3D Automated X-ray Inspection (AXI)

Saki's automated high-resolution 3D X-ray inspection and measurement systems enable high image quality defect detection. Saki's systems are based on reliable hardware design, superior reliability, safety, and ease of maintenance, and are backed by a worldwide service and support network.

Saki's 3D inline AXI product line consists of the:

  • BF-X2 225kV system for semiconductor and insulated gate bipolar transistor (IGBT) power module inspection
  • BF-X2 160kV in-line 3D automated X-ray inspection system for high power resolution
  • BF-X3 system for printed circuit board assembly

Saki 3D AXI systems are based on Saki's unique Planar Computed Tomography (PCT) technology that captures 3D images of slices of the board, package, or module and reconstructs them in real time in a high-speed production setting. The process completely separates the top and bottom-side images of the board, measures components and features, determines placement variance and warpage, identifies and classifies the defects, such as dry joints and voids, and generates the associated data. The systems are built on a one-ton granite base with a rigid gantry structure for stability that delivers extremely reliable, consistent, clear images and results and ensures the thermal stability, parallelism, and flatness necessary for perfect positioning. All Saki systems adhere to the highest safety requirements and are based on European standards.

High-resolution 3D data is used for all image acquisition, inspection, and analysis. A high-resolution image of each defect is displayed immediately, enabling prompt viewing and analysis and eliminating the need for further analytical equipment. Such precision machine control, 3D reconstruction, 3D inspection, and 3D viewing are all unique developments of Saki.

Stable, Reliable Systems

All Saki AXI systems are built with a highly rigid, two-layer gantry structure on a one-ton granite base to maintain precise control of the detector and inspection object in very high-speed environments. Mounting both the sample and detector stages on both sides of the granite maintains straightness, flatness, and parallelism at a high level. Each axis is driven directly by a linear motor to achieve highly defined performance, positioning control, and excellent repeatability, even at high speed. This robust mechanism provides high reliability, with long-term stability, to ensure the integrity of the Planar CT's high-resolution inspection results.

Saki's Software Suites

Saki's AXI systems achieve even greater efficiency with Saki's software suites (see software). The BF-Monitor Repair Terminal, installed on an offline PC, allows operators to verify defects in 3D images. Using the mouse to select and maneuver images for any portion of the entire PCBA, makes it seem as if the part were being visualized in the palm of the operator's hand. The BF2-Editor offline programming software allows the user to automatically create inspection parameter data directly from the CAD data.


The BF-X2, 3D X-ray inspection system, with its adjustable system using 160kV or 225kV micro-focus open X-ray tubes, broadens the range of objects able to be inspected. It is the ideal inspection platform for various test applications, including a wide range of solutions for non-destructive testing (NDT). Its customized solutions can be used in the semiconductor industry to inspect electronic components and solder in applications such as flip chip attachment, laser through-hole (LTH) inspection, and in packaging to identify voids in microscopic pores such as in through-silicon vias (TSV). For the power industry, it can be used to detect defects in soldering of IGBT power modules. 100% of head-in-pillow and non-wetting defects can be identified. Saki's many years of AOI technology and experience have been incorporated into designing the BF-X2 to meet the demands of both high-mix and high-volume production environments.

The BF-X2's 3D planar computed tomography (PCT) technology measures the size, volume, and location of defects and generates the associated data. Based on this data, the BF-X2's software determines the dimensions of each component. PCT provides high resolution in both the horizontal and vertical directions, producing high-resolution images even for the bottom side of the printed circuit board assembly (PCBA). It completely detects PCB warpage and joints and then automatically corrects for such factors by using a combination of imaging and CT reconstruction principles. This enables the BF-X2 to produce a seamless 3D image of the entire PCBA, even though the original image data was obtained through various FOV captures.



Saki's BF-X3 3D automated X-ray inspection (AXI) system is a unique 3D system which is used after the reflow process in the printed circuit board assembly (PCBA) process. It inspects not only the soldering of BGAs, LGAs, and QFNs, but also the most widely used components on today's PCBs, like chips, leaded ICs, and even plated through-hole components. The system measures, as well as inspects, with an X-Y resolution of 13-30μm, and is programmable in 1μm increments.

The BF-X3 is a true 3D X-ray system. Saki's system works on the basis of reconstruction. The automated inspection process completely separates the top and bottom-side images of the board so images are not affected by back-side mounting. Saki's PCT technology utilizes a high-resolution image composed from 200 imaging slices acquired through the board, solder joints, and components, whereas other AXI machines only use about five slices for imaging.

The system is equipped with a 130kV closed X-ray tube. This 16W high-output tube, with its very small focal point, enables the BF-X3 to acquire the best high-definition images of any AXI system on the market. High reliability, combined with auto-conditioning and self-diagnostic functions, ensure a long operating life of the tube.

The BF-X3's new generation, high-precision flat panel detector increases the field-of-view threefold without compromising image resolution. This significant throughput increase makes the BF-X3 the perfect solution for inline inspection.

Saki's BF-X3 combines the image layers, measures components and features, determines placement variance and warpage, and analyzes their internal structures for a true volumetric representation of continuous 3D images without joints. Reconstruction of images is done on-the-fly, for every solder joint, creating 3D data for the entire sample. Defects are identified and classified, including 100% of head-in-pillow defects, voids, and dry joints. This results in best-in-class Cpk and gage repeatability and reproducibility, which is particularly critical in aerospace, medical, automotive, and other applications where failure is not an option.

AXI inspects for:

  • Absence of solder
  • Bridging
  • Dry joints
  • Fillet defects
  • Foreign material
  • Head-in-pillow and non-wetted defects
  • Insufficient solder
  • Lifted bump
  • Lifted chips
  • Lifted leads
  • Misalignment
  • Opens
  • Presence or absence of components
  • Shorts
  • Tombstones
  • Voids

Components and packages that are usually inspected are:

  • Aluminum electrolytic capacitors
  • Ball grid arrays (BGAs)
  • Chip scale packages (CSPs)
  • Chip type parts
  • Connectors
  • Diodes
  • Land grid array (LGA)
  • Module chips
  • Power transistors
  • Quad flat no-leads (QFN)
  • Quad flat packs (QFPs)
  • Small outline packages (SOPs)
  • Tantalum Capacitors
  • Transistors