PCB design considerations

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PCB design considerations [Copy link]

PCB design considerations
1. Overlapping pads
Overlapping pads (except surface mount pads), that is, overlapping holes, will cause drill bits to break and wires to be damaged due to multiple holes in one place when drilling.

2. Abuse of graphic layers
1. Violation of conventional design, such as designing the component surface on the BOTTOM layer and the welding surface on the TOP layer, resulting in errors in the front and back sides when editing the file.
2. If there are grooves that need to be milled in the PCB board, they should be drawn using the KEEPOUT LAYER or BOARD LAYER layer, and other layers should not be used to avoid wrong milling or no milling.

3. Special-shaped holes
If there are special-shaped holes in the board, use the KEEPOUT layer to draw a filling area of the same size as the hole. The length/width ratio of the special-shaped hole should be ≥2:1, and the width should be >1.0mm, otherwise, the drill will easily break when processing the special-shaped hole, causing processing difficulties.

IV. Placement of characters
1. The characters cover the SMD pads, which brings inconvenience to the continuity test of the printed circuit board and the welding of components.
2. The characters are designed to be too small, which makes screen printing difficult and makes the characters unclear.

5. Setting of the aperture of single-sided pad
1. Single-sided pads are generally not drilled. If drilling holes needs to be marked, the aperture should be designed to be zero. If a value is designed, a hole will be drilled when the drilling data is generated, which will affect the appearance of the board at the least and the board will be scrapped at the worst.
2. If drilling holes is required for single-sided pads, special markings must be made.

6. Drawing pads with filled blocks
Drawing pads with filled blocks can pass DRC inspection when designing circuits, but it is not acceptable for processing, because such pads cannot directly generate solder mask data. When applying solder mask, the filled block area will be covered by the solder mask, making it difficult to solder the device.

VII. There are too many fill blocks in the design or the fill blocks are filled with very thin lines
1. The generated photolithography data is lost and the photolithography data is incomplete.
2. Since the fill blocks are drawn one by one with lines during photolithography data processing, the amount of photolithography data generated is quite large, which increases the difficulty of data processing.

8. The pad of the surface mount device is too short.
This is for the continuity test. For the surface mount devices that are too dense, the distance between the two feet is quite small, and the pad is also quite thin. The installation test must be staggered up and down (right and left). If the pad is designed to be too short, although it does not affect the device mounting, it will make the test needle misaligned.

9. The spacing between large-area grids
is too small. The margins between the lines of the large-area grid are too small (less than 0.30 mm), which will cause short circuits during the printing process.

10. The distance between the large area copper foil and the outer frame is too close.
The distance between the large area copper foil and the outer frame should be at least 0.20mm. When milling the outer shape, if the copper foil is milled, it is easy to cause the copper foil to warp and cause the flux to fall off.

11. Unclear design of the outer frame
Some customers have designed outer lines on the KEEP LAYER, BOARD LAYER, TOP OVER LAYER, etc., and these outer lines do not overlap, making it difficult to determine which one is the outer line during molding.

12. Placement of lines:
Do not draw the connection between two pads intermittently. If you want to thicken the line, do not repeat the placement of the line, but directly change the line WIDTH. This way, it is easy to modify when modifying the line.

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