Do you know how to place special components on a PCB? Engineers must follow many specific rules and guidelines in PCB design in accordance with PCB design principles.
Below, we’ll briefly introduce some considerations for placing certain special components on a PCB.
Layout Requirements for Crimp Connectors
1) Engineers must not place any components taller than 3 mm within 3 mm of the surface of male-to-female or female-to-male crimp connectors.
In addition, engineers must not place soldered components within 1.5 mm of the surface.
On the reverse side of the crimp connector, no components shall be located within 2.5 mm of the center of the connector’s pin holes.
2) No components are allowed within 1 mm of the perimeter of straight male or straight female crimp connectors;
If engineers install a protective sleeve on the back of a straight male or straight female crimp connector, they must not place components within 1 mm of the sleeve’s edge.
If engineers do not install a protective sleeve, they must not place components within 2.5 mm of the crimp hole.
3) For live plug-and-socket pairs of grounding connectors used with European-style connectors, engineers must not place components within 6.5 mm of the tip of the long pin.
Engineers must not place components within 2.0 mm of the tip of the short pin.
4) For the long pin of a 2 mm FB power single-pin connector, engineers must not place components within 8 mm of the front end of the corresponding single-board socket.
Layout Requirements for Heat-Sensitive Components
1) When laying out components, place heat-sensitive components (such as electrolytic capacitors and crystal oscillators) as far away as possible from high-heat components.
2) Engineers should place heat-sensitive components close to the component under test.
They should also place them away from high-temperature areas.
This arrangement prevents other heat-generating components from affecting them and causing erroneous operation.
3) Place components that generate heat but are heat-resistant near the air outlet or at the top of the board.
However, if they cannot withstand high temperatures, place them near the air inlet as well.
Take care to stagger their positions relative to other heat-generating and heat-sensitive components in the direction of airflow.
Layout Requirements for Polarized Components
1) Engineers should orient polarized or directional THD components consistently and arrange them neatly.
2) Polarized SMCs should be oriented as consistently as possible on the board;
Engineers should arrange components of the same type neatly and aesthetically. (Polarized components include electrolytic capacitors, tantalum capacitors, diodes, etc.)
Layout Requirements for Through-Hole Reflow Soldering Components
1) For PCBs with non-conveyor-side dimensions greater than 300 mm, avoid placing heavy components in the center of the PCB whenever possible.
This minimizes the impact of the weight of through-hole components on PCB warpage during soldering.
It also reduces the impact of the insertion process on components already mounted on the board.
2) Engineers should place components near the side where insertion operations will take place to facilitate insertion.
3) For long components (such as memory module sockets), it is recommended that their long axis align with the direction of conveyance.
4) The distance between the edges of through-hole reflow soldering component pads and QFP, SOP, connectors, and all BGAs with a pitch ≤ 0.65 mm must be greater than 20 mm;
The distance from other SMT components must be > 2 mm.
5) The distance between the bodies of through-hole reflow soldering components must be greater than 10 mm.
6) The distance from the edge of the pad of a through-hole reflow soldering component to the conveyor side must be ≥10 mm, and the distance to the non-conveyor side must be ≥5 mm.
Conclusion
Proper placement of special components is essential for ensuring PCB reliability, manufacturability, and long-term performance.
By following specific layout guidelines for crimp connectors, heat-sensitive components, polarized components, and through-hole reflow soldering components, engineers can avoid issues such as thermal interference, assembly difficulties, soldering defects, and mechanical stress.
A well-planned PCB layout not only improves electrical performance but also enhances production efficiency and product stability.
Therefore, engineers should carefully consider component spacing, orientation, heat distribution, and assembly requirements throughout the PCB design process to create high-quality and reliable electronic products.
