K. Chomsuwan

Eddy-current testing probe with spin-valve type GMR sensor for printed circuit board inspection

This paper proposes an eddy-current testing (ECT) probe composed of a spin-valve giant magnetoresistance (SV-GMR) sensor and a meander coil for the inspection of bare printed circuit board. The SV-GMR sensor serves as a magnetic sensor for the ECT probe to sense the variation of the magnetic field distribution occurred on the printed circuit board. The SV-GMR sensor is used specifically to detect the changing magnetic field distribution occurred at the defect point. The characteristics of the proposed probe are discussed in this paper. The comparisons of signal-to-noise ratios obtained from ECT probe with SV-GMR sensor and with solenoid coil verify that the applying of SV-GMR sensor to the ECT probe can improve the PCB inspection results.

A Novel Needle-Type SV-GMR Sensor for Biomedical Applications

Cancer is the most deadly disease in the world today. There is a variety of different treatment methods for cancer, including radiotherapy and chemotherapy with anticancer drugs that have been in use over a long period of time. Hyperthermia is one of the cancer treatment methods that utilizes the property that cancer cells are more sensitive to temperature than normal cells. The control of temperature is an important task in achieving success using this treatment method. This paper reports the development of a novel needle-type nanosensor based on the spin-valve giant magnetoresistive (SV-GMR) technique to measure the magnetic flux density inside the body via pricking the needle. The sensor has been fabricated. The modeling and experimental results of flux density measurement have been reported. From the information of flux density, the temperature rise can be estimated to permit the delivery of controlled heating to precisely defined locations in controlled hyperthermia cancer treatment. The actual experiment with human is under investigation

Bare PCB Inspection System With SV-GMR Sensor Eddy-Current Testing Probe

This paper describes bare printed circuit board (PCB) inspection based on eddy-current testing (ECT) technique with high scanning speed. A high-frequency ECT probe composed of a meander coil as an exciting coil and the spin-valve giant magnetoresistance (SV-GMR) sensor was fabricated and is proposed. The ECT probe was designed based on crack inspection over flat surface, especially suitable for microdefect detection on high-density bare PCB. The ECT signal detected by the SV-GMR sensor was acquired by high-speed A/D converter for applying the signal processing based on digital technique. Harmonic analysis based on Fourier transform was used to analyze the ECT signal at fundamental frequency in order to increase inspection speed and this technique allowed the ECT probe to scan bare PCB, with high sampling frequency and with high-spatial resolution inspection. Experimental results verified the possibility and the performance of the proposed PCB inspection system based on ECT technique

Improvement on Defect Detection Performance of PCB Inspection Based on ECT Technique With Multi-SV-GMR Sensor

This paper describes the improvement on the defect detection performance of printed circuit board (PCB) inspection based on the eddy-current testing (ECT) technique with the multispin-valve giant magnetoresistance (SV-GMR) sensor. To obtain the ECT signal in the same scanning line, SV-GMR sensors are mounted on the exciting coil in the same column parallel with the scanning direction. Harmonic analysis based on the Fourier transform is used to analyze the signal from the SV-GMR sensor in order to increase scanning speed. Then signal averaging is applied to the ECT signal in order to improve the signal-to-noise ratio. Experimental results are performed to verify the inspection performance

Conductive micro-bead array detection by high-frequency eddy-current testing technique with SV-GMR sensor

Applying of eddy-current testing (ECT) probe with spin-valve giant magnetoresistive (SV-GMR) sensor to high frequency excitation provides the feasibility of micro-defect detection for example high-density printed circuit board inspection. In this paper, the detection of conductive micro-bead with 250 to 760 /spl mu/m diameter, and its feasibility are discussed. The analytical model is discussed and compared with experimental results to verify that the proposed technique is able to detect conductive micro-bead.

Application of Giant Magnetoresistive Sensor for Nondestructive Evaluation

This paper describes the applications of spin-valve type giant magnetoresistance sensor (GMR) for nondestructive evaluation. One is the eddy-current testing (ECT) probe which enables us to inspect micro defect and to detect micro conductors. The proposed ECT probe was applied to the inspection of bare printed circuit board and the recognition of micro solder bead for IC surface mounting package. Another is the measurement of the density of magnetic fluid injected in living body for the hyperthermia treatment. For this purpose, the needle type GMR probe was developed. The experimental results verify the possibility of the proposed system.

Conductive microbead detection by Helmholtz coil technique with SV-GMR sensor

We present an eddy-current test (ECT) method for detecting conductive microbeads on a nonconductive substrate. A Helmholtz coil is used to generate an exciting magnetic field. The magnetic fields, generated by eddy-currents in a Pb-Sn microbead, are detected by a spin-valve giant magnetoresistive (SV-GMR) sensor. The experimental results are compared to an analytical solution for the magnetic field over the microbead. Early results for the detection of a grid of microbeads are also presented.

Conductive Microbead Array Detection Based on Eddy-Current Testing Using SV-GMR Sensor and Helmhlotz Coil Exciter

Eddy-current testing (ECT) using a spin-valve giant magnetoresistance (SV-GMR) sensor has been applied to detecting conductive micro-beads and also flaws on a printed circuit board. This paper presents the detection of conductive micro-bead arrays with the gap between SV-GMR sensor and bead for scanning probe. The experimental results can confirm the proposed probe ability for detection of conductive micro-bead array.

Metallic Bead Detection by Using Eddy‐Current Probe with SV‐GMR Sensor

The progress of the ECT probe with micro magnetic sensor becomes possible to apply to various applications. The detection of micro metallic bead used for electric packaging has been reported in this paper. We proposed micro ECT probes with meander coil as exciter and spin‐valve giant magneto‐resistance (SV‐GMR) as receiver. Micro metallic bead(solder ball) with the diameter of 0.25 to 0.76 mm is used as a measuring object. We discuss the detection and alignment of metallic bead by using ECT technique.

PCB Conductor Dimension and Alignment Inspection with GMR Based ECT Probe

Eddy current testing (ECT) probe consisted of spin‐valve giant magneto‐resistance (SV‐GMR) sensor and meander type exciter coil applied to printed circuited board (PCB) conductor dimension and alignment inspection is proposed in this paper. High‐frequency excitation up to 18 MHz is allowed to inspect the thin PCB conductor, less than 10 μm. The proposed ECT probe characteristics and configuration were presented. The inspection results were shown that the proposed ECT probe will provide an accurate inspection.