Study on the Terahertz Nondestructive Testing Method for Multi-chip Package Inspection using a Resonant Slit-type Probe with Rounded Matching Structure

This paper presents a terahertz (THz) non-destructive testing (NDT) method for multi-chip package (MCP) inspection. A resonant slit-type probe was used to obtain high resolution while using a source in the low Th frequency region for the Th inspection. However, the conventional resonant slit structure is difficult to manufacture due to the thin thickness of the slit, as well as the problem of increasing the change of the resonance frequency and the loss of reflection due to the thickness error of the slit. A resonant slit-type probe with a rounded matching structure was proposed to improve the coupling efficiency while improving the slit thickness problem in the Th region. The proposed probe can reduce the resonance frequency change according to the thickness error while maintaining the high coupling efficiency despite the increase of the slit thickness. It is possible to reduce the FWHM by more than 40% by using the proposed structure than the conventional resonant slit structure in the foreign object detection simulation using the slit probe. A probe with a resonant frequency of 205 GHz using the proposed structure was fabricated by electroforming and compared with VNA measurement results and CST MWS simulation results. From the measurement results, it was confirmed that the proposed probe has a simple structure and high coupling efficiency. Using the pulsed THz system, the transmission characteristics of the semiconductor chip according to the polarization direction were verified, and it was confirmed that the semiconductor inspection using the THz wave was possible. A continuous (CW) THz inspection system that can be applied to process inspection has been established. A THz transceiver module based on directional coupler and a THz transceiver module based on Magic-tee have been constructed. In addition, FPGA-based high-speed lock amplifiers have been built to improve detection rates for process inspections. Standard samples were used to verify the performance of the measurement system and probes. It was confirmed that the magic-based THz transceiver module is more suitable for defect detection. The probe structure fabricated using the proposed structure was able to detect defects of 100 µm, and the high - speed signal detection module was able to detect defects stably even at a sample moving speed of 1000 mm/s. In the semiconductor chip inspection, a lateral inspection method has been proposed because the conductivity of the semiconductor surface is high. The CST Microwave Studio simulation confirmed that side inspection enabled void detection. A lateral inspection system was constructed and a void of 500 ㎛ in diameter in the multi-chip package was detected. In addition, a simple contrast-transformed image filter is applied to the detected image so that defects in the laminated structure can be easily discriminated. As a result, it is confirmed that THz wave system using the proposed probe is a new inspection tool for detecting voids of multi-chip package.|본 논문에서는 다중 칩 패키지 검사를 위한 테라헤르츠 비파괴 검사 방법을 제시하였다. 테라헤르츠파 검사를 위해 저주파 영역의 테라헤르츠 광원을 사용하면서도 고해상도의 분해능을 얻기 위한 방법으로 공진형 슬릿 프로브를 적용하였다. 그러나 종래의 공진형 슬릿 구조는 슬릿 두께가 얇아 제작이 어려울 뿐만 아니라 슬릿 두께 오차에 따른 공진주파수 변화 및 반사손실(Return loss)이 증가하는 문제가 발생한다. 테라헤르츠파 영역에서의 슬릿 두께 문제를 개선하면서도 결합 효율을 높이기 위한 방법으로 둥근 정합 구조를 가진 공진형 슬릿 프로브를 제안하였다. 제안 된 프로브는 슬릿 두께의 증가에도 불구하고 높은 결합 효율을 유지함과 동시에 두께 오차에 따른 공진주파수 변화를 감소시킬 수 있다. 또한, 슬릿 프로브를 이용한 이물 검출 시뮬레이션에서 기존의 공진형 슬릿 구조보다 제안된 구조를 이용함으로써 반치폭 (FWHM)을 40% 이상 감소시킬 수 있었다. 제안된 구조를 적용한 공진 주파수가 205 GHz인 프로브를 전기도금 방식으로 제작하였으며, VNA 측정 결과와 CST MWS 시뮬레이션 결과와 비교하였다. 