Mini LED Chip Becomes The Most Beneficial Part In LED Market

Mini LED chips enjoys the characteristics of high efficiency, high reliability, high brightness, and fast response time of small-pitch LED.

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Chapter 1 What is Mini LED?

Chapter 2 Flip Chip on Mini LED

Chapter 3 The Development of Global Mini LED Industry

Chapter 4 The Achievement of Chinese Manufacturers in the Field of Mini LED Chips

Chapter 5 Technical Characteristics and Difficulties of Mini LED Chips

Chapter 6 The Bright Future of Mini LED Market

What is Mini LED

Mini LEDs are much smaller than regular LEDs, and diodes smaller than 0.2mm are often classified as mini LEDs. Mini-LED is a new display technology that can improve contrast and have deeper blacks than traditional LED panels.

The mini LED chip size is 50-200 microns. From the perspective of different application fields, mini LEDs are mainly used in smartphones, automobiles, TVs, and monitors. Among them, the application of mini LEDs in the monitor industry has the largest market share, accounting for 68.38% of the market in 2020; while TV LEDs ranked second with a market share of 20.85%.

Mini LED technology principle

Mini LED adopts a direct-type backlight method, which can be regarded as an upgraded version of ordinary LCD screens.

Mini LED reduces the size of traditional LED backlight lamp beads, thereby realizing more precise and dense backlight partitions, and with the control of Local Dimming, it improves brightness and contrast and enhances visual perception. 

Under the same conditions, Mini LED not only makes up for the shortcomings of OLED’s easy screen burn-in but also is better than OLED in terms of cost. While improving the picture, it also has a cost advantage.

Low Power Consumption, High Refresh Rate Mini LED Chip

MBI5759 is an S-PWM LED driver chip with integrated 32 scan switches and 48 constant current source outputs. The overall size of the BAG package is small, which is convenient for design and layout. 

MBI5759 can realize a multi-pulse adjustment function for grayscale control, and also divide the on-time into multiple shorter times to increase the output imaging refresh rate. And a global clock frequency multiplier has been added to double the refresh rate.

The chip also integrates a 48-bit shift register, and each unique register can convert the input serial data into grayscale pixel output. The 48 constant-current output values of MBI5759 are not affected by the load voltage, and the output current can be changed through an external resistor. 

In terms of imaging, S-PWM can solve the problem of screen stroboscopic, and the MBI5759 chip can adjust the corresponding output brightness by processing video data. The advantage of this chip is that it has a new generation of data transmission interface to reduce the wiring between the control chip and the driver chip to reduce EMI interference, and a built-in intelligent power saving mode to reduce system power consumption.

Flip-Chip COB on Mini LED chip

Flip-chip COB is expected to become the mainstream packaging method of Mini LED

There are two main packaging forms for LED small-pitch display chips: SMD and COB.

SMD full color (formal package): Upstream lamp bead manufacturers encapsulate lamp cups, brackets, wafers, leads, epoxy resin, and other materials into lamp beads of different specifications. Downstream display manufacturers use high-speed placement machines to solder lamp beads on circuit boards with high-temperature reflow soldering to make display units with different pitches.

COB full-color (flip-chip packaging): COB (Chip On Board) is a packaging technology, that is, RGB chips are packaged on the circuit board, and the wafers and leads are directly packaged on the circuit board through silicone resin, eliminating the need for SMD packaged lamp bead packaging, patch, reflow soldering, and other processes have greatly improved the stability and viewing comfort of small-pitch LED products. 

The COB packaged lamp beads are solid-sealed on the PCB board with epoxy resin. The epoxy resin has a strong affinity with the PCB board and has the characteristics of high hardness, strong pressure resistance, and impact resistance, so it is not afraid of static electricity, bumps, and shocks. , bendable, wear-resistant, easy to clean, and durable, it is expected to become the mainstream packaging method for LED small-pitch display P1.1 and below markets.

The Advantages of Flip Chip Mini LED Chips

1

Lower chip thermal resistance, lower junction temperature, improved device life and color stability.

2

Better visual consistency, uniform current distribution, unobstructed surface, light from five sides, good viewing angle and uniformity.

3

No need for gold wire, dense arrangement, the opportunity to break through the lower limit of the dot pitch of symptom chips, and simplify the structure of the display module.

4

Better reliability, large-area electrodes are directly connected to the substrate, multiple intermediate steps are removed, and the sensitive area is fully covered.

