PCB board design: how do you to set the mark point

PCB board design: how do you to set the mark point

After the PCB board is finished, it is necessary to mount the components. Now the mounting of the components is done by machine. The mark point will be used in the SMT / SMT.

One, what's a mark point?

The Mark point, also known as the reference point, provides a reference point for the mounting of all components in the mounting process. Therefore, the Mark point is essential for SMT production.

Two, the effect and category of MARK point

MARK point classification:

Single board Mark, need to be used when mounting monolithic PCB, on the PCB board;

Panel board MARK, patch PCB need to be used, generally on the side of the process;

Local Mark to improve the accuracy of mounting certain components, such as QFP-BGA packaging;

The mark point is made up of tag points / feature points and open spaces, as shown in the following figure:

Three, design of triple Mark points

All SMT boards must have Mark points, and the associated SPEC of the Mark points is as follows:

1. Shape

   Mark points are required to be marked as solid circles.

2. Form

   A complete MARK point consists of a marker / feature point and an open area.

3. Position

   Mark points are located relative to the diagonal line of the circuit board and are separated as far as possible, preferably at the longest diagonal position. Therefore, MARK points must appear in pairs. As shown in the following figure:

   

Four, size

The minimum diameter of the Mark dot mark is generally 1.0 mm and the maximum diameter is generally 3.0 mm. As shown in the following figure:

Five,edge distance

Mark points must be more than 5.0mm from the edge of the PCB (the machine must hold the minimum PCB spacing, and must be in the PCB board rather than on the edge, and meet the minimum Mark point open degree requirement, note: the distance indicated is the edge distance, not the MARK point as the center.

Six, open degree requirement

There must be an open area with no other circuit characteristic or mark around the mark. When the radius of the open area r ≥ 2R and R is the radius of MARK point r up to 3R, the recognition effect of the machine is better.