PCB News - Discussion on the deficiencies in PCB design

Discussion on the deficiencies in PCB design

1. 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, it may be difficult to solder the board with components.

2. For example, a four-layer board is designed with four layers of TOP mid1 and mid2 bottom, but it is not placed in this order during processing, which requires explanation.

2. Graphics layer abuse

1. Some useless connections were made on some graphics layers. The original four-layer board was designed with more than five layers, which caused misunderstandings.

2. Save trouble during design. Take the Protel software as an example to draw lines on each layer. Use the Board layer to draw, and use the Board layer to mark the lines. In this way, when performing light drawing data, because the Board layer is not selected, the connection is missed The open circuit may be short-circuited due to the selection of the board layer marking line, so the graphic layer is kept intact and clear when designing.

3. Violation of conventional design, such as component surface design in Bottom layer and welding surface design in Top, causing inconvenience.

Third, the pad overlap

1. The overlap of the pads (except the surface mount pads) means that the holes overlap. In the drilling process, the drill bit will be broken due to multiple drilling in one place, resulting in hole damage.

2. Two holes in the multilayer board overlap. For example, one hole is an isolation disk and the other hole is a connection pad (flower pad). In this way, the film will appear as an isolation disk after drawing, resulting in scrap.

Fourth, draw pads with filler blocks

Drawing pads with filler blocks can pass the DRC inspection when designing the circuit, but it is not good for processing. Therefore, similar pads cannot directly generate solder mask data. When the solder resist is applied, the filler block area will be covered by the solder resist, resulting in the device Difficulty in welding.

Five, single-sided pad aperture setting

1. Single-sided pads are generally not drilled. If the drilling needs to be marked, the hole diameter should be designed to be zero. If the value is designed, then when the drilling data is generated, the hole coordinates will appear at this position, and there will be a problem.

2. Single-sided pads should be specially marked if they are drilled.

Sixth, the electrical ground layer is also a flower pad and a connection

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

Seven, random characters

1. The SMD soldering pad of the character cover pad brings inconvenience to the continuity test of the printed board and the soldering of the components.

2. The character design is too small, making screen printing difficult, and too large will cause the characters to overlap each other and make it difficult to distinguish.

The above is an introduction to the deficiencies in PCB design. Ipcb is also provided to PCB manufacturers and PCB manufacturing technology.