A PCB is simply a thin board that contains integrated circuits and other electronic components. It will appear in almost every kind of electronic equipment, is the basis of the entire electronic product, PCB design is particularly important. This article summarizes some of the common design mistakes in PCB design for your reference.
A, the character of the chaotic placement
1, the character cover pads SMD solder, to the printed board through testing and welding of components inconvenience.
2, the character design is too small, causing difficulties in screen printing, too large to make the characters overlap each other, difficult to distinguish.
Second, the abuse of graphics layer
1, in some graphics layer to do some useless connection, originally four-layer board but designed more than five layers of lines.
2, design to save time, Protel software, for example, to each layer of the line with Board layer to draw, and Board layer to scratch the label line, so that when the light drawing data, because the Board layer was not selected, missed the connection and break, or will be short-circuited because of the choice of Board layer of the label line, so the design must keep the graphics layer integrity and clarity.
3, against the conventional design, such as component surface design in the Bottom layer, solder surface design in the Top, causing inconvenience.
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Third, the pad overlap
1, the pad (in addition to the surface paste pad) overlap, meaning that the overlap of the hole, in the drilling process will lead to broken drill bit because of multiple drilling in one place, resulting in damage to the hole.
2, multilayer board in two holes overlap, such as a hole for the isolation disk, another hole for the connection disk (flower pads), so that after drawing out the negative performance for the isolation disk, resulting in scrap.
Fourth, the single-sided pad aperture settings
1, single-sided pads are generally not drilled, if the drilling needs to be marked, its aperture should be designed to zero. If the value is designed so that when the drilling data is generated, this location appears to be the coordinates of the hole, and the problem arises.
2, single-sided pads such as drilling should be specially marked.
Five, with the filling block to draw pads
With filler block drawing pads in the PCB design line can pass the DRC check, but for processing is not possible, so the class pad can not directly generate solder resist data, in the solder resist on, the filler block area will be covered by solder resist, resulting in device soldering difficulties.
Sixth, the electrical ground layer and the flower pad is connected to the line
Because the power supply designed as a flower pad method, the ground layer and the actual image on the printed board is the opposite, all the connecting lines are isolated lines, which the designer should be very clear. Here by the way, drawing several groups of power or several ground isolation line should be careful not to leave a gap, so that the two groups of power short-circuit, nor can cause the connection of the area blocked (so that a group of power is separated).
Seven, processing level is not clearly defined
1, a single panel design in the TOP layer, such as not adding a description of the positive and negative do, maybe made out of the board loaded with devices and bad welding.
2, for example, a four-layer board design using TOP mid1, mid2 bottom four layers, but the processing is not placed in this order, which requires instructions.
Eight, PCB design in the filler block too much or filler block with a very thin line filling
1, there is a loss of light drawing data generated, light drawing data is not complete.
2, because the filler block in the light drawing data processing is used to draw line by line, so the amount of light drawing data generated is quite large, increasing the difficulty of data processing.
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Nine, surface mount device pad is too short
This is for the through test, for too dense surface mount device, the spacing between its two feet is quite small, the pad is also quite thin, install test needle, must be up and down (left and right) staggered position, such as the pad design is too short, although does not affect the device installation, but will make the test needle wrong not open position.
Ten, the spacing of large-area grid is too small
Composition of large-area grid line with the line between the edge is too small (less than 0.3mm), in the manufacturing process of the printed circuit board, figure transfer process after the development of the shadow is easy to produce a lot of broken film attached to the board, resulting in broken lines.
Eleven, a large area of copper foil from the outer frame of the distance is too close
Large area copper foil from the outer frame should be at least 0.2mm spacing, because in the milling shape such as milling to the copper foil is easy to cause copper foil warping and caused by the problem of solder resist off.
Twelve, shaped hole is too short
Shaped hole length / width should be ≥ 2:1, width should be > 1.0mm, otherwise, the drilling machine in the processing of shaped holes are very easy to break the drill, resulting in processing difficulties and increased costs.
XIII. Uneven graphic design
Uneven plating layer caused by graphic plating, affecting the quality.
XIV. Unclear design of shape border
Some customers design shape lines in Keep layer, Board layer, Top over layer, etc. and these shape lines do not overlap, making it difficult for pcb manufacturers to judge which shape line should prevail.