Common problems in PCB circuit design

      PCB circuit designers need to according to the circuit diagram, in the PCB circuit design to achieve the required functions. PCB circuit design is a very complex and highly technical work, usually PCB circuit design of the primary will encounter a lot of problems.


        First, the overlap of the pad

1, the pad (except surface welded plate) overlap that hole overlap in the drilling process because many drilling in a drill hole lead to broken, leading to injury.

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

        Two, the abuse of graphic layer

1, in some of the graphics layer to do some useless connections, it was four, but the design of the five layers of the line, so that misunderstanding.

2, the design plan, for example with Protel software on each layer by layer to draw some lines of Board, and using Board layer to draw line, so in light painting data, because no Board layer, missing connection circuit, or because the Board layer line and short-circuit. Because of the design of graphic layer keep complete and clear.

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

        Three, the character of the place

1, the character cover pad SMD welding, to the printed circuit board test and the component of the welding inconvenience.

2, the character design is too small, resulting in the difficulty of screen printing, too assembly to make the characters overlap each other, it is difficult to distinguish.

        Four, one side of the disk aperture settings

1, one side pads are generally not drilling, if the drilling need to be marked, the aperture should be designed to zero. If the design values, so in the drilling data, the position appeared hole coordinates, and problems.

2, one side pads such as drilling should be special labeling.

        Five, with the filling block painting pad

Filling blocks for painting pad in the design of the line can be checked by DRC, but for processing is not enough, so the class pads directly generate resistance welding data can not, in the solder, the solder resist filling block area will be covered, resulting in difficult welding device.

        Six, the electrical formation and flower pad is connected

Because the design of the power supply, the formation and the actual printed board on the image is the opposite, all the lines are isolated line, this point designers should be very clear. By the way, should be careful to draw a few sets of power line isolation or farming, cannot leave a gap, so that the two groups of power circuit, also can cause the regional blockade of the connection (so that a group of separated power).

        Seven, the definition of the level of processing is not clear

1, single panel design in the TOP layer, such as do not add the pros and cons to do, maybe the board is made out of the device and not a good welding.

2, for example, the design of a four TOP mid1, bottom mid2 four, but not in order to place the process, which requires a note.

        Eight, the design of the filling block too much or filled with a very fine line

1, resulting in the loss of the phenomenon of light drawing data, the data is not completely painted.

2, because the filling block in the light of the data processing is to use a line to draw a line, so the amount of light generated by the large amount of data, increased the difficulty of data processing.

        Nine, surface mount device pad is too short

This is the on-off test, for the surface mount device too dense, the distance between the feet is quite small, the pad is quite fine, install the test needle, must be under the staggered position (left and right), such as the pad design is too short, although does not affect the device installation, but will make the wrong needle test don't open position.

        Ten, large area of the grid spacing is too small

A large area of the grid lines between the edges of the line is too small (less than 0.3mm), in the production process of the printed board, the transfer process after the show is easy to produce a lot of broken film attached to the board, resulting in broken.

       Eleven, a large area of copper from the frame too close

A large area of copper from the frame should be at least more than 0.2mm spacing, because in the milling form such as milling to copper foil copper foil is easy to cause the warped and solder resist caused by the falling off problem.

Twelve, the outline design of the frame is not clear

Some customers in the layer Board, layer Top, over layer Keep and so on are designed to shape the line and these lines do not coincide, resulting in PCB manufacturers are difficult to determine which line as the standard.

       Thirteen, graphics design is not uniform

When the pattern is carried out, the coating is uneven and the quality is affected.

Fourteen, the application of the grid line is too large, to avoid foaming at SMT.


 

(Source: Inside information)

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