측정 결과로부터 제안 된 프로브가 구조적으로 간단하면서도 높은 결합 효율을 가짐을 확인하였다. 펄스형 테라헤르츠파 시스템을 구성, 반도체 칩의 편광 방향에 따른 투과 특성을 검증하여 테라헤르츠파를 이용한 반도체 검사가 가능함을 확인하였다. 공정 검사 적용이 가능한 연속형 테라헤르츠파 검사 시스템을 구축하였다. 방향성 커플러 (Directional coupler) 기반의 테라헤르츠파 송수신기 모듈과 매직 티 (Magic-tee) 기반의 테라헤르츠파 송수신기 모듈을 구성하였다. 또한, 공정 검사를 위한 검출 속도를 개선하기 위해 FPGA 기반의 고속 락인앰프 (lock-in amplifier)가 제작되었으며 반도체 표면의 도전성을 고려한 표준 샘플을 제작하여 측정 시스템과 프로브의 성능 검증을 위해 사용되었습니다. 매직 티 기반의 테라헤르츠파 트랜시버 모듈이 결함 검출에 더 적합함을 확인하였으며, 시스템을 이용한 프로브의 공간 분해능 검증 결과 100 µm의 공간 해상도을 가졌다. 또한, 고속 신호 처리 모듈을 이용하여 1000mm/s의 고속 이동 중에도 안정적으로 영상 검출이 가능함을 확인하였다. 반도체 칩을 이용한 검사에서는 반도체 표면의 높은 도전성으로 반사형 테라헤르츠파 시스템으로는 Void 검출이 어려워 측 방향(lateral) 검사 방식을 제안하였다. CST Microwave Studio 시뮬레이션을 통하여 측 방향 검사로 보이드 (Void) 검출이 가능함을 확인하였다. 측 방향 검사 시스템을 구성하였으며 적층 반도체 내의 직경 500 ㎛의 보이드를 검출하였다. 또한, 검출 영상에 간단한 콘트라스트 스트레칭 변환 영상 필터를 적용하여 프로브 구조에 따른 검출 신호를 개선함으로써 적층 구조 내의 결함을 쉽게 판별이 가능하도록 하였다. 결과적으로 제안된 프로브를 적용한 테라헤르츠파 시스템이 적층 반도체 내의 Void 검출을 위한 새로운 검사 방법임을 확인하였다.1. Introduction 1 1.1 Motivation 1 1.2 Outline 3 2. Background 5 2.1 Multi-chip package inspection technology and their Limit 5 2.1.1 Multi-chip package inspection using ultrasound 5 2.1.2 Multi-chip package inspection using infra-Red (IR) 6 2.1.3 Multi-chip package inspection using X-ray 8 2.2 THz inspection technology 9 2.2.1 Advantages of THz inspection technology 9 2.2.2 Issues in the THz inspection technology 12 2.2.3 THz technology for multi-chip package inspection 16 3. Resonant slit-type probe 19 3.1 Design of a resonant slit-type probe 19 3.1.1 Advantages of resonant slit-type probe 19 3.1.2 Theory of resonant slit-type probe 20 3.1.3 Resonant slit-type probe for THz wave 23 3.1.4 Matching structure of resonant slit-type probe 27 3.2 Resonant slit-type probe with rounded matching structure 27 3.2.1 Resonant slit-type probe with rounded matching structure 27 3.2.2 Fabrication of slit-type probe with rounded matching structure 34 3.2.3 Measurement of slit-type probe with rounded matching structure 37 4. Experimental setup 39 4.1 Components for CW THz imaging system 40 4.1.1 CW THz source 40 4.1.2 CW THz detector 41 4.1.3 FPGA based on fast lock-in amplifier 41 4.1.4 Fabrication of standard sample 48 4.2 CW THz Transceiver module for multi-chip package inspection 51 4.2.1 Design of THz transceiver module 51 4.2.2 Magic-tee based THz transceiver 56 4.2.3 Directional coupler based THz transceiver 56 5. Measurements and results 59 5.1 Verification of performance of THz imaging system 59 5.1.1 Measurement of spatial resolution of resonant slit-type probe with rounded matching structure 59 5.1.2 High-speed signal processing and image acquisition 60 5.2 Semiconductor chip inspection using pulsed THz wave 65 5.2.1 Inspection system using pulsed THz wave 65 5.2.2 Semiconductor chip inspection using pulsed THz wave 67 5.2.3 Transmission characteristics according to the polarization 72 5.3 Semiconductor chip inspection using CW THz wave 73 5.3.1 Semiconductor chip inspection using CW THz system based on directional Coupler 77 5.3.2 Semiconductor chip inspection using CW THz system based on magic-tee 80 5.3.3 Semiconductor chip inspection using CW THz wave 83 5.4 Multi-chip package inspection using CW THz wave 83 5.4.1 THz propagation in voids of multi-chip package in lateral inspection 83 5.4.2 Multi-chip package inspection using lateral inspection methode 85 5.4.3 Improvement of void image using image processing technique 89 5.4.4 Another application using slit-type probe (Food inspection) 93 6. Conclusion 99 Reference 103Docto

Development, Optimization and Clinical Evaluation Of Algorithms For Ultrasound Data Analysis Used In Selected Medical Applications.

