The past two years, full-color surface mount (SMD) Outdoor LED display has been more widely used, rapid increase market size, these products are still many problems in practical applications. Here we would SMD outdoor four-line display and outdoor display performance will be some discussion.
First, the basic structure of the internal analysis modules available
The four of us in terms of common outdoor LED display modules available from internal structure analysis.
1, a single lamp
SMDLED lights, external dimensions of 5.0mm × 5.0mm × 2.5mm, its built-in red, green, and blue chips, namely triple can be used as a pixel display; line LED lights, external dimensions of 3.0mm × 4.1mm × 6.3mm, its built-in single color chips, at least red, green, and blue lights of different colors each one bolted together to form a full-color display pixels. So from a pixel point of view, it is much smaller than the volume of SMD lamp line lights. However, due to in-line light is a single light package, large volume, highly positive high, light legs, so it is still intact and strong degree and cooling degree than SMD lamps.
2, welding
Two different light welding. SMD lamps pads and the PCB pad surface contact welding, and lamp pins line is through the PCB pad holes after welding, showing the extent of the latter's welding firm should be better than former. Actually SMD lamps more prone Weld phenomenon, or bad phenomenon occurs in the transport and use, which bring more trouble to use and maintain. Especially when using the outdoor environment is more severe, and this is more important. Therefore, to ensure the welding quality is one of the quality assurance SMD outdoor display key factor.
3, sealing method
Both lamps plate sealing method is the same, the sealing material is currently mostly used silicone. However, we can see a large difference in the thickness of the two lights on silica gel plates, SMDLED lights thickness of about 1 ~ 1.5mm, a thickness of about line LED lamp 3.5 ~ 4.5mm, therefore, the latter sealing the lamp and the PCB better protection. Of course, the specific advantages and disadvantages are also concerned with the potting process.
See, for high density, better use of the environment of the display, you can choose SMDLED display. Requirements for low density, harsh environments screen, select line LED display better.
Second, the cell module production process analysis
From the production process point of view, SMD display unit modules and module line display unit, mainly in welding and gluing these two points are different, the rest no big difference.
1, welding
SMD soldering process display unit modules are mainly adhesive (conductive plastic), SMT, welding, these processes are suitable for large-scale mechanized production, the position of the lamp is structured after welding.
Welding line of modular units mainly plug lights, welding, cut legs. Although a dedicated automated machinery, but its production efficiency is low. Further, due to higher light leg, so the production process is easy to bend, thereby changing the direction of the light, and the subsequent step affects the quality of the display.
2. Glue
Glue SMD display process unit module should be more stringent demands more, because its layer is thinner, so how much should strictly control the operation of the module is placed horizontally and glue, each module should be strictly consistent.
Line display unit module Glue process requires slightly more, because its layer is thicker, so the level of the operation and the amount of plastic modular placement number of requirements are relatively relaxed. But before potting response lamp to organize, to ensure consistent normal direction of the axis of the lamp and the PCB board.
Either way, the plastic surface flatness and consistency should maintain a high level, otherwise, it will affect the display quality.
Third, reliability analysis
For reliability, the main difference between the three aspects.
1, sealing problems
As previously mentioned tightness, SMD lamps and lamp module with respect to the line and modules to be somewhat less so in water, moisture, UV and other harsh environmental factors somewhat less reliable.
2, the heat problem
Full-color SMD light red, green, blue triple package, namely three wick enclosed in a small space, thereby generating the heat. LED lights on the line, the only one inside the package each lamp wick, and light legs, so the heat is not a problem.
In addition, due to the low brightness SMD lamps, to achieve high brightness outdoor requirements, the driver current is generally larger than the light-line, which further exacerbated the heat.
3. failures
Due to packaging, cooling, and environmental issues, so the failure rate is higher than the line SMD lamp lights. Currently, full-color outdoor display with SMD lamp failure rate within 3000 hours should be less than five hundred thousandths.
Fourth, the Optical Properties
Optical performance, we focus on brightness, viewing angle, uniformity three areas.
1, brightness
Currently universality, the brightness of the same size SMD outdoor screen brightness than the lower line of the display lights. In other words, to achieve the brightness line light display, the quality SMD lamps should be better, the drive current may be larger. In point spacing of 16mm (P16) of the display, for example, at present, SMD display the entire screen brightness of 5000cd / m2 or more, and line lights display, the entire screen brightness can reach 7000cd / m2 or more is not difficult.
2. Perspective
Horizontal viewing angles are much better than SMD lamps light line angle (vertical angle Similarly), of course, different types of light in the figure is different, but the perspective is better than SMD lamps light line is an indisputable fact. In general, the viewing angle SMD display up to 110 degrees, and line lights display angle of up to about 90 degrees.
3, with light and color mixing
Full-color SMD lights are red, green, blue triple structure, which put three chips together into the same cups, chip spacing is small and neat uniform, and therefore works well with light and color mixing.
Line of red, green and blue lights three oval synthesis of a pixel, from a different direction to their paired synthesized light is difficult to achieve consistent, but due to the large spacing between the wick, it is also problematic blending , especially when viewed up close, blending well the problem is more prominent.
In addition, the direction of the light emitted by SMD lights on the display to maintain a good consistency. Because light line in the production process is difficult to maintain a consistent direction of the lamp, so the directivity of the light emitted is difficult to maintain consistency. Therefore SMD display images more delicate than in-line lamps.
4. Attenuation
Since the driving current, the chip spacing is small, the heat is difficult, SMD lamp brightness decay rate faster than the line light, color consistency more easily deteriorated.
DIP lamp each chip individually packaged and high brightness, drive current, heat, attenuation is relatively small.
Therefore, the attenuation characteristics of SMD lamp lights to be worse than the line to overcome these shortcomings, the need for better chip and packaging materials.
V. Summary
Through the above analysis and comparison, we believe SMD lamps made with full-color display, viewing angle, with light and good color mixing effect, exquisite images, brightness belongs to the middle level, suitable for large-scale automated production. But the high failure rate and decay rate, ability to adapt to the harsh environment badly, good for environmental, high density and less demanding display brightness.
DIP lamp made with full-color display, sealing, high brightness, environmental adaptability, suitable for long-distance viewing. But the perspective of smaller, somewhat less uniform color, slightly more complex production processes. Currently production line lights full color display various aspects of performance need not be a problem for the general.
Thus brightening Jiangsu Electronics analysis: Outdoor SMD LED display is the future trend of development
Since the surface-mount LED display brightness is low, and the waterproof, moisture, ultraviolet index reach the requirements of the fight against harsh outdoor environments, has been the outdoor full color LED display is the world-line devices. The full-color surface mount LED display can only be widely used in indoors. But it is undeniable that the variety in color reproduction, many aspects of color consistency, uniformity, viewing angle, the picture overall effects have traditional LED screen light does not go beyond the line characteristics and advantages.