The Principle Of Chip Placement Machine

Arch type
The component feeder and substrate (PCB) are fixed, and the patch head (with multiple vacuum suction nozzles) moves back and forth between the feeder and the substrate, takes the component out of the feeder, adjusts the position and direction of the component, and then places it on the substrate. Because the patch head is installed on the X/Y coordinate moving beam of the arch type, it is named.
Adjustment method of component position and direction of the arch type placement machine:
1. Mechanical centering adjustment of position, nozzle rotation adjustment of direction. This method can achieve limited accuracy and is no longer used in later models.
2. Laser recognition, X/Y coordinate system adjustment of position, nozzle rotation adjustment of direction. This method can realize recognition during flight, but cannot be used for ball grid array components BGA.
3. Camera recognition, X/Y coordinate system position adjustment, nozzle rotation direction adjustment. Generally, the camera is fixed, and the patch head flies over the camera for imaging recognition. It takes a little longer than laser recognition, but it can recognize any component. There are also camera recognition systems that can realize recognition during flight. There are other sacrifices in the mechanical structure.
This form is limited in speed due to the long distance the patch head moves back and forth. Generally, multiple vacuum suction nozzles are used to pick up materials at the same time (up to ten) and a double-beam system is used to increase the speed. That is, the patch head on one beam picks up materials while the patch head on the other beam places components. The speed is almost twice as fast as the single-beam system. However, in actual applications, the conditions for simultaneous material picking are difficult to achieve, and different types of components need to be replaced with different vacuum suction nozzles, and there is a time delay in changing the suction nozzle.
The advantages of this type of machine are: the system structure is simple, high precision can be achieved, and it is suitable for components of various sizes and shapes, even special-shaped components. The feeder is in the form of strips, tubes, and trays. It is suitable for small and medium-sized batch production, and multiple machines can also be combined for large-scale production.
Turret type
The component feeder is placed on a single-coordinate moving trolley, the substrate (PCB) is placed on a workbench that moves in an X/Y coordinate system, and the patch head is installed on a turret. When working, the trolley moves the component feeder to the material picking position, and the vacuum suction nozzle on the patch head picks up the component at the material picking position, rotates to the patch position (180 degrees from the material picking position) through the turret, and adjusts the position and direction of the component during the rotation process, and then the component is placed on the substrate.
Method for adjusting the position and direction of the component:
Camera recognition, X/Y coordinate system adjustment position, nozzle self-rotation adjustment direction, camera fixed, patch head flying over the camera, image recognition.
Generally, there are more than ten to twenty patch heads installed on the turret, and each patch head is installed with 2~4 vacuum suction nozzles (earlier models) to 5~6 vacuum suction nozzles (existing models). Due to the characteristics of the turret, the action is refined, and the actions of selecting and changing the suction nozzle, moving the feeder into position, picking up components, component identification, angle adjustment, table movement (including position adjustment), and placing components can all be completed in the same time cycle, so the real high speed is achieved. The fastest time cycle reaches 0.08~0.10 seconds per component.
This model is superior in speed and suitable for mass production, but it can only use components packaged in strips. If it is a dense-footed, large integrated circuit (IC), it cannot be completed with only tray packaging, so it still depends on other models to work together. This equipment has a complex structure and is expensive. The latest model is about US$500,000, which is more than three times that of the arch type.
Composition
There are many types of current placement machines, but whether it is a fully automatic high-speed placement machine or a manual low-speed placement machine, its overall layout is similar. The fully automatic placement machine is a high-precision automated equipment controlled by a computer, integrating optics, machinery and electricity. It is mainly composed of a frame, PCB transmission and bearing mechanism, drive system, positioning and centering system, placement head, feeder, optical recognition system, sensor and computer control system. It can quickly and accurately place SMD components through functions such as absorption-displacement-positioning-placement.
Frame
The frame is the foundation of the machine. All transmission, positioning mechanisms and feeders are firmly fixed on it, so it must have sufficient mechanical strength and rigidity. At present, there are various types of frames for placement machines, mainly including integral casting and steel plate welding. The first type has strong integrity, good rigidity, small deformation, and stable operation, and is generally used in high-end machines; the second type has the characteristics of simple processing and low cost. The specific structure of the frame selected by the machine depends on the overall design and load-bearing capacity of the machine. It should be stable, easy and vibration-free during operation.
PCB conveying and carrying mechanism
The conveying mechanism is an ultra-thin belt conveying system installed on the guide rail. Usually, the belt is installed on the edge of the track. Its function is to send the PCB to the predetermined position, and then send it to the next process after the patch. The conveying mechanism is mainly divided into two types: integral and segmented. In the integral method, the entry, patch and delivery of the PCB are always on the same guide rail. The limit block is used for positioning, the positioning pin is positioned upward, the clamping mechanism is used to clamp the PCB, and the support rod on the support plate is supported upward to complete the positioning and fixing of the PCB. The positioning accuracy of the positioning pin is low. When high precision is required, an optical system can also be used, but the positioning time is longer. The segmented type is usually divided into three sections. The first section is responsible for receiving the PCB from the upper technology, the middle end is responsible for PCB positioning and clamping, and the latter section is responsible for sending the PCB to the next process. Its advantage is to reduce the PCB transmission time.
Drive system
The drive system is a key structure of the placement machine and the main indicator for evaluating the accuracy of the placement machine. It includes an XYZ transmission structure and a servo system. Its functions include supporting the movement of the placement head and supporting the PCB load level.