From Lamp to Micro LED display packaging development trends | Part-1

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The continuous development of LED display devices towards full color, small size, low current, high reliability and low cost makes LED packaging device packaging technology more and more important but also facing huge challenges. Mustang LED article provides a brief overview of the development of LED display device packaging methods, which mainly include in-line (lamp), sub-surface mount, and surface mount three-in-one (SMD Screen).

SMD Screen

The future prospect technologies of LED display device packaging, such as small spacing, COB packaging and Micro LED packaging, and new technologies.

From the perspective of the industrialization process of the LED display market, the development of LED display device packaging has gone through dot-matrix module packaging in the 1980s, in-line packaging, sub-surface mount, and surface mount packaging that appeared after the 1990s. , as well as the more popular small-pitch device packaging that appeared after 2011.

From simple assembly to the current control of the production process, LED display packaging has experienced stages of technological innovation. The packaging link is no longer a simple assembly link, but a link that tests the production process and technical level.

The development history of LED display device packaging

The packaging methods of LED display devices mainly include dot matrix module, direct plug-in, sub-surface mount, surface mount three-in-one, COB, Micro LED, etc. Different packaging methods have their own advantages and disadvantages and are suitable for different LED displays.

Screen application fields. LED display screens have also experienced the transition from single color (such as single red, single green, single yellow, etc.), to dual colors and the current mainstream RGB full color. From the early days when they were mainly used outdoors to the current rise of small spacing indoors, from low resolution The evolution towards wide color gamut and high resolution.

These different packaging methods not only promote the progress of LED displays. But are also a process of continuous self-innovation. The following is an introduction to several methods and the current status of the development process of LED display device packaging.

At present, the mainstream LED display device packaging methods are mainly lamp and SMD Screen three-in-one, which account for more than 95% of the display market. Therefore, the three-in-one lamp and SMD will be introduced below; COB and Micro LED will be introduced in the development trend.

Direct plug-in type

The direct-pin type LED chip (Lamp) was the first LED product successfully developed and put on the market. The technology is mature and there are many varieties. Usually, one end of the bracket has a “bowl-cup-shaped” structure, and the LED chip is fixed in the “bowl-cup-shaped” structure, and then potted and packaged.

Potting is to first inject liquid epoxy resin into the LED mold cavity, then insert the pressure-welded pin-type LED bracket and place it in the oven to solidify the epoxy resin, and then remove the LED from the mold cavity to form an LED.

In-line packaging technology has a simple manufacturing process, low cost, and has a high market share. At present, LEDs with direct plug-in pin packages usually emit light in a single color (red, green, blue) and are used in large-screen dot matrix displays, indicator lights and other fields.

In the early days, full-color LED displays were made by splicing three or four Lamp LED devices in red, green and blue as one pixel.

In recent years, RGB three-in-one Lamp LED devices have also been developed to meet the requirements of high-brightness, high resolution, and high-efficiency splicing. At present, direct plug-in LEDs are mainly used in large screens with outdoor point spacing above P10. Their brightness and reliability advantages are obvious.

However, since outdoor point spacing is also developing toward high density, direct plug-in LEDs are limited to 3 red, green, and blue LEDs. It is difficult to achieve high density if the device is inserted separately, so outdoor point spacing below P10 is gradually replaced by SMD Screen devices.

SMD Screen package

Surface mount three-in-one (SMD) LED emerged in 2002 and gradually occupied the market share of LED display devices, shifting from pin-type packaging to SMD. Surface mount packaging is to bond and weld single or multiple LED chips to a metal bracket with a plastic “cup-shaped” outer frame (the outer pins of the bracket are connected to the P and N poles of the LED chip respectively), and then pour them into the plastic outer frame.

The liquid encapsulation glue is sealed, then baked at high temperature to form, and finally cut and separated into individual surface mount packaging devices.

Since surface mount technology (SMT) can be used, the degree of automation is high. Compared with pin-type packaging technology, SMD Screen LEDs perform well in terms of brightness, consistency, reliability, viewing angle, and appearance.

SMD LEDs are smaller, lighter, and suitable for reflow soldering, especially suitable for indoor and outdoor full-color display applications. SMD LEDs can be divided into bracket-type TOP LEDs and chip (Chip) LEDs.

The former often uses PLCC (Plastic Leaded Chip Carrier) brackets, while the latter uses PCB circuit boards as the carrier of LED chips. PLCC brackets have low cost, but there are problems such as poor air tightness, poor heat dissipation, uneven light emission, and reduced luminous efficiency in applications.

In addition, there are PCT and EMC material brackets with better performance and light efficiency, but due to their high price, they have not been widely used in LED display devices.

At present, the most widely used LED display market is top-emitting TOP LED devices, followed by Chip LED, which is commonly used in small spacing indoors. Several common sizes of SMD LEDs, such as 2020, 1515, and 3528, are generally divided by pad size.

The soldering pad is an important channel for heat dissipation. Common SMD LED soldering pads include outdoor 3.5mm×2.5mm, 2.7mm×2.7mm, and indoor 1.5mm×1.5 mm, 1.0mm×1.0mm, etc. In recent years, with the segmentation of the LED display market application environment. The requirements for SMD Screen LED devices are different.

For example, outdoor LED displays require high waterproofing, high brightness, and UV resistance. Among them, the high waterproof function is mainly achieved through the waterproof structural design of the bracket, bending and stretching to extend the path of water vapor, and at the same time, adding waterproof grooves, waterproof steps, waterproof holes, etc. inside the device to achieve multiple waterproofing.

Outdoor SMD Screen for pole

As for high brightness, it is mainly achieved by spraying a high-reflective wall on the inner wall of the cup to enhance light reflection. For outdoor UV resistance, high-performance silicone encapsulation is gradually used to replace traditional epoxy resin.

For indoor LED displays, the industry generally pursues high contrast and high resolution. SMD Screen LED device packaging is developing towards small sizes (such as 0808, 0606, 0505) to meet the needs of the high-resolution LED display market, but the size of SMD Screen devices has certain limitations.

When the packaging size develops towards 0808 smaller size packaging, the packaging process difficulty increases sharply and the yield rate decreases, resulting in increased costs. This is mainly limited by factors such as the equipment accuracy of die bonding, wire bonding, dicing (punching), and wire bonding.

In addition, the cost of terminal applications will also increase, mainly reflected in the accuracy of placement equipment and placement efficiency.

Thank you for understanding, I hope this will help you. We will continue our discussion on Part 2. Mustang LED is a professional LED display Contractor. We deliver a wide range of display, display rental, and display results worldwide. If you want to know more random information; please click to read: How Does No-Claim Bonus Work in Car Insurance in Pakistan?

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