How to avoid common mistakes in PCB production

2018-11-23 21:19Writer: qyadminReading:

Common mistakes in PCB production

  PCB circuit board production process requirements are extremely strict, which requires familiarity with the PCB board manufacturing process, and the production equipment and testing equipment are accurate to produce a good PCB board. Many PCB board manufacturers are not very long. If you are, you may encounter some common mistakes, take a look at what is there, and how to avoid it!

  One. The pads overlap.

  1. Causes heavy holes, which cause breakage and hole damage during drilling due to multiple holes in one place.
  2. In the multi-layer board, there are both lands and spacers in the same position, and the board is made to be isolated and connected incorrectly.

  Second, the graphics layer is not standardized

   1. Violation of conventional design, such as the design of the component surface in the Bottom layer, the welding surface design on the TOP layer, causing misunderstanding.
  2. There are a lot of design garbage on each layer, such as broken lines, useless borders, labels, etc.

  Third, the characters are unreasonable

  1. Characters cover the SMD soldering piece, which brings inconvenience to PCB continuity detection and component soldering.
    2. Characters are too small, making screen printing difficult, too large will make characters overlap each other, difficult to distinguish, the font is generally > 40mil.

  Fourth, single-sided pad setting aperture

  1. Single-sided pad is generally not drilled, and its aperture should be designed to be zero. Otherwise, when drilling data is generated, the coordinates of the hole appear at this position. For example, the hole should be specially specified.
  2. If the single-sided pad is to be drilled, but the aperture is not designed, the software will treat the pad as an SMT pad when outputting the ground and ground data, and the inner layer will drop the isolation disk.

  Fifth, draw pads with padding

  Although this can be checked by DRC, the solder resist data cannot be directly generated during processing, and the pad is covered with the solder resist and cannot be soldered.

  Sixth,

       the electric ground layer design both the heat sink and the signal line, and the positive image and the negative image are designed together and there is an error.

  Seventh The spacing of large-area grids is too small.

       The spacing of grid lines is <0.3mm. During the PCB manufacturing process, the pattern transfer process produces broken film after development to cause wire breakage.

  Eighth

       The pattern should be at least 0.2mm or more from the outer frame (V-cut is 0.35mm or more), otherwise the copper foil will be lifted and the solder resist will fall off during the external processing. The appearance quality will be affected (including the multilayer board). Layer copper).

  Ninth

       the shape of the frame design is not clear Many layers have been designed with a frame, and do not coincide, making it difficult for PCB manufacturers to determine which line to form, the standard frame should be designed in the mechanical layer or BOARD layer, the internal hollowing out to be clear.

  Tenth

       When the graphic design is uneven, the current distribution is uneven when the pattern is electroplated, which affects the uniformity of the plating layer and even causes warpage.

  Eleventh shaped hole is short

  The length/width of the shaped hole should be >2:1 and the width should be >1.0mm, otherwise the CNC drilling machine cannot be processed.

  Twelfth, undesigned milling shape positioning hole

  If possible, design at least 2 positioning holes with a diameter of >1.5mm in the PCB.

  Thirteenth, the aperture is unclear

  1. The aperture mark should be marked as metric as much as possible, and in increments of 0.05
  2. Combine the apertures that are likely to be merged into one library area as much as possible.
  3. Whether the tolerances of metallized holes and special holes (such as crimping holes) are clearly marked.

  Fourteenth, the inner layer of the multi-layer board is unreasonable

  1. The heat sink pad is placed on the isolation tape, and it is easy to be connected after drilling.
  2. The isolation belt is designed with a gap and is easy to misunderstand.
  3. The isolation strap design is too narrow to accurately determine the network.

  Fifteenth, buried blind hole plate design problem

       SO,How to avoid common mistakes in PCB production?

  The significance of designing buried blind plates:

  1. Increase the density of multi-layer boards by more than 30%, reduce the number of layers and reduce the size of multi-layer boards.
  2. Improve PCB performance, especially control of characteristic impedance (wire shortening, aperture reduction)
  3. Improve PCB design freedom d. Reduce raw materials and costs, which is conducive to environmental protection.
  

       In a word

       PCB board production, no matter what company, will encounter some big and small problems, but the way to deal with the problem and the ability to prevent it is very important. If a problem occurs repeatedly but has not been resolved, then the PCB manufacturer should review it. Of course, when choosing a PCB manufacturer, try to choose the strength + technology precipitation time is long, after all, experience is still very important.

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