SMT production equipment is fully automatic, high precision, high speed, high efficiency and so on. PCB design must meet the requirements of SMT equipment. The design requirements of SMT production equipment include: PCB shape, size, positioning hole and clamping edge, reference Mark, assembling board, selection of component packaging and packaging form, PCB design output file, etc.

When designing PCB, the shape of PCB should be considered first. When the size of PCB is too large, the printed line is long, the impedance increases, the anti-noise ability decreases, and the cost increases. Too small, the heat dissipation is not good, and adjacent lines are susceptible to interference. At the same time, the accuracy and specification of PCB shape dimension directly affect the manufacturability and economy of production and processing. The main content of PCB shape design is as follows.

(1) Length-width ratio design

Printed board shape should be as simple as possible, generally rectangular, length to width ratio of 3:2 or 4:3, its size should be as close to the standard series size, in order to simplify processing I art, reduce processing costs. The surface of the board should not be designed too large, so as not to cause deformation when reflow welding. The size and thickness of the board should match, thin PCB, the board size should not be too large.

What are the requirements of PCB design for SMT production equipment

(2) PCB shape

PCB shape and size are determined by the PCB transmission mode and mounting range of the mounting machine.

① When THE PCB is positioned on the mounting workbench and transferred through the workbench, there is no special requirement for the appearance of the PCB.

② When the PCB is directly transmitted by rail, the PCB shape must be straight. If it is a profiled PCB, the process edge must be designed so that the outside of the PCB forms a straight line, as shown in Figure 5-80.

③ Figure 5-81 shows PCB rounded corners or 45. Chamfering diagram. In PCB shape design, it is best to process the PCB into rounded corners or 45. Chamfer to prevent sharp Angle damage to PCB conveyor belt (fiber belt).

(3) PCB size design

PCB size is determined by mounting range. When designing PCB, it is necessary to consider the maximum and minimum mounting size of the mounting machine. PCB maximum size = maximum mounting size of mounting machine; Minimum PCB size = minimum mounting size of mounting machine. The range of mounting for different types of mounting machines is different. When the PCB size is smaller than the minimum mounting size, the board must be used.

(4) PCB thickness design

Generally, the plate thickness allowed by the mounting machine is 0.5 ~ Smm. The thickness of PCB is generally in the range of 0.5-2mm.

① Only assemble integrated circuits, low-power transistors, resistors, capacitors and other low-power components, in the absence of strong load vibration conditions, the size of the PCB within 500mmx500mm, the use of thickness of 1.6mm.

② Under the condition of load vibration, the size of the plate can be reduced or the supporting point can be strengthened or increased, and the thickness of 1.6mm can still be used.

③ When the plate surface is larger or unable to support, 2-3mm thick plate should be selected.