Friday, 29 May 2020

Non-Destructive Short Fault Localization in Advanced IC Packages Using Electro Optical Terahertz Pulse Reflectometry

Zee, B., W. Qiu, J. Alton, T. White, M. Igarashi, and D. Sullivan. "Non-Destructive Short Fault Localization in Advanced IC Packages Using Electro Optical Terahertz Pulse Reflectometry." In ISTFA 2019: Proceedings of the 45th International Symposium for Testing and Failure Analysis, p. 9. ASM International, 2019.

We demonstrate how electro optical terahertz pulse reflectometry (EOTPR) can be used in conjunction with a new one-dimensional lump circuit simulation software to quickly and non-destructively isolate faults in advanced IC packages. In the case studies presented, short failures are accurately located in a series of advanced IC package.

full paper can be seen at

Thursday, 28 May 2020

Terahertz diffractive structures for compact in-reflection inspection setup

Siemion, A., P. Komorowski, M. Surma, I. Ducin, P. Sobotka, M. Walczakowski, and E. Czerwińska. "Terahertz diffractive structures for compact in-reflection inspection setup." Optics Express 28, no. 1 (2020): 715-723.


Two diffractive optical elements are used to create a compact raster THz scanning setup in reflective configuration. The first one focuses the radiation into the small focal spot on the sample, while the second one collects reflected radiation and focuses it on the detector. To assure small size of the setup and large apertures of optical elements, structures work in the off-axis geometry. Thus, the focal spot is formed 100 mm after and 60 mm below the optical axis of the element, which measures 75 mm in diameter. The designed iterative algorithm allows further minimization of these values.

The refractive index for all frequencies in sub-THz range is equal to approximately 1.59 and the absorption coefficient corresponding to the frequency of 520 GHz is equal to 2.39 cm−1 . These measurements have been conducted using Teraview Spectra 3000 spectrometer for the sample of 3D printing material before manufacturing. Manufactured lenses measure 75 mm in diameter and up to 0.98 mm 

Wednesday, 27 May 2020

Breast Cancer Detection With Low-Dimensional Ordered Orthogonal Projection in Terahertz Imaging

Chavez, Tanny, Nagma Vohra, Jingxian Wu, Keith Bailey, and Magda El-Shenawee. "Breast Cancer Detection with Low-dimension Ordered Orthogonal Projection in Terahertz Imaging." IEEE Transactions on Terahertz Science and Technology (2019).

This article proposes a new dimension reduction algorithm based on low-dimensional ordered orthogonal projection, which is used for cancer detection with terahertz (THz) images of freshly excised human breast cancer tissues. A THz image can be represented by a data cube with each pixel containing a high-dimensional spectrum vector covering several THz frequencies, where each frequency represents a different dimension in the vector. The proposed algorithm projects the high-dimensional spectrum vector of each pixel within the THz image into a low-dimensional subspace that contains the majority of the unique features embedded in the image. The low-dimensional subspace is constructed by sequentially identifying its orthonormal basis vectors, such that each newly chosen basis vector represents the most unique information not contained by existing basis vectors. A multivariate Gaussian mixture model is used to represent the statistical distributions of the low-dimensional feature vectors obtained from the proposed dimension reduction algorithm. The model parameters are iteratively learned by using unsupervised learning methods, such as Markov chain Monte Carlo or expectation maximization, and the results are used to classify the various regions within a tumor sample. Experiment results demonstrate that the proposed method achieves apparent performance improvement in human breast cancer tissue over existing approaches such as one-dimensional Markov chain Monte Carlo. The results confirm that the dimension reduction algorithm presented in this article is a promising technique for breast cancer detection with THz images, and the classification results present a good correlation with respect to the histopathology results of the analyzed samples.

"The reflection measurements were taken by using a TPSSpectra 3000 pulsed THz imaging and spectroscopy system (from TeraView Ltd., U.K.). The diagram of the system is shown in Fig. 2(a). The system uses a Ti:Sapphire laser that produces an 800-nm pulse to excite the THz emitter and the THz receiver. Upon excitation, the THz emitter generates a time-domain THz pulse, as shown in Fig. 2(b). The Fourier transform of the pulse, as shown in Fig. 2(c), demonstrates a power spectrum of pulse ranging from 0.1 to 4 THz. This emitted pulse is made incident on the sample through a set of mirrors, and the reflected pulse from the sample is directed toward the THz receiver [8]. In the reflection mode measurements, both the THz emitter and the detector are offset 30◦ with respect to the normal direction on the sample. To obtain the THz-reflected signal at each pixel on the tissue to produce an image, the scanning stage was set to move in increments of 200-μm step size using a stepper motor"

Tuesday, 26 May 2020

TeraCota (Terahertz Coating thickness analysis)

TeraCota is a non-contact, multi-layer coating thickness sensor that uses pulsed terahertz light. The operating principles of this sensor are similar to those of pulsed ultrasound, without the need for coupling fluid.
This sensor uses a broadband pulse of terahertz light to illuminate the coated surface from a short distance. The reflected signal contains reflections at the interface of adjacent coating layers, and it is analysed to determine the thickness of each layer.
The automotive paint process is the initial application area to determine the thickness of individual paint layers following baking. For this application, a successful operation has been demonstrated on all types of basecoats encountered: solid, metallic, and pearlescent.
For qualification, the results are compared with the values obtained from standard thickness sensing modalities (optical microscopy, magnetic gauge, and pulse ultrasound). This article also presents the results of initial field trials carried out in a production environment with a demonstrator system, which is the precursor to handheld and robot-mounted production-ready systems.

Monday, 25 May 2020

Exploring the Robustness of Terahertz-Based at-Line Porosity Measurements for Realising a Non-Destructive Dissolution Assay of Tablets during Manufacturing

Bawuah, Prince, Daniel Markl, Daniel Farrell, Mike Evans, Alessia Portieri, Andrew Anderson, Daniel Goodwin, Ralph Lucas, and Axel Zeitler. "Exploring the Robustness of Terahertz-Based at-Line Porosity Measurements for Realising a Non-Destructive Dissolution Assay of Tablets during Manufacturing." In 2019 AIChE Annual Meeting. AIChE, 2019.

To achieve a continuous downstream manufacturing process with in-process quality monitoring and real-time release testing capabilities, different process analytical technologies (PATs) such as laser scattering methods, near infrared (NIR) spectroscopy, and Raman spectroscopy can be deployed to, for example, measure the particle size of raw materials and powder blends as well as to detect the content uniformity of powder blends and tablets. However, the use of the above-mentioned PAT methods to directly measure and quantify the bulk properties of tablets, e.g. porosity, that govern the mass transport processes and mechanical changes in tablets during disintegration and dissolution, are limited. For example, NIR methods to quantify tablet hardness typically probes surface properties only and these measurements are not necessarily..........

"Terahertz time-domain measurements of all the batches were acquired using a TeraPulse 4000 (TeraView Ltd., Cambridge, UK). The porosity was extracted from the measured terahertz effective refractive index using Bruggeman's effective medium theory [1,5]."