Requirements for PCB component layout placement.
The layout rules of PCB components should strictly refer to the content of (1), and the specific requirements are as follows:
1. The orientation of component placement (orientation)
A. After considering the wiring, assembly, welding and maintenance requirements, the placement direction of the components should be unified as much as possible. The components on the PBA are required to have a unified direction as much as possible, and the components with positive and negative poles must also have a unified direction.
B. For the wave soldering process, the component placement direction requirements are as shown in the figure:
Due to the shadow effect of wave soldering, the component direction is 90° to the soldering direction, and the element of the wave soldering surface
The height of the piece is limited to 4mm.
C. For the hot air reflow soldering process, the placement direction of the components has little effect on soldering.
D. For PCBs with components on both sides, larger and denser ICs, such as QFP, BGA, and other packaged components are placed on the top layer of the board, and plug-in components can only be placed on the top layer, and the other side of the plug-in component (bottom layer) Only small components and chip components with a small number of pins and loosely arranged can be placed. The cylindrical surface mount components should be placed on the bottom layer.
E. For the structure of the vacuum fixture, the maximum height of the components on the back of the board should not exceed 5.5mm; if the standard acupressure test fixture is used, the maximum height of the components on the back of the board should not exceed 10mm.
F. Considering the actual working environment and self-heating, etc., heat dissipation factors should be taken into consideration when placing components.
Note:
1. The arrangement of components should be conducive to heat dissipation. Fans and radiators should be used if necessary. It is especially important to add radiators to small-sized and high-calorie components.
2. High-power MOSFETs and other components can be coated with copper to dissipate heat, and try not to radiate sensitive components around these components. If the power is extremely high and the heat is extremely high, a heat sink can be added for heat dissipation.
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