Japan Electronics And Information Technology Industries Association Research Articles

A Multi-Hysteresis Control for Minimizing Battery Charging Time Within Industrial JEITA Guidelines

In common industrial practices, the Japan Electronics and Information Technology Industries Association (JEITA) guideline is widely adopted for battery temperature regulations. However, the conventional JEITA-compliant temperature-regulated current control (TRCC) is generally designed without considering the charging speed. To address this issue, a multi-hysteresis temperature-regulated current control (MTRCC) is proposed in this paper. The proposed MTRCC is designed based on the conventional JEITA-compliant TRCC by dividing the hysteresis band for each temperature reference from one to multiple. As a result, the number of charging current levels is increased from three to multiple, such that the charging speed can be improved according to the analysis. The proposed control inherits the simple and effective temperature regulations of the conventional control, while enhancing the charging speed without additional hardware costs. This approach has potential to be an alternative of the state-of-the-art TRCC in JEITA guidelines for single-cell charging applications. Empirical results validate that the proposed MTRCC (with four hysteresis bands) can achieve faster charging than the conventional control at four different ambient temperatures and the charging speed improvement is more significant when the ambient temperature is higher.

Improvement of Lithium-Ion Battery Charging From the State-of-the-Art Industrial JEITA Guidelines to a Hybrid Temperature-Regulated Current Control

This article addresses some practical issues of the Japan Electronics and Information Technology Industries Association (JEITA) battery charging guidelines and common industrial practices. The issues involve the temperature-dependent charging profile that may not lead to optimal charging time. A hybrid temperature-regulated current control (HTRCC) is proposed and compared with common JEITA charging profile in order to minimize the charging time within the thermal limits of the battery. The form factor of the charging current is used for a quick verification that HTRCC can shorten the charging time. Based on an electro-thermal battery model, the minimum charging speed improvement rate compared to JEITA charging profile is also predicted. Practical measurements of the charging profile and charging time are included to confirm the theoretical analysis.

Study on Whisker Growth on Solder Joints—Part I: Study on Acceleration Test Method

The shift to lead-free tin-based solder in electronics has created a frequent observation of whisker growth from the plated tin surface. With an expectation that the tin whisker growth is not limited to the tin-plated surface, a three-year project of the Japan Electronics and Information Technology Industries Association (JEITA) for a study of whiskers on lead-free electronics was initiated in 2006, as one of the Strategic Core Technology Advancement Programs funded by Organization for Small and Medium Enterprises and Regional Innovation Japan. This paper reports one of the results of this JEITA project, relating to whisker formation from solder joints and its acceleration test methods. When samples were submitted to soldering process and then exposed to a high-temperature, high-humidity environment, a portion of the solder surface became unevenly corroded (oxidized). Tin in the area between corrosion received the stress and formed tin whiskers. Since soldering flux with bromine content exhibited a tendency to create whisker relatively fast, the influence of temperature and relative humidity was studied with this type of flux. The results from this test were analyzed for acceleration factors and found to have a good linearity in Arrhenius plotting with varied temperatures and a constant humidity, with a calculated activation energy of 0.84 eV. Combined with the test results with constant temperature and varied humidity, the same characteristic formulas for whisker growth from the plated tin surface under high temperature/humidity in the reports of the International Electronics Manufacturing Initiative were found to be also applicable to the cases of solder joints. The constants in the formulas, however, were found to be approximately equal to those for the humidity behavior of the conductive adhesive/tin plating interface or those found for electrochemical migration.

