Scanning Acoustic Microscope System Research Articles

Novel Water Probe for High-Frequency Focused Transducer Applied to Scanning Acoustic Microscopy System: Simulation and Experimental Investigation.

A scanning acoustic microscopy (SAM) system is a common non-destructive instrument which is used to evaluate the material quality in scientific and industrial applications. Technically, the tested sample is immersed in water during the scanning process. Therefore, a robot arm is incorporated into the SAM system to transfer the sample for in-line inspection, which makes the system complex and increases time consumption. The main aim of this study is to develop a novel water probe for the SAM system, that is, a waterstream. During the scanning process, water was supplied using a waterstream instead of immersing the sample in the water, which leads to a simple design of an automotive SAM system and a reduction in time consumption. In addition, using a waterstream in the SAM system can avoid contamination of the sample due to immersion in water for long-time scanning. Waterstream was designed based on the measured focal length calculation of the transducer and simulated to investigate the internal flow characteristics. To validate the simulation results, the waterstream was prototyped and applied to the TSAM-400 and W-FSAM traditional and fast SAM systems to successfully image some samples such as carbon fiber-reinforced polymers, a printed circuit board, and a 6-inch wafer. These results demonstrate the design method of the water probe applied to the SAM system.

An innovative application of double slider-crank mechanism in efficient of the scanning acoustic microscopy system

This paper proposes an innovative application of double slider-crank mechanism, which is utilized to develop a fast scanning module (FSM) of the scanning acoustic microscopy (SAM) system for evaluating the quality of 12-inch silicon wafer, that is, WFSAM system. In this application, the slider displacement and velocity are two critical parameters that must be carefully calculated to ensure the WFSAM system operates properly. Based on the scanning requirements, the slider displacement and velocity were calculated to determine the operation parameters of WFSAM system. A custom sample with known dimensions was prepared to scan using WFSAM system, which validated the WFSAM capabilities in order to provide internal information with accurate measurement. The quality of two 12-inch silicon wafers was evaluated using the WFSAM system. Finally, the design process of slider-crank mechanism is illustrated by a flowchart, which is used to develop the FSM of SAM system for inspecting any sample size.

Development of fast scanning module with a novel bubble solution applied to scanning acoustic microscopy system for industrial nondestructive inspection

Scanning acoustic microscopy (SAM) system is a powerful nondestructive instrument owing to its capability to provide internal information and defect positions inside a material. In industrial applications of SAM, the scanning time plays an important role in enhancing efficient inspection of the product line. Several studies have used the traditional SAM system, which develops based on linear motor to inspect industrial samples, but the inspection time remained relatively long and cost-prohibitive. Herein, we reported a low-cost fast SAM (FSAM) system that provided the image results in a short time while maintaining their high resolution. In this design, FSAM fast scanning module (FSM) was developed by exploiting the slider-crank mechanism, which was optimized for a specific product to substantially reduce the inspection time. During the scanning process, bubbles were generated due to the rapid movement of transducer into the water, namely the bubble cavitation. The bubbles restricted the ultrasound wave propagation, which resulted in the bad image quality. The bubble cavitation phenomenon was examined using the incompressible flow theory to investigate the bubble inception, which was defined based on the pressure value around transducer. The bubbles appeared in areas where the pressure less than the vapor pressure. Using the OpenFOAM to analyze the pressure value, the bubble problem was solved by a novel solution that used a bubble reduction plate attaching to the transducer. The coin and aluminum samples with known dimensions and internal structure were prepared to scan using the FSAM system, which validated the simulation results and FSAM capabilities in providing good images with internal information and accurate measurements. Finally, FSAM system was designed and developed to successfully inspect industrial samples in a short time, such as an integrated circuit chip, printed circuit board, welded sheets, and silicon wafer. Using the FSAM system to scan welded sheets, the scanning time were reduced by approximately 77% compared to the traditional SAM system. These results demonstrate that the FSAM system is a potential instrument for industrial nondestructive inspection.

Development of Scanning Acoustic Microscopy System for Evaluating the Resistance Spot Welding Quality

ABSTRACT Scanning acoustic microscopy (SAM) system (TSAM-400) was designed and developed for evaluating the quality of resistance spot welding (RSW) joints of 1.5 mm-thick SUS 316 stainless steel sheets under different welding parameters. Indentation and nugget information (diameter and shape) were used for evaluating the RSW quality. SAM A-scan signals were used to calculate the indentation. The nugget diameter was determined in the C-scan image. Internal information (nugget shape, splashes, and defects) was visualized in the B- and C-scan images. In addition, the spot weld area was treated to examine the surface topography effect. The nugget diameters of treated and untreated areas were measured and compared to conclude that the surface topography effect can be neglected in the quality evaluation by SAM system. By implementing TSAM-400, some specimens were successfully tested with a scanning area of 55 × 15 mm2, and a scanning time of 33.5 s corresponding to a B-scan frame rate of 4.5 Hz, and a resolution of 0.1 × 0.1 mm2. Finally, the good input parameters for welding two 1.5 mm-thick SUS 316 were determined by analyzing the results from TSAM-400.

