All Questions on Automated X-ray Inspection Answered -II

Automated X-ray Inspection (AXI) has become one of the important methods of detecting structural defects on PCB packages. In the previous post, we have discussed how AXI technology helps PCB manufacturers to identify concealed defects in complex PCB packages. In this post, we will discuss how PCB manufacturers are deriving value from various X-ray inspection technologies.

What are the Different Types of AXI Technologies Employed by PCB Manufacturers?

The following are important types of AXI technologies employed by PCB manufacturers:

  • Manual X-ray Inspection: This technique is similar to Manual Visual Inspection (MVI), with the only difference that the system operator interprets defects seeing the X-ray images. Manual X-ray inspection is suited for failure analysis, and have limited defect detection capabilities.
  • 2 Dimensional X-ray Inspection: This is a conventional transmission X-ray technology. X-rays are produced at a fixed point source, and made to pass through the PCBA. These rays produce an image at the detector, which transfers it to the hardware – a computer. Analysis of the image is performed by the operator handling the computer. However, 2D X-ray inspection works well, while working with a single-sided PCBA with a single layer of solder joints. Multilayered or double-sided boards have lots of solder joints on both sides, which may produce distortions in the final image. 2D X-ray inspection is mainly used for inspecting defects in single-sided printed circuit boards in automotive applications.
  • 3D X-ray Inspection: This technique is also referred as 3D Digital Tomosynthesis. It creates a 3D image by reconstructing several transmission images, which are taken at different levels. Each slice image is reconstructed for clarity, and integrated with infinite number of images to produce clearest sliced images. Today, 3D X-ray inspection is widely employed during PCBA production, and ideal for inspecting double-sided boards with high soldering density.
  • 3D Laminography: It is different format of 3D X-ray inspection, where the detector, as well as the X-ray source, is moved in a circular pattern. These elements are synchronized out of phase at 180º to each other. The X-ray is integrated around the revolution, and sent to the computer. The image provides a complete view of the features in a one plane of the board. This technique is suited for inspection of high-density double-sided boards.

When is AXI Used?

Automated X-ray inspection is used during the following:

  • The Assembly Process: AXI is implemented in various stages of PCB assembly.
  • Bulk Production: AXI is used in combination with In-circuit Testing (ICT) to identify a large spectrum of defects.
  • Prototyping and Low Volume Production: This technique helps identify various minor concealed defects during the prototyping and low volume production phase, which may affect the PCBs in the long run.
  • Process Control: Automated X-ray inspection helps a shop to improve its performance by providing additional insights on measurement data on the solder joints and attribute data (defects).

The effectiveness of the Automated X-ray Inspection technique has contributed to its acceptance as one of the most reliable inspection techniques in the PCB industry. These days most of the manufacturers and buyers are opting for X-ray inspection service for their PCBs to ensure high-quality products. So, if you are planning on buying your PCB anytime soon, ensure that they have cleared an AXI inspection. Accelerated Assemblies is one such provider of high-quality PCBs, which have cleared AXI inspection.