Foreword：

In recent years, with the rapid development of chips, materials, equipment, processes and other technologies, LED display technology, as an important information display technology, is undergoing revolutionary changes. Among the many innovations, the bracketless pinless integrated packaging technology has attracted widespread attention with its unique advantages and status, and has become a leading force in promoting LED display technology into a new era. The pursuit of bracket-free is our ultimate goal, and pin removal is the process of our efforts to achieve this goal. In fact, the bracketless lead-free integrated packaging technology is not unfamiliar to us. As early as 2010, the COBIP (Chip On Borad Integrated Packaging) technology patent and application appeared for the first time in the direct display industry, and this technology is the bracket-free lead-free integrated packaging technology. The primary form of integrated packaging technology. The reason why the article emphasizes "bracket-free pin removal" is that we have discovered many interesting problems and phenomena during the practice of integrated COB industry technology. One of the important findings is: "The reliability of the LED display panel has an important correlation with the number of bracket pins of the packaged device. To completely solve the problem of excessive failures of LED display panels, the best proactive solution is packaging The technology is to remove the bracket pins. The more thoroughly the bracket pins are removed, the better the panel failure problem will be solved." This is also an important understanding we gained during the research.

Figure 1. Two packaging system technologies in the LED direct display industry

So far, two industrial system technologies dominated by packaging technology have emerged in the LED direct display industry, namely the bracket-pin type single-device packaging lamp driver separation system technology and the bracket-free pinless integrated packaging lamp driver integration system technology. , as shown in Figure 1. Through in-depth practical research on COBIP technology, we deeply feel the need to systematically classify packaging technologies in the direct display industry. Compared with traditional scaffolding technology, new system technology is emerging, providing theoretical support for COBIP technology and revealing the endogenous nature of the industrialization of COBIP technology. Stent system technology has dominated the development of the industry for more than 30 years, and the trend in the next few decades will be dominated by stent-less system technology. Moving from separation to integration is not only the main theme, but also the only way for LED display technology. The research topic of packaging system technology is huge, and we look forward to having in-depth discussions with you in the future. This article focuses on briefly introducing the core content of bracketless leadless integrated packaging technology.

Throughout the LED direct display industry chain, we have ushered in the era of 4K and 8K display in the 5G environment of the Internet of Things. At the same time, the fine-pitch display technology of Mini LED and Micro LED has also brought about process bottleneck challenges. The products and industrialization standards related to each major platform have raised the most important and critical genetic evaluation index of LED display panels to one million levels. With the country's struggle to achieve dual-carbon goals, the development needs of a resource-saving society and the emergence of various new display technology application forms, the determination of corporate products to enter the civilian consumer market has become increasingly prominent. In such an environment, we can't help but ask, if packaging technology does not engage in "bracket-free pin removal", will it be enough to meet future development needs?

1. Core characteristics of technology

1. Design features

Bracketless leadless integrated packaging is a systematic technology that adopts an integrated design concept. The core of its design features lies in the deep integration of the underlying supporting technologies of LED display panels, such as LED chips, driver IC chips, PCB circuit boards, etc., to achieve an integrated design of lamp drivers and display pixels. The unique feature is that the bracket and pin elements used in device packaging technology in traditional designs are removed, and the architectural solution of separate lamp drivers is abandoned. LED chips and driver IC chips can be more closely integrated, realizing a lamp driver integration or a lamp driver and pixel in-package architecture solution, thereby improving the overall integration of the LED display panel.

2. Process characteristics

The production process of traditional system technology LED display panels adopts device-level welding technology after packaging. In contrast, the production process of new system technology LED display panels adopts chip-level welding technology in packaging. This process not only solves the problems of welding process and first pass rate in advance, but also has higher precision challenges.

Figure 2. Bare chip-level high-precision solid-welding COBIP technology

3. Product features

The new system technology LED display panel is an integrated lamp driver or lamp driver on one board, rather than the separate lamp driver architecture of two boards of traditional system technology.

4. Industry characteristics

Compared with traditional system technology industries, new system technology has a higher degree of industrial integration. The first generation of COBIP technology realized the vertical integration of industrial links in the industry, that is, the integrated production of packaging companies and display screen manufacturing companies. The second-generation COCIP technology goes a step further and can realize cross-industry horizontal integration between industries, that is, the integrated production of COBIP companies in the direct display industry and packaging companies in the driver IC industry.

