What is PCB Design?

The design of the printed circuit board is based on the circuit schematic diagram to realize the functions required by the designer. The design of the printed circuit board mainly refers to the layout design, which needs to consider various factors such as the layout of external connections, the optimal layout of internal electronic components, the optimal layout of metal connections and vias, electromagnetic protection, and heat dissipation. Good layout design can save production costs and achieve good circuit performance and heat dissipation performance.

AiPCBA has a professional PCB design team and a professional service team. Our designers have more than 8 years of industry experience and more than 15 years of senior designers. We mainly use Cadence Allegro, Pads, Protel, and other software, and can independently complete the high-speed, high-density, digital-analog hybrid PCB layout design of PC motherboards, industrial control boards, and consumer electronics motherboards, medical equipment, communication electronics, optical networks, and other electronic products.

AiPCBA is based on printed circuit board design and manufacturing services, and actively creates a one-stop business of PCB design, PCB manufacturing, SMT assembly, and components sourcing. Learn More About AiPCBA Turnkey PCB Assembly.

Preparation before PCB design

PCB Design Layout Check

General Rules for PCB Design

First, consider the size of the PCB size. When the PCB size is too large, the printed circuit lines are long, the impedance increases, the anti-noise capability decreases, and the cost also increases. If it is too short, the heat dissipation is not good, and the adjacent printed circuit lines are easily disturbed. After the PCB size is determined, the location of the special components is determined. Finally, according to the functional units of the circuit, all components of the circuit are laid out.

A.Shorten the connection between high-frequency components as much as possible, and try to reduce their distribution parameters and mutual electromagnetic interference. Components susceptible to interference should not be placed too close to each other, and input and output components should be kept as far apart as possible.

B.There may be a high potential difference between some components or wires, and the distance between them should be increased to avoid accidental short circuits caused by the discharge. Components with high voltage should be arranged as far as possible in places that are not easily accessible by hand during debugging.

C.Components' weights are more than 15g and should be secured with brackets and then soldered. Those components that are large, heavy, and generate a lot of heat should not be installed on the printed board but should be installed on the chassis bottom plate of the whole machine, and the heat dissipation problem should be considered. Thermal elements should be kept away from heating elements.

D.For the layout of adjustable components such as potentiometers, adjustable inductance coils, variable capacitors, and micro switches, the structural requirements of the whole machine should be considered. If it is adjusted in the machine, it should be placed on the printed circuit board where it is convenient to adjust. If it is adjusted outside the machine, its position should be adapted to the position of the adjustment knob on the chassis panel.

B.The layout is centered around the core components of each functional circuit. Components should be evenly, neatly, and compactly arranged on the PCB, minimizing and shortening the leads and connections between components.

C.For circuits operating at high frequencies, the distribution parameters between components should be considered. In general, the components should be arranged in parallel, so that it is not only beautiful, but also easy to install and weld, and it is easy to volume production..

A.The wire used at the input and output terminals should avoid being adjacent to each other as much as possible, and it is best to add a ground wire between the circuit.

B.The minimum width of printed circuit board wires is mainly determined by the adhesion strength between the wires and the insulating substrate and the value of the current flowing through them. When the thickness of the copper foil is 0.5 mm and the width is 1-15 mm, the temperature rise will not be higher than 3 ℃ when passing a current of 2 A. Therefore, the width of the wire is 1.5 mm to meet its requirements. For integrated circuits, especially digital circuits, wires with a width of 0.02 to 0.3 mm are usually selected. Of course, use as wide as you can, especially power and ground wires. The minimum spacing of conductors is mainly determined by the worst-case insulation resistance and breakdown voltage between conductors. For integrated circuits, especially digital circuits, as long as the process allows, the spacing can be less than 0.1 to 0.2 mm.

PCB Design Considerations

1)PCB design needs to set different points at different stages, and use large grid point for device layout in the layout stage.

2)For large devices such as IC and non-positioning connectors, the grid point accuracy of 50~100mil can be used for layout. For passive small devices such as resistors, capacitors and inductors, 25mil grid points can be used for layout. Large grid-point accuracy facilitates device alignment and layout aesthetics.

3)In general, all components should be arranged on the same side of the printed circuit board. Only when the top components are too dense, some devices with limited height and low heat generation, such as chip resistors, chip capacitors, and chip IC can be placed on the bottom layer.

4)Avoid arranging important signal lines such as clock and reset signals on the edge of the PCB.

5)The distance between the chassis ground wire and the signal wire is at least 4 mm. Keep the aspect ratio of the chassis ground wire less than 5:1 to reduce inductive effects.

6)Devices and lines that have been positioned are locked with the LOCK function, so that they cannot be mishandled in the future.

7)The minimum wire width should not be less than 0.2mm (8mil). In high-density and high-precision printed circuits, the wire width and spacing are generally 12mil.

8)When designing the traces between the IC pins of the DIP package, when two lines are passed between the two pins, the diameter of the pad can be set to 50mil, and the line width and line spacing are both 10mil. When only one line passes between the two feet, the diameter of the pad can be set to 64mil, and the line width and line spacing are both 12mil.

9)When the diameter of the pad is 1.5mm, in order to increase the peel strength of the pad, an oblong pad can be used, and the length is not less than 1.5mm and the width is 1.5mm.

10)When the design encounters a thin wire connected to the pad, the connection between the pad and the wire should be designed into a water drop shape, so that the pad is not easy to peel, and the wire and the pad are not easily disconnected.

Turnkey PCB Assembly in AiPCBA

AiPCBA not only has rich design experience in PCB design but also is a manufacturer that provides a one-stop PCBA service. The one-stop PCBA service we offer is from PCB manufacturing, BOM sourcing, PCB assembly, SMT, THT, PCBA testing, product assembly, packaging, and delivery. You just need to deal with your design while we take care of the rest. This is also what AiPCBA has always advocated, simplifying the customers’ work. Our customers only need to focus on design, and AiPCBA is responsible for purchasing and producing and delivering products at the fastest speed.