Multilayer PCB Design PCB Layout Copper Laying

There are several reasons for Copper Laying In General

1.EMC.For large areas of power supply laying copper, will play a shielding role, such as PGND play a protective role.2.PCB process requirements. Generally, in order to ensure the plating effect or the lamination is not deformed, the PCB board with less wiring is coated with copper.3.Signal integrity requirements.

Give high-frequency digital signal a complete backflow path, and reduce DC network wiring. Of course, there is also heat dissipation, special device installation require to lay copper, and other reasons.

First, a great advantage of laying copper is to reduce the ground wire impedance (a large part of the anti-interference is caused by the reduction of the ground wire impedance). There is a lot of peak current in the digital circuit, so it is more necessary to reduce the ground wire impedance.

The significance of Copper Laying

1. Laying copper and ground wire are connected, which can reduce the return circuit area.2, a large area of laying copper is equivalent to reducing the resistance of the ground wire, reducing the pressure drop. From these two points, both digital and analog circuits should be copper-plated to increase the ability to resist interference.

Although the integration of semiconductors is getting higher and higher, many applications have ready-made system-on-chips, and many powerful and out-of-the-box development boards are becoming more and more accessible, but the use of electronic equipment in many applications still needs to be used. Custom PCB. In one-off development, even ordinary PCBs can play a very important role.

PCB is the physical platform of design and the most flexible component in the original component electronic design. This article will introduce several golden rules of PCB design. Since the birth of commercial PCB design 25 years ago, these rules have not changed and are widely applicable to various PCB design projects. Are they more mature for young electronic design engineers? The circuit board manufacturer is very instructive.

The following section describes the ten most effective design rules that electronic design engineers should keep in mind when using design software to achieve design layout and commercial manufacturing. Engineers do not have to implement these rules in chronological order or relative importance, they can drastically change product designs by simply following them.

Copper Laying Rule 1

Choose the right grid-set and always use grid spacing that matches most components. Although multi-grid seems to be effective, engineers can avoid problems when setting the interval, and if they can think more at the beginning of the PCB layout design, they can maximize the application of the board. Since many devices are available in various package sizes, engineers should use the product that best suits their design. In addition, polygons are critical to the placement of copper on the circuit board. When performing copper-clad copper, multi-grid plates usually have polygonal filling deviations. Although not as standard as single grids, they provide the required board life. .

Copper Laying Rule 2

Keep the path shortest and most direct. It sounds simple, but you should keep in mind at each stage, even if it means changing the board layout to optimize the wiring length. This is especially true for analog and high-speed digital circuits, where system performance is always partially limited by impedance and parasitic effects.

Copper Laying Rule 3

Use the power plane to manage the distribution of power and ground as much as possible. For most PCB design software, power layer copper is a faster and simpler choice. By connecting a large number of wires in the common connection, the highest efficiency and minimum impedance or voltage drop current can be guaranteed, while providing sufficient ground return paths. If possible, run multiple power lines in the same area of ​​the circuit board to verify that the ground layer covers most of the PCB layer, which helps the interaction between the lines running on adjacent layers.

Copper Laying Rule 4

Group related components with required test points. For example, placing the discrete components required by OpAmp operational amplifiers closer to the device allows bypass capacitors and resistors to work with them, helping to optimize the wiring length mentioned in Rule 2, while also enabling testing and fault detection . It becomes easier and easier.

Copper Laying Rule 5

Repeat the copy of the required circuit board on another larger circuit board for PCB imposition. Choosing the size of the equipment that best suits the manufacturer can help reduce prototyping and manufacturing costs. First, make the circuit board layout on the panel, contact the circuit board manufacturer to get the preferred size specifications for each panel, then modify your design specifications and try to repeat your design multiple times within these panel sizes.

Copper Laying Rule 6

Integrate component values. As a designer, you will choose discrete components with high or low component values ​​but the same performance. By integrating within a small set of standard values, the bill of materials can be simplified and costs can be reduced. If you have a series of PCB products based on the value of your preferred equipment, then you’d better be able to make the right inventory management decisions in a longer period of time.

Copper Laying Rule 7

‘Perform design rule checking (DRC) whenever possible. Although it only takes a short time to run the DRC function on PCB software, in a more complex design environment, as long as you perform checks during the design process, you can save a lot of time. This is a good habit. Every wiring decision is crucial, and you can always remind you of the most important wiring by implementing DRC.

Copper Laying Rule 8

Use screen printing flexibly. Screen printing can be used to mark various useful information for future use by panel manufacturers, service or test engineers, installers or equipment specialists. Not only need clear function and test point labels but also indicate as much as possible the direction of components and connectors, even if these comments are printed on the lower surface of the components used on the circuit board (after board assembly). The complete application of screen printing technology on the lower surface of the board reduces repetitive labor and simplifies the production process.

Copper Laying Rule 9

Decoupling capacitors must be selected. Don’t try to optimize your design by avoiding decoupling power lines and following the limitations in the component data sheet. Capacitors are inexpensive and rugged, so you can spend as much time assembling capacitors while following Rule 6 and using standard values ​​to keep your inventory tidy.

Copper Laying Rule 10

Generate PCB manufacturing parameters and verify them before submitting them for production. Although most motherboard manufacturers are happy to download and verify it for you, it is best to export the Gerber file yourself and use a free viewer to check whether it meets expectations to avoid misunderstandings. By personally verifying, you may even find some negligent errors, thus avoiding losing production by following the wrong parameters.

As circuit designs become more extensive and internal teams rely more and more on reference designs, the above basic rules will still be a feature of printed circuit board design, which we believe is very important for PCB design. By clarifying these basic rules, developers can flexibly increase the value of their products and make full use of the circuit boards they manufacture. Even if you are not familiar with circuit board design, remember these basic rules to speed up the learning process and increase your confidence.

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