Development of Fast Scanning Module Applied to Scanning Acoustic Microscopy System for Industrial Nondestructive Inspection

Development of Fast Scanning Module Applied to Scanning Acoustic Microscopy System for Industrial Nondestructive Inspection

Use of Ultrasound Microscopy for Ex Vivo Analysis of Acoustic Impedance in Mouse Liver with Steatohepatitis

Scanning acoustic microscopy reveals information on histology and acoustic impedance through tissues. The objective of the present study was to investigate whether acoustic impedance values in the liver over time reflect the progression of steatohepatitis through different grades and stages, and whether this approach can visualize histologic features of the disease. Mice were divided into two groups: a control group and a steatohepatitis group prepared by keeping the mice on a methionine and choline-deficient diet for 56 weeks. The hepatic lobe was excised for measurement of impedance and observation of microscopic structure using a commercially available scanning acoustic microscopy system with a central frequency of 320 MHz. Scanning acoustic microscopy revealed that acoustic impedance through liver tissue with steatohepatitis temporarily decreased with the degree of fat deposition and then increased in parallel with the progression of inflammation and fibrosis. However, the acoustic images obtained did not allow discrimination of detailed microstructures from those seen using light microscopy. In conclusion, estimation of acoustic impedance appears to have potential clinical applications, such as for monitoring or follow-up studies.

비파괴 검사용 고주파 초음파 트랜스듀서 제작

The development of high frequency ultrasonic transducer is crucial for detecting cracks or internal defects of some materials such as semiconductors, PCBs, and display panels with a size of few microns for the scanning acoustic microscopy (SAM) system. In this study, high frequency ultrasonic transducer was fabricated with a 13 μm thick ZnO film deposited on a sapphire substrate by DC sputtering machine. Ultrasonic transducer with 100 MHz center frequency, -6 dB bandwidth of 21% and the insertion loss of -68 dB was designed for the SAM system. Experimental results show that high frequency ultrasonic transducer device may have potential for high resolution application of nondestructive test and can be applied for various acoustic imaging system such as photoacoustic imaging in the future.

Speed of sound evaluation considering spatial resolution in a scanning acoustic microscopy system capable of observing wide spatial area

The dependence of the speed of sound (SoS) in sliced rat organs on the spatial resolution was investigated through ultrasound analysis at high frequencies (80 and 250 MHz). The radio-frequency echo signals from target were acquired by a scanning acoustic microscopy system developed by the authors that can observe a sample with a transducer. The SoS was evaluated by correcting for the time of flight difference obtained from the wide area measurement. The dependency of the SoS on the spatial resolution was evaluated by applying different filtering methods. Stable analysis was possible after time correction, and fine textures reflecting the microstructure could be observed. The application of different filters to the results obtained at 250 MHz resulted in average SoS values that were similar to those obtained at 80 MHz. These results suggest that the primary targets evaluated 80 and 250 MHz are connective tissue and single cells, respectively.

A power cycling degradation inspector of power semiconductor devices

We have proposed a failure analysis based on a real-time monitoring of power devices under acceleration test. The real-time monitoring enables to visualize the mechanism that leads to a failure by obtaining the change of structure inside the device in time domain with high spatial resolution. In this paper, we presented a new analytical instrument based on the proposed failure analysis concept. The essential functions of this instrument are (1) power stress control, (2) non-destructive inspection and (3) water circulation. An original design power-stress control system and a customized scanning acoustic microscopy system enable us a non-destructive inspection inside the device under power cycling test. This instrument exhibits a great advantage especially to monitor failure mechanisms without having to open the module.

Acoustic Impedance Analysis with High-Frequency Ultrasound for Identification of Fatty Acid Species in the Liver

Acoustic properties of free fatty acids present in the liver were studied as a possible basis for non-invasive ultrasonic diagnosis of non-alcoholic steatohepatitis. Acoustic impedance was measured for the following types of tissue samples: Four pathologic types of mouse liver, five kinds of FFAs in solvent and five kinds of FFAs in cultured Huh-7 cells. A transducer with an 80-MHz center frequency was incorporated into a scanning acoustic microscopy system. Acoustic impedance was calculated from the amplitude of the signal reflected from the specimen surface. The Kruskal–Wallis test revealed statistically significant differences (p < 0.01) in acoustic impedance not only among pathologic types, but also among the FFAs in solvent and in cultured Huh-7 cells. These results suggest that each of the FFAs, especially palmitate, oleate and palmitoleate acid, can be distinguished from each other, regardless of whether they were in solution or absorbed by cells.

