The component layout should be designed according to the SMT chip processing production equipment and process characteristics and requirements. Different processes, such as reflow soldering and wave soldering, have different layouts for components. During double-sided reflow soldering, there are also different requirements for the layout of side A and side B. Selective wave soldering and traditional wave soldering also have different requirements.
The basic requirements of the SMT process for component layout design are as follows:
The distribution of components on the printed circuit board should be as uniform as possible. Large-mass components have a large heat capacity during reflow soldering, and excessive concentration will easily lead to low local temperature and lead to virtual soldering. At the same time, the uniform layout is also conducive to the balance of the center of gravity. It is not easy for components, metallized holes and pads to be damaged.
The arrangement direction of components on the printed circuit board, similar components should be arranged in the same direction as much as possible, and the characteristic direction should be the same, which is convenient for component mounting, welding and testing. For example, the positive electrode of the electrolytic capacitor, the positive electrode of the diode, the single-pin end of the triode, and the first pin of the integrated circuit are arranged in the same direction as possible. All part numbers are printed in the same orientation.
The size of the SMD rework equipment heating head should be left around the large components to be able to operate.
Heat-generating components should be kept as far away from other components as possible, and are generally placed in corners and ventilated positions in the chassis. The heating components should be supported by other leads or other supports such as heat sinks, so that the heating components and the surface of the printed circuit board maintain a certain distance, with a minimum distance of 2mm. The heating element connects the heating element body to the printed circuit board in the multi-layer board. It is designed as a metal pad, and is connected with solder during processing, so that the heat can be dissipated through the printed circuit board.
Temperature-sensitive components should be kept away from heat-generating components. Such as triodes, integrated circuits, electrolytic capacitors and some plastic-shell components, etc., should be kept away from bridge stacks, high-power components, radiators and high-power resistors as much as possible.
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