May 20, 2023 
Design requirements following the below points
1. The surface of the PCB should have at least three reference points, and the positions and distances between the three points should be as far away as possible.
2. Components with a pitch of less than 0.6mm for large BGAs and large precision ICs should have local reference points.
3. The distance between multiple fine-pitch components is relatively close, and its area can be treated as components or panels.
4. There should also be a reference point for the jigsaw puzzle.
5. The layout of the reference points should be distributed in four corners, and the reference points of the components should be distributed along the diagonals of the components.
6. The distance between the reference points meets the requirements of use.
7. The design of the reference point should ensure that its corresponding bottom inner background is consistent. The bottom inner layer should avoid wires.
PCB benchmark graphics size requirements
1. Shape: solid circles, triangles, rhombi, squares, crosses, hollow circles, ellipses, etc. are all available, and solid processes are preferred in PCB design.
2. Dimensions: the diameter of a solid circle is 1.0-2.0 mm, preferably 1.5 mm; the side length of a solid square is 2 mm; the side length of a solid rhombus is 2 mm; the length of a cross line is 2 mm; The reference point for ultra-small boards and high-density layouts can be appropriately reduced, but not less than 0.5mm in diameter and not more than 3mm in diameter.
3. Surface: Bare copper, tin-plated, and gold-plated can be used, and cannot be covered by a solder mask, and the plating layer must be uniform and not too thick.
4. Surroundings: Considering the contrast between the color of the solder mask material and the environment, there must be a non-soldering area of 1-2 times the diameter of the reference point around the reference point, and be careful not to set the reference point on a large-area grounded grid. Within the distance of 3 times the reference radius of the optical positioning reference mark, other pads and printed wires should not be set.
Summarize design requirements for PCB Benchmark
The benchmark of the PCB board is a set of graphics used for the optical positioning of the entire printed circuit board. Generally set 3, all on the corner of the printed circuit board, the larger the distance, the better. When 2 points are arranged diagonally, do not be symmetrical with the printed circuit board (do not arrange in the radial direction), otherwise, it is easy to cause the wrong direction of the patch. On printed circuit boards with a length less than 200mm, set at least 2 reference points, Mark. When the length of the printed circuit board is greater than or equal to 200mm, set 4 Marks, and set 1~2 Marks on or near the center line of the length of the printed circuit board.
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