Attentions for PCB Design
Source:This stationAuthor:admin Addtime:2018-10-25 Click:
1.Overlap of the PAD
Overlap of the bonding pad (except surface welding ) means the overlap of the holes, in the drilling process the hole may loss because of too much drilling in the same place,then the bits broken, the hole was damaged.
a.Overlap of the PAD (except surface soldering ) means the overlap of the holes, in the drilling process the hole may break or damage due to many drillings in the same place.
b.Two holes overlapped in multilayer board, if a hole in the isolation pad, another hole in the connection pad, then the film performance as isolation pad, cause the board scraped.
2.Abusing the graphics layer
a.Adding some useless connecting lines in graphics layers, for example, designed a four layers board but designed five layers track, to cause misunderstanding.
b.In order to save trouble when design, with Protel software as an example, use Board layer to paint the lines in each layers. and then use Board layer to paint callout lines, finally when light painting, open circuit occurred because losing choose Board layer and missing the contacting lines , or short circuit occurred because selecting the labeling lines of Board layer. so please keep the graphics layer is complete and clear when design.
C. Against the conventional design, such as component design on the Bottom layer, and soldering design on the Top will both cause inconvenience.
3.Misplacing the legend
a.Legend cover SMD soldering on soldering, resulted in inconvenience of on-off testing components .
b.If the legend are too small, it is difficult to print , If they are too big, that will be difficult to distinguish.
4.Aperture Setting of single -side PAD
a.Generally, single -side pad not drilling, drilling need be marked, the aperture shall be zero.If the aperture is known, when drilling data occurred, this location will display the hole coordinate, then problem occurred.
b.Drilling of single -side pad need remark distinctly.
5.Using filled block paint pad
Using filled block paint pad can pass the DRC check, but useless for production, because this kind of pad can not generate the solder mask data, and when use solder mask oil, the filled block will be covered, that will be difficult to place the components.
6.Electric layer is thermal pad and wire at the same time
Because the power designed with thermal pad, the ground layer image is opposite with the real board. All the wires are shielding wires. The designer should know this well. By the way, please carefully draw a set of power supply and shielding wires, don’t leave a gap there to cause short out of the power.
7.The definition of processing is not clear
a.Single sided board is designed on the top, if you don’t state it, maybe it’s not convenient to solder the components on the finished boards.
b.For example, a 4 layers board which is designed like this ‘top mid1, mid2 bottom’, but if the sequence is not like this when we process it, then you need point it out.
8.Too many filled block or using extremely thin wire in the design
a. Some light painting data lose, the light painting data is incomplete.
b.Because the filled block is drawn one by one when processing the data, the quantity of those data is quite large, which make the data processing harder.
9.The Pad of SMD is too short
For on-off test, if the SMD is too dense, the space between two pins is small, and the pad is also quite thin. When we install testing probes, we should stagger up and down(left and right). Although, short pad does not influence the components installation, but can make the testing staggered.
10.The space between those grids is too small
The edge between the lines which compose the grids is small(less than 0.3mm), in the process of making the board, after film developing, the process of transforming drawing will generate some broken films which stick to the board and result in disconnection.
11.Large area of copper foil close to the frame.
Large area of copper foil should ensure at least 0.2 mm spacing from the outer frame, because when routing, for example, the routing on the copper foil may easily cause the copper foil warped and then soldmask fall off .
12.Unclear frame design
Some customers designed outlines in Keep layer, Board layer, Top over layer and these outlines are mismatching, that make difficult for the PCB manufacturer to subject to which outlines..
13 .Graphic design is uneven
Uneven coating occurred when making graphics plating, which will affects the quality.
14. Using gridlines when the laying large copper area to avoid bubbles when SMT.