Figure 1: Isolated credit card EMV chip contact pad and microchip sides
To combat the rise in card skimming and other credit card fraud activities, most credit cards now contain a small EMV chip to boost card security. (EMV stands for Europay, Mastercard, and Visa, which are the three companies that created the EMV standard.) The magnetic strip on the back of cards contains a single identification code unique to the card that can easily be intercepted and duplicated into fraudulent cards by unscrupulous actors. With the introduction of EMV chips into cards, a unique card ID is created through the chip interface at the point of each successive transaction on the card. Thus, even if the purchase ID is obtained by a criminal, future attempts to utilize the card ID will be declined since the ID number is constantly changing.
Semiconductor chips are intrinsic to the delivery of secure payments worldwide and are used in billions of credit and debit cards for validation of authenticity and protection against counterfeit card fraud. Micro-CT allows for the examination of the microelectronics assembled into the EMV chip card package.
X-Ray Microscopic Imaging of Microelectronics
We examined a credit card EMV chip assembly using our high-resolution SkyScan 1272 micro-CT at an isotropic voxel size of 3.5 µm, and then imaged a smaller volume of interest within the chip at an isotropic voxel size of 1 µm. The SkyScan 1272 is a good match for this project due to its high resolution and moderate power, allowing us to examine small components within the microelectronic assembly.
As with all micro-CT imaging, to maximize our resolution we physically removed the chip from the larger credit card sample to reduce our total sample size and allow higher geometrical magnification of the EMV chip. We trimmed off all excess card content beyond the EMV chip contact pad as shown in Figure 1. When possible, it is helpful to minimize the physical size of a sample of interest by removing unnecessary portions of the sample to allow for a smaller working distance from the X-ray source and therefore a higher magnification. After imaging the full chip at an isotropic voxel size of 3.5 µm, the sample was repositioned within the instrument and a second dataset was collected on a smaller region of interest. The second region of interest focused on a few wires and their connection to the microchip within the sample at a voxel size of 1 µm using the “object outside field of view” reconstruction option.
As shown in Figure 2, DataViewer is used to straighten and align datasets after reconstruction. The ability to load datasets into a linked 3D viewing mode provides great control over the final orientation and cropping of your dataset. For microelectronic samples, the ability to make small changes to the orientation of the sample within DataViewer allows us to align the package components to be as planar as possible to facilitate easier visualization and interpretation.
As shown in Figure 3, CTVox provides us with an interactive volumetric model of the dataset rendered in real time. It often helps provide a clearer view of the location of features within the sample in 3D space compared to the representations possible in DataViewer. Through careful control of the histogram function, we isolated the densest regions of the sample while ignoring all lower density signals related to organic components, such as the credit card or glue used to contain the EMV assembly.
Using clipping planes within CTVox, we digitally dissect the live view of the dataset as shown in Figure 4. In this view, we observe six connections between electrodes within the device, facilitating input from the card contact pad to the microchip at the center of the assembly. Individual wires lead into different locations on the microchip from the contact pad allowing for power transfer from the credit card endpoint to the chip to run the encrypted security calculation at each transaction.
In examining the highest resolution volume of interest dataset in DataViewer, we are able to view individual components of the microchip despite their much lower X-ray attenuation than the larger metal component’s as shown in Figure 5.
Within our laboratory, we also utilize Simpleware ScanIP software (Version U-2022.12; Synopsys, Inc., Mountain View, USA) to import our Bruker SkyScan micro-CT data and then produce optimized 3D models. As with CTAnalyzer, Simpleware ScanIP software allows us to utilize advanced segmentation tools interactively with the dataset to create models of different components which all have similar X-ray attenuation (Figure 6). In total we created four masks for the dataset with a mask corresponding to the microchip (red), wires (pink), electrical contacts (green), and the contact pad (blue). A traditional global thresholding method would not work to separate these components in the dataset since there is significant overlap in signal intensity among them. Using Simpleware ScanIP, we made use of the ability to hand paint masks using threshold values, morphological opening and closing operations, Boolean subtractions, and mesh refinement tools to produce the models used in this project.
Figure 7: Maverick 3D renderings from the underside of the EMV chip highlighting individual components
After isolating each component from one another, we imported our meshes into Maverick Render Indie to create high resolution photo realistic renderings and videos of our scan data as shown in Figure 7, highlighting both a general overview of the assembly as well as a closer inspection of the connections between the contact pad and the microchip.
Among the SkyScan product line, the SkyScan 1272 represents our highest resolution desktop instrument and is traditionally thought of as a great fit for imaging organic and ceramic samples. However, for the right project the SkyScan 1272 also provides useful data for micro-electronics imaging.
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|Sample||Chip Overview||Chip VOI|
|Filter||0.5 mm Al + 0.038 mm Cu||0.5 mm Al + 0.038 mm Cu|
|Voxel Size (µm)||3.5||1|
|Exposure Time (ms)||2082||4929|
|Rotation Extent (deg.)||360||360|
|Scan Time (HH:MM:SS)||12:01:32||23:39:25|
These scans were completed on our SkyScan 1272 micro-CT system at the Micro Photonics Imaging Laboratory in Allentown, PA. Reconstructions were completed using NRecon 2.0 while visualization and volumetric inspection of the 2D and 3D results were completed using DataViewer and CTVox. The EMV chip components were converted to a STL volumetric models using Synopsys’ Simpleware ScanIP software with the CAD add-on module (Synopsys, Inc., Mountain View, USA) before 3D rendering using Maverick Render Indie (Random Control, Madrid, Spain).
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*Simpleware software (Synopsys, Inc., Mountain View, USA) enables you to comprehensively process 3D image data (MRI, CT, micro-CT, FIB-SEM…) and export models suitable for CAD, CAE and 3D printing. Use Simpleware software’s capabilities to visualize, analyze, and quantify your data, and to export models for design and simulation workflows. Simpleware™ is a trademark of Synopsys, Inc. in the U.S. and/or other countries.