X-ray testing has become the mainstream technology for SMT testing

Due to increasingly fierce market competition, electronic product manufacturers are particularly concerned about how to improve product yield and output. The impact of which testing technology is adopted in the SMT production line on the above two points is crucial.

Currently, circuit boards are becoming increasingly complex, and traditional ICT testing is greatly limited. As the density of circuit boards continues to increase, ICT testing must constantly increase the number of test connections, which will have two drawbacks: first, it will lead to an exponential increase in the cost of testing programming and needle bed fixtures. 2、 This will lead to errors in ICT testing and an increase in the number of retests. Another challenge to ICT is the constantly decreasing pin distance. At present, high pin packaging includes PGA, QFP, BGA, etc., and their packaging density can reach several hundred pins per square centimeter. This pin density makes it difficult for the test probe to detect and cannot add dedicated test pads. Therefore, ICT testing can no longer meet the testing requirements of circuit boards from Russia and Japan, and electronic manufacturers need to find new testing methods.

The Automatic Optical Inspection (AOI) system is a detection system developed in recent years, mainly based on optical systems, usually used before and after reflux. AOT can inspect the quality of welding, as well as the quality of light plates, solder paste printing, and surface mount. But the disadvantage of AOI system is that it cannot detect circuit errors, and it is also powerless to detect invisible solder joints and double-sided soldered PCBs.

X-ray detection technology is currently the best method for testing the welding quality of ball grid arrays (BGA) and the occluded tin balls. It is an early, non electrical, non-contact technology for identifying process defects, reducing process work. The progress in this field includes fault data and component level diagnosis. X-ray detection technology has developed rapidly since its inception, from 2D inspection to the current 3D inspection method. The 3D inspection method adopts a layered technique, which focuses the beam on any layer and projects the corresponding image onto a high-speed rotating receiving surface. Due to the high-speed rotation of the receiving surface, the image at the focal point is very clear, while the images on other layers are clear. Therefore, the 3D inspection method can independently image the solder joints on both sides of the circuit board. The 3D inspection method can also perform multi-layer image "slicing" detection on invisible solder joints such as BGA, that is, thoroughly inspect the top, middle, and bottom of the BGA welding connection. X-ray detection technology has a high coverage rate of process defects, usually up to 97%.

In recent years, due to the trend of miniaturization and higher working frequency of IC products, the difficulty of circuit board testing has gradually increased. For motherboard testing, the industry generally uses X-ray testing, AOI testing, and ICT testing methods for testing. Among them, X-ray testing can meet the requirements of high frequency and is regarded as the future star of testing technology by the industry.