Testing method of assembling multilayer PCB circuit board
For the completion of multilayer PCB testing requirements, has produced a variety of testing equipment. The Automatic optical Inspection (AOI) system is usually used for the test of the layered front layer, and after the layer, the X-ray system monitors the accuracy of the alignment and the small defects; The scanning laser system provides a method for detecting the layer before reflow. These systems, combined with the intuitive detection of the production line and the automatic placement of components, are instrumental in ensuring the reliability of the final assembly and welding board.
However, even if these efforts minimize the defect, it is still necessary to assemble the final test of the multilayer PCB circuit board, which is perhaps the most important because it is the final unit of the product and the entire process evaluation.
The final test of assembling multilayer PCB circuit board may be done by means of moving or by automation system, and often by using two methods together. "Manual" means an operator uses an optical instrument to visually inspect the board and make a correct judgment about the defect. Automated systems use computer-aided graphical analysis to identify defects, and many people believe that automated systems contain all detection methods except for manual light detection.
X-ray technology provides a method for evaluating the presence of solder thicknesses, distributions, internal voids, cracks, welds, and solder balls (Markstein, 1993). The ultrasonic will detect voids, cracks, and interfaces that are not connected. Automatic optical inspection evaluates external features such as bridging, tin melt and shape. Laser detection can provide three-dimensional images of external features. Infrared detection detects an internal weld point failure by comparing the weld point heat signal with a known good solder point.
It is noteworthy that these automatic detection techniques have been found to be unable to detect all defects in the limited testing of assembled multilayer PCB boards. Therefore, manual visual inspection methods must be combined with automated detection methods, especially for those with a small number of applications. The combination of X-ray detection and manual optical detection is the best method to detect the defects of the Assembly board.
The multilayer PCB circuit board assembled and welded has the following defects:
1 components missing;
2 components failure;
3 The installation error of the components, not alignment;