What is placement rate?
The so-called placement rate refers to the ratio of the number of components accurately mounted on the PCB board to the number of components actually picked up by the nozzle in a unit of time. Components picked up by the nozzle that are not accurately mounted on the PCB board at the specified location are called rejects. The main reasons for discarded parts also include the influence of the feeder, the influence of the nozzle, the influence of the component detection system and other factors.
Influence of the Feeder
There are several types of feeder drives, such as motor drive, mechanical drive and cylinder drive.
Take the mechanical drive as an example, due to the feeding mechanism of high-speed access to the feeder, after a long period of time, the feeder pawl wear and tear, resulting in the pawl can not drive the tape reel plastic tape normal peeling, so that the suction nozzle can not complete the work of picking up the pieces, thus affecting the speed of loading.
In addition, long-term use or improper operation of the operator will also lead to its pressure tape cover plate, thimble, spring and other movement mechanism to produce deformation, corrosion and so on, resulting in the device suction bias, standing piece or suction device.
Therefore, the feeder should be regularly checked, for wear and tear should be repaired immediately, can not be repaired should be replaced in a timely manner.
The influence of SMT nozzle
SMT suction nozzle is also another important factor affecting the mounting rate, caused by internal and external reasons.
The internal reason is that the vacuum negative pressure is not enough. Suction nozzle in the pick and place before the automatic conversion of the head of the mechanical valve, from blowing to vacuum adsorption, will produce a certain amount of negative pressure. When the filter in the vacuum pump is contaminated and clogged, it will cause insufficient negative vacuum pressure, affecting the suction efficiency of the suction nozzle.
External causes often manifest themselves in the form of aging and rupture of rubber air tubes, aging and wear of seals, etc., as well as clogging of the suction nozzle caused by the large amount of waste debris generated by cutting off components packaged in paper braided tape.
Therefore, check the cleanliness of the nozzle daily, and clean or replace the nozzle and filter that are clogged or have poor pickup to ensure good condition.
Influence of component inspection system
Component detection system is necessary to improve the placement rate. Component detection system is divided into component thickness detection identification system and optical identification system.
After a long time of use, component thickness detection and identification system of the linear sensor is easy due to dust, debris, oil contamination affects the detection ability. Optical camera system of light source strength will also gradually decline, due to the light intensity of the light source decreases, the camera converts the gray value will also decrease, when the gray value is reduced to a certain value, the image will not be recognized.
Therefore, the device detection system needs to do regular calibration testing.
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Post time: Nov-27-2023