1. Put the most important part first

What is the most important part?

Every part of the circuit board is important. However, the most important thing in the circuit configuration is these, you can call them “core components”. They include connectors, switches, power sockets, etc. In your PCB layout, put most of these components first.

2. Make the core/large components the center of the PCB layout

The core component is the component that realizes the important function of the circuit design. Make them the center of your PCB layout. If the part is large, it should also be centered in the layout. Then place other electrical components around the core/large components.

3. Two short and four separate

Your PCB layout should meet the following six requirements as much as possible. The total wiring should be short. The key signal should be short. The high voltage and high current signals are completely separated from the low voltage and low current signals. The analog signal and the digital signal are separated in the circuit design. The high frequency signal and the low frequency signal are separated. The high frequency parts should be separated and the distance between them should be as far as possible.

4. Layout standard-uniform, balanced and beautiful

The standard circuit board is uniform, gravity-balanced and beautiful. Please keep this standard in mind when optimizing the PCB layout. Uniformity means that the components and wiring are evenly distributed in the PCB layout. If the layout is uniform, gravity should also be balanced. This is important because a balanced PCB can produce stable electronic products.

5. First perform signal protection and then filter

PCB transmits various signals, and different parts on it transmit their own signals. Therefore, you should protect the signal of each part and prevent signal interference first, and then consider filtering the harmful waves of electronic parts. Always remember this rule. What to do according to this rule? My suggestion is to place the filtering, protection and isolation conditions of the interface signal close to the interface connector. Signal protection is performed first, and then filtering is performed.

6. Determine the size and number of layers of the PCB as early as possible

Determine the size of the circuit board and the number of wiring layers in the early stages of the PCB layout. it’s necessary. The reason is as follows. These layers and stacks directly affect the wiring and impedance of the printed circuit lines. Moreover, if the size of the circuit board is determined, the stack and width of the printed circuit lines need to be determined to achieve the expected PCB design effect. It is best to apply as many circuit layers as possible and distribute the copper evenly.

7. Determine PCB design rules and constraints

In order to successfully perform routing, you need to carefully consider the design requirements and make the routing tool work under the correct rules and constraints, which will greatly affect the performance of the routing tool. So what should I do? According to priority, all signal lines with special requirements are classified. The higher the priority, the stricter the rules for the signal line. These rules include the width of the printed circuit lines, the maximum number of vias, parallelism, mutual influence between signal lines, and layer restrictions.

8. Determine DFM rules for component layout

DFM is the abbreviation of “design for manufacturability” and “design for manufacturing”. DFM rules have a great influence on the layout of parts, especially the ptimization of the automobile assembly process. If the assembly department or PCB assembly company allows moving components, the circuit can be optimized to simplify automatic routing. If you are not sure about DFM rules, you can get free DFM service from PCBONLINE. The rules include:

In the PCB layout, the power supply decoupling circuit should be placed near the relevant circuit, not the power supply part. Otherwise, it will affect the bypass effect and cause the pulsating current on the power line and the ground line to flow, thereby causing interference.

For the direction of the power supply inside the circuit, the power supply should be from the final stage to the previous stage, and the power supply filter capacitor should be placed near the final stage.

For some main current wiring, if you want to disconnect or measure current during debugging and testing, you should set a current gap on the printed circuit line during PCB layout.

In addition, if possible, the stable power supply should be placed on a separate printed board. If the power supply and circuit are on a printed board, separate the power supply and circuit components and avoid using a common ground wire.

Why?

Because we don’t want to cause interference. In addition, in this way, the load can be disconnected during maintenance, eliminating the need to cut part of the printed circuit line and damage the printed circuit board.

9. Each equivalent surface mount has at least one through hole

During fan-out design, there should be at least one through hole for each surface mount equivalent to the component. In this way, when you need more connections, you can handle internal connections, online testing, and reprocessing of the circuit on the circuit board.

10. Manual wiring before automatic wiring

In the past, in the past, it has always been manual wiring, which has always been a necessary process for printed circuit board design.

Why?

Without manual wiring, the automatic wiring tool will not be able to successfully complete the wiring. With manual wiring, you will create a path that is the basis for automatic wiring.

So how to route manually?

You may need to pick and fix some important nets in the layout. First, route key signals manually or with the help of automatic routing tools. Some electrical parameters (such as distributed inductance) need to be set as small as possible. Next, check the wiring of key signals, or ask other experienced engineers or PCBONLINE to help check. Then, if there is no problem with the wiring, please fix the wires on the PCB and start routing other signals automatically.

Precautions:

Due to the impedance of the ground wire, there will be common impedance interference of the circuit.

11. Set constraints and rules for automatic routing

Nowadays, automatic routing tools are very powerful. If constraints and rules are set appropriately, they can complete almost 100% routing.

Of course, you must first understand the input parameters and effects of the automatic routing tool.

To route signal lines, general rules should be adopted, that is, the layers through which the signal passes and the number of through holes are determined by setting constraints and disallowed wiring areas. Following this rule, automatic routing tools can work the way you expect.

When completing a part of the PCB design project, please fix it on the circuit board to prevent it from being affected by the next part of the wiring. The number of routing depends on the complexity of the circuit and its general rules.

Precautions:

If the automatic routing tool does not complete signal routing, you should continue its work to manually route the remaining signals.

12. Optimize routing

If the signal line used for restraint is very long, please find reasonable and unreasonable lines, and shorten the wiring as much as possible and reduce the number of through holes.

Conclusion

As electronic products become more advanced, electrical and electronic engineers must master more PCB design skills. Understand the above 12 PCB design rules and techniques and follow them as much as possible, you will find that PCB layout is no longer difficult.