The assessment of soft and hard tissues is critical when selecting appropriate protocols for restorative and regenerative therapy in the field of dental surgery. The chosen treatment methodology will have significant ramifications on healing time, success rate and overall long-time oral health. Currently used diagnostic methods are limited to visual and invasive assessments; they are often user-dependent, inaccurate and result in misinterpretation. As such, the clinical need has been identified for objective tissue characterization, and the proposed novel ultrasound-based approach was designed to address the identified need. The device prototype consists of a miniaturized probe with a specifically designed ultrasonic transducer, electronics responsible for signal generation and acquisition, as well as an optimized signal processing algorithm required for data analysis. An algorithm where signals are being processed and features extracted in real-time has been implemented and studied. An in-depth algorithm performance study has been presented on synthetic signals. Further, in-vitro laboratory experiments were performed using the developed device with the algorithm implemented in software on animal-based samples. Results validated the capabilities of the new system to reproduce gingival assessment rapidly and effectively. The developed device has met clinical usability requirements for effectiveness and performance

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Today, low-cost sensors in various civil engineering sectors are gaining the attention of researchers due to their reduced production cost and their applicability to multiple nodes. Low-cost sensors also have the advantage of easily connecting to low-cost microcontrollers such as Arduino. A low-cost, reliable acquisition system based on Arduino technology can further reduce the price of data acquisition and monitoring, which can make long-term monitoring possible. This paper introduces a wireless Internet-based low-cost data acquisition system consisting of Raspberry Pi and several Arduinos as signal conditioners. This study investigates the beneficial impact of similar sensor combinations, aiming to improve the overall accuracy of several sensors with an unknown accuracy range. The paper then describes an experiment that gives valuable information about the standard deviation, distribution functions, and error level of various individual low-cost sensors under different environmental circumstances. Unfortunately, these data are usually missing and sometimes assumed in numerical studies targeting the development of structural system identification methods. A measuring device consisting of a total of 75 contactless ranging sensors connected to two microcontrollers (Arduinos) was designed to study the similar sensor combination theory and present the standard deviation and distribution functions. The 75 sensors include: 25 units of HC-SR04 (analog), 25 units of VL53L0X, and 25 units of VL53L1X (digital).The authors are indebted to the Spanish Ministry of Economy and Competitiveness for the funding provided through the research project BIA2017-86811-C2-1-R, directed by José Turmo, and BIA2017-86811-C2-2-R, directed by Jose Antonio Lozano-Galant. All these projects are funded with FEDER funds. Authors are also indebted to the Secretaria d’ Universitats i Recerca de la Generalitat de Catalunya, Catalunya, Spain for the funding provided through Agaur (2017 SGR 1482). It is also to be noted that funding for this research has been provided for Seyedmilad Komarizadehasl by the Spanish Agencia Estatal de Investigación del Ministerio de Ciencia Innovación y Universidades grant and the Fondo Social Europeo grant (PRE2018-083238).Peer ReviewedPostprint (published version

Intelligent system for accurate measurement of intima-media thicknesses as markers of atherosclerosis

Abstract – One of the anatomical methods for diagnosis of atherosclerosis involves measurement of intima-media thickness (IMT) using ultrasound. However these measurements are quite complicated using conventional approaches; for this reason we are developing an intelligent measurement system that will potentially enable inexpensive and accurate IMT measurements. In this paper the IMT measurement system architecture is discussed along with the algorithm to post-trigger the ultrasonic scans. Experimental results obtained in vivo are presented and discussed. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2881

