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What are the advantages of PCB "Yin and Yang board" in SMT patch processing?
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What are the advantages of PCB "Yin and Yang board" in SMT patch processing?

In the electronic assembly manufacturing industry, there are generally two types of [Mirror Board]. The first type is the Different side mirror board with the front and back reversed. Or the first side of one board and the second side of another board are on the same side of the board; The other type is the Same side mirror board where all the pieces are on the same side but left and right are reversed, such as the layout of pdpd.

There are two reasons why an electronics manufacturer may require the adoption of the design:

1. Can make full use of the advantages of smt long line to achieve greater printing efficiency

Whether the overall efficiency of an SMT is good or not can be judged simply by the presence of idle machines. If no machines can be idle at all, then we can say that the efficiency of the SMT line has reached 100%.

But is it really that easy to be 100% efficient? As the printing speed of SMT machine gets faster and faster, SOC (System On Chip) parts become more and more popular, there are less and less parts on a board. However, I haven't seen any rapid progress in solder paste printing machine. So now the bottleneck of many SMT lines instead appears in the solder paste press, that is, the solder paste press does not have a rest, while other more expensive machines are waiting.

Well, let's say that the time it takes to print a solder plate is about 20 seconds (depending on the length of the printing), and let's say that the next pick & place takes less than 20 seconds to complete, then the rest of the machine's time is idle. It is like buying a high-end Ferrari sports car, but it does not move in the garage. Because every machine on SMT is very expensive, we should make full use of their value as much as possible, and do not let them have any idle time, so that we can make money with it.

Therefore, some people come up with the way of Panelization to increase the use time of pasting machine, so as to greatly improve its use efficiency; However, we can not therefore let the solder paste printing machine wait empty, so that there is a positive and reverse Yin and Yang plate, so that more different parts can appear on the same board at the same time, so that the SMT long line with multiple pasting machines can give full play to its role.

Another important purpose is so that the upper and lower printing can be completed with only one line, and there is no need to waste the time of changing the line.

2. It can save the space wasted by bare board, which is to improve the efficiency of Panelization and save money

In order to mass produce and keep costs down, circuit board manufacturers usually buy some basic standard size boards at a quantity price, such as 16.16"x16.16", 18.32"x18.32", 20.32"x20.32"... Etc. Some may also purchase only some of the more heavily used substrate sizes, rather than the full range.

For some circuit boards that are not square shape, the design of the Yin and Yang board can have the opportunity to squeeze more than one to two circuit boards in the same subgrade board, so that the use efficiency of the board can be improved, and the purpose of cost saving.

Because the price of the circuit board is calculated based on the utilization rate of the substrate, if the same size of the substrate is used, the appearance of A design can only produce one circuit board, and B design can produce two circuit boards, the price of A board will be twice that of B board. For more information, see How to Select the number of PCB Boards.

Unfortunately, although the use of [Yin and Yang board] plate has the advantage of increasing efficiency and saving costs, but the two [Yang and Yang board] design also has its own shortcomings and limitations.


Iii. Wiring

This is a very important link in PCB design, PCB wiring has single-sided wiring, double-sided wiring and multi-layer wiring. There are two ways of wiring: automatic wiring and interactive wiring. In the wiring process to pay attention to the following problems:

(1) Line length. The copper wire should be as short as possible, especially in high frequency circuits. The corner of the copper wire should be rounded or beveled. The right Angle or sharp Angle will affect the electrical performance in the case of high frequency circuits and high wiring density. In addition, in double-sided wiring, the two sides of the wire should be perpendicular to each other, oblique or curved line, avoid parallel to each other, to reduce parasitic capacitance.

(2) line width. The width of the copper wire should be able to meet the requirements of electrical characteristics and easy to produce as the criterion, its minimum value depends on the current flowing through it, but generally should not be less than 0.2mm, if the plate area is large enough, the width of the copper wire should not be less than 0.3mm. The relationship between ground and power cable is: ground > Power cord > Generally, the width of the power cable is 1.2-2.5mm, and the width of the signal cable is 0.2-0.3mm.

(3) line spacing. The spacing between adjacent copper coated wires should meet the electrical safety requirements, and in order to facilitate production, the wider the spacing, the better. The minimum distance should be able to withstand at least the peak value of the voltage applied. Generally, the distance between 2000V potential difference copper wires should be greater than 2mm. In the case of low wiring density, the spacing should be as wide as possible. Usually, the line spacing should not be less than 0.3 mm.

(4) shielding and grounding. The common ground wire for copper wire should be placed on the edge of the circuit board as much as possible. On the circuit board should be as much as possible to retain the copper foil ground wire, so that the shielding ability can be enhanced.

Four, concluding remarks

PCB board drawing design is a complex and simple process. For the same circuit or the same instrument, even if the circuit with exactly the same components and parameters, the result may be very different due to the different component layout design and electrical wiring direction. Therefore, it is necessary to combine the three aspects of how to correctly design the structure of PCB component layout and the correct choice of wiring direction and the overall instrument process structure. Reasonable process structure can not only eliminate the noise interference caused by improper wiring, but also facilitate the installation, debugging and maintenance in production.

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