PCB design is an important stage before PCB circuit board production. A reasonable and perfect design can not only save production costs, but also enable the circuit board to achieve good circuit performance and heat dissipation. Let the engineers summarize for you what are the common problems in PCB circuit board design.
1. Single-sided pads: Do not use filler blocks as pads for surface mount components, but single-sided pads.
2. Vias and pads: Do not use pads instead of vias.
3. Requirements for text: characters and labels should be avoided as much as possible, especially the pads of surface mount components and the pads on the Bottem layer, and no characters and labels should be printed. If the characters are printed on the large copper sheet, the characters are printed after spraying tin, and the characters are not cut; the characters outside the board are all deleted.
4. Requirements for solder mask green oil: For those designed according to the specifications, the solder joints of components are represented by pads, and these pads (including vias) will not be soldered automatically. In addition to the pad, if some areas on the board need to be free from solder mask ink, solid graphics should be used on the corresponding layer to express the area where solder mask ink should not be applied. For boards with BGA, the via pads must be covered with green oil on the component surface.
5. Requirements for the copper laying area: Whether the large area of copper laying is made into a grid or solid copper laying, the distance from the edge of the board is required to be greater than 0.5mm.
6. The expression of the shape: the shape processing drawing should be drawn on the Mech1 layer, and it is best to write the word CUT and the size in the groove; when drawing the outline of the square hole, square groove, etc., the arc of the turning point and the end point of the processing should be considered.
7. The expression method of opening a long hole on the pad: the drilling diameter of the pad should be set to the width of the long hole, and the outline of the long hole should be drawn on the Mech1 layer. Note that the two ends are arcs, and the installation size should be considered.
8. Expression of metallized holes and non-metallized holes: For through-layer pad holes without any description, hole metallization will be done. If hole metallization is not required, it must be marked on the Mech1 layer with arrows and text . For special-shaped holes, square slots, square holes, etc. in the board, if the edges are surrounded by copper foil, please indicate whether the holes are metallized.
9. How to set the hole size when the component pin is square: Generally, when the side length of the square pin is less than 3mm, it can be assembled with a round hole, and the hole diameter should be set slightly larger than the diagonal value of the square (considering dynamic fit).
10. When multiple different boards are drawn in one file, it is necessary to draw a border for each board on the Mech1 layer, leaving a 100mil spacing between the boards.
11. The relationship between the setting of the drilling aperture and the minimu value of the pad: when placing components in the early stage of general wiring, the component foot diameter, pad diameter, via hole diameter and via plate diameter should be considered, so as to avoid problems caused by modification after wiring. the inconvenience.
