Summary of Ten Defects in PCB Board Design Process
1. Uncertain definition of processing level
Single sided PCB is designed in TOP layer. If it is done in reverse and forward without explanation, maybe the PCB board is made and fitted with devices, which are not easy to weld.
2. Large area copper foil is too close to 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, it is easy to cause the warping of copper foil and the loss of solder resistance caused by it.
3. 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 leads to the difficulty of device welding.
4. Electric stratum is a flower pad and a connection
Because the power supply is designed as flower pad mode, the stratum is contrary to the image on the actual printed circuit board. All connections are isolation lines. When drawing several sets of power supply or several ground isolation lines, care should be taken not to leave gaps, so that two sets of power supply can be short-circuited and the connecting area can not be blocked.
5. Character Arrangement
Character cap SMD solder pad brings inconvenience to PCB on-off test and component welding. Character design is too small, resulting in screen printing difficulties, too large will overlap characters, difficult to distinguish.
6. Surface Mount Device Pad Too Short
This is for on-off testing. For overly dense surface mounted devices, the distance between feet is quite small, and the pad is quite thin. To install the test needle, it must be staggered up and down. For example, the pad design is too short, although it does not affect the device installation, it will make the test needle staggered.
7. Aperture Setting of Single Side Welding Pad
One-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 hole coordinate will appear and the problem will arise when the drilling data are generated. One-sided pad, such as drilling holes, should be specially marked.
8. Overlapping of welding pads
In the drilling process, the drill bit will be broken and the hole will be damaged because of multiple drilling in one place. Two holes overlap in the multi-layer board, and the negative is shown as isolation disk after drawing, resulting in scrap.
9. Filling too many blocks or filling blocks with very thin lines in design
There is a loss of light-drawing data, and the light-drawing data is incomplete. 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.
10. Graphic Layer Abuse
Some useless wiring is made on some graphics layers, but the four-layer board has designed more than five layers of wiring, which causes misunderstanding. Violation of conventional design. Graphic layer should be kept intact and clear when designing.