The Development of Global Mini LED Industry

2020 global mini led industry market share

Development and prediction

The growth of mini LED industry

The Achievements of Chinese Manufacturers in the Field of Mini LED Chips

The Asia-Pacific region is the largest revenue market in the global mini LED industry. In 2020, this region will occupy 57.52% of the global market share, with market revenue of US$145 million. 

North America and Europe ranked second and third with 19.82% and 18.44% of the market share. However, through data analysis and model derivation. We predict that the market share of the Asia-Pacific region in the global mini LED industry will continue to decline. 

And it is predicted to drop to 53.51% by 2025. On the contrary, during the period, there will be varying degrees of increase in the market share of North America and Europe.

The world’s leading companies in the mini LED industry are all from the Asia-Pacific region. The top 3 companies are Epistar and San’an Optoelectronics from China and Nichia from Japan. 

In 2020, their market shares are 23.19%, 20.19%, and 17.67%, respectively. The top three companies occupy more than 70% of the industry’s market share, which shows that the industry’s market concentration is relatively high.

Epistar manufactures and sells LED chips and epitaxial wafers. The company’s products are sold in Taiwan and exported around the world. Today, Epistar has become a major global LED supplier and has partnered with some of the world’s leading brands to promote LED applications on mobile screens, laptops, TVs, and other devices.

San’an Optoelectronics was established in November 2000. It is mainly engaged in the R&D, production, and sales of full-color ultra-high brightness LED epitaxial wafers, mini LED chips, III-V compound semiconductors, microwave communication ICs and power devices, and optical communication components.

In 2014, after completing the GaAs high-speed semiconductor and GaN high-power semiconductor projects, San’an Optoelectronics increased the industrialization of LED epitaxial chip R&D and manufacturing and invested in the IC industry. 

Relying on its advantages, it invested 33.3 billion yuan in 2018 to develop III-V compound semiconductor materials, LED epitaxial wafers, chips, microwave ICs, optical communications, radio frequency filters, power electronics, SIC materials and devices, special devices, and other industries. 

After the project is fully completed by 2022, San’an Optoelectronics will occupy a place in the entire high-end compound semiconductor industry chain and become a leading enterprise in terms of technical strength and production capacity.

HC Semitek’s LED chip production capacity ranks second in the world. And HC Semitek’s business covers LED chips, LED epitaxial wafers, sapphire substrates, and other fields. As early as 2019, it has established a focus on adjusting the industry, focusing on the deployment of the Mini/Micro LED industry to impact the high-end display market.

At present, HC Semitek has reached a cooperative relationship with Huawei in the Mini LED chip business with its high mass production capacity and advanced process technology. The smart screen V75 Super released by Huawei previously uses Sanan Optoelectronics Mini LED chips. 

According to HC Semitek’s first-half financial report, revenue in the first half of the year was 1.594 billion yuan, a year-on-year increase of 49.20%, of which Mini LED product revenue increased by 140% year-on-year.

Technical Characteristics and Difficulties of Mini LED Chips

However, mini LEDs bring challenges to electrode structure design, soldering flatness and ease of soldering, and packaging freedom. From the display point of view, the mini LED chip size is very small, when the red light chip is transferred in the flip-chip packaging process, the whole process is very complicated, and the chip transfer technology, yield, and reliability of the use process are technical difficulties.

From a backlight point of view, products such as TVs and laptops require ultra-thin. So mini LEDs must maintain a small optical distance (OD), and requirements for light output control of mini-LED chips and color consistency during the use of LCD panels are higher. 

It can be seen that technical barriers have brought a lot of challenges to the development of the mini LED industry.

It can be seen from the above that mini LED has a great advantage over other competitors under the current situation faced by LEDs. Based on this, various manufacturers are also studying it. Small pitch chips are similar, but there are many differences. Its technology has the following characteristics and difficulties:

1、Chip

a. Chip miniaturization.Because Mini LED requires the pixel spacing to be less than 1mm, which also requires Mini LED chips to be smaller. At present, mini LED chips generally require less than 200um, which puts forward higher requirements for lithography and etching in the LED chip production process, especially since the existing mature production equipment is difficult to meet the production of chips less than 100um. 

In the case of small-sized chips, the flatness of the welding surface, the design of the electrode structure, the ease of welding, the adaptability to welding parameters, and the package tolerance are all the difficulties and the key points of chip design. 

