[ Date Time : 2013-8-12 ] [ Comments : 0
AXI is only in recent years the rise of a new testing technology. When the assembled circuit board (PCBA) inside the machine along the rail into the post, located on the circuit board side has a X-Ray Emission control the emission of X-rays through the circuit board after being placed in the bottom of the detector (typically video image machine) to accept, because solder can contain a large number of X-ray absorption of lead, and is therefore through the glass fiber, copper, silicon and other materials than X-ray irradiation in the solder joints on the X-ray by the amount absorbed, and was black spots produce good images, makes the analysis of solder joints become very intuitive, so simple image analysis algorithm can automatically and reliably test solder joint defects.
2D AXI technology from the previous test to the current 3D test. The former transmission X-ray test for the single board soldered joints can produce clear video, but now widely used for mounting double-sided circuit board, the effect will be poor solder joints on both sides of the video will overlapping is extremely difficult to distinguish. The 3D test stratified technology, will focus the beam to any level and the corresponding image projected onto the surface of the acceptance of a high-speed rotation, high-speed rotation so as to accept at face images are very clear focal point, while the other layer image was eliminated, so 3D test can separate circuit board solder joints on both sides of the image.
3DX-Ray technology can be tested in addition to double-sided circuit board mounted outside, but also for those who are not visible, such as BGA solder joints, etc. Multi-Image "slice" test, that is, BGA solder joints on the top, middle and bottom to thoroughly examined. At the same time take advantage of this method can also be measured through-hole (PTH) solder joints, check whether the substantial hole in the solder, thereby greatly improving the quality of solder connections.
ICT test is the most commonly used manufacturing process test method, which has strong ability and quick test failure rate, etc. The technology for large quantities, product manufacturers in terms of shape, it is very convenient and fast. However, for small quantities, the product variety of users, the need for frequent replacement needle bed, so not suitable. Same time, because now more and more complex circuit boards, the traditional circuit-contact test are greatly restricted by, through ICT and functional test is difficult to diagnose defects. With most of the complex circuit board density increasing, the traditional testing methods can only increase the test-line tester access points.
However, with the increase of access points, test programming and fixture costs of needle-bed fold rise exponentially. Develop test procedures and fixtures usually require several weeks, more complex circuit board may need more than a month. In addition, the increase in the number of ICT Contact ICT test will result in errors and increase the number of repeat test. AOI Technology is not the above problems, it does not require needle bed, the computer program driven camera automatically scans the sub region PCB, capture images, the test pad and a database to compare the parameters of qualified, through image processing, check the PCB on the defect. Very short test program development time and flexibility are the biggest advantages of AOI. AOI in addition to visual inspection can detect the defects can not be identified, AOI also the production process the quality of each process and the emergence of the type of defect, etc. collection, feedback to return, for process control analysis and management personnel. But the AOI system also has shortcomings, such as the circuit can not detect the error, while not visible solder joint inspection can not do anything. And through our research, we found that AOI test technology in practical application process will be some problems:
1) AOI test conditions on the higher, for example, when PCB warping may result as a change in focus testing failures, and if the test conditions to relax, but also fail to test purposes.
2) AOI by identifying elements such as shape or text to determine whether the component is affixed wrong so often changes if the component type (such as provided by the different components), such parameters need to frequently change the component library, otherwise it will lead to miscarriage of justice.
AXI technology is currently testing a relatively mature technology, high coverage of the process defects, usually above 97%. The process defects are generally accounted for 80% -90% defects and may not be visible on the solder joint inspection, but the AXI technology can not test circuit electrical performance deficiencies and failure. Nevertheless, AXI technology in electronic communications industry is optimistic about prospects, such as Shanghai Bell, Qingdao Lucent and others are using this new technology.
Application from the current situation, with two or more technology combined with the test strategy is a trend. Compensation for each technology are the shortcomings of other technologies: From the AXI technology and ICT technology combined test situation, on the one hand, X-ray focus on the quality of solder joints. It may confirm the existence of components, but can not confirm whether the correct components, direction and values are correct. On the other hand, ICT can determine the direction and value components, but can not decide whether the weld is acceptable, especially the bottom of the solder joint in the package body components such as BGA, CSP and so on. Specifically, with the AXI technology, the current AXI systems and ICT systems can "talk to each other", which is known as "Aware Test" The technology can eliminate some of repeated testing between the two. By reducing the ICT / AXI redundant test coverage can greatly reduce the number of ICT's contacts. This simplified the original test ICT test only 30% of access points can maintain the current high test coverage, reduced test access points ICT ICT test time can be shortened to speed up ICT programming and reduce the cost of ICT fixtures and programming. The two to three years in the past years, by combined testing technology, in particular yes AXI / ICT portfolio test Fuza there had been a circuit board's amazing the growth, Erjuzengzhang accelerating, because there are more industry-leading manufacturers realize this Shengchan advantages of the technique, and its put into use.