The vision system plays an important role in successful placement equipment. Highly accurate optics, flexible lighting, and high-resolution cameras integrate the best circuit and device images, so modern algorithms can be used to obtain critical corrections for board, component, and feeder changes Feedback. By using advanced visual technology devices, a higher level of placement rate can be achieved. Reducing defects in picking up will help improve the production volume of the entire production line and increase economic efficiency.
Vision systems are generally divided into top, bottom, head, or laser alignments, depending on the location or type of camera. Figure 5 shows a typical patch visual alignment system.
(1) The top-view camera is mounted on the patch head and is used to search for a target (called a reference) on the circuit board so that the circuit board can be placed in the correct position before mounting.
(2) Look-up camera For detecting components in a fixed position, CCD technology is generally used. Prior to installation, components must be moved over the camera for visual alignment. It looks as if it is a bit time-consuming. However, since the head must be moved to the feeder collecting element, if the camera is installed between the pick-up position (from the feeding place) and the mounting position (board), the acquisition and processing of the video can be performed simultaneously during the movement of the mounting head. This will shorten the mounting time.
The current CCD hardware performance has a considerable level. Development of "Back-Lighting" and "Front-Lighting" technologies (see Figure 6) and programmable lighting control to better cope with various components in the development of CCD hardware. Placement needs. For example, a simple element such as RC can be illuminated from behind, and the vision system can reliably center on only the outline of the body. Conversely, the OFP and other dense pin devices are preferably front-illuminated, displaying the complete pins distributed around the package so that the vision system can reliably identify the alignment. Some BGAs have visible traces on the underside of the component that may confuse the vision system. These components require a side lighting system. It will illuminate the solder ball from the side, not the bottom trace, so the vision system can check the solder ball distribution and correctly identify the components.
(3) The head camera is directly mounted on the patch head, generally adopting the 1ine-sensor technology, and the detection of the components is completed during the process that the picking element is moved to the designated position. This technique is also called "flying centering technology". Can greatly improve the placement efficiency.