source:News release time:2022-09-16 Hits: Popular:PCB Assembly company
With the development of the times and the advancement of science and technology, the replacement of electronic products is rapid, and more and more integrated functions are integrated, and products are developing towards high-end, refinement, portability, and personalization. In the process of PCB design and production, engineers should consider whether the designed board will have an impact on subsequent production. A little carelessness will cause errors in details, resulting in serious consequences.
The editor summarizes and analyzes the common problems in the PCB design process, hoping to bring some help to everyone's design and production work and avoid mistakes!
1. The graphic design is uneven. When the pattern is electroplated, the current distribution is uneven, which affects the uniformity of the coating and even causes warpage.
2. The electrical formation design is wrong. Both the heat sink and the signal line are designed, the positive and negative images are designed together, and there is an error.
3. Draw pads with fill blocks. In this way, although the DRC inspection can be passed, the solder mask data cannot be directly generated during processing, and the pads covered with solder resist cannot be soldered.
4. The special-shaped hole is short. The length/width of the special-shaped hole should be >2:1 and the width >1.0mm, otherwise the CNC drilling machine cannot process it.
5. The positioning hole for milling shape is not designed. If possible, design at least 2 positioning holes with a diameter of >1.5mm in the PCB board.
6. The pads overlap. Causes heavy holes, and when drilling, the broken drill and hole damage are caused by multiple drilling in one place. In a multi-layer board, there are both connection pads and isolation pads at the same location.
7. The large area grid spacing is too small. The grid line spacing is less than 0.3mm. During the PCB manufacturing process, the pattern transfer process produces broken films after development, which leads to wire breakage, which increases the difficulty of processing.
8. The inner layer of the multilayer board is unreasonable. The heat dissipation pad is placed on the isolation belt, and it is easy to be unable to connect after drilling. There are gaps in the isolation belt design, which is easy to misunderstand. The isolation belt design is too narrow to accurately judge the network.
9. The use of the graphics layer is not standardized. Violating the conventional design, such as designing the component surface on the Bottom layer and the soldering surface on the TOP layer, causing misunderstandings. There is a lot of design rubbish on the layers like broken lines, useless borders, callouts, etc.
10. The characters are unreasonable. Characters cover SMD solder tabs, which brings inconvenience to PCB continuity detection and component soldering. If the characters are too small, it will make screen printing difficult, and if the characters are too large, the characters will overlap each other and be difficult to distinguish. The font is generally >40mil.
11. The graphics are too close to the outer frame. The spacing should be at least 0.2mm or more (more than 0.35mm at the V-cut), otherwise the copper foil will warp and the solder resist will fall off during the external processing, which will affect the appearance quality (including the inner layer of the copper skin of the multi-layer board).
12. The aperture marking is not clear. The hole diameter should be marked in metric system as much as possible, and it should be incremented by 0.05. The hole diameters that may be merged should be merged into one reservoir area as much as possible, and the tolerance of metallized holes and special holes (such as crimp holes) should be clearly marked.
13. The design of the outline frame is not clear. Many layers are designed with borders, and they do not overlap, making it difficult for PCB manufacturers to determine which line to form. The standard border should be designed on the mechanical layer or the BOARD layer, and the internal hollowing out should be clear.
14. Set the aperture on the single-sided pad. The single-sided pad is generally not drilled, and its hole diameter should be designed to be zero. Otherwise, when the drilling data is generated, the coordinates of the hole will appear at this position. If the drill hole is drilled, special instructions should be given. If the single-sided pad needs to be drilled, but the aperture is not designed, the software will treat this pad as an SMT pad when outputting electrical and ground data, and the inner layer will lose the isolation plate.
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