Destruction failure analysis and international reliability test standard for power devices

The demand of power devices such as IGBT is expected to continue to increase in the future for Electric Vehicles (EV), Hybrid Electric Vehicles (HEV), and industrial applications. Power devices are affected by stresses, such as large current and abrupt temperature changes, which differ from those of normal semiconductor devices, so how to ensure the reliability is an important issue. Especially in practical use, the comprehension of destruction, which comprises the great majority of failures, and the control approach, are key points. We would like to explain some measures to reduce the number of destruction failures.To ensure the power device quality and reliability, the special evaluation and qualification methods are important; however, if we follow the international standards for testing, a large amount of evaluation samples are needed. So in Japan Electronics and Information Technology Industries Association (JEITA), activities such as standardizing of the power device reliability test method and making a qualification guideline for automotive applications are being performed. In this lecture, we will first explain the trend of power devices and the state of the measures for the destruction failures. Then we will describe the outline of the reliability standard of the power devices, the qualification guideline formulation state for high reliability applications in Japan and the issues of quality and reliability for compound semiconductors.

Conditions of Exciting Coils Used in Evaluation of Shielding Factor of Magnetically Shielded Rooms for Uniform Magnetic Field

To shield the environmental magnetic noises, magnetically shielded rooms (MSRs) are used for biomagnetic measurements, etc. The sources of environmental noises are far away from the MSR, in such a way that almost uniform magnetic field is applied to the MSR. To evaluate the shielding factor SF <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</i> for the uniform magnetic field in a construction site, the magnetic noises are applied by coils. However, SFs depend on the size and position of the coils, so a standardization of the method for accurately evaluating SF <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</i> using coils is being discussed in the Japan Electronics and Information Technology Industries Association (JEITA). In JEITA, we have already proposed and verified the method of estimating SF <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</i> 's by smaller coils placed near MSRs in the low frequency region without eddy current effect. In this paper, the suitable size and position of coils, such that the errors of the SF <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</i> 's estimated and directly evaluated are within 10%, on various shapes of MSRs are obtained using 3-D linear magnetostatic field analysis. Moreover, to correct SFs when the magnetic noises are applied to MSRs through a reinforced concrete wall, etc., the effect of wall on the applied magnetic field is also obtained from the experiment. Finally, the suitable coil conditions and the correction method are verified by the experiment using an actual double-layered MSR.

Method for Evaluating Shielding Factor of Magnetically Shielded Room for Uniform Magnetic Field Using Exciting Coil

To shield environmental magnetic noise, magnetically shielded rooms (MSRs) made of ferromagnetic materials are used for biomagnetic measurements. The shielding performances of MSRs are usually represented by the shielding factor, SF. The source of environmental noise is far away from the MSR, so that almost uniform magnetic field is applied to the MSR. Therefore, the shielding factor SF0 for uniform magnetic field needs to be evaluated. To evaluate SF at a construction site, magnetic noise is applied to the MSR by coils. However, the magnetic noise generated by coils is not uniform, and SFs depend on the sizes and positions of the coils and are not unique for the same MSR. Therefore, standardization of a method to evaluate SF0 accurately using coils is being discussed by the Japan Electronics and Information Technology Industries Association (JEITA). We discuss here a method for estimating the SF0s of MSRs by placing a smaller coil near the MSR under the condition with very low frequency, in which the eddy current effect can be neglected, using both 3D linear and nonlinear magnetostatic field analyses and measurements. A method to estimate SF0s by extrapolation using simple numerical expressions representing the relation between the SF and the size and the position of the coil is proposed in the 3D linear magnetostatic analysis. The proposed method is applied to an experiment with a single-layered MSR under ideal conditions. Namely, MSR is placed in a spacious building so that the experiment is not affected by the steel frames and the reinforcing bars of the building. Moreover, the door of MSR does not affect its SFs. In these conditions, we were able to accurately estimate SF0s in the experiment.

Method for Evaluating Shielding Factor of Double Layered Magnetically-Shielded Rooms for Uniform Magnetic Field Using Exciting Coils Placed on One Side

