1)Mark point is used for optical positioning of solder paste printing and component placement. According to the function of Mark point on PCB, it can be divided into pieceboard Mark point, single board Mark point and local Mark point (also known as device-level Mark point).
2) There should be at least three Mark points on the process edge of the panel and the board without the panel, which are l-shaped and the diagonal Mark points are not symmetrical about the center.
3) The boards to be assembled should have Mark points as far as possible. If there is no place for Mark points, Mark points should not be placed on the boards.
4) If there are mounting components on both sides, there should be Mark dots on each side.
5) If several SOP devices are close to each other (≤100mm) to form an array, they can be considered as a whole and two local Mark points can be designed at their diagonal positions.
6) For QFP with lead center distance ≤ 0.5mm and BGA with lead center distance ≤ 0.8mm, local Mark points should be set in the diagonal near the center point of the component for accurate positioning.
Design specification and dimension requirements:
1) The shape of Mark point is a solid circle with a diameter of 1mm. The material is copper and the surface is sprayed with tin. Attention should be paid to the smoothness, smooth and neat edges, and the color is obviously different from the surrounding background color. The welded window is concentric with the Mark point and has a diameter of 3mm for the splice and veneer and 1mm for the local Mark point.
2) In order to increase the contrast between Mark point and substrate, copper foil can be laid below Mark point. Mark points on the same board should have the same inner background, that is, whether there is copper foil under Mark point should be consistent.
3) In order to ensure the identification effect of printing and patch, there shall be no wiring and silk screen marks of pad hole test points within the range of Mark points, so as not to be CUT by V-cut slot and cause machine identification failure.
4) Mark points of veneer and jigsaw should be designed as components, and partial Mark points should be designed as part of component package. It is convenient to assign accurate coordinate value for positioning.
5) The Mark point on the board shall be no less than 5mm from the center of the board edge; Mark point on process edge, center distance from plate edge is not less than 3mm.
