PCB board MARK point introduction
As we all know, when we get the board from the PCB board factory, we need to mount the components. Now the components are mounted by machine (SMT). The mark point will be used in SMT.
First, what is the mark point
The Mark point, also called the reference point, provides a reference point for the placement of all components in the placement process. Therefore, Mark points are critical to SMT production.
Second, MARK point role and category
MARK point classification:
Single board MARK, which needs to be used when mounting a single PCB, on the PCB board;
Jigsaw MARK, need to be used when mounting the PCB, generally on the edge of the process;
Local MARK, used to improve the accuracy of mounting certain components, such as QFP, BGA and other packages;
The mark point is composed of mark points/feature points and open areas, as shown in the following figure:
Third, MARK point design specifications
All SMT boards must have a Mark point, and the relevant SPEC of the Mark point is as follows:
Mark points are marked as solid circles.
A complete MARK point includes: marker points/feature points and open areas.
The Mark points are located relative to each other on the diagonal of the board and are separated as far as possible, preferably at the longest diagonal position. Therefore, MARK points must appear in pairs. The details are as follows:
The minimum diameter of the Gigabit PCB factory for Mark points is typically 1.0 mm and the maximum diameter is typically 3.0 mm. As shown below:
5. The edge distance
The Mark point must be ≥5.0mm from the edge of the printed board (the minimum spacing requirement of the machine clamping PCB), and must be in the PCB board instead of the board edge, and meet the minimum Mark point space requirement, note: the distance is the edge Distance, not centered on MARK.
6. Air temperature requirements
Around the Mark mark, there must be an open area with no other circuit features or marks. The radius of the open area is r≥2R, R is the radius of the MARK point, and when the r reaches 3R, the machine recognition effect is better.