To shield the environmental magnetic noises, magnetically shielded rooms (MSRs) are used for biomagnetic measurements, etc. The sources of environmental noises are placed far away from the MSR, in such way that almost uniform magnetic fluxes are applied to the MSR. Therefore, to specify the shielding performance of MSR, the shielding factor SF? for the uniform magnetic flux density should be evaluated. To evaluate SF?, in a construction site, the magnetic noise is applied by coils. However, SF's depend on the size and position of the coil. Therefore, to accomplish a standardization of the method for evaluating SF?, accurately, by coils, the method for estimating SF?'s by smaller coil placed near MSR is being investigated in JEITA (Japan Electronics and Information Technology Industries Association). In JEITA, we have already proposed the method of estimating SF?'s by the extrapolation using simple numerical expressions representing the relations between the SF and the size, position of coil. The proposed method was verified by the actual single-layered MSR using coils placed on double sides. In this paper, the method of estimating SF? of the double-layered MSR, using coils placed only on one side of MSR and taking account of door effect, is investigated using 3D nonlinear magnetic field analysis and measurements. By using the analysis, it is shown that the single coil should be set in front of the door. Moreover, SF?'s estimated by using the measured data with the optimal coil setting can almost represent the tendencies of the true SF?.

Microstructure of External Stress Whiskers and Mechanical Indentation Test Method

Lead-free commercial products have been dramatically increasing in the world markets as the restriction of certain hazardous substances (RoHS) directive in the European Union has been enacted. At the same time, the problem of “tin whiskers” has become one of the most serious problems in the industry. Growth of tin whiskers is believed to be related to residual stress inside the tin plating film and external compressive stress. Whiskers in fine-pitch connectors have affected the practical production of advanced digital equipment. The Japan Electronics and Information Technology Industries Association (JEITA) has proposed a new testing method to evaluate tin whiskers, especially for the fine-pitch connectors. This paper describes the microstructures of external stress whiskers and the mechanical indentation test method.

Keeping the tigers at bay [Japan's electronic industry

The Japanese technology industry has been struggling to compete with its neighboring tiger economies and the growing strength of China as a manufacturing base for consumer electronics and computer goods. The Japan Electronics and Information Technology Industries Association (JEITA), however, is confident that Japan can remain a high-tech powerhouse and take on the neighboring competition. JEITA believes that Japan can do this with innovation and increased spending on research and design in the form of joint ventures between Japanese companies with overseas companies. In addition, the government has also established the Council for Science and Technology Policy in the Cabinet Office, which is tasked to formulate the nation's science and technology policies.

Standardization of Characterization of Bulk Microdefects and Denuded Zones in Annealed CZ Si

The requirement to standardize measurement methods for BMD (Bulk Micro Defect) density and DZ (Denuded Zone) CZ silicon has lead to the establishment of a SEMI standard for annealed CZ silicon wafers. Therefore, it was decided that we should aim at standardizing the preferential-etching and 90-degrees laser- scattering tomography techniques as a collaborative work between JEITA (Japan Electronics and Information Technology Industries Association) and JSPS (Japan Society of Promotion of Science) 145th Committee. In this work, we carried out a set of round robin tests and examined whether we could jointly standardize both the preferential-etching and the 90 degrees laser-scattering methods. This resulted in a standardized measurement protocol for BMD density and DZ width, which has become known as the JEITA standard EM 3508 [1].

Whisker test methods of JEITA whisker growth mechanism for test methods

As the industry moves toward lead-free electronics, a replacement for the traditional tin-lead plating is required. Pure tin is the coating of choice for many suppliers, but there is a well-known problem with the growth of tin whiskers. A whisker is comprised of a tin crystal which, after an incubation period, grows with time. Whiskers may grow long enough to cause shorts in electronic circuits. A test method is required for evaluating the reliability risk inherent in tin whiskers. The Japanese government requested the Japan Electronics and Information Technology Industries Association (JEITA) to establish test methods for solderability, reliability, whisker, and migration for lead-free electronics. The goal of this subcommittee was to propose the test methods for tin whiskers by March 2004. The committee carried out a literature survey, and developed hypotheses for whisker growth, which was then applied to test methods. Two types of studies were undertaken. One is a fundamental study to verify the hypothesis. The other looked at accelerated tests to develop recommended test conditions. As a result, we found that the diffusion of copper, oxidation, and thermal cycling all influence tin whisker growth. This paper describes the results of the fundamental studies and reports on the JEITA whisker growth mechanism.