Zairyo-to-Kankyo
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ONLINE ISSN: 1881-9664
PRINT ISSN: 0917-0480

Zairyo-to-Kankyo Vol. 49 (2000), No. 11

  • Corrosion Damages of Resin Encapsulated Semiconductor Devices and its Preventions

    pp. 641-648

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    Corrosion damages of the electronics components have been become important in the reliability of the several machines and systems. The corrosion mechanisms of resin encapsulated semiconductor devices have change for the applied testing conditions. For example, in the accelerated testing method, corrosion damages was occurred by crevice corrosion or delamination in the leadframe/resin interface. In order to precise evaluations, it needs to be examined in mild environments which used conditions of semiconductor parts.
  • Corrosion in The Electrical or Electronic Components of Telecommunications Equipment

    pp. 649-654

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    The provision of economical telecommunications service requires effective maintenance management of a huge infrastructure of telecommunications equipment. A major maintenance concern is corrosion of the many metal components in telecommunications equipment. This paper examines the corrosion of the electrical or electronic components in telecommunications equipment, for example, corrosion in past conventional telephone switching equipment such as cross-bar switches that use mechanical contacts, the electrolytic corrosion in telephone jacks, and the sulfurization corrosion of Ag line patterns on semiconductor substrates. In addition, we examine the problem of corrosion in the closed packages of outdoor equipment caused by an accumulation of sea salt particles, dust, and humidity in the future.
  • The Present Situation of Corrosive Gas Test for Electronic Parts

    pp. 655-663

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    To evaluate corrosion resistance and reliability of electronic device in operation and storage condition, corrosive gas tests are performed. Recently many kind of mixed gas tests with low concentration are investigated in some technical committees, and adopted in international standards, ISO, IEC, and Japanese industrial standard (JIS). Our study results indicated that SO2 and NO2 mixed gas test was suitable for simulating the ordinary environment. The mixed gas test with ozone accelerates the corrosion of copper, while simulating the ordinary environment. Impedance measurement results reflect the effect of corrosive gas.
  • Corrosion and Its Prevention of Thin Film Magnetic Head

    pp. 664-668

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    Thin film magnetic heads for high recording density rigid disk drives are composed of ceramics and metal multilayers. These metals take important role for read and write of information storage. It is a vital wound if the thin film metals suffer corrosion attack. Therefore, corrosion of thin film magnetic heads has been studied with surface analysis and electrochemical techniques in several related organizations. The author hopes some data introduced in this paper would helpful for comprehension of corrosion of magnetic heads and for prevention of the corrosion.
  • Development of Laminate Material for Enviromental Friedly TULC

    pp. 669-674

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  • Evaluation of Intergranular Corrosion of Austenitic Stainless Steel by Acoustic Microscope

    pp. 680-683

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    Experiments were performed to confirm the applicability of acoustic microscopy to evaluate intergranular corrosion of austenitic stainless steel. While cold working slightly increased surface wave velocity, but the effects of surface roughness, solution heat treatment and sensitizing treatment on surface wave velocity were very small. Surface wave velocity on specimens corroded in Strauss solution decreased according to sensitizing time at various sensitizing temperatures. This decrease of surface wave velocity by intergranular corrosion coincided with corrosion depth. From these results, it was concluded that the degree of intergranular corrosion can be evaluated by the measurement of surface wave velocity.
  • Difference in Corrosion Behavior of Pure Iron and Carbon Steel in Short-time Exposure Test

    pp. 684-689

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    Corrosion behavior of pure iron and carbon steel in short-time exposure test was examined in detail by electrochemical methods. Though the corrosion resistant of pure iron was better than that of carbon steel in the initial stage of exposure test, the amount of corrosion losses for pure iron was more than that for carbon steel after 6 month-exposure test. From the results of ESCA analysis and various electrochemical measurements, it was found that the oxide film formed on pure iron in the initial stage of exposure test was more stable and difficult to be attacked by chloride ions than that formed on carbon steel. On the other hand, after 6 month-exposure test, it was indicated that the amount of γ-FeOOH that was reduced to magnetite easily was abounding in the rust of the pure iron in comparison with that of the carbon steel.
  • Atmospheric Penetration Depth on Stainless Steels in contact with NaCl, MgCl2 and Sea Salt under Relative Humidities of 33, 50 and 75% at Room Temperature

    pp. 690-695

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    Atmospheric corrosion behavior of for stainless steels in contact with chlorides was studied in laboratory atmosphere. According to Shoji's method, nine droplets, each of which consist of 5μl of 0.5N Cl- solution, were put on a stainless steel specimen and were dried up. Thus-prepared specimens were exposed in a humidity-controlled chamber for three to six months. Penetration depth at the deposit strongly depended on RH and the maximum value of penetration depth was obtained at 50% RH for 430 steel and at 33% RH for 304 steel with the deposits of sea salt and MgCl2, while no penetration was observed with the deposit of NaCl at 33% and 50% RH. Under RH of 75% all the three kinds of salt gave no penetration for 430 and 304 steels. The test was extended to seven other steels, and penetration was summarised in terms of Pitting Resistance Equivalent=[%Cr]+3.3[%Mo]+16[%N].
  • Active Dissolution of Type 304 Stainless Steel enhanced by Dithionite Ions in Amidosulfuric Acid Solution

    pp