2. Advantages

1. Theoretical advantages

1.1 Complete theoretical framework

Through a systematic summary of COBIP technology, the new system technology has formed a theoretical core - "removing pins from the bracket" and a relatively complete theoretical system. This provides a theoretical basis for the future generation technology and industrialization development that will evolve within the framework of this system.

1.2 The imagination space of technological evolution

As the first generation technology within the new system technology framework, COBIP technology is the primary form of new system technology development and the threshold technology for future development. The second generation of technologies, such as COCIP and CNCIP, has completed the problems that COBIP technology cannot solve. It is about to drive the IC to bare crystal and achieve the goal of completely removing the pins from the bracket. In the future, there is still huge room for imagination in the evolution of generation difference technology within the new system technology framework, but it will all follow the theoretical principle of bracket-free pinless integration.

2. Technical advantages

2.1 Solve the bottlenecks faced by traditional technologies

Traditional system technologies have reached the development ceiling in meeting the requirements of new display technologies, while new system technologies can continue to promote industrial development. Its advantages are reflected in solving the problems of LED display panel failure, thermal conductivity, heat dissipation, light attenuation, etc., improving the reliability, thermal conductivity and optical consistency of the product, and improving the dynamic response speed of video signal processing. The LED display panel has Perfect heat distribution significantly improves display quality.

2.2 Changes in product characteristics

With the continuous evolution of new system technology, the properties of LED display products will undergo fundamental changes, becoming thinner, more flexible, and more transparent, evolving to the ultimate goal - thin film display materials. LED display products are no longer limited to traditional screen display technology, but are developing towards diversified application forms such as sticker displays, card displays, bag displays, wearable displays, scroll displays and film displays.

Figure 3. Bracket-free lead-free integrated packaging CNCIP technology

3. Industrialization advantages

3.1 Improvement of resource utilization efficiency

The vertical and horizontal integration of new system technologies within the industry can better utilize human, material and material resources, meet the needs of social development for resource-saving industries, and achieve standardization, intelligence, scale, pulsation, customization and Intensive coordination and balance.

3.2 High-quality development

Achieving industry standardization and large-scale development, improving product quality, and reducing product costs are the advantages of new system technology in industrialization. This will drive the LED direct display industry towards high-quality development.

4. Social development advantages

4.1 Save social resources

Products using new system technology have obvious advantages in carbon trajectory evaluation and social resource saving effects. The new system technology is expected to better realize the country's struggle to achieve dual carbon goals, and has received strong support from national industrial policies.

5. Market advantage

5.1 Expand the consumer market

The reliability, low cost and diversified application forms of the new system technology will make it easier for products in the LED direct display industry to enter the civilian consumer market, thereby expanding the market scale and making the industry scale no longer stagnant at tens of billions.

5.2 High reliability products

With the promotion of new system technology, LED direct display products will become more reliable, and product quality and industrial scale will no longer be a contradiction, thereby better meeting market demand.

3. Standards and genetic evaluation indicators

1. Standard

New System Technology actively participates in the formulation of LED display product standards. The group standards involved include:

l"General Technical Specifications for Mini LED Commercial Displays" T/SLDA01-2020

This standard adopts the classification of LED display products according to packaging system technology for the first time, which is of epoch-making significance.

l"Technical Specification for Green and Low-Carbon Product Evaluation Mini LED Display" T/CIET 224-2023

l"Product Carbon Footprint Evaluation Guidelines for Mini LED Displays" T/CIET225-2023

l"General Technical Specifications for Vehicle Optical Information Interaction Systems" T/GOTA005-2022

In the future, new system technology will continue to participate in the formulation of more LED display product standards, expanding and improving relevant standards.

2. Genetic evaluation indicators

Genetic evaluation indicators are used to test the reliability and failure resistance of LED display panels, which are similar to the relationship between human body strength and genetic factors. These evaluation indicators are of great significance to the packaging system technology used in LED display panels.

lTotal failure rate evaluation criteria

It is recommended to use the total failure rate as the evaluation index, including the front-board failure rate (pixel out-of-control rate) and the rear-board failure rate (driver IC out-of-control rate), see Figure 4.

