The challenge of small-pitch LED display to the chip end_LED display manufacturer|Huaze Optoelectronics

Compared with other display technologies, LED display has the advantages of self-illumination, excellent color reproduction, high refresh rate, power saving, and easy maintenance. The two characteristics of high brightness and super large size achieved through splicing are the decisive factors for the rapid growth of LED displays in the past two decades. In the field of super-large outdoor LED display, no other technology can compete with LED display technology so far. However, in the past, LED display screens also had its shortcomings, such as the large spacing between the packaged lamp beads, resulting in low resolution, which is not suitable for indoor and close viewing. In order to improve the resolution, it is necessary to reduce the spacing between the lamp beads, but the size of the lamp beads is reduced. Although the resolution of the entire screen can be improved, the cost will rise rapidly. The excessive cost affects the large-scale commercial application of small-pitch LED displays. . In recent years, thanks to the efforts of chip manufacturers and packaging manufacturers, IC circuit manufacturers and screen manufacturers, the cost of single package devices has become lower and lower, LED display package devices have become smaller and smaller, and LED display pixel pitches have increased. The smaller and the higher the resolution, the advantages of small-pitch LED display in indoor LED display display are becoming more and more obvious. At present, small-pitch LED displays are mainly used in advertising media, stadiums, stage backgrounds, municipal engineering and other fields, and continue to develop markets in the fields of transportation, broadcasting, and the military. It is estimated that by 2018, the market size will be close to tens of billions. It can be predicted that in the next few years, the small-pitch LED display will continue to expand its market share and occupy the market space of DLP rear projection. According to China Everbright Securities Research Institute, by 2020, the replacement rate of small-pitch LED displays for DLP rear projections will reach 70% to 80%. The author has worked in the blue-green LED chip manufacturing industry and has been engaged in product development for many years. From the perspective of product design and process technology, we will discuss the requirements for blue-green LED chips in the development of small-pitch LED displays, as well as possible countermeasures on the chip side. Small-pitch LED display's demand for LED chips As the core of the LED display, the LED chip plays a vital role in the development of small-pitch LEDs. The current achievements and future development of small-pitch LED displays depend on the unremitting efforts of the chip side. On the one hand, the indoor LED display dot pitch has been gradually reduced from the early P4 to P1.5, P1.0, and P0.8 in development. Correspondingly, the size of the lamp beads has been reduced from 3535 and 2121 to 1010. Some LED display manufacturers have developed 0808 and 0606 sizes, and some LED display manufacturers are even developing 0404 sizes. As we all know, shrinking the size of packaged lamp beads will inevitably require a reduction in chip size. At present, the surface area of u200bu200bblue-green chips for small-pitch LED display screens commonly used in the market is about 30 mil2, and some LED display chip manufacturers have mass-produced 25mil2 or even 20mil2 chips. On the other hand, as the surface area of u200bu200bthe chip becomes smaller and the single-core brightness decreases, a series of problems that affect display quality have also become prominent. First of all, the requirements for the grayscale of the LED display screen. Unlike outdoor LED display screens, the difficulty in the demand for indoor LED display screens lies not in brightness but in grayscale. At present, the brightness requirement of indoor large-pitch LED display is about 1500cd/m 2-2000 cd/m2, and the brightness of small-pitch LED display is generally about 600cd/m 2-800cd/m2, which is suitable for long-term eye-catching LED display. The best brightness of the screen is about 100cd/m2-300cd/m2. One of the current problems with small-pitch LED displays is 'low brightness and low gray.' That is, the gray scale at low brightness is not enough. To achieve 'low brightness and high graySince the black bracket has weak reflection on the chip, the chip is required to have sufficient brightness. The second is the uniformity of LED display. Compared with conventional LED display screens, the smaller the spacing will cause problems such as afterglow, darker first scan, reddish low brightness and uneven low gray. At present, in response to problems such as afterglow, first scan dark and low gray and red, both the packaging side and the IC control side have made efforts to effectively alleviate these problems. The uniformity of brightness under low grayscale has also been corrected point by point. Technology has eased. However, as one of the root causes of the problem, the chip side needs more effort. Specifically, the uniformity of brightness under small current is better, and the consistency of parasitic capacitance is better. The third is the reliability of the led display. The current industry standard is that the allowable value of the dead light rate of the LED display is one in ten thousand, which is obviously not suitable for the small-pitch LED display. Due to the high pixel density of the small-pitch LED display and the short viewing distance, if there are 10,000 LEDs, there will be 1 dead light, and the effect is unacceptable. In the future, the dead-light rate needs to be controlled at one hundred thousandths or even one millionth to meet the long-term use needs. In summary, the author analyzes the series of challenges facing the LED chip end with the development of small-pitch LED displays, and gives improvement plans or directions one by one. It should be said that there is still a lot of room for the optimization of LED chips. How to improve is still waiting for the industry to use their ingenuity and make continuous efforts.