PCB design translates electrical schematics into a functional product, and its quality directly impacts production efficiency and product reliability. For beginners, mastering PCB layout can be challenging despite familiarity with design software, and common issues often arise. Here, seasoned engineers from KKPCB share their PCB layout insights to help avoid these pitfalls and inspire best practices.

Component Placement Sequence

The recommended order for placing components on a PCB is as follows:

1. Place Fixed Components
   Begin with fixed-position components that integrate with the product’s physical structure (power sockets, switches, connectors). Once these are positioned, use the LOCK function in your design software to prevent accidental displacement.
2. Place Special and Large Components
   Next, add special components such as ICs, transformers, and heat-generating parts.
3. Place Smaller Components
   Lastly, add smaller passive components to complete the layout.

Edge Spacing for Components

Components should ideally be at least 3mm from the PCB edge, or the distance should match the PCB thickness. This spacing allows room for manufacturing processes such as wave soldering and shape processing. If space constraints necessitate placing components near the edge, consider adding a 3mm auxiliary border with a V-shaped groove, which can be broken off during assembly.

High-Voltage and Low-Voltage Isolation

For PCBs carrying both high and low voltage circuits, isolate components accordingly. The isolation distance varies by required withstand voltage, generally 2mm for 2000V, increasing with higher voltages. For example, a 3000V withstand voltage requires at least 3.5mm separation. Grooves can be used to enhance creepage distance and improve insulation between high and low voltage areas.

PCB Routing Guidelines

1. Optimize Trace Lengths
   Trace length should be minimized, especially in high-frequency circuits, to reduce parasitic effects and signal degradation.
2. Use Rounded Corners
   Sharp angles can affect performance in high-frequency applications. Use rounded bends for better signal integrity.
3. Avoid Parallel Traces on Multi-Layer PCBs
   For two-sided boards, place traces on adjacent layers perpendicularly to reduce parasitic coupling.
4. Separate Input and Output Traces
   To prevent feedback loops and interference, avoid parallel routing of input and output signals and add ground traces between these lines if possible.

Trace Widths

The trace width must support electrical performance and be producible. Typically:

• The minimum trace width should be no less than 0.2mm.
• For high-density layouts, 0.3mm spacing and width can suffice.
• In high-current applications, a 1-1.5mm trace can handle up to 2A with minimal temperature rise when the copper thickness is 50µm.

Spacing Between Conductors

Minimum spacing should meet safety standards, including operating and peak voltages. The following considerations are essential:

• For high and low-level signal lines, increase spacing where possible.
• If the wiring density is low, space between traces can be further widened to enhance signal integrity.

Grounding and Shielding

1. Ground Line Placement
   Arrange the common ground trace along the PCB edge, reserving as much copper for grounding as possible. This not only improves shielding but also enhances transmission line characteristics.
2. Looped or Meshed Grounding
   In multi-component layouts, especially with high-power elements, loop or mesh the ground to reduce ground potential differences and improve noise immunity.
3. Align Power and Ground Planes with Data Flow
   To suppress noise, parallel power and ground planes with the data flow direction. Multi-layer PCBs can use additional layers as ground and power planes, placing these internal layers while signals run on external ones.

KKPCB provides global customers with one-stop services from PCB layout, prototype PCB proofing, PCB manufacturing, PCBA processing (including SMT and DIP), PCBA testing, PCBA product assembly and outbound packaging. You could provide a Gerber file or BOM list to us, we will offer the finished PCB products or PCB assembly which are satisfied with you.