14 Common Problems in PCB design

I. Overlap of pad

1. The overlap of the pad (except the surface sticking to the pad) means the overlap of the hole. In the drilling process, the drill bit will be broken because of multiple drilling in a place, leading to the damage of the hole.

2, the two holes in the multilayer plate overlap, such as a hole position for the isolation plate, the other hole position for the connection plate (welding plate), so that the film is drawn after the performance of the isolation plate, resulting in scrap.

Two, graphic layer abuse

1, in some graphic layer to do some useless connection, originally is four layers of the board but designed more than five layers of the line, causing misunderstanding.

2, the design diagram save trouble, take Protel software as an example to all the layers of the line with the Board layer to draw, and use the Board layer to mark the line, so in the light drawing data, because did not select the Board layer, miss the line and open, or because of the selection of the Board layer of the line and short circuit, so the design to keep the graphic layer complete and clear.

3, against the conventional design, such as component surface design in the Bottom layer, welding surface design in the Top, causing inconvenience.

Three, the character is misplaced

1. Character cover pad SMD weld, which brings inconvenience to on-off test of printed board and component welding.

2, the character design is too small, resulting in screen printing difficulties, too large so that the characters overlap each other, difficult to distinguish.

Four, the setting of single-side pad aperture

1. Single side pad is generally not drilled. If drilling needs to be marked, its aperture should be designed to be zero. Problems arise if the values are designed so that the coordinates of the holes appear at this location when the borehole data is generated.

2, single-side welding pad such as drilling should be specially marked.

Five, use the filler block to draw the pad

Drawing pad with filler blocks can pass DRC inspection when designing lines, but it is not feasible for machining. Therefore, welding resistance data can not be generated directly by similar pad. When applying solder resistance, the filler block area will be covered by solder resistance, resulting in difficulty in welding devices.

Six, the electric formation is flower welding pad is wired

Because the power supply is designed as a flower pad, the formation is opposite to the image on the actual printed board, and all the lines are isolation lines, which the designer should be very clear about. By the way, care should be taken when drawing isolation lines for several groups of power supplies or for several types of land, so as not to leave gaps that short circuit the two groups of power supplies or cause the area of the connection to be blocked (so that one group of power supplies is separated).

7. The definition of processing level is not clear

1, single panel design in the TOP layer, such as positive and negative without instructions, may be made out of the board installed on the device and not good welding.

2. For example, TOP mid1 and mid2 bottom are used in the design of a four-layer board, but they are not placed in such order during processing, which requires clarification.

8. Too many filling blocks in the design or filling blocks are filled with very thin lines

1. The phenomenon of loss of optical drawing data is generated, and the optical drawing data is incomplete.

2. Because the filling block is drawn line by line in the processing of optical drawing data, the amount of optical drawing data generated is quite large, which increases the difficulty of data processing.

Nine, surface mount device welding pad is too short

This is for the on-off test, for too dense surface mount devices, the spacing between the feet is quite small, the pad is also quite thin, installation test needle, must be up and down (left and right) staggered position, such as pad design is too short, although it does not affect the installation of devices, but will make the test needle wrong not open.

Ten, the spacing of large area grid is too small

The edge between the grid lines of a large area is too small (less than 0.3mm). In the manufacturing process of printed board, many broken films are likely to be attached to the board after the drawing process is finished, resulting in broken lines.

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

A large area of copper foil should be at least 0.2mm away from the outer frame, because in the milling shape, such as milling to copper foil is easy to cause copper foil warping and caused by the flux loss problem.

Twelve, the outline frame design is not clear

Some customers have designed contour lines for Keep layer, Board layer, Top over layer and so on, and these contour lines do not coincide, which makes it difficult for PCB manufacturers to judge which contour line shall prevail.

13. Uneven graphic design

In the process of graphic plating cause uneven coating, affect the quality.

14. Special-shaped holes are 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 easy to break when processing special-shaped holes, causing processing difficulties and increasing costs.