X-ray analysis: Industrial micro-computed tomography (µCT) and high-resolution laminography (HRCL), e.g. of printed circuit boards

Topic

Micro-computed tomography (µCT) and high-resolution computed laminography (HRCL) are computer-aided imaging X-ray procedures. They are used to produce sectional images from raw data. Fraunhofer IKTS uses the sectional images to generate three-dimensional representations for non-destructive materials diagnostics, e.g. of printed circuit boards. The images visualize material defects, such as air pockets, cracks and pores, which can be detrimental to safety and quality.

X-ray diagnostics at Fraunhofer IKTS

Radiography Micro-computed tomography (µCT) High-resolution computed laminography (HRCL)
Radiography is used to create simple 2D images of the studied object from all directions in space. µCT is used to create complex 3D data sets of any studied object. HRCL is a special CT process wherein small partial areas of flat assemblies, such as printed circuit boards, can be examined in high resolution.
Typical applications
  • Insight into the internal structure of objects of all kinds (e.g. from nature, art, technology) for measuring purposes
  • Void analysis of solder connections (see image)
  • Detection of weak spots in joints using X-ray at an angle
  • Visualization of cracks which cannot be found by radiography
  • Exact localization of structural weak spots (air pockets, cracks,...)
  • Visualization of virtual sectional planes in the studied object
  • Creation of data sets for rapid prototyping
  • Fast visualization of cracks in joints and components of electronic circuit carriers (printed circuit boards), without any preparation required
  • Examination of embedded systems in CFRP printed circuit boards

 

Void analysis (plane-related) on BGA balls.

X-ray CT of the cochlea of a guinea pig.

Bonding wires and bumps with enclosed pores.

Areas of application for micro-computed tomography (µCT)

 

Industrial micro-computed tomography (µCT) is a well-established analytical method for technical and scientific applications. It is currently gaining in significance for art and cultural goods as well. Micro-computed tomography as a process is ideal where the task is to detect air pockets, cracks, pores and other types of material inhomogeneity within an object, no matter its shape. µCT enables the non-destructive, three-dimensional testing of objects with high spatial resolution.

The X-ray CT device installed at Fraunhofer IKTS can be adapted to suit our clients’ needs. It is possible to examine very small components, e.g. from the electronics industry, as well as larger objects, such as works of art or fossils.

 

Measuring principle of micro-computed tomography (µCT)

Operating principle of micro-computed tomography (µCT).

The test object is placed on a rotating table between the X-ray tube and the detector in such a way that it is possible to partially or fully radiate through it. While the computer tomography is performed, the rotating table with the specimen turns 360°. The rotating motion is performed in 800 to 1600 angular steps. This results in projections in different orientations. In parallel with the measurement, a computer cluster reconstructs the volumetric model of the test specimen.

Immediately after the measuring process is complete, a 3D volume data set is available for analysis. The volume data set mainly represents the spatial density distribution of the specimen. Within the 3D volume data set, spatial sectional images can be produced in any orientation. This enables a precise assessment of the test specimen regarding its internal structure (pores, cracks, air pockets, material inhomogeneity, etc.).

The 3D volume data set enables the geometric measurement of distances, angles, arcs and surfaces, or the determination of partial volumes of areas with varying densities, which manifest as varying shades of gray. In addition, it is possible to extract surface data of the test object and process them using 3D CAD software. The 3D data thus gained can be used for rapid prototyping applications. The CT analyses are documented in the form of sectional images or 3D animations in the standard formats TIF, JPG, AVI or MPEG.

Device specifics of micro-computed tomography (µCT)  You will receive from us
  • 225 kV micro-focus X-ray tube
  • Area detector, 2048 x 2048 pixels
  • Max. real resolution: > 900 nm
  • Max. specimen size: < 600 mm (largest expansion); can be larger if partial areas are tested
  • Max. specimen weight: < 6 kg
  • Non-destructive testing
  • Fully reconstructed data set in a format of your choice
  • Support in using the data visualization software
  • If requested, an individual evaluation of your test data

Examples from medicine and biology

X-ray CT of the root canal of a tooth.

