Practical Tips | Six Principles for Excellent PCB Circuit Board Design

The following aspects are routinely considered during PCB component layout: (1) Does the PCB shape match the overall equipment? (2) Is the spacing between components reasonable? Are there horizontal or height conflicts? (3) Is panelization required for the PCB? Are process edges reserved? Are mounting holes reserved? How are positioning holes arranged? (4) How to place the power supply module and handle heat dissipation? (5) Is the placement of components requiring frequent replacement convenient for replacement? Are adjustable components easy to adjust? (6) Is the distance between heat-sensitive components and heat-generating components considered? (7) What is the EMC performance of the entire board? How to layout to effectively enhance anti-interference capability?

Regarding the spacing between components, the distance requirements vary for different packages, and rule-based constraint setup in Altium Designer is overly complex and difficult to implement. Generally, lines are drawn on the mechanical layer to mark the outer dimensions of components, as shown in Figure 1. This allows designers to roughly judge the spacing when other components approach. This method is highly practical for beginners and helps them develop good PCB design habits.

Based on the above analysis, common PCB layout constraint principles are classified as follows.

(1) Under normal conditions, all components shall be placed on the same side of the PCB. Only when the top layer is overcrowded can some low-height and low-heat-dissipation components (such as chip resistors, chip capacitors, chip ICs, etc.) be placed on the bottom layer. (2) On the premise of ensuring electrical performance, components shall be placed on the grid and arranged parallel or perpendicular to each other for neatness and aesthetics. Component overlapping is generally not allowed; components shall be arranged compactly, and input and output components shall be separated and kept away from each other as much as possible without crossing. (3) Sufficient distance shall be maintained between components or wires with high voltage differences to avoid accidental short circuits caused by discharge or breakdown; layout space for these signals shall be prioritized. (4) High-voltage components shall be placed as far as possible in areas inaccessible to hands during debugging. (5) Components at the board edge shall be kept at a distance of at least two board thicknesses from the edge. (6) Components shall be evenly distributed across the board to avoid dense and sparse areas, improving product reliability.

(1) After placing fixed components, arrange the positions of each functional circuit unit one by one according to the signal flow direction, and perform local layout around the core component of each functional circuit. (2) Component layout shall facilitate signal transmission and maintain a consistent signal direction as much as possible. In most cases, the signal flow direction is arranged from left to right or top to bottom; components directly connected to input and output terminals shall be placed close to input/output connectors or plugs.

(1) Increase the distance between components with strong radiated electromagnetic fields and components sensitive to electromagnetic induction, or add shielding covers for shielding. (2) Avoid mixing high-voltage and low-voltage components and interleaving components with strong and weak signals as much as possible. (3) For components that generate magnetic fields (such as transformers, speakers, inductors, etc.), layout shall minimize the cutting of magnetic field lines on printed wires; the magnetic field directions of adjacent components shall be perpendicular to each other to reduce mutual coupling. Figure 2 shows inductors arranged perpendicular to each other at 90°.

(4) Shield interference sources or easily interfered modules, and the shielding cover shall be well grounded. The shielding cover layout is shown in Figure 3.

(1) Heat-generating components shall be preferentially placed in positions conducive to heat dissipation; separate heat sinks or small fans can be installed if necessary to reduce temperature and minimize impact on adjacent components, as shown in Figure 4. (2) High-power integrated blocks, high-power transistors, resistors, etc., shall be placed in easy-to-cool positions and separated from other components by a certain distance. (3) Heat-sensitive components shall be closely attached to the measured components and kept away from high-temperature areas to avoid malfunction caused by other heat-generating components. (4) When components are placed on both sides, heat-generating components are generally not placed on the bottom layer.

For adjustable components such as potentiometers, variable capacitors, adjustable inductor coils, and micro-switches, the layout shall comply with the structural requirements of the overall equipment: if adjusted externally, their positions shall match the adjustment knobs on the chassis panel; if adjusted internally, they shall be placed in easy-to-adjust positions on the PCB.


About Maxipcb
We offer one-stop solutions for design, simulation, testing, PCB manufacturing, component procurement and SMT assembly, enabling efficient development, rapid deployment and risk control across the full product lifecycle.
Serving the world in communications, industrial automation, aerospace, automotive, semiconductor and beyond, we build a safer, more connected future together.