LED display assembly is a complex and tedious process, requiring highly skilled engineers at every stage to ensure the precision and quality of the LED display product. Industry insiders know that LED displays are composed of many modules, and each module is assembled from numerous LED chips. The assembly process is meticulous, with each step carefully executed to avoid affecting the display's performance. To meet the requirements of large-area, high-brightness, and dynamic display applications, as well as the matching requirements with the LED drivers, four main LED display connection methods are introduced below:
1. Series Assembly of the Entire LED Screen: In a simple series connection, LEDs 1-n are connected end-to-end, ensuring equal current flow during operation. Another method is an improved version of series connection 1.1 with bypass.
2. Parallel Assembly of the Entire LED Screen: This includes simple parallel connections and independently matched parallel connections. In the simple parallel connection, LEDs 1-n are connected end-to-end, ensuring equal voltage across each LED during operation. This method, while not highly reliable, employs an independent matching parallel connection to address this issue. It features good driving performance, complete protection for individual LED displays, no impact on other operations during failure, and compatibility with displays exhibiting significant differences.
3. LED Display Cross-Array Assembly: The cross-array configuration is primarily designed to improve the reliability of LED displays and reduce the failure rate.
4. LED Display Hybrid Assembly: This method combines the advantages of both parallel and series connections mentioned above. It includes two types: one is a series-then-parallel hybrid connection, and the other is a parallel-then-series hybrid connection.
Each of these four LED display assembly and connection methods has its own advantages and disadvantages. The most suitable connection method should be selected based on the specific application. Many engineers often overlook this, leading to various connection failures in LED displays, ultimately affecting product quality and reducing user trust. Therefore, in LED display assembly, details determine success or failure!
Through the appropriate connection of light-emitting diode chips (including series and parallel connections) and a suitable optical structure, the light-emitting segments or points of a light-emitting display can be constructed. These light-emitting segments or points can be used to form digital tubes, symbol tubes, star-shaped tubes, matrix tubes, level display tubes, etc. Digital tubes, symbol tubes, and star-shaped tubes are generally referred to as stroke displays, while stroke displays and matrix tubes are collectively called character displays.
Technological advancements in LEDs are the biggest driving force behind the expansion of market demand and applications. Initially, LEDs were used as miniature indicator lights in high-end equipment such as computers, audio equipment, and video recorders. With the continuous advancement of large-scale integrated circuits and computer technology, LED displays are rapidly emerging and gradually expanding into stock market displays, digital cameras, PDAs, and mobile phones.
LED displays integrate microelectronics, computer technology, and information processing. With their advantages such as vibrant colors, wide dynamic range, high brightness, high definition, low operating voltage, low power consumption, long lifespan, shock resistance, and stable and reliable operation, they have become the most advantageous next-generation display medium. LED displays are widely used in large squares, commercial advertising, stadiums, information dissemination, news releases, securities trading, etc., meeting the needs of different environments.
The basic semiconductor digital tube consists of seven strip-shaped light-emitting diode chips arranged as shown in Figure 12. It can display numbers from 0 to 9. Its specific structures include "reflector type," "seven-segment bar type," and "mono-integrated multi-digit type," etc.
(1) Reflector type digital tubes are generally made of white plastic with a seven-segment shell containing reflective cavities. Individual LEDs are attached to printed circuit boards aligned with the seven reflective cavities of the reflector. The LED chip is located at the center of the bottom of each reflective cavity. Before mounting the reflector, φ30μm silicon-aluminum wires or metal leads are connected between the chip and the corresponding metal strips on the printed circuit board using a pressure welding method. Epoxy resin is dripped into the reflector, and then the printed circuit board with the chip is aligned and bonded to the reflector, followed by curing.
Reflector type digital tubes have two packaging methods: open-sealed and solid-sealed. Solid-sealed methods use epoxy resin with scattering agents and dyes, and are mostly used for single or double-digit devices. Open-sealed methods involve covering the top with a filter and a light-diffusing film. To improve the reliability of the device, transparent insulating glue must be applied to the chip and the base plate, which also improves light efficiency. This method is generally used for displays of numbers with four or more digits (or symbols).
(2) The bar-shaped seven-segment display is a hybrid packaging form. It involves cutting gallium phosphide or gallium phosphide wafers into strips containing one or more LEDs, then attaching the seven strips to a Kovar frame (shaped like the Chinese character "日"). The internal leads are then connected using a pressure bonding process, and finally encapsulated with epoxy resin.
(3) The monolithic integrated multi-digit display uses integrated circuit technology to create numerous seven-segment display graphics on a large circular substrate of luminescent material. Qualified chips are selected through dicing, aligned, and mounted on a printed circuit board. Leads are then connected using a pressure bonding process, and a "fisheye lens" shell is placed on top. These are suitable for small digital instruments.
(4) The manufacturing method of symbol tubes and star-shaped tubes is similar to that of digital tubes.
(5) Matrix tubes (light-emitting diode dot matrix) can also be manufactured using a similar process to monolithic integrated multi-digit displays.