X-ray CT of a human petrous pyramid (left: bone structure; right: ear canal; center: combination).

X-ray CT of a dragonfly’s head.

Examples from art and culture

X-ray CT of a single-hand necklace watch, manufactured around 1600 (exhibit of Staatliche Kunstsammlungen Dresden). Micro CT reveals the clockwork, showing its operating principle and precise workmanship.

X-ray CT of a shamanic cult object – rattle. Micro CT provides a nondestructive look inside.

X-ray CT of a historic vessel from the Chimù culture. Micro CT makes the content of this opaque vessel visible without destroying the artefact.

Examples from technical design and technology

X-ray CT of a battery.

X-ray CT of a cell phone.

X-ray CT of a gear shifting cover.

Examples from materials science

X-ray CT of a ceramic filter structure.

X-ray CT of a ceramic mug.

X-ray CT of a concrete drilling core sample.

Areas of application of high-resolution computed laminography (HRCL)

 

X-ray computed tomography (CT) is a very convenient method for analyzing about 90 percent of all test objects without destroying them. However, the smallest defects on large-area surfaces can be detected with X-ray CT only if the respective area in which they occur is separated from the test object. Electronic printed circuit boards are an example for this: Due to the mostly large-area geometry of the specimen, the resolution with which they can be examined is often insufficient. In most cases where X-ray CT is used, the distance between the X-ray source and the specimen is too large for a precise examination of smaller partial areas.

To solve this problem, Fraunhofer IKTS has developed an X-ray tomography process which is able to analyze partial areas of large-area circuit carriers, such as printed circuit boards, in high resolution and without destroying the test object. We call it ‘high-resolution computed laminography’, or in short: HRCL. In HRCL, Fraunhofer IKTS offers a unique feature, since the specimen can be examined in high resolution (up to 1.5 µm³) while using only one single rotation. The extensive preparation of the specimen is no longer required.

 

Measuring principle of high-resolution computed laminography (HRCL)

Operating principle of high-resolution computed laminography (HRCL).

High-resolution computed laminography (HRCL) is an optimized version of cone-beam tomography. With its modified orientation of X-ray tube and X-ray detector, HRCL enables bringing the planar specimen very close to the X-ray source while retaining the full rotational freedom. The modified measurement setup and an optimized reconstruction algorithm mean that high-resolution analyses of printed circuit boards are no longer a problem.

For instance, it is possible to analyze  control boards for automotive and power electronics, as well as embedded systems, in a non-destructive way, even though a very high local resolution is required in order to represent small areas of large-area specimens. HRCL is an adequate replacement for characterizing specimens through metallurgical grinding. Following the measurement, the specimens can be used for further characterization or reinstalled in their original location.

Another strength of high-resolution computed laminography (HRCL) is the extraction of surface data which can be processed further using 3D CAD software. As in µCT, the 3D data thus gained can be used for rapid prototyping applications.

Device specifics of high-resolution computed laminography (HRCL)

You will receive from us

  • 225 kV micro-focus X-ray tube
  • Area detector, 2048 x 2048 pixels
  • Max. real resolution: > 1.5 µm
  • Max. specimen diagonal: < 300 mm (< 700 mm with restrictions in the measuring range)
  • Max. specimen weight: < 6 kg
  • High-resolution examination without any preparation required
  • Fully reconstructed data set in a format of your choice
  • Support in using the data visualization software
  • If requested, an individual evaluation of your test data

Examples from electronics

X-ray bar anode above a BGA for crack detection at the solder connection.

3D visualization of a BGA ball with cracks and voids.

Crack through the interposer of a BGA.

Faulty connection of a via with the solder ball Solder ball torn away from the bank contacts.

Manufacturing-related defect at the transition from the rest ring of a via.

2D view of a 100 % crack in a BGA ball.