PCB layout is laying conductive signal path connecting the various devices, like decorate the road, connecting the city by car.
Road construction requires a return to a two-line, PCB routing the same principle, you need two lines form a loop ,for the low-frequency circuit point is a circuit; for the electromagnetic field in terms of speed it is the transmission line, the most common, such as differential signals line. Such as USB, cable, etc.
We can say that the differential signal lines, is the ideal model for connecting devices signals. The higher the signal requirements, the more you want to close the differential signal lines.
When the device is very much in a board, if distribute it as the differential lines: one problem is PCB area is too large, the second problem is should be distribute into 2N lines heavy workload, It is very difficult, so the actual needs of the people for the proposed multi-layer PCB the concept, The typical is the double-sided PCB board. The bottom layer as a common reference circuit wiring ,so only distribute N + 1 lines, PCB layout is also greatly reduced
Common reference circuit, we often say that the reference ground, for most embedded industry, because the signal is digitized ,signal quality requirements is not very high. Using whole Layer of reference ground not only reduce the board size, but also improve efficiency , it saves time. In fact, the board is reduced to shorten the length of the signal line, and some may be offset because the reference to the signal quality degradation caused problems, so in practice, such incorporation by reference to the effect of PCB layout, the difference was similar to the ideal model line
In the dual-panel design, usually there are often cross-line, you need to do cross-line jumper to ground switching, noted that this jumper can not too long, if too long, easy to split reference ground, especially for some signal line high quality requirements, refer to the bottom it can not be split. Otherwise the signal circuit was completely destroyed, reference ground line will be useless. generally speaking, reference ground line only suitable for short jumper with signal lines, signal cables distribute on top layer, or use more layers of PCB board
PCB layout carrier is a PCB board, general reference ground to the PCB edge 1mm from nearby, the signal from the reference line to the near edge of 1mm, so the signals are confined within the PCB board, this way can be reduced EMC radiation
In our life, we can see PCB find PCB everywhere, the telephone, computer, car, radio, etc; it is a used in many electronics products. PCB looks like just a simple board, but it is a necessary part in most of the electronics products. Putting a simple PCB can make the smart phones smarter and slimmer. Comparing the machine, it has small body and takes small space in the machine; it allows the mounting of other electronic components directly on to it. So, what is PCB? Today, we are going to get some basic knowledge of PCB.
The full name of PCB is Printed Circuit Board. It has different layers, from single layer to multilayer. Printed circuit board is a non conducted board, such as plastic and glass on to it which the pattern is printed by conducting metal such as copper. This allows the current to pass only through the conducting pattern at the required rate, which is controlled by using resistors, transistors and amplifiers.
For creating a PCB, we need finish four main steps, which is designing, printing, etching and completing the board. Now, we will have a simple introduction of these four steps one by one.
Designing is the very beginning of one PCB created. For designing a PCB, we must use designing software. This step is the most important part and the function of a device is depended by how the circuit designed. But please note that if you design the circuit faultily, all of work at creating of the board might be wasted. So, the engineer must be very careful. Once the design finished, we will get a Gerber file and it will be used to build the board.
After finishing the design, we can go on and enter into printing process. This is the stage where the circuit design is stenciled on copper covered circuit board. The pattern of the circuit is created by using non corrosive ink, so that only the pattern of the circuit will be remained when the board is immersed in etching process.
Now, we are at the third stage where the board is immersed in an etching process that is a mixture of hydrogen peroxide and muriatic acid. The etching dissolves or melts away the unprotected copper coating and only the circuit design which was covered with noncorrosive ink remained. The printing which consists of lines of copper that remained on the board, this is called trances. The circuit board is finally washed in neutralizing bath or cold water to remove any traces of the remaining etching.
Finally, the board goes into the drilling step. Drilling holes, where the components will be attached. Once this step is finished, the PCB is ready to be used.
This is just a simple explanation of the production process of the printed circuit board. Every factory has their different manufacturing process. We still need to work hard to get deeper knowledge of PCB.