PCBA Tech - SMT placement machine mechanical positioning

YAMAHA placement machine is a medium-speed placement machine with full-vision system optical alignment. It is well-known in the smt industry for its good cost performance and stable performance. In actual smt production, the optical positioning system of the placement machine has high reliability and good positioning accuracy. However, during the entire PCB placement process, the stability of the PCB positioning after optical recognition positioning and the final placement accuracy are affected by the mechanical Positioning has a great influence (except for the use of component local MARK), and the adjustment and inspection of the mechanical positioning system are often neglected in the manufacturing process. What is more serious is that the deviation caused by the mechanical positioning system is often more concealed and difficult to detect, which increases the manufacturing process. Difficulty in discovering problems in the process, thereby reducing equipment utilization and increasing equipment use costs. Next, the editor will continue to explain and analyze the content in the article "Discussion on the mechanical positioning of the smt multi-function placement machine".

2. Phenomenon and reasons of mechanical positioning failure of hole positioning method:

1) Loose positioning pin

When the positioning pin is loose, the PCB and the positioning pin will shake slightly in the mounting component, and the position of the mounted component will shift irregularly.

2) The positioning pin is too low

When the positioning pin is too low, the plane of the positioning pin φ4mm is lower than the PCB plane, and there is a gap between the positioning hole and the positioning pin, the PCB will move during mounting, and the component will shift irregularly due to positioning failure.

3) The positioning pin is too high

When the positioning pin is too high, the plane of the positioning pin φ4mm is higher than the PCB plane, so that the PCB is topped and the PCB is not flat, and even the PCB process edge is broken, which affects the placement accuracy.

4) Wear of positioning pin

When the positioning pin is worn, the reasons and phenomena are similar to those caused by the positioning pin being too low.

5) The center distance between the active needle and the driven needle is inconsistent with the PCB process hole distance

When the center distance between the active needle and the driven needle is not appropriate, the PCB will be elongated and deformed or compressed and deformed in the X direction, which will affect the accuracy of the mounted components in the X direction.

3. Requirements of YAMAHAYV1002 mechanical positioning:

To ensure the reliability and placement accuracy of the mechanical positioning of the YAMAHAYV1002 placement machine, the mechanical positioning should meet the following requirements:

1. Edge positioning

1) The Main Stopper must be about 2mm higher than the guide rail plane, which means that the plane on the PCB is lower than the plane on the Main Stopper during positioning;

2) The width of the guide rail is greater than the width of the PCB by about 0.5mm;

3) Pushin keeps about 0-0.5mm gap with PCB;

4) The height of the thimble Pin is appropriate, and the Pin moves horizontally under the PCB smoothly and without obstruction, and there must be no obvious gap. At the same time, all the Pins have the same height to ensure the level of the PCB.

2. Hole positioning

1) The positioning pin has a proper jacking height, the plane of the positioning pin φ4mm is in the lower plane of the PCB, the outer circle of the positioning pin is closely matched with the positioning hole of the PCB board, and the contact extrusion strength is appropriate;

2) The height of the thimble pin is appropriate, and the pin moves smoothly under the PCB without obvious gaps. All the pins have the same height to ensure the level of the PCB;

3) The center distance between the positioning driven needle and the moving main needle is the same as the center distance of the positioning hole of the PCB board. When adjusting the machine, first relax the driven needle. After positioning the PCB, let the positioning hole adjust the position of the driven needle freely, and then Tighten the follower needle.

Four, concluding remarks

The adjustment and inspection of the mechanical positioning system is the most basic work in the debugging of the multi-function placement machine, and it is also a very important work. It is often ignored or underestimated in the actual manufacturing process, which often brings a lot of trouble to the manufacturing process. In the actual smt patch proofing or processing and production, first select the appropriate PCB mechanical positioning method according to the actual situation of the PCB, and then strictly follow the requirements for the mechanical positioning components such as the stop, the width of the track, the positioning pin, the thimble, and the side clamp. Adjust and check to ensure the reliability of the mechanical positioning system, so as to ensure the placement accuracy of the components and give full play to the effectiveness of the placement machine.