and uniformity is better, the consistency of the parasitic capacitance is better.

The third is the problem of reliability, the current industry standard is LED dead lamp rate to allow the value of 1/10000, obviously not suitable for small pixel pitch LED display, because the pixel density is large of small pixel pitch display ,the viewing distance of near, If 10000pcs led lamp, there are 1 piece failure lamp, the effect is not acceptable. the failure lamp rate of the future needs to be controlled at 1/100000 or even a part of a million to meet the needs of long-term use.

In general, with the development of small pixel pitch LED, the demand for LED chip: size reduction, the relative brightness promotion, small current brightness uniformity, good parasitic capacitance consistency, high reliability.