Micro X-ray Computed Tomography (CT) Scanning & Analysis

One of the most powerful and insightful non-destructive techniques in Exponent’s investigation toolbox is the use of X-ray computed tomography (CT) to visualize and measure the interior of inanimate objects. Similar to CAT scans in medical applications, CT scanning provides a three-dimensional view of an object’s internal components while distinguishing between a wide variety of materials such as metals, plastics, ceramics, or soft tissues (Figure 1). Different from conventional medical CAT-scanning, industrial CT systems (also XCT or micro-CT depending on the system) use higher-power X-rays to enable imaging of objects composed of high-density materials, such as building materials, soil and rock, electronics (Figure 2), medical implants (Figure 3), or batteries (Figure 4), and can resolve details as small as a few micrometers (i.e., as thin as a strand of spider silk).

Exponent routinely employs CT analysis of a wide variety of objects to support failure analysis investigations, quality/reliability assessments, and intellectual property, regulatory, and products liability litigation support. These analyses typically require no sample preparation or modification. Exponent owns and operates several industrial CT systems in the U.S., the U.K., and China, and we collaborate with industrial and academic institutions to extend our range of capabilities for sample sizes and materials across the globe. Using advanced techniques, Exponent can leverage CT data to perform complex product analyses, such as measuring dimensional changes inside batteries during cycling, wear mapping in medical devices, quantifying void spaces in cast parts, assessing product compliance, and identifying the model and manufacturer of failed components.

Figures

3D CT rendering and virtual cross section of a painted Russian nesting doll

Figure 1.  3D CT rendering and virtual cross section of a painted Russian nesting doll made of wood. The image at the center shows that wood and paint respond differently to X-rays, allowing separate examination of the components. The image to the right shows the misalignment of the inner dolls and a fracture in the wood of the innermost doll (right image, yellow arrow). The same principles apply when determining the internal alignment of components in a consumer electronics product or locating a fracture in a plastic or ceramic component.

CT 3D renderings of an RC controller circuit board

Figure 2.  CT 3D renderings of an RC controller circuit board. Images to the right exhibit magnified views of the logic component and voids in the solder connecting it to the circuit board. Voids, if excessive (e.g., >25% in ball grid array solder joints), can compromise reliability by degrading electrical, mechanical, and thermal coupling between the component and the board.

Orthogonal virtual cross sections of a total hip arthoplasty device

Figure 3.  Orthogonal virtual cross sections of a total hip arthroplasty device with a modular sleeve (left image, orange box) on the stem portion of the device. A gap between the stem and modular sleeve as well as a contaminant in the modular junction can be seen in both cross sections (blue boxes), showing how CT can be leveraged to assess the condition of the modular components, their assembly, and whether there is biological material such as bone or soft tissue confined within the interface.

Orthogonal virtual cross sections of the lithium-ion battery in a headphone

Figure 4.  Orthogonal virtual cross sections of the lithium-ion battery in a headphone. Electrode alignment variation (middle image, red arrow) and contamination (right image, yellow arrow) present in this battery, both of which may lead to performance and/or safety issues, can be detected with this technique. 

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