Extraction of anthropological data with ultrasound

This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University.Human body scanners used to extract anthropological data have a significant drawback, the subject is required to undress or wear tight fitting clothing. This thesis demonstrates an ultrasonic based alternative to the current optical systems, that can potentially operate on a fully clothed subject. To validate the concept several experiments were performed to determine the acoustic properties of multiple garments. The results indicated that such an approach was possible. Beamforming is introduced as a method by which the ultrasonic scanning area can be increased, the concept is thoroughly studied and a clear theoretical analysis is performed. Additionally, Matlab has been used to demonstrate graphically, the results of such analysis, providing an invaluable tool during the simulation, experimental and results stages of the thesis. To evaluate beamfoming as a composite part of ultrasonic body imaging, a hardware solution was necessary. During the concept phase, both FPGA and digital signal processors were evaluated to determine their suitability for the role. An FPGA approach was finally chosen, which allows highly parallel operation, essential to the high acquisition speeds required by some beamforming methodologies. In addition, analogue circuitry was also designed to provide an interface with the ultrasonic transducers, which, included variable gain amplifiers, charge amplifiers and signal conditioning. Finally, a digital acquisition card was used to transfer data between the FPGA and a desktop computer, on which, the sampled data was processed and displayed in a coherent graphical manner. The beamforming results clearly demonstrate that imaging multiple layers in air, with ultrasound, is a viable technique for anthroplogical data collection. Furthermore, a wavelet based method of improving the axial resolution is also proposed and demonstrated

Nondestructive Evaluation of Adhesive Bonds via Ultrasonic Phase Measurements

The use of advanced composites utilizing adhesively bonded structures offers advantages in weight and cost for both the aerospace and automotive industries. Conventional nondestructive evaluation (NDE) has proved unable to reliably detect weak bonds or bond deterioration during service life conditions. A new nondestructive technique for quantitatively measuring adhesive bond strength is demonstrated. In this paper, an ultrasonic technique employing constant frequency pulsed phased-locked loop (CFPPLL) circuitry to monitor the phase response of a bonded structure from change in thermal stress is discussed. Theoretical research suggests that the thermal response of a bonded interface relates well with the quality of the adhesive bond. In particular, the effective stiffness of the adhesive-adherent interface may be extracted from the thermal phase response of the structure. The sensitivity of the CFPPLL instrument allows detection of bond pathologies that have been previously difficult-to-detect. Theoretical results with this ultrasonic technique on single epoxy lap joint (SLJ) specimens are presented and discussed. This technique has the potential to advance the use of adhesive bonds - and by association, advanced composite structures - by providing a reliable method to measure adhesive bond strength, thus permitting more complex, lightweight, and safe designs

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A non-intrusive sensor for in-situ measurement of recession rate of heat shield ablatives. An ultrasonic wave source is carried in the housing. A microphone is also carried in the housing, for collecting the reflected ultrasonic waves from an interface surface of the ablative material. A time phasing control circuit is also included for time-phasing the ultrasonic wave source so that the waves reflected from the interface surface of the ablative material focus on the microphone, to maximize the acoustic pressure detected by the microphone and to mitigate acoustic velocity variation effects through the material through a de-coupling process that involves a software algorithm. A software circuit for computing the location off of which the ultrasonic waves scattered to focus back at the microphone is also included, so that the recession rate of the heat shield ablative may be monitored in real-time through the scan-focus approach

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This thesis studies optoelectronic devices and the integration of these components onto optoelectronic multi chip modules (OE-MCMs) using a combination of packaging techniques. For this project, (1×12) array photodetectors were developed using PIN diodes with a GaAs/AlGaAs strained layer structure. The devices had a pitch of 250μm, operated at a wavelength of 850nm. Optical characterisation experiments of two types of detector arrays (shoe and ring) were successfully performed. Overall, the shoe devices achieved more consistent results in comparison with ring diodes, i.e. lower dark current and series resistance values. A decision was made to choose the shoe design for implementation into the high speed systems demonstrator. The (1x12) VCSEL array devices were the optical sources used in my research. This was an identical array at 250μm pitch configuration used in order to match the photodetector array. These devices had a wavelength of 850nm. Optoelectronic testing of the VCSEL was successfully conducted, which provided good beam profile analysis and I-V-P measurements of the VCSEL array. This was then implemented into a simple demonstrator system, where eye diagrams examined the systems performance and characteristics of the full system and showed positive results. An explanation was given of the following optoelectronic bonding techniques: Wire bonding and flip chip bonding with its associated technologies, i.e. Solder, gold stud bump and ACF. Also, technologies, such as ultrasonic flip chip bonding and gold micro-post technology were looked into and discussed. Experimental work implementing these methods on packaging the optoelectronic devices was successfully conducted and described in detail. Packaging of the optoelectronic devices onto the OEMCM was successfully performed. Electrical tests were successfully carried out on the flip chip bonded VCSEL and Photodetector arrays. These results verified that the devices attached on the MCM achieved good electrical performance and reliable bonding. Finally, preliminary testing was conducted on the fully assembled OE-MCMs. The aim was to initially power up the mixed signal chip (VCSEL driver), and then observe the VCSEL output