Drawing design is important for PCB, so how to check if it doesn't goes wrong?

After the circuit board wiring is settled, check the PCB for rules to ensure that the circuit board meets the design requirements. All nets should be connected correctly. Commonly used inspection items in design rules are as follows:

Check the distance between wires, wires and component pads, wires and vias, component pads and vias. Make sure they are reasonable and meet production requirements.

Check whether the width of the power line and the ground line is appropriate, whether the coupling between the power supply line and the ground line is tight, and whether there is a place where the ground line can be widened.

Pay attention to the key signal lines. For example, take away the shortest ones, protection lines, input lines and output lines.

See whether the analog circuit and the digital circuit have their own independent ground wires.

See whether the graphics (such as icons and labels) added to the PCB cause the short circuit.

Modify some defective lines.

See whether there is a process line on the PCB, whether the solder mask meets the requirements of the production process, whether the size of the solder mask is appropriate, and whether the character mark is pressed on the device pad.

The outer frame edge of the power ground layer in the multilayer board should be reduced. For example, the copper foil of the power ground layer is exposed, which is easy to cause the short circuit.

There are two design rule inspection results: one is Report output, which generates a report of inspection results. The other one is On Line inspection, which is to inspect the electrical rules and wiring rules of the circuit board during the wiring process.

Some issues

In the manufacturing of printed circuit boards, we encounter a lot of finished products that do not meet the expected design due to many reasons. Usually, the film is designed by the customer and printed on the circuit board. If it is a problem with the drawing, the PCB manufacturer is powerless.

Text

Here is a common issue. The text is too small to be printed. Otherwise, they will be printed in one piece. You can't see them clearly. The minimum text size required by PCB manufacturers is 0.8*1.5 mm. If it is smaller, it will be unclear when printed. In addition, the text can't be placed on pads. Remove it.

Via to line, via to hole

In the design, there must be at least 0.2 mm spacing from via to line, and 0.3 mm spacing from hole to hole. In the production process, vias, pads, and lines all need to be compensated of. The original drawings need to leave a gap to facilitate the processing of the production drawings. There is enough space for compensation. If the production drawings do not compensate, the finished product will definitely be smaller than the design after etching.

Distance from holes and lines to the edge of the board

Sometimes, design holes and lines are next to the exterior line. Usually the distance from the line to the shape needs to be kept above 0.5 mm to ensure that the line has position compensation. Don't let it touch the line when making the shape.

The hole is more than 0.5MM from the outer profile line, and position compensation is reserved. If it is less than 0.5 mm, copper will be exposed on the edge of the board when the finished product is done. If the edge of the board does not accept exposed copper, it needs to be treated with copper removal. After the copper is removed, the pad will be slightly smaller.