The Background Of LED Significant Screen Packaging

LED significant screen has the advantages of high color saturation, wide dynamic range, long life, high brightness, seamless splicing, etc., becoming a very advantageous large screen display carrier. As the level of LED significant screen technology in China continues to improve, the scale continues to expand, according relevant institutions predict that in the next few years, the global market demand for LED significant screens will continue to maintain rapid growth, and the average annual growth rate will exceed 20%, is expected to 2020, the global LED significant screen market size will reach 30 billion U.S. dollars, China will be the most important manufacturing base.

At present, LED significant screen has been widely used in advertising media, cultural performances, stadiums, high-end conference rooms, traffic control, high-end car show, etc., and only in recent years has the emergence of a transparent screen, curved screen, and shaped screen, but also to further expand the LED significant screen market. LED significant screen development prospects are extremely broad, is towards higher brightness, better weather resistance, higher luminous density, higher luminous uniformity, and higher reliability direction. and higher reliability.

LED significant screen packaging is in the midstream of the LED significant screen industry chain and plays a key role in the whole industry chain. From the industrialization history of the LED significant screen market, the development of LED significant screen device packaging has experienced the dot matrix module package in the 1980s, the inline package that appeared after the 1990s, the sub-surface paste, surface paste package, and the more popular small pitch device package that appeared after 2011. From simple assembly to the current control of the production process, LED significant screen packaging has gone through a stage of technological innovation. The packaging link is no longer a simple assembly link, but a test of the production process and technical level of the link.

The Development History Of LED Significant Screen Packaging

The packaging of LED significant screen devices mainly includes dot matrix module, in-line, sub-surface, surface mount, COB, Micro LED, etc. Different packaging methods, each with their advantages and disadvantages, apply to different LED significant screen applications. Accordingly, the LED significant screen has also experienced the evolution from monochrome (such as single red, single green, single yellow, etc.), dual-color, and the current mainstream RGB full color, from the early mainly for outdoor to the current rise of indoor small pitch, from low resolution towards wide color gamut, high resolution. These different packaging methods not only promote the progress of LED significant screens, but also the process of continuous self-innovation. The following is an introduction to the development process of LED significant screen device packaging in several ways and the current situation.

Dot-matrix module and sub-surface paste have been eliminated and rarely used, and the current mainstream LED significant screen device packaging methods are mainly lamp and SMD trio, both of which account for more than 95% of the display market. So the following is the introduction of lamp and SMD triplet; while COB and MicroLED are introduced in the development trend.

(1) . Lamp LED Significant Screen Packing Structure

LED significant screen chip in-line pin type (Lamp) was the first LED LED significant screen product successfully developed and put on the market, with mature technology and a wide variety. Figure 1 shows the common Lamp LED significant screen package structure, usually with a "cup-shaped" structure at one end of the holder, the LED significant screen chip is fixed in the "cup-shaped" structure, and then the potting package is used. Potting is to inject liquid epoxy resin into the LED cavity first, then insert the pin-type LED significant screen holder and put it in the oven to let the epoxy resin cure, and then remove the LED from the cavity. The LED are then separated from the cavity and molded into LED significant screen products.

The inline package technology has a high market share due to its simple manufacturing process and low cost. At present, LEDs in the inline pin packages are usually monochromatic (red, green, blue) light-emitting applications in large screen dot matrix displays, indicators, and other fields. In the early days, the full-color LED significant screen was made by splicing 3 or 4 Lamp LED significant screen devices of red, green, and blue as one pixel. In recent years, RGB 3-in-1 Lamp LED devices are also being developed to meet the requirements of high brightness, high resolution, and high-efficiency splicing. At present, the direct insert LED is mainly used in outdoor point pitch above P10 large screen, its brightness advantage, and reliability advantage is more obvious, but because the outdoor point pitch is also towards the direction of high density, direct insert is limited by the red, green and blue 3 devices individually inserted, it is difficult to high density, so in the outdoor point pitch below P10 gradually replaced by SMD devices.

(2) . SMD LED Significant Screen Packing Structure

SMD LEDs emerged in 2002 and gradually took over the market share of LED significant screen devices, shifting from pin-based packaging to SMD. N pole of the LED chip), and then to the plastic frame inside the potting of liquid packaging adhesive, and then high-temperature baking molding, and finally cut and separated into a single surface mount package devices. Because surface mount technology (SMT) can be used, the degree of automation is high.

Compared with the pin-type packaging technology, SMD LED significantly screens to performs well in terms of brightness, consistency, reliability, viewing angle, and appearance.

SMD LED significant screens are smaller, lighter, and suitable for reflow soldering, especially for indoor and outdoor full-color display applications. SMD LED significant screens can be divided into TOP LED significant screens and Chip LED significant screens. The former often uses PLCC (Plastic Leaded Chip Carrier) holder, and the latter The former often uses a PLCC (Plastic Leaded Chip Carrier) holder, while the latter uses a PCB as the carrier for the LED significant screen chips. The former often uses PLCC (Plastic Leaded Chip Carrier) holder, and the latter uses PCB as the carrier of LED significant screen chips. uneven luminescence and reduced luminous efficiency. In addition, there are also PCT and EMC brackets with better performance and luminous efficiency, but considering the high price, it is not widely used in LED significant screen devices.

Currently, the most used LED significant screen market is the top-out type TOP LED significant screen device (Figure 2), followed by Chip LED, which is commonly used for indoor small pitches. several sizes of common SMD LED significant screens, such as 2020, 1515, and 3528, are generally divided by pad size. The pad is an important channel for its heat dissipation. Common SMD LED significant screen pads to include 3.5 mm × 2.5 mm and 2.7 mm × 2.7 mm for outdoor, and 1.5 mm × 1.5 mm and 1.0 mm × 1.0 mm for indoors. In the past few years, with the breakdown of the LED display market application environment, the requirements for SMD LED significant screen devices are different. For example, for outdoor LED significant screens, high waterproof, high brightness, and UV resistance are required. Among them, the high waterproof function is mainly through the waterproof structure design of the bracket, bending and stretching to extend the path of water vapor, while adding waterproof grooves, waterproof steps, and waterproof holes inside the device to achieve multiple waterproof. And high brightness, mainly by spraying high reflective walls in the inner wall of the cup to enhance light reflection. For outdoor UV resistance, a high-performance silicone encapsulant is gradually adopted to replace the traditional epoxy resin. Another example is indoor LED significant screen, the industry is generally pursuing high contrast and high resolution.

SMD LED significant screen device packaging is moving toward smaller sizes (such as 0808, 0606, and 0505) to meet the needs of the high-resolution LED significant screen market, but SMD device size has certain limitations. When the package size to 0808 smaller size package development, the process difficulty of the package increased sharply, and the yield decreased, resulting in increased costs. This is mainly limited by factors such as the precision of equipment for solid crystal, soldering line, scribing (punching and cutting), and soldering line. In addition, the cost in the end application will also increase, mainly in the precision of the placement equipment, placement efficiency, etc.