1. Orientation of component placement
A. The placement direction of components should be unified as far as possible after considering wiring, assembly, welding and maintenance requirements. The components on the PBA should have a unified direction as far as possible, and the components with positive and negative poles should also have a unified direction.
B. For the wave soldering process, the placement direction requirements of components are shown as follows:
Because of the shadow effect of wave soldering, the component direction and welding direction is 90°, wave soldering surface element
Part height limit is 4mm.
C. For the hot air reflow welding process, the placement direction of components has little influence on welding.
D. For PCB with components on both sides, components packaged with larger and denser IC, such as QFP and BGA, should be placed on the top layer of the board, plug-in components can only be placed on the top layer, the other side of the plug-in components (bottom layer) can only be placed on smaller components and patches with fewer pins and loose arrangement, columnar surface mount devices 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 plate shall not exceed 5.5mm; If a standard needle pressure test fixture is used, the element on the back of the board shall not exceed a maximum of 10mm.
F. Considering the actual working environment and its own heat, components should be placed to consider the factors of heat dissipation.
Note:
1. The arrangement of components should be conducive to heat dissipation. If necessary, use fans and radiators.
2. High power MOSFET and other components can be cooled by copper, and try not to release heat sensitive components around these components. If the power is particularly large, the heat is particularly high, you can add heat sink for heat dissipation.
