What are the common problems encountered in the process of PCB circuit board proofing design? do you know? Let us introduce to you below!
1. Stacking of pads
1.1. The stacking of pads (except the surface mount pads) means the stacking of holes. During the drilling process, the drill bit will be broken due to repeated drilling in one place, resulting in hole damage.
1.2. Two holes in the multi-layer board are stacked. For example, one hole is a barrier disk, and the other hole is a connecting disk (flower pad). After drawing the negative, it appears as a barrier disk, and the composition is invalid.
2. Indiscriminate use of the graphics layer
2.1. Some useless connections have been made on some graphics layers. It was originally a four-layer board, but more than five-layer circuits were planned, which caused misunderstanding.
2.2. Save effort when planning. Taking Protel software as an example, use the Board layer to draw the lines on each layer, and use the Board layer to mark the lines. In this way, when the light drawing data is performed, since the Board layer is not selected, leakage will occur. If the connection is dropped and the circuit is broken, it may be short-circuited due to the selection of the marked line of the Board layer, so keep the graphics layer intact and clear when planning.
2.3. Violation of conventional planning, such as the component surface is planned on the Bottom layer, and the welding surface is planned on the Top layer, which is inconvenient to form.
3, the random placement of characters
3.1. The SMD solder tab of the character cover pad brings inconvenience to the on-off inspection of the printed board and the welding of components.
3.2. If the characters are too small, it will be difficult to screen printing, and if the characters are too large, the characters will be stacked on each other, making it difficult to distinguish.
4. Setting of single-sided pad aperture
4.1. The single-sided pad is generally not drilled. If the drilled hole needs to be marked, the hole diameter should be planned to be zero. It is assumed that the values are planned so that when drilling data occurs, this orientation presents the coordinates of the hole, which presents a problem.
4.2. Single-sided pads such as drilled holes should be specially marked.
5. Draw pads with padding blocks
Drawing pads with filling blocks can pass the DRC inspection when planning the circuit, but processing is not possible, so the pads cannot directly generate solder mask data. Equipment welding is difficult.
6. The electrical ground is both a flower pad and a connection
Due to the power supply designed into the flower pad method, the ground layer is opposite to the image on the actual printed board, and all connections are barrier lines, which should be very clear to the planner. By the way, when drawing the barrier lines of several groups of power sources or fields, care should be taken not to leave gaps to short-circuit the two groups of power sources, nor to close the area of the connection (so that one group of power sources is separated).
7. The definition of processing level is not clear
7.1. The single-panel is designed on the TOP layer. If the front and back are not explained, the produced board may be equipped with equipment and not easy to be welded.
7.2. For example, when a four-layer board is planned, four layers are selected, but they are not placed in this order during processing, which requires clarification.
8. There are too many filling blocks in the planning or the filling blocks are filled with extremely thin lines
8.1. The light drawing data is lost, and the light drawing data is incomplete.
8.2. Because the filled blocks are drawn one by one during the light-drawing data processing, the amount of light-drawing data generated is appropriately large, which increases the difficulty of data processing.
9. The surface mount equipment pad is too short
This is for on-off inspection. For surface mount equipment that is too dense, the distance between the two feet is appropriately small, and the pads are also appropriately thin. The device inspection needle must be staggered up and down (left and right), such as soldering. If the disk is too short, although it will not affect the equipment, it will make the inspection needle in the wrong position.
10. The interval of the large area grid is too small
The edge between the same lines that make up a large area of grid lines is too small (less than 0.3mm). During the manufacturing process of the printed board, after the image transfer process is completed, many broken films are easily attached to the board, resulting in broken lines.
11. The large area copper foil is too close to the outer frame
The distance between the large-area copper foil and the outer frame should be at least 0.2mm, because when milling the shape, if it is milled onto the copper foil, it will easily cause the copper foil to warp and the solder resist drop caused by it.
12. The shape and border planning is not clear
Some customers have planned outline lines and these outline lines do not overlap, and it is difficult for PCB manufacturers to determine which outline line is subject to.
13. Uneven graphic planning
In the process of pattern plating, the coating layer is uneven, which affects the quality.
14. The special-shaped hole 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 is very easy to break the drill when processing the special-shaped hole, which makes the processing difficult and increases the cost.
English
Chinese