LED Lighting PCB Assembly
Introduction to LED PCB Technology
From smartphones to kitchen appliances, electronic products play an important role in our daily work. At the heart of every electronic product is a printed circuit board (PCB). It is the basis of most electronic products today. These components have a number of configurations that allow them to provide a variety of functions. With the expansion and development of electronic products in various industries, LED lighting PCB printed circuit boards and assembly applications are also constantly developing. Today, the use of PCB covers almost every industry and continues to develop into new industries and applications.
Application of LED PCB Assembly:
LED PCB can be integrated into many lighting applications because of its excellent energy efficiency, low cost PCB manufacturing and maximum design flexibility, for example:
1. Traffic lights PCB;
2. Car headlight PCB;
3. Military lighting PCB;
4. Street and tunnel lighting PCB;
5. Airport runway lighting PCB;
6. Street lamp lighting PCB;
7. Photovoltaic (solar) lighting PCB;
8. Flashlights and lanterns PCB;
9. Light in the hospital operating room;
10. Factory lighting PCB;
11. PCBA kitchen appliances and so on.
LED PCB technology offered by the PCB maker has evolved into a level that gives a rise to many innovations of many new products. A good example is the development of PCB for LED lighting. The LEDs are welded to a circuit board and the chip generates light when it is electrically connected. The cooling fin and ceramic base are used to connect the chip to absorb heat and cool the whole process.
LED PCB tends to generate a lot of heat, which makes cooling by conventional means laborious. Therefore, a metalcore LED circuit board is usually chosen to improve the heat dissipation capacity of LED. In particular, aluminium is often used to make circuit boards for LED lights. Aluminum PCB usually consists of a thin layer of conductive dielectric material that can relocate and dissolve heat compared to an unyielding PCB, providing excellent coherence.
LED PCB Board Design
1、 Design flow from schematic diagram to PCB
Establish component parameters - > input principle net list - > design parameter setting - > manual layout - > manual wiring - > verify design - > recheck - > cam output.
2、 Parameter setting
The distance between adjacent conductors must meet the electrical safety requirements, and the distance shall be wider as far as possible in order to facilitate operation and production. The minimum spacing shall at least be suitable for the withstand voltage. When the wiring density is low, the spacing of signal lines can be appropriately increased. For signal lines with a great difference between high and low levels, the spacing shall be as short as possible and increased. Generally, the routing spacing is set to 8mil. The distance from the inner hole edge of the pad to the edge of the printed board shall be greater than 1mm, so as to avoid pad damage during processing.
3、 Component layout
The practice has proved that even if the circuit schematic design is correct and the printed circuit board design is improper, it will have an adverse impact on the reliability of electronic equipment. Therefore, when designing a printed circuit board, we should pay attention to the correct method. Each switching power supply has four current circuits:
(1) AC circuit of power switch;
(2) Output rectifier AC circuit;
(3) Input signal source current loop;
(4) Output load current loop. The input circuit charges the input capacitor through an approximate DC current, and the filter capacitor mainly plays a role in broadband energy storage. Similarly, the output filter capacitor is also used to store the high-frequency energy from the output rectifier and eliminate the DC energy of the output load circuit. Therefore, the terminals of input and output filter capacitors are very important. The input and output current circuits should be connected to the power supply only from the terminals of filter capacitors.
The best way to establish the layout of the switching power supply is similar to its electrical design. The best design process is as follows: place the transformer; Design the switching current circuit of power supply; Design output rectifier current circuit; A control circuit connected to an AC power supply circuit; The input current source circuit and input filter are designed.
The switching power supply contains high-frequency signals. Any printed line on LED PCB can play the role of antenna. The length and width of the printed line will affect its impedance and inductive reactance, thus affecting the frequency response. Even a printed line passing through a DC signal will be coupled to an RF signal from an adjacent printed line and cause circuit problems. Therefore, all printed lines passing through AC current should be designed as short and wide as possible, which means that all components connected to printed lines and other power lines must be placed close to each other. The length of the printed line is directly proportional to its inductance and impedance, while the width is inversely proportional to its inductance and impedance. The length reflects the wavelength of the printed line response. The longer the length, the lower the frequency that the printed line can send and receive electromagnetic waves, and it can radiate more RF energy. According to the current of the printed circuit board, try to increase the width of the power line and reduce the loop resistance. At the same time, make the direction of the power line and ground wire consistent with the direction of the current, which helps to enhance the anti-noise ability. When conducting global cabling, the following principles must be followed:
(1) Wiring direction: from the welding surface, the arrangement direction of components shall be consistent with the schematic diagram as far as possible, and the wiring direction shall be consistent with the wiring direction of the circuit diagram. Because various parameters are usually required to be tested on the welding surface in the production process, this is convenient for inspection, commissioning and maintenance in production (Note: on the premise of meeting the requirements of circuit performance, whole machine installation and panel layout).
(2) When designing the wiring diagram, the routing shall minimize bends, the line width on the printed arc shall not change suddenly, and the wire corner shall be ≥ 90 degrees, so as to make the line simple and clear.
(3) No cross circuit is allowed in the printed circuit. For lines that may cross, two methods of "drilling" and "winding" can be used, that is, let a lead "drill" through the gap at the foot of other resistors, capacitors and triodes, or "wind" from one end of a lead that may cross In the past, the circuit was very complex under special circumstances. In order to simplify the design, it was also allowed to use a wire jumper to solve the cross circuit problem. Because the single panel was adopted, the in-line components were located on the top surface and the surface mount devices were located on the bottom surface, the in-line devices could overlap with the surface mount devices during layout, but the pad overlap should be avoided.
After the wiring design is completed, it is necessary to carefully check whether the wiring design conforms to the rules formulated by the designer, and confirm whether the rules formulated to meet the requirements of the printed board production process. Generally, it is necessary to check whether the distance between lines, line and component pads, line and through holes, component pads and through holes and through holes and through holes is reasonable and meet the production requirements. Whether the width of the power line and the ground wire is appropriate, and whether there is any place in the LED PCB where the ground wire can be widened.
According to the "PCB Checklist", the contents include design rules, layer definition, linewidth, spacing, pad and via settings, and also focus on rechecking the rationality of device layout, routing of power supply and ground wire network, routing and shielding of high-speed clock network, placement and connection of decoupling capacitors, etc.
7、 Design output
Precautions for outputting photo files in LED PCB Board Design: the layers we need to output include wiring layer (bottom layer), silkscreen layer (including top layer silkscreen and bottom layer silkscreen), solder resist layer (bottom layer solder resist), drilling layer (bottom layer), and also generate drilling file (NC drill); When setting the layer of the silkscreen layer, do not select the part type, select the outline, text and lines of the top layer (bottom layer) and the silkscreen layer. When setting the layer of each layer, select the board outline. When setting the layer of the silkscreen layer, do not select the part type, and select the outline, text and line of the top layer (bottom layer) and the silkscreen layer; When generating drilling files, use the default settings of PowerPC and do not make any changes.