Experience Summary - Easily get the key points of PCB layout design

writer: G January 23, 2018

PCB layout tips:

1. According to the flow of the circuit arrangement of the location of each functional circuit unit, so that the layout of the signal flow, and make the signal as consistent as possible.

2. The core components of each functional unit as the center, around him to layout. Components should be uniform, overall, compact arranged on the PCB, minimize and shorten the leads and connections between the various components.

3. Working under high frequency circuit, to consider the distribution of parameters between components. General circuit components should be arranged in parallel as much as possible, so that not only beautiful, but also easy to install dry, easy to mass production.


PCB layout rules:


1. Different components on the circuit board near the pad between the minimum spacing should be 1MM or more.

2. Under normal circumstances, all the components should be arranged on the same side of the circuit board, only the top layer of the device is too dense, can some highly limited and the heat of small devices, such as chip resistors, chip capacitors, paste IC and other low-level.

3. To ensure the electrical properties of the premise, the components should be placed on the grid parallel to each other or vertical arrangement, in order to neat, beautiful, in general, do not allow components overlap; components arranged in compact, components in the entire layout should be Distribution, density and consistency.

4. Away from the edge of the circuit board is generally not less than 2MM. The best shape of the circuit board is rectangular, aspect ratio of 3: 2 or 4: 3. Circuit board is larger than 200MM by 150MM, should consider the circuit board can withstand Mechanical strength.


The general order of components to be placed:

1. Place and structure closely with the components, such as the power outlet, lights, switches, connectors and so on.

2. Place special components, such as large components, heavy components, heating components, transformers, ICs and so on.

3. Place small components.


Layout check:

1. The circuit board size and drawing requirements processing size is consistent.

2. All levels of conflict. Such as components, frame, the level of private printing is reasonable.

3. The layout of components is balanced, arranged in neat rows, whether it has all finished cloth.

4. Commonly used components are easy to use. Such as switches, plug-in board equipment, to be replaced frequently, such as components.

5. Thermal components and heating components distance is reasonable.

6. Heat dissipation is good.

7. The line interference problems need to be considered.


Special components and layout design:


In the PCB, the special components refers to the high-frequency part of the key components, the circuit of the core components, easily interfered with the components, with high-pressure components, heat components, and some of the opposite sex components , The location of these special components need careful analysis, with the layout of the circuit to meet the functional requirements and production needs. Improper placement of them can create circuit compatibility issues and signal integrity issues that can lead to PCB design failures.

In the design of how to place special components first consider PCB size. PCB size is too large, the printing line long, increased impedance, decreased resistance to drying, the cost increases; too small, the heat is not good, and the adjacent lines susceptible to interference. After determining the size of PCB, in determining the pendulum position of special components. Finally, according to the functional unit, the layout of all the components of the circuit. The location of special components in the layout generally follow the following principles:

1. Try to shorten the connection between high-frequency components, try to reduce their distribution parameters and mutual electromagnetic interference. Disturbed components can not be too close to each other, the input and output should be as far away as possible.

2. Some components or wires may have a higher potential difference, should increase their distance, in order to avoid discharge caused by accidental short circuit. High-voltage components should be placed in the reach of hand.

3. The weight of more than 15G components, available bracket to be fixed, and then welded. Those heavy and hot components, should not be placed on the circuit board, should be placed on the main chassis of the bottom plate, and consider the heat problem. Thermal components should be kept away from heat components.

4. And the potentiometer, adjustable inductance coil, variable capacitors, micro-switches and other adjustable components layout should consider the structural requirements of the entire block wrench, some commonly used switch, the structure allows, should Place in easy reach of your hand. The layout of components to a balanced, dense degree, not top-heavy.

The success of a product, one should pay attention to the intrinsic quality. But to take into account the overall appearance, both more perfect wrench, to be successful products.


PCB layout design grid points set tips:

Design in different stages need to set different points, in the layout stage can be used to carry large grid layout of the device;

For IC, non-locating connectors and other large devices, you can use the 50 ~ 100mil lattice accuracy of the layout, and for passive components such as small capacitors and inductors, the use of 25mil lattice layout. The precision of the large grid facilitates the alignment and layout of the device.


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