Fatty-acid species identification by quantitative high-frequency acoustic impedance measurements

Accurate discrimination of non-alcoholic steatohepatitis (NASH) from simple steatosis is a critical issue in current clinical practice because NASH can progress to cirrhosis or even liver cancer. Some studies reported that the free fatty acids (FFA) composition of the liver changes with the progression of NASH. Therefore, an ultrasound-based diagnostic tool could be based on measurements of the acoustical properties of FFAs. This study investigated how FFAs influence the acoustical properties of liver cells at a microscopic level using scanning acoustic microscopy (SAM) with four pathological types of mouse livers, five kinds of FFAs in solution, and five kinds of FFAs in cultured cells. A SAM system based on an 80-MHz center-frequency transducer was employed. The acoustic impedance was computed from the echo amplitude and the pressure-reflection coefficient. One-way ANOVA showed statistically significant differences (p < 0.01) in acoustic impedance among pathological types. NASH was found to have the low...

Detection Resolution Analysis of Scanning Acoustic Microscopy Used in Electronic Packaging

Scanning Acoustic Microscopy (SAM) has been a powerful non-destructive testing tool used in electronic packaging and material characterization. With the development of 3D electronic packaging, internal dimensions of electronic packaging are getting more and more smaller, and the detection accuracy of existing non-destructive testing technology is far behind the requirements of manufacturing technology. In this study, a set of practical SAM system was developed independently by our Lab. And its detection resolution was analyzed using high frequency focused transducers with center frequency ranging from 20 MHz to 100MHz. The experimental results show that the lateral resolution of the ultrasonic transducer with 100MHz central frequency can reach about 40 microns, which is consistent with calculated resolution. Comparing with Sparrow criteria, Rayleigh criteria is more coherent with the experimental results.

Scanning acoustic microscopy for characterization of gastric lesions

Study objectiveA scanning acoustic microscope (SAM) is a device that uses ultrasound (frequency, 120 MHz) to image an object. Because the harder the tissue, the more the speed of ultrasound, SAM can provide data on the elasticity of tissues and lesions. Can SAM discriminate normal and pathological lesions of stomach?Materials and MethodsFormalin‐fixed paraffin‐embedded sections of gastric lesions 10 um in thickness were used. We compared gastric lesions between SAM and light microscope (LM) images.ResultsSAM system discriminated gastric components and demonstrated distinct acoustic images such as adenocarcinomas, carcinoids, lymphomas leiomyomas(Figure) and GIST. Areas with thick fibrous portion and desmoplastic reactions associated with cancer invasion showed the greater speed‐of‐sound (SOS). Cell density portions also demonstrated the faster SOS than sparse area.SAM provided the following benefits over LM: (1) images were acquired in only a few minutes without special stainings, (2) analysis by SAM system could be helpful to understand ultrasonic endoscopic images, and (3) digitized SOS data could be statistically compared among different lesions of stomach.This work was supported by Japan Society for the Promotion of Science KAKENHI Grant Number 24590445.

Pulmonary imaging with a scanning acoustic microscope discriminates speed-of-sound and shows structural characteristics of disease

Tissue elasticity can be detected using a scanning acoustic microscope (SAM), whereby acoustic images are created from the speed of sound through tissues. This system discriminated pulmonary tissue components and demonstrated distinct acoustic images of the lung; these results corresponded well to those obtained using the conventional microscope. SAM provides the following benefits: (1) images are acquired in only few minutes without requirement for staining, (2) basic data is obtained for low-frequency ultrasonic examination, and (3) speed of sound from each lesion is digital and comparable among diseases. Comparative analysis of cancer invasion, post-inflammatory fibrosis, and deposition disease was possible using the data obtained with the system, and the results showed good correlation with those using the conventional microscope and by clinical diagnosis. The SAM system is applicable not only to pulmonary diseases but also to various diseases in other organs.

The Acoustic Micro Integrated Detection Technique for Silicon Wafer Processing

This document presents an integrated detection method for the whole cycle of silicon wafer processing based on Scanning Acoustic Microscope (SAM). It can be used for thickness and chamfering measurement, surface and subsurface testing, internal defects detection and identification. A SAM system was designed for silicon processing and silicon-based devices fabrication. It has more favorable measuring accuracy and quantitative analysis ability than the traditional inspection equipments using for wafer process such as infrared detector.

