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Explain the difficulties of PCB proofing design in detail
29Nov
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Explain the difficulties of PCB proofing design in detail

1、 Unclear definition of PCB proofing processing level

The single panel is designed on the TOP layer. If no instructions are given, it may be possible to make boards and install devICes without welding.

2、 Large area copper foil is too close to the outer frame

The distance between the large area copper foil and the outer frame shall be at least 0.2mm, because it is easy to cause the copper foil to be warped and the solder resist to fall off when milling the shape.

3、 PCB proofing filler block drawing pad

Drawing pads with filler blocks can pass DRC inspection during PCB design, but not for processing. Therefore, solder resistance data cannot be directly generated for such PCB pads. When solder resistance is applied, the filler block area will be covered by solder resistance, resulting in difficulty in device welding.

4、 PCB proofing electrical layer is both a patterned pad and a connecting wire

pcb board

Because the power supply is designed as a flower pad, the image on the stratum is opposite to that on the actual printed board. All lines are isolation lines. When drawing several groups of power supplies or several types of ground isolation lines, care should be taken not to leave gaps, short circuit two groups of power supplies, or block the connection area.

5、 PCB proofing characters misplaced

The SMD pad of the character cover pad brings inconvenience to the on-off test of the printed circuit board and component welding. The character design is too SMAll, which makes screen printing difficult, and too large makes characters overlap and difficult to distinguish.

PCB design

6、 PCB proofing surface mount device pad is too short

This is for on-off test. For a device mounted on a too close surface, the distance between its two pins is quite small, and the pad is also quite thin. When installing the test pin, it must be staggered up and down. If the pad design is too short, it will not affect the device installation, but it will make the test pin stagger.

7、 Single face aperture setting

Single side pads generally do not drill holes. If the holes need to be MARKed, the hole diameter should be designed as zero. If the numerical value is designed, the hole coordinates will appear at this position when the drilling data is generated, which will cause problems. Single side pads such as drilling holes shall be specially marked.

8、 PCB proofing pad overlap

In PCB proofing and drilling process, the drill bit will be broken due to multiple drilling at one place, resulting in hole damage. The two holes in the Multilayer board are overlapped, and the negative film is shown as a spacer plate, resulting in scrapping.

9、 Too many filler blocks in PCB proofing design or filler blocks are filLED with extremely fine lines

The photo data is lost and incomplete. Because fill blocks are drawn one by one with lines during photo data processing, the amount of photo data generated is quite large, which increases the difficulty of data processing.

10、 Graphic layer abuse

Some useless connections have been made on some graphic layers, but the original four layer PCB board has more than five layers of circuits designed, causing misunderstanding. Violation of conventional design. The graphic layer shall be complete and clear during design.

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