Figure 4. Research on the total failure of LED display panels

Formula: Total failure rate = failure rate before the plate + failure rate behind the plate

lProduct evaluation criteria when leaving the factory

It is recommended that the total failure rate be controlled within the following range:

Total failure rate ((0-9)/PPM) = pixel out-of-control rate ((0-4.5)/PPM) + driver IC out-of-control rate ((0-4.5)/PPM)

lEvaluation criteria after 10,000 hours of product use

It is recommended that the total failure rate be controlled within the following range:

Total failure rate ((10-30)/PPM) = pixel out-of-control rate ((5-15)/PPM) + driver IC out-of-control rate ((5-15)/PPM)

lPay attention to the evaluation criteria in group standards

We are concerned that in the above-mentioned T/SLDA01-2020 group standard, this indicator is more stringent than what we recommended. It is just a pity that the evaluation indicator of the driver IC out-of-control rate is missing. We think it should be given when the subsequent standard is added. consider. See Figure 5.

Figure 5. Evaluation criteria for pixel out-of-control rate indicators in the T/SLDA01-2020 group label

3. Future prospects

The new system technology will continue to play an active role in standard setting and participate in the formulation of more LED display product standards. In addition, the proposed genetic evaluation index standard suggestions are expected to play a role in promoting high-quality development in the new era, comprehensively and scientifically evaluate the reliability of LED display panels, and bring the industry into a new era of millions of levels (single digits/PPM) .

4. Re-understanding of COB technology

From the perspective of the development of packaging system technology, we will re-understand the two development routes of COB technology in the LED direct display industry, see Figure 6.

Figure 6. Two technical routes for COB packaging in the LED direct display industry

1. COBLIP（Chip On Board Limited Integrated Packaging）

This is a development route of COB technology, known as COB limited integration packaging technology. In this technology, COB is used to make pixel integrated packaging on the light board to form an independent packaged device with a bracket and pins. The device is then soldered to the PCB board with the driver IC device and circuitry. This belongs to the COB technology within the technical framework of the bracket-pin type single-device package lamp driver separation system. Typical examples include the three-in-one full-color dot matrix module technology that appeared in 2007 and the IMD or Nin1 technology that appeared after 2016. These technologies are referred to as device-based COB technologies.

2. COBIP（Chip On Board Integrated Packaging）

This is another development route of COB technology, which uses COB for multi-pixel integrated packaging on a PCB board, and welds driver IC devices on the other side of the same PCB board. This realizes a lamp driver integrated packaging technology on one board, which is the first generation technology within the technical framework of a bracket-less pinless integrated packaging lamp driver integrated system, and is referred to as integrated COB technology.

3. Evaluation of two COB technologies

Through research on LED display panel failures and actual case data, it was found that there are significant differences in the evaluation of pixel out-of-control rate indicators between device-based COB technology and integrated COB technology. Device-type COB technology can usually only reach the 100,000 level, which is about 50/PPM, while the integrated COB technology has the ability to enter the million level (within (0-9)/PPM).

Key ideas:

lThe reliability of the LED display panel is closely related to the number of bracket pins of the packaged device.

lAlthough device-type COB technology has improved in pin removal, it has not yet broken away from the constraints of the bracket-type system technology framework.

lIntegrated COB technology has made exciting progress in industrial development, especially in Mini LED direct display products. The endogenous driving force is its use of bracket-free pin-based integrated packaging technology.

lThe integrated COB technology + RGB full flip-chip combination solution is currently considered to be the best technical route for realizing Mini LED direct display products.

4. Outlook and warnings

lFrom the perspective of new system technology development, integrated COB technology is only an entry-level threshold technology, not the ultimate high-end target solution.

lIntegrated COB technology needs to be viewed objectively, rationally and impartially, not only to see its inherent growth momentum but also to see its shortcomings, and not to equate its excessive myth with Micro LED products.

lIntegrated COB technology does not yet have the ability to realize Micro LED products.

By recognizing the development of COB technology in the LED direct display industry, we can better understand its technical characteristics, limitations and future development directions.

5. Challenges faced by technology and predictions of future development

1. Challenges faced by technology

Although the bracket-less pinless integrated packaging technology has achieved remarkable results in the field of direct display Mini LED products, it still faces some challenges:

lIncreased manufacturing complexity: Highly integrated designs may increase the complexity of the manufacturing process and place higher demands on the process.

lHeat dissipation effect: How to ensure the heat dissipation effect of the product while maintaining a high degree of integration is a problem that needs to be solved, especially for high-brightness, high-power consumption display products.

These challenges require in-depth industry coordination and cooperation in materials, equipment and process solutions to find breakthrough points to solve, but they have attracted global attention and the industry is working together to deal with them.

