March 22, 2021
Summary of SEPRAYS milling cutter PCB splitter: 13 common problems in PCB board design. This paper mainly elaborates the 13 common problems in the design of PCB boards from 13 aspects. I hope that everyone can avoid them. All the PCB boards designed and produced are of high quality.
I. Overlapping of Pads
1. The overlap of the pad (except the surface pad) means the overlap of the holes. In the drilling process, the drill bit will be broken due to repeated drilling in one place, resulting in the damage of the holes.
2. The overlap of two holes in the multilayer plate, such as one hole is the isolation disk and the other hole is the connecting disk (flower pad), which renders the negative as the isolation disk, resulting in scrap.
II. Abuse of Graphics Layer
1. Some useless connections have been made on some graphics layers, but four-layer boards have designed more than five layers of lines, which causes misunderstanding.
2. It's easy to draw drawings when designing.
Take Protel software as an example to draw lines at all layers with Board layer, and mark lines with Board layer. In this way, when drawing data, the circuit will be broken because the Board layer is not selected, the connection will be missed, or the short circuit will be caused by choosing the marking line of Board layer, so the integrity and clarity of the graphic layer will be maintained in the design.
3. Contrary to conventional design, such as component surface design in Bottom layer, welding surface design in Top, causing inconvenience.
1. Character cap SMD solder pad brings inconvenience to the on-off test of PCB and the welding of components.
2. Character design is too small, which makes screen printing difficult. Too large will make characters overlap with each other and difficult to distinguish.
4. Aperture Setting of Single Side Welding Pad
1. Single-sided pad usually does not drill holes. If drilling holes need to be marked, the hole diameter should be designed to be zero. If the numerical value is designed, the coordinate of the hole will appear and the problem will arise when the drilling data are generated.
2. One-sided pad, such as drilling holes, should be specially marked.
5. Painting pads with filler blocks
The filler pad can be inspected by DRC in the design of circuit, but it is not suitable for processing. Therefore, the filler pad can not generate resistance data directly. When the upper flux is applied, the filler pad area will be covered by the flux, which makes it difficult to weld the device.
6. Electric stratum is flower pad and connection
Because of the power supply designed as a patterned pad, the stratum is contrary to the image on the actual printed circuit board, and all the connections are isolated lines, which the designer should be very clear. By the way, when drawing a few sets of power supply or isolation lines in several places, we should be careful not to leave a gap, which will shorten the two sets of power supply, or block the area of the connection (so that a group of power supply is separated).
7. Uncertain Definition of Processing Level
1. Single panel is designed in TOP layer. If it is not done in the right or wrong way, the panel may be equipped with devices and not welded well.
2. For example, when designing a four-ply board, TOP mid1 and mid 2 bottom are used, but they are not placed in this order during processing, which requires explanation.
8. Too many filling blocks in the design or filling blocks with very thin lines
1. There is a phenomenon of losing light-drawing data, and the light-drawing data is incomplete.
2. Because filling blocks are drawn one by one in the process of optical data processing, the amount of optical data generated is quite large, which increases the difficulty of data processing.
9. Surface Mount Device Pad Too Short
This is for on-off testing. For overly dense surface mounted devices, the distance between the feet is quite small, and the pad is quite thin. Installation of the test needle must be in a staggered position from top to bottom (left and right). For example, the design of the pad is too short, although it does not affect the device installation, it will make the test needle staggered.
10. The spacing of large area grids is too small
The edges between the lines that make up a large area of grids are too small (less than 0.3mm). In the process of PCB manufacturing, a lot of film fragments are easily attached to the board after developing, resulting in wire breakage.
11. Large area copper foil is too close to the outer frame
The distance between large area copper foil and outer frame should be at least 0.2 mm, because when milling the shape of copper foil, such as milling to the copper foil, it is easy to cause the copper foil warping and the loss of solder resistance caused by it.
12. Uncertainty in the design of outline frame
Some customers have designed contour lines in Keep layer, Board layer, Top over layer and so on. These contour lines do not coincide, which makes it difficult for PCB manufacturers to determine which contour line is the right one.
13. Uneven Graphic Design
In the process of graphic electroplating, the coating is not uniform and the quality is affected.
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