“The component layout should be designed according to the smt chip processing production equipment and process characteristics. Different processes, such as smt patch reflow soldering and wave soldering, have different layouts of components: when double-sided reflow soldering, there are also different requirements for the layout of the main and auxiliary surfaces, and so ON.
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The component layout should be designed according to the smt chip processing production equipment and process characteristics. Different processes, such as smt patch reflow soldering and wave soldering, have different layouts of components: when double-sided reflow soldering, there are also different requirements for the layout of the main and auxiliary surfaces, and so on.
(1) The distribution of components on the PCB should be as uniform as possible.
(2) 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 mounting, welding and testing.
Process requirements and multi-faceted consideration of component layout design
(3) A certain maintenance gap should be left around the large device, and the size of the heating head of the SMD rework equipment can be left for operation.
(4) The heating element should be kept as far away from other components as possible, and it is generally placed in the corners and in the ventilated position of the chassis.
(5) Keep temperature-sensitive components away from heating elements.
(6) The layout of components and parts that need to be adjusted or replaced frequently, such as potentiometers, adjustable inductance coils, variable Capacitors, micro switches, fuses, buttons, plug-ins, etc., should be considered in the overall structure requirements. , in a position for easy adjustment and replacement.
(7) Fixing holes should be provided near the terminals, plug-in parts, the center of the long string terminals and the parts that are often subjected to force, and there should be a corresponding space around the fixing holes to prevent deformation due to thermal expansion and warping during wave soldering. phenomenon.
(8) For some parts (such as transformers, electrolytic capacitors, piezoresistors, bridge stacks, radiators, etc.) that have large body (area) tolerances and low precision and require secondary processing, the interval between them and other components is the same as the original one. On the basis of the setting, add a certain amount of wealth.
(9) Do not place valuable components on the corners, edges, or near connectors, mounting holes, slots, cutting, gaps and corners of the PCB. These positions are high stress areas of the PCB, which are easy to Causes cracks or cracks in SMT chip processing solder joints and components.
(10) The component layout should meet the process requirements and spacing requirements of smt processing reflow soldering and wave soldering.
①When mixing on one side, the smt patch mounting and plug-in components should be placed on the A side.
②When double-sided reflow soldering is used for mixed assembly, it is required that the FPCB design should arrange the large components on the main (A) side and the small components on the axis (B) side. The design of components placed on the axis (B) side should follow the following guidelines. The positioning holes of the printed board and the positions to be occupied by the fixing brackets should be reserved.
(12) When the PCB area is too large, in order to prevent the PCB from bending when passing through the tin furnace, a 5-10mm wide space should be left in the middle of the PCB without placing components, which is used to prevent the PCB from bending when passing through the furnace. or support.
(13) When the mass of the axial component exceeds 5g, there is a high vibration requirement, or when the mass of the component exceeds 15g, there is a general requirement, it should be rounded with a bracket, and then welded. There are two fixing methods: one is firmly clamped to the board with the use of a skimable retaining clip; the other is fixed to the board with adhesive. Those components that are large, heavy and generate a lot of heat should not be installed on the printed board, but should be installed on the chassis bottom plate of the whole machine.