/How to design pcb manufacturing component orientations and spacing
The layout design of components is especially important in order to improve the welding efficiency of pcb manufacturing during pcb manufacturing production. The spacing and direction of some components will affect the welding quality. Two factors are mainly considered for the components direction.
1. Weldingdirection , that is, the direction of the wave or reflow soldering;
2. The same kind components are rehearsed in the same direction as much possible, asthe characteristic direction is the same, so as to facilitate the mounting, soldering and detection of components, such as the polarity of the electrolytic capacitor, the positive pole of the diode, and the first pin rehearsal direction of the integrated circuit as consistent as possible.
When the pcb circuit board enters the reflow soldering, in order to make the two soldering ends of the SMC and the pins on both sides of the SMD synchronously heated, the soldering defects of tombstoning, shifting, and soldering end are separated from the pads due to the inability of the soldering ends of the components to be synchronously heated. The long axis of the SMC on the PCB should be perpendicular to the direction of the conveyor belt of the reflow oven. The long axis of the SMD should be parallel to the direction of the conveyor belt of the reflow oven. During the wave soldering, in order to make the two soldering ends of the SMC and the soldering ends of the SMD simultaneously contact the solder peaks, the long axis of the SMD should be parallel to the direction of the wave soldering machine, as shown in Figure 1, and the component layout and the direction of arrangement should follow the principle of smaller components in front and avoiding mutual shield as much as possible.
Pcb manufacturing component spacing design, in order to ensure that the PCB does not occur bridging connection between the solder joints, and leave a certain maintenance gap around the large components, when distributing components, pay attention to the minimum spacing between components. The wave soldering craft is slightly wider than the reflow soldering craft. The minimum spacing between surface mount components of typical pcb assembly density is as follows:
(1) 1.25mm between chip components, SOT, between SOP and chip components
(2) 2mm between SOP, SOP and QFP
(3) 2.5mm between PLCC and chip components, SOP and QFP
(4) 4mm between PLCC
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