2. Forecast of future development

Looking at the problem from the perspective of system technology, we believe: "The future development direction of the industry will still be dominated by packaging technology." Driven by the influence of COBIP technology as the underlying supporting technology for Mini LED products, 2020 will become an important historical time node for the development of the direct display industry. In the 10 years from this moment to 2030, we see that industry system technology is going through an overlapping transition period from separation to integration. It is also a golden period for industrial technology to transform from low-end to high-end. During this period, various concepts and technologies in the industry were dazzling, making it difficult to distinguish between true and false, and at a loss as to what to do. The radical, confused, anxious, and fearful mental states exhibited by colleagues in the industry are very normal. The systematic classification ideas and methods of packaging technology may help you understand the past, clarify your ideas, and see the direction. In the first half of the transition period, that is, in the first five years, the industrial scale of integrated COB technology fine-pitch display products is expected to surpass traditional technology. Under its promotion, these products will bring new system technology advantages and average annual cost and price advantages, and enter more general and professional application fields. For example, the integrated COB vehicle rear window transparent advertising display product is used in the field of outdoor mobile media operations at home and abroad, as shown in Figure 7. Integrated COB outdoor small-pitch and regular-pitch display applications, integrated COB indoor, semi-outdoor, outdoor and rental high-brightness, low power consumption, low attenuation, anti-collision high-end transparent display applications and high-reliability integrated COB High performance and low maintenance for professional display applications. In the second half of the transition period, the industrial scale development of integrated COB technology will accelerate. Iterative applications will rapidly penetrate into the traditional LED display field and continue to open up more new application areas. The pace of development may change exponentially during this period. After the 10-year period, the industry's industrial technology iteration has been basically completed, and it will enter the post-COB integration era. Bracketless lead-free integrated packaging technology will be deeply rooted in the hearts of the people.

Bracketless leadless integrated packaging uses its own strong technical capabilities and advantages to drive, integrate and integrate industrial resources to improve production efficiency, reduce costs and improve product performance. With the support of new system technology, the LCD industry and LED direct display industry will merge with each other. Mini LED and Micro LED technology will become more mature. The new system technology will overflow its influence and be used more in LCD. In backlight panel manufacturing, the scale of the industry has expanded dramatically, and they will drive the popularization of new technologies in high-end commercial displays, TVs, monitors and other fields. It will also bring more coordinated and aesthetically pleasing display application solutions to outdoor media, smart cities, architecture and displays, and promote the upgrade of LED display technology. Combined with intelligent and Internet technologies, LED display technology and products will achieve more intelligent functions and enhance user experience. The one-board integrated architecture concept of the new system technology will use more environmentally friendly materials and processes to significantly reduce energy consumption, save resources and reduce the impact on the environment. The unique advantages and product application forms of the new system technology will rapidly expand into new application scenarios, such as AR/VR, driverless driving, vehicle-mounted optical information interaction, smart home appliances and homes, wearable displays, stickable displays, convenience It carries intelligent connected splicing displays, offline green energy energy-saving displays, rolling shutter displays, UAV stage design and high-altitude 3D displays and other military and civilian fields.

Figure 7. Integrated COB technology vehicle rear window transparent advertising sticker products are used in vehicle-mounted mobile media operations

Once we enter the post-COB integration era, with the further improvement of equipment and process technology capabilities, and the continuous advancement of materials, wireless communications, light-sensing micro-power supply and other technologies, within the foreseeable time, we believe: "There should be at least two The technology will be integrated into that magical board without brackets and without pins. At that time, what we call the ultimate ideal goal of membrane display technology roll products will appear. People can cut and paste display materials at will. Today we are everywhere Visible crystal film screen concept products still have a long way to go to achieve this goal, which requires the joint efforts of underlying technology and process technology to make breakthroughs. In short, achieving the goal is no longer a dream.

Conclusion：

As mentioned above, the only way to go is by no means empty talk, and we hope that industry colleagues will take it seriously. As an important part of the new LED display technology, the integrated packaging technology without brackets and pin removal is leading the development direction of LED display technology with its unique technical characteristics and wide application prospects. Facing various challenges, we will continue to work hard to continuously promote innovation and breakthroughs in this technology, and contribute our strength to create a more brilliant future for LED display technology.

Please note that this article only represents my personal opinion and is intended to inspire others. If there is anything inappropriate, please criticize and correct it. At the same time, I hope that colleagues in the industry can get inspiration and help from it and jointly promote the progress of LED display technology.

（End）