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Double Board Design Steps

Shenzhen Inno Circuit Co.,Ltd | Updated: Jul 14, 2017

The two-layer circuit board ground wire is designed to form a grid-shaped frame, that is, in the printed circuit board side of the more parallel to the ground, the other side for the copy board vertical ground, and then they cross the place with metal holes connected (Hole resistance is small).

In order to take into account each IC chip should be installed near the ground, often every 1 ~ 115cm cloth a ground, so dense ground to make the signal loop area smaller, Double Layers PCB is conducive to reducing radiation. The ground network design method should be in the cloth signal line before, Double Layers PCB otherwise it is more difficult to achieve.

Principle of signal wiring for double - layer circuit board

Double-layer circuit board in the rational distribution of components to determine, followed by the first design to copy the power cord, and then cloth important line --- sensitive line, high-frequency line, after the cloth line --- low-frequency line. The key leads are preferably independent of the power supply, ground circuit, lead and very short, so sometimes in the key line edge of a ground line close to the signal line, Double Layers PCB let it form the smallest working loop.

Four-layer board top, the bottom of the wiring principle with the two-tier circuit board signal line, but also the first cloth key crystal, crystal circuit, clock circuit, CPU and other signal lines, must follow the circulation area as small as possible principle.

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 differential mode radiation definition: the circuit current flowing in the signal loop, the signal loop will produce electromagnetic radiation, Double Layers PCB 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

Where the radiation field strength is close to the operating frequency f2, the circulation area A, the operating current I, such as when the radiation field strength is the same as the operating frequency f2 When the operating 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 are as good as the reliability. The bigger the better, the narrower the signal jumps, The larger the wave component, the wider, Double Layers PCB 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.

Double Layer Board - Wiring Tips

It is appealing to use the autorouter to design pcb. In most cases, automatic routing of pure digital circuits (especially low-frequency signals and low-density circuits) will not be a problem. However, when attempting to use the cabling software to provide cabling for analog, mixed-signal, or high-speed circuits, there may be problems and potentially serious circuit performance problems.

 There are many things to consider about wiring, but the more troublesome problem is grounding. If the ground path is started by the upper layer, the grounding of each device is connected to the ground via the cable on the layer. For each device in the lower layer, a ground circuit is formed by connecting the upper hole on the right side of the circuit board to the upper layer. The immediate red flag that the user sees when checking the routing mode indicates that there are multiple ground loops. In addition, the lower ground circuit is at a level. Double Layers PCB Can reduce the digital switching δi / δt on the impact of analog circuits. It should be noted that the two double-layer circuit board in the lower part of the circuit board has a ground plane. This is designed so that engineers can quickly see the wiring when doing troubleshooting, often in the device manufacturer's demonstration and evaluation board. But the more typical approach is to lay the ground plane on the top of the board to reduce the electromagnetic interference (emi).

Double layer circuit board - Design steps

1, prepare the circuit schematic

2, create a new pcb file and load the component package library

3, planning circuit board

4, into the network table and components

5, automatic component layout

6, layout adjustment

7, network density analysis

8, wiring rules set

9, automatic routing

10, manually adjust the wiring