SMT Modern Electronic Assembly Testing Technology

SMT Modern electronic assembly Testing Technology
At present, the miniaturization of electronic products will inevitably make the components continue to develop in the direction of miniaturization, which puts forward high requirements for the quality inspection technology of SMT products The following introduces several main detection methods SMT products, the working principle and detection technology of related detection equipment, and the corresponding improvement methods after lead-free The inspection technologies used mainly include manual visual inspection (MVl), automatic visual inspection (AVl), automatic optical inspection (A01), online circuit inspection (ICT), and automatic X-ray inspection (AXl), function test (FT), need test (FP) and other methods
SAKI AOI appearance. Compared with other testing technologies, AOI can be used in multiple locations on the production line. At present, AOI is mainly used for 3 test processes:
1) After printing, SMT solder paste shall be checked to find defects in the printing process in time and minimize welding defects caused by poor printing of solder paste. 100% 2D and 3D detection methods are usually used to detect the location of solder paste deposits. thick

2) Check after placement to check the defects produced during the printing and placement of solder paste.
3) The inspection after SMT reflow is mainly to check the defects after welding.
There are many forms to apply AOI technology to Surface Mount Technology, but the basic principle is the same, that is, to obtain the image of the measured object through optical means. Generally, the illumination image of the detected object is obtained through a sensor (camera) and digitally processed. Then, to some extent, this method of comparison, analysis, inspection and judgment is equivalent to automatic and intelligent manual visual inspection.
AOI system is a kind of precision equipment involving many disciplines. According to science and technology, AOI system can be divided into four parts: precision machinery, power control, image processing (CCD camera or vision system) system and software system. The main modules can also be divided into functions as required.
1. The control system of control system AOI mainly completes the following functions: x, y precision worktable for m-level precision motion control, motion control in z-axis direction (CCD camera system), image acquisition, automatic positioning of PCB board, automatic control of vacuum solenoid valve, etc. The control system of AOI is composed of the main control computer, motion control card, video card, input/output intermediate panel, etc. It realizes the control of three coordinates and peripheral input/output interfaces, ensures the accuracy and rapid response of motion, and realizes the functions of the whole machine in coordination with mechanical and visual modules. The main control computer is the core of the whole control system. It realizes the data acquisition and transmission, analysis and processing functions of the whole machine, and sends instructions to each part to complete the mechanical transmission, image processing and detection functions. The motion control card mainly realizes the acquisition of three coordinate motion control signals, the transmission of various processing data and the execution of action commands. The image card mainly completes the image acquisition and conversion of PCB board.
2. CCD camera system module CCD camera system is mainly composed of camera, video card and LED program controlled light source. LED is a kind of solid state semiconductor device, called light-emitting diode, which can directly convert electricity into light. The video image signal collected by the camera is transmitted to the image acquisition card, and the image acquisition card is controlled to complete the image acquisition. After the main control computer processes the captured video image, the result returns to the main control program, and the image can be observed in real time through the display and other corresponding control processes can be completed. In the CCD camera system of AOI, the optical lighting is completed by the LED light source, whose main function is to control the switch, brightness and direction of the light source. CCD camera system can perform real-time image acquisition, close acquisition, read image and display image through human-computer interface control system. When the human-machine interface system sends out a work command, the CCD camera system realizes automatic scanning. The camera system can effectively identify PCB boards in various states.
3. PCB board of precision mechanical system module has been checked, and the worktable of AOI system must automatically move to the camera position for image capture Even if the program has set the data related to these operations, if the machine parameters change due to the change of mechanical motion accuracy, etc, Unable to complete the correct detection process In order to realize the precise operation of the precision worktable, the precise ball screw driven by AC servo motor and the rolling linear guide rail are used to realize the position closed-loop control