In the production process of Mini LED chips, the full-testing and full-scoring mode with low operating efficiency are also used. For processing a large number of chips with high density and high precision, there is a problem of low efficiency in both production and testing. This also virtually increases the cost of Mini LED chips.

b. Red light flip-chip, since the flip-chip does not require wire bonding, it is suitable for bottom-resistant transfer, but the production yield and reliability of the chip during the transfer technology process are not high.

c. Consistency and reliability. Mini LED chips as display chips have higher requirements for product consistency and reliability. Consistency is the key indicator which includes low current consistency, consistency under no current, high and low consistency, uniform color consistency, small and consistent capacitance, etc. Due to the complex use environment of Mini LED display, the maintenance difficulty is high, which requires higher reliability of Mini LED chips. 

Generally speaking, Mini LED chip manufacturers carry out strict production control in the production process to ensure product indicators. stability;

2、Packaging

a. High-efficiency die-bonding and patch. Since the chip size of Mini LED is mainly 50-200um, the usage of Mini LED chips and lamp beads per unit area is huge and the arrangement is very close, higher requirements are placed on the flatness of the welding surface and the line accuracy, and the adaptability of welding parameters and packaging. Tolerance requirements are also more stringent. 

Therefore, the bonding of high-efficiency and high-precision Mini LED chips has become a problem for Mini LEDs. Traditional solder paste bonding can easily lead to chip soldering drift and increase porosity, which cannot meet the high-precision solid-finishing requirements of Mini LEDs. 

Higher-precision die-bonding substrates and die-bonding equipment have become an urgent problem to be solved. When the traditional placement machine mounts MiniLED packaged devices below P1.0, since the accuracy is required to be below 25um, the traditional placement machine must reduce the placement speed to 30-50% of the original placement speed. 

A more efficient placement machine that greatly reduces the production efficiency of the display is also a major problem faced by Mini LED in the future.

b. Thin packaging.When MiniLED is used as a backlight, products require the thinner, the better. However, when the thickness of the PCB is less than 0.4mm, in the reflow soldering molding process, due to the different thermal expansion system between the resin substrate and the copper layer, it may cause chip welding. 

During the molding process, the difference in thermal expansion coefficient between the packaging glue and the PCB will also lead to glue cracking. Due to the slight color difference or circuit problem of the chip or lamp bead, it may lead to a difference in display or backlight effect, which will harm the display effect of mini LED.

c. Reliability and yield, the use environment of Mini LED display are relatively complicated. If the water vapor in the air penetrates through the packaging material or bracket and infiltrates the electrodes in the LED chip, it is easy to cause a short circuit or other phenomena. 

At the same time, due to the dense arrangement of Mini LED products, the packaged devices used have increased exponentially. Considering the difficulty and cost of Mini LED maintenance, this requires Mini LED packaged devices to have relatively high reliability.

3、PCB backplane

Under the premise that Mini LEDs are thinner and lighter, the high requirements for display and backlight effects have brought new challenges to the processing accuracy of the PCB backplane, such as thickness uniformity, flatness, and alignment. 

In addition, there are a large number of LED chips and driver ICs on the PCB backplane, which requires the Tg point of the backplane to be higher than 220°C, and the PCB backplane needs to be subjected to various external forces during the MiniLED processing to maintain the backplane. Thickness uniformity, dimensional stability, etc., also require the back sheet to have high physical properties such as tear resistance, humidity, and heat resistance.

The Bright Future of Mini LED chip Market

Mini LED enjoys the characteristics of high efficiency, high reliability, high brightness, and fast response time of small-pitch LED, but the technical difficulty is lower than that of micro-LED, so it is easier to mass-produce. 

Therefore, mini LEDs are a transition solution between fine pitch LEDs and micro LEDs, and products will be upgraded rapidly. In addition, compared with OLED, mini LED also has advantages in yield, cost, energy-saving effect, and display performance. 

At present, COB and IMD, the two key packaging technologies of mini LEDs, have made breakthroughs, which will strongly promote the rapid development of mini LEDs in the field of LCD backlight and display.

Display technology

OLED

Mini LED

Type of technology

Self-luminous

Self-luminous/backlight

Lifespan

Medium

Long(100000)hours

Reaction time

Microsecond

Nanosecond

Cost

Medium

Low

Energy consumption

Medium

Low

Color gamut

>100%

80%-110%

Viewing angle

Medium

High

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