PCB (Printed Circuit Board), the Chinese name for the printed circuit board, also known as printed circuit board, is an important electronic components, is the support of electronic components, electronic components is the carrier of electrical connections. Because it is made using electronic printing, it is called "printed" circuit board.
And Double Layer PCB board that is double-layer circuit boards, double-layer circuit board on both sides of this circuit board wiring, but to use the two sides of the wire, must be between the two sides have the appropriate circuit connection Caixing. The "bridge" between such circuits is called a guide hole. The guide hole is in the pcb, filled with or coated with metal holes, it can be connected with the two sides of the wire. Use PROTEL to draw double-sided pcb board, in TopLayer (top layer) to draw wire connection components, is in the top drawing board; select BottomLayer (bottom), in the bottom of the wire to connect components, is the bottom of the drawing board. Above is to draw Double Layer PCB, meaning a pcb board in the top and bottom are painted wire. The double panel solves the difficulty of wiring in the single panel because of the wiring (which can pass through the hole to the other side), that is, both sides are wiring, components can be welded on the front, can also be welded in the opposite, it is more suitable for use Single-panel more complex on the circuit. In the case of
Double Layer PCB board - design and routing principles
The two-layer board ground wire is designed to form a grid-shaped frame, that is, the parallel lines are printed on the side of the printed circuit board, and the other side is the vertical ground of the copy board, and then connected with the metal via holes Hole resistance is small). In the case of
In view of each IC chip should be provided near the ground, often every 1 ~ 115cm cloth a ground, so dense ground to make the signal loop area smaller, is conducive to reducing radiation. The ground network design method should be in the cloth signal line before, Double Layer PCB otherwise it is more difficult to achieve. In the case of
Two - layer pcb board signal line wiring principle
Double board in the rational layout of the components to determine, followed by the first design to copy the power cord, and then cloth important line --- sensitive lines, high-frequency line, after the cloth line --- low-frequency line. The key leads are preferably a separate power supply, ground circuit, lead and very short, so sometimes the edge of the line with a line close to the signal line, let it form the smallest working loop. In the case of
Four-layer board top and bottom of the wiring principle with the two-layer signal line, but also the first cloth key crystal, crystal circuit, clock circuit, Double Layer PCB CPU and other signal lines, must comply with the principle of small circulation area as small as possible. In the case of
PCB IC circuit work, the front mentioned many times in front of the circulation area, the actual source of its difference in the concept of differential mode radiation. Such as the definition of differential mode radiation: the circuit current flowing in the signal loop, the signal loop will produce electromagnetic radiation, because this current is differential mode, so the signal loop radiation is called differential mode radiation, the radiation Field calculation formula: E1 = K1 · f2 · I · A / γ
In the formula: E1 --- differential mode copy board circuit space γ radiation field intensity from the differential mode radiation formula can be seen, the radiation field strength and the operating frequency f2, circulation area A, operating current is proportional to, such as when After the work frequency f is determined, the size of the circulation area is the key factor that can be directly controlled in our design. At the same time, the working speed and current of the circulation should not satisfy the reliability. The bigger the better, the narrower the signal jumps, The larger the wave component, the wider, the higher the electromagnetic radiation, the greater the power the current must be large (the above has been pointed out), which we do not expect. The faster the circuit switch, the smaller the area allowed. In the case of
The key to the line, if possible around it can be surrounded by the ground. After the PCB copy board is finished, Double Layer PCB the available ground will cover all the voids, but it must be noted that these covered ground lines should be shorted with the low impedance of the large strata, so that good results can be achieved (Note: Should meet the conditions, such as creepage distance, etc.).