PCBA Tech - Analysis on the mounting speed of smt placement machine

Placement speed refers to the ability of the placement machine to place components in a unit time. It is generally expressed by the number of components per hour or each component placement cycle, such as 60000 points/h or 0.06s/component. Generally, in the parameters of the smt placement machine, the placement speed is only the theoretical speed, and it is calculated based on the ideal state such as the minimum pick-up time of the nozzle, the shortest movement distance from the pick-up position to the placement position and the minimum placement distance. The theoretical speed; and it is only the theoretical time for component placement, and does not include auxiliary time such as transmission time and preparation time. In this article, I mainly explain the auxiliary time in the process of smt placement.

In the actual smt patch proofing or processing and production, the time to be considered is as follows:

1. Circuit board transfer and positioning time: the mounted circuit board is transferred from the work surface to the lower machine or waiting position, and the waiting circuit board is transferred from the upper machine or waiting position to the machine work surface. The practice of transmission usually takes 2.5-5s, and some special devices can reach 1.4s.

2, PCB circuit board reference point correction time: Due to the transmission of the circuit board, the warpage of the circuit board and the requirements of placement accuracy, etc., the reference point positioning on the circuit board is the best way. Generally speaking, a reference point can only correct the deviation of the circuit board in the X and y directions; two reference points can correct the deviation of the circuit board in the X and y directions and the deviation of the angle; 3 reference points can correct the circuit board in the X and y directions The deviation and the deviation of the angle, and the warping deformation caused by the double-sided board after the reflow has been pasted on one side.

3. Suction nozzle replacement time: Since there are various components on the printed circuit board, different suction nozzles are required, and the suction nozzle on the placement head often cannot absorb all types of components. Therefore, the general platform type machine design There is an automatic nozzle replacement function.

4. Component feeding and sucking time: Generally, components should be fed in place before sucking, but when sucking continuously on the same material station, if the feeding time of the next material is longer than the time of replacing another sucking shaft to suck the material, paste Loading the head requires time to wait for the components to be fed. The suction time of the component includes the suction nozzle moving to the top of the component, the suction nozzle is driven by the Z axis to the component suction position to contact the suction nozzle, the vacuum of the suction nozzle is opened, and the suction nozzle with the component moves back and forth under the drive of the Z axis. high.

5. Workbench moving time: For turret machines, it refers to the time when the X and Y worktables drive the printed circuit board from the previous position to the position where it will be mounted; for platform machines, it refers to the cantilever The time when the X and Y drive shafts drive the placement head to move from the previous position to the position where it will be placed now.

6. Component recognition time: refers to the time for the camera to capture the component image when the component recognizes the camera through the component. For turret machines, since the turret rotates at a certain frequency, and the time for a single component to take pictures is less than the time for component retrieval and placement, the recognition time for rotary machine components is basically negligible.

7. Component placement time: The suction nozzle brings the component to the top of the placement pad. The suction nozzle is driven by the Z axis to drop to the height of the patch and contacts the solder paste on the pad. The vacuum of the suction nozzle is closed and leaves the pad. The height of the piece, the blowing of the suction nozzle is opened to ensure that the component is not brought up with the departure of the suction nozzle, and the suction nozzle returns to the original height.

In short, the actual placement speed of the smt placement machine is much lower than its marked theoretical speed. Depending on the number, distribution, types, types, and characteristics and forms of the placement machine on the circuit board, the actual placement speed of the placement machine is usually only 50% to 75% of the theoretical speed.