Mark point, also known as reference point, provides a common localizable circuit pattern for all steps in FPC FPC FPC assembly process. Therefore, the Mark point of FPC FPC is crucial to SMT production. All SMT patch boards must have a Mark point, and the relevant SPEC of the Mark point is as follows:
- The shape requires the Mark point to be marked as a solid circle; A complete Mark point includes marked points (or feature points) and open areas. The minimum diameter of Mark point mark is 1.0mm, and the maximum diameter is 3.0mm. The size change of mark point mark on the same printed board cannot exceed 25um.
- Mark points are located at the diagonal relative position on the circuit board or combination board and separated as far as possible. It is better to distribute at the longest diagonal position; To ensure the SMT mounting accuracy, FPC FPCs must have at least one pair of mark points that meet the design requirements and can be identified by the SMT machine, that is, there must be a single mark.
- The distance between the Mark point (edge) and the edge of the printed board must be ≥ 5.0mm (the minimum spacing requirement for the machine to clamp the FPC), and must be within the FPC board rather than at the board edge, and meet the minimum clearance requirement for the Mark point. It is emphasized that the distance between the edge of Mark point and the edge of plate is ≥ 5.0mm, not the center of Mark point.
- Around the Mark point mark, there must be an open area without other circuit features or marks. The radius of the open area circle r ≥ 2R, R is the radius of the Mark point. When r reaches 3R, the machine recognition effect is better. It is often found that the open area of the Mark point is covered by the character layer or cut by the V-CUT, which makes the SMT machine unable to recognize.
- Mark point marks can be bare copper, clear anti oxidation coating protected bare copper, nickel or tin plating, or solder coating. The surface flatness of the mark point should be within 15um. The best performance can be achieved when there is a high contrast between the Mark point mark and the substrate material of the printed board. The inner background of all Mark points must be the same.