PCB manufacturing equipment has the characteristics of automatic, high precision, high speed and high efficiency. PCB design must meet the requirements of pcb equipment. The PCB design and production equipment requirements include: PCB shape, size, positioning holes and clamping edges, reference marks (Mark), panel, selection of component packaging and packaging methods, PCB design output files.
PCB shape and size design
When designing a PCB, first consider the shape of the PCB. When the external dimensions of the PCB are too large, the printed lines are long, the impedance is increased, the noise resistance is reduced, and the cost is also increased; if the size is too small, the heat dissipation is not good, and the adjacent strips are susceptible to interference. At the same time, the accuracy and specifications of the PCB shape and size factor directly affect the manufacturability and economy of the PCB production and processing. The main contents of the PCB shape design are as follows.
(1) Aspect ratio design
The shape of the printed circuit board should be as simple as possible, generally rectangular, with an aspect ratio of 3:2 or 4:3. The size should be as close as possible to the standard series size, so as to simplify the processing technics and reduce the cost. Do not design the Pcb board too large to avoid deformation during reflow soldering. The size of the pcb board should match the thickness of the board. For a thin PCB, the board size should not be too large.
(2) PCB shape and size are determined by the PCB transmission method and mounting range of the placement machine.
1 .When the PCB is positioned on the mounting workbench, there is no special requirement for the shape of the PCB when transferring the PCB through the workbench.
2 .When the PCB is directly transported by the rail, the PCB shape must be straight. If it is a profiled PCB, the technics edge must be designed to form a straight line outside the PCB, as shown in Figure 1.
3 .Figure 2 is a schematic diagram of the PCB fillet or 45″ chamfer. It is best to process the PCB into rounded corners or 45″ chamfers when designing the PCB to prevent the PCB from being damaged by the acute angle when loading board (fiber belt).
(3) PCB size design
The PCB size is determined by the mounting range. When designing a PCB, it is important to consider the maximum and minimum placement size of the placement machine. PCB maximum size = maximum placement size of the placement machine; PCB minimum size = minimum placement size of the placement machine.
The mounting range of different types of placement machines is different. When the PCB size is smaller than the minimum placement size, the panel mode must be used.
(4) PCB thickness design
Generally, the board thickness allowed by the pcb placement machine is 0.5~5mm, and the thickness of the PCB is generally in the range of 0.5~2mm.
1.Only assembly of integrated circuits, small power transistors, resistors, capacitors and other small power components, in the absence of strong load vibration, the size of the PCB within 500mm × 500mm, the using thicknazess is 1.6mm.
2.Under the condition of load vibration, the size of the board can be reduced or the support point can be increased, and the thickness of 1.6 mm can still be used.
3.When the pcb board is large or unable to support, 2~3mm thickness board should be selected.
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