Development of a Practical Scanning Acoustic Microscopy

Scanning acoustic microscopy (SAM) is a powerful non-destructive testing tool used in electronic, material and medical testing area. Commercial SAM products are generally too expensive to be extended to common users. Therefore, a practical SAM system had been developed using high-frequency ultrasonic focus transducers, a wide-band pulse transmitter/receiver, a high-speed data acquisition card, and a high-precision motion system. The SAM system's precision and function can meet the requirement of practical test adequately, and the cost is much lower compared to commercial products. Several kinds of imaging method were introduced, and the SAM system has the ability to accomplish full-wave data acquisition.

Ultrasonic Tissue Characterization of Atherosclerosis by a Speed-of-Sound Microscanning System

We have been developing a scanning acoustic microscope (SAM) system for medicine and biology featuring quantitative measurement of ultrasonic parameters of soft tissues. In the present study, we propose a new concept sound speed microscopy that can measure the thickness and speed of sound in the tissue using fast Fourier transform of a single pulsed wave instead of burst waves used in conventional SAM systems. Two coronary arteries were frozen and sectioned approximately 10 microm in thickness. They were mounted on glass slides without cover slips. The scanning time of a frame with 300 x 300 pixels was 90 s and two-dimensional distribution of speed of sound was obtained. The speed of sound was 1680 +/- 30 m/s in the thickened intima with collagen fiber, 1520 +/- 8 m/s in the lipid deposition underlying the fibrous cap, and 1810 +/- 25 m/s in a calcified lesion in the intima. These basic measurements will help in the understanding of echo intensity and pattern in intravascular ultrasound images.

Microelectronic package characterisation using scanning acoustic microscopy

In a highly competitive market, reliable techniques for manufacturing quality control of electronic devices are demanded. Characterisation of modern microelectronic package integrity becomes more difficult due to the continued miniaturisation of electronic device and the complexity of advanced micro-assembling technologies such as chip-scale packages and 3D IC stacks. In this paper, sparse representations of acoustic signals are sought to improve the scanning acoustic microscopy (SAM), a common non-destructive tool for failure analysis of microelectronic packages. Sparse representation of an ultrasonic signal is obtained by decomposing it in an overcomplete dictionary. Detection and location of ultrasonic echoes are then performed on the basis of the resulting redundant representation. The method offers a solution to the deconvolution problem for restoration of the ultrasonic reflectivity function. It can restore closely space overlapping echoes beyond the resolution of the conventional SAM system. It also produces high resolution and accurate estimates for ultrasonic echo parameters, i.e., time-of-flight, amplitude, centre frequency, and bandwidth. These merits of the proposed method are explored in various potential applications for microelectronic package characterisation.

Twenty years’ development of acoustic microscopy for medicine and biology

Since 1985, scanning acoustic microscope (SAM) systems for medicine and biology has been developed and have been equipped for investigation of acoustic properties of various organs at Tohoku University. There are three objectives of SAM for biomedicine. First, it is useful for intraoperative pathological examination because staining is not required. Second, it helps understanding lower frequency ultrasonic images such as echography or intravascular ultrasound because SAM provides microscopic acoustic properties. Third, it provides information on biomechanics of tissues and cells. The most important feature of our SAM is to measure attenuation and sound speed of soft tissues by analyzing the frequency-dependent characteristics of amplitude and phase. Recently, a new-concept acoustic microscopy using a single pulsed wave instead of burst waves used in conventional SAM systems was proposed. Application of SAM has also been broadened and it covers not only myocardium and atherosclerosis in cardiology but also skin, bone, cartilage, tendon, and muscle in dermatology and orthopedic surgery. Higher resolution acoustic microscopy with over 500 MHz enabled us to visualize cultured cells and it can be applied for quality assessment of regenerated skins and cartilage. Impedance acoustic microscopy and 3-D acoustic microscopy are developed for in vivo tissue imaging.

Characterization of Material Degradation in Epoxy Film Based on Scanning Acoustic Microscopy (SAM)

In order to evaluate the degradation of the epoxy coating in nuclear power plants, acoustic wave velocities of epoxy films are measured using defocused scanning acoustic microscopy system(SAM). Unlike metals, the surface of the epoxy coating on the concrete liner is so thin and wavy that the conventional ultrasonic techniques for acoustic velocity of epoxy coating are hard to apply. Acoustic velocities of bulk waves are determined from V(z,t) curves of mode-converted waves generated in the film by SAM. Epoxy films are fabricated and degraded under various accelerated aging conditions, and both of longitudinal and shear wave velocities of the epoxy film are measured. Approximately 10% of reduction in acoustic wave velocity is observed from experimental results when the aging is developed fully in epoxy films. It is also found that longitudinal wave is more sensitive to deterioration of epoxy coating than transverse wave.