The definition of automated X-ray inspection (AXI)
Automated X-ray inspection (AXI) is an inspect technology based on the same principles as AOI. It uses X-rays instead of visible light as its source to automatically check the features that are usually hidden from view. X-rays are highly penetrating and can penetrate many substances that are opaque to visible light. The X-ray inspection will produce images of the inspected object and reveal structures inside the object to check the size, position, or other detect features. The penetration of the X-ray is used by PCBA manufacturers to assure the PCB quality control.
The application of automated X-ray inspection (AXI) in PCB inspection
In recent years, BGA, QFN, CSP, and flip-chip are widely used in various fields of electronics manufacturing. The solder joints in these area array packages are hidden under the package, which makes the traditional inspection devices challenging to perform well in PCB inspection. Besides, the miniaturization of the components package and high-density of the PCB also push the AXI to be a popular inspection method in modern PCB fabrication. Because X-ray can penetrate internal packages and check the quality of the solder joints.
The defects can be detected in automated X-ray inspection (AXI)
AXI makes it possible for insufficient solder, solder short, poorly soldered, and other problems of solder joints to be "seen". And different situations hidden to the eye due to the PCB density can be noted during AXI.
The test PCB absorbs X-rays to varying degrees due to its own density and atomic weight. Therefore, the image on the receiver will be significantly different, the higher the density, the stronger the absorption of X-rays, and the clearer the shadow image. The closer to the X-ray tube results larger the image, and the further away from the X-Ray tube, the smaller the image.
When there are defects such as slag inclusion, porosity, and incomplete soldering, the detect areas will form bright spots and bright lights. We can basically judge it as a solder short if there is a gray "bridge" between the solder joints. If the shadow of the pins and soldering pads do not match in the X-ray inspecting image, this indicates that the components have shifted due to abnormal solder paste volume or SMT deviation. In conclusion, the X-ray inspection can detect issues in PCB assembly, and the X-ray inspection image can help determine the root causes of given defects. AXI is of great help in quality control for complex components.
What' s more, AXI can use not only 2D or two-dimensional technology but also the machines using 3D technology, which can significantly improve the performance of the AXI. All in all, the demands for AXI are greatly increased, and AXI has brought new technology to the SMT inspection method, which can be considered as the best choice for PCBA manufacturers to improve the manufacturing process and product quality further. NEXTPCB promises that all the PCB will be tested by AXI before shipping out to customers.