PCB design is based on the circuit schematic diagram to achieve the functions required by circuit designers. Printed circuit board design mainly refers to layout design, which needs to consider the layout of external connections. Optimized layout of internal electronic components. The optimal layout of metal wires and through holes. Electromagnetic protection. Heat dissipation and other factors. Excellent layout design can save production cost and achieve good circuit performance and heat dissipation performance. In the process of PCB design, we should pay attention to the following problems:

1、 Overlap of pads

1. The overlap of pad (except for the pad attached on the surface) means the overlap of holes. In the drilling process, drill bit will be broken due to multiple drilling at one place, resulting in hole damage.2. Two holes overlap in a multilayer board. For example, one hole is an isolation plate, and the other is a connection pad (solder pad). In this way, the negative is shown as an isolation plate, resulting in scrapping.

2、 Abuse of graphic layer

1. Some useless wires have been made on some graphic layers, but more than five layers of circuits have been designed for the original four layer boards, which causes misunderstanding.2. Taking Protel software as an example, the board layer is used to draw the lines of each layer, and the board layer is used to draw the marking line. In this way, when photo drawing data, because the board layer is not selected, the connection line is missed and the circuit is short circuit, so the graphic layer is complete and clear during the design.3. It violates the conventional design, such as the component surface is designed in the bottom layer, and the welding surface is designed at the top, causing inconvenience.

3、 Character shuffling

1. Character cover pad SMD solder is inconvenient for PCB on-off test and component welding.2. The character design is too small, resulting in screen printing difficulties, too often make characters overlap each other, difficult to distinguish.

4、 Setting of single side pad aperture

1. Generally, single-sided pad is not drilled. If the drilling needs to be marked, the hole diameter should be designed as zero. If the numerical value is designed, the coordinates of the hole will appear at this position when the drilling data is generated, which will cause problems.2. Single side pad such as drilling shall be specially marked.

5、 Draw pad with filler block

The pad drawn with filler block can pass the DRC inspection when designing the circuit, but it is not suitable for processing. Therefore, the solder mask data cannot be generated directly. When the solder mask is applied, the area of the filler block will be covered by the solder resist, which leads to the difficulty of device welding.

6, The electrical ground layer is also a flower pad and a connection

Because the power supply is designed as a flower pad, the ground layer is opposite to the image on the actual printed board. All the connections are isolated lines. The designer should be very clear about this. By the way, when drawing several sets of power supplies or ground isolation lines, you should be careful not to leave gaps, short-circuit the two sets of power supplies, and not cause the connected area.6. The electrical ground layer is also a flower pad and a connection. Line Because the power supply is designed as a flower pad, the ground layer is opposite to the image on the actual printed board. All the connections are isolated lines. The designer should be very clear about this. By the way, when drawing several sets of power supplies or ground isolation lines, you should be careful not to leave gaps, short-circuit the two sets of power supplies, or block the connected area (make one set of power supplies separate).

7.The processing level is not clearly defined

1. The single-sided board is designed on the TOP layer. If the front and back are not specified, the manufactured board may not be easy to be soldered with components installed. 2. For example, a four-layer board is designed with four layers of TOP, mid1, mid2, and bottom, but the processing is not placed in this order, which requires explanation.

8. There are too many filler blocks in the design or the filler blocks are filled with very thin lines

1. The gerber data is lost, and the gerber data is incomplete. 2. Because the filling block is drawn with lines one by one when processing the light drawing data, the amount of light drawing data generated is quite large, which increases the difficulty of data processing. (Make a group of power supplies be separated).

9. The surface mount device pad is too short

This is for the continuity test. For a surface mount device that is too dense, the spacing between the two pins is quite small, and the pad is also quite thin. To install the test pin, it must be staggered up and down (left and right), such as the pad The design is too short, although it does not affect the installation of the device, but it will make the test pin not open.

10. The spacing of large-area grids is too small

The edges between the same lines that make up a large area of ​​grid lines are too small (less than 0.3mm). In the printed board manufacturing process, after the image transfer process is completed, it is easy to produce a lot of broken films attached to the board, causing wire breakage.

11. The distance between the large area copper foil and the outer frame is too close

The distance between the large area copper foil and the outer frame should be at least 0.2mm, because when milling the shape of the copper foil, it is easy to cause the copper foil to warp and the solder resist falling off caused by it.

12. The design of the outline frame is not clear

Some customers have designed contour lines for Keepoutlayer, Board layer, Top over layer, etc., and these contour lines do not overlap, which makes it difficult for PCB manufacturers to determine which contour line shall prevail.

13. Uneven graphic design

In the process of pattern electroplating, the plating layer is not uniform, which affects the quality.

14. The hole of the irregular component is too short

The length/width of the special-shaped hole should be ≥2:1, and the width should be >1.0mm. Otherwise, the drilling machine will easily break the drilling when processing the special-shaped hole, which will cause processing difficulties and increase costs.