Double-layer PCB board design and wiring principles

This article describes the principles of double-layer pcb board design and wiring. By reading this article, you can better understand the principles of double-layer pcb board design and wiring, so that you can correctly carry out double-layer pcb board design and wiring.

Double-layer pcb boards are double-layer circuit boards, which have wiring on both sides of the board, but to use the wires on both sides, there must be a proper circuit connection between the two sides. This “bridge” between the circuits is called a pilot hole. A pilot hole is a small hole in the PCB, filled or coated with metal, which can be connected to the wires on both sides. When you draw a double-sided pcb board with PROTEL, you draw the wires on the top layer to connect the components, that is, you draw the board on the top layer; select BottomLayer and draw the wires on the bottom layer to connect the components, that is, you draw the board on the bottom layer. If you have a need for components soldered on a PCB.

The above is to draw a double-layer PCB, meaning that the wires are drawn on both the top and bottom layers of a PCB board. The double panel solves the difficulty in the single panel because of the interleaved wiring (which can be conducted through holes to the other side), i.e. there is wiring on both the front and back side, and components can be soldered on the front side or the back side, it is more suitable for use in more complex circuits than the single panel.


What are Double layer PCB board – design and wiring principles?

The double-layer board ground is designed as a grid-like enclosure formation, i.e. more parallel ground lines are laid on one side of the printed board and the other side is a vertical ground line for the copy board, which is then connected with metallized vias where they cross (the vias should have a small resistance).

To take into account that each IC chip near should have a ground, often every 1 to 115cm cloth a ground, so that the dense ground so that the signal loop area is smaller, conducive to reducing radiation. The ground network design method should be in the cloth before the signal line, otherwise, it is more difficult to achieve.

What is Double-layer pcb board signal line wiring principle?

Double-layer board in a reasonable layout of components to determine, immediately after the first design of the ground network copy board power lines, and then cloth important lines – sensitive lines, high-frequency lines, after the cloth general lines – low-frequency lines. Key leads preferably have an independent power supply, ground circuit, and leads and are very short, so sometimes in the key line side cloth, a ground line is immediately adjacent to the signal line so that it forms the minimum working circuit.

Four-layer board top and bottom wiring principles with double-layer board signal lines, but also first cloth key crystal, crystal circuit, clock circuit, CPU, and other signal lines, be sure to comply with the principle of the smallest possible loop current area.

Printed circuit board IC circuit work, mentioned several times before the loop current area, the actual it comes out in the concept of differential mode radiation. Such as the definition of differential mode radiation: circuit work current flow in the signal loop, this signal loop will produce electromagnetic radiation because this current is the differential mode, so the signal loop generated by the radiation is called differential mode radiation, the radiation field strength of the formula: E1 = K1 – f2 – I – A / γ

Where: E1 – the radiation field strength at γ of the printed board circuit space of the differential mode copy by the differential mode radiation formula can be seen, the radiation field strength and the working frequency f2, loop area A, work current I proportional, such as when the working frequency f determined, the size of the loop area is the key factors that can be directly controlled in our design, while the working speed of the loop, the current as long as it meets the reliability, not the larger the better, the signal on the jump The narrower the jump along the next jump, the greater its harmonic component, the wider, the higher the electromagnetic radiation, the greater the power of its current is bound to be large (as already pointed out above), which we do not expect.

Below are given several logic circuits that can meet the radiation class B standard allowed for the reference value of the loop current area. As can be seen, the faster the circuit switches, the smaller the area allowed.

Critical links can be surrounded by an earth wire if possible. After the PCB has been wired, all gaps can be covered by ground lines, but care must be taken that these cover lines are shorted to low impedance couplings with large ground layers so that good results can be achieved (note: conditions such as creepage distances should be met where gaps are required).

What are Double-layer pcb boards – wiring tips?

The use of automatic routers for PCB design is attractive. In most cases, automatic routing is not so problematic for purely digital circuits (especially for low-frequency signals and low-density circuits). However, when attempting to use the auto wiring tools provided by the wiring software for analog, mixed-signal, or high-speed circuits, problems can arise and can cause very serious circuit performance problems. There are many things to consider about wiring, but one of the more vexing issues is the grounding method. If the grounding path starts at the upper level, each device is connected to the ground via a tie wire on that level. For each device on the lower level, the ground loop is formed by connecting the through-hole on the right side of the board to the upper level.

The immediate red flags that the user will see when checking the wiring pattern indicate the presence of multiple ground loops. In addition, the ground loops on the lower level are connected at a horizontal line. This reduces the impact of digital switching δi/δt on the analog circuit. It should be noted, however, that both double-layer boards have a ground plane on the lower level of the board. This is designed to allow the engineer to see the wiring quickly when troubleshooting and is often found on device manufacturers’ demonstration and evaluation boards. However, it is more typical to lay a ground plane on the top layer of the board to reduce electromagnetic interference (EMI).

What are Double-layer pcb board – design operation steps?

1. Prepare the circuit schematic

2. Create a new PCB file and load the component package library

3. Planning the board

4. Load the network table and components

5. Automatic layout of components

6. Layout adjustment

7. Network density analysis

8. Wiring rules setting

9. Automatic wiring

10. Manual adjustment of wiring

What are Double layer PCB board – PCB design experience (embedded hardware experience)?

  • Clearance spacing is generally 10mil minimum, 5mil minimum for high-density wiring
  • Lines from the solder socket, at least 10mil out of the line, and then change direction, do not slant out of the line, will produce sharp angles, not beautiful
  • Use double holes for the main power line (higher current) to prevent one hole from failing to work.
  • Power inlet capacitor using 100uf and 104 ceramic way outlet capacitor capacity should be large enough to meet the circuit requirements (high current will not pull down the voltage instantly). The closer the shutdown diode is to the output pins of the power supply chip, the better
  • Power supply part resistors and capacitors to account for power, packaging to meet the power requirements
  • Multiple RF circuits, you can cross the RF cloth on different layers to reduce interference
  • To pay attention to the location of the lead, to meet the schematic, not the same signal can be any location can be led out
  • The same characteristics of the signal line wiring signal characteristics to be the same, the distance as long as possible, the same number of holes
  • Some power supply decoupling capacitors filter capacitors can be placed on the opposite side of the pin to save space and shorten the wiring distance
  • Wiring using warp and weft wiring, the upper and lower layers of wiring clear, but also to reduce over-hole, reduce interference
  • Strictly account for the rated current and rated power of the power supply chip when drawing the schematic diagram, so that it meets the actual load requirements
  • Wiring should be placed around straight plug-in components, not in the core wiring area, which will produce interpolation and affect the warp and weft alignment. Prevent interpolation, because when soldering may scratch the group soldering layer of the line, so when soldering the pin may produce adhesion
  • Copper laying under the network chip is prohibited
  • Soldering crystal strict drop, because the excessive shock will affect its performance
  • The four corners of the board should be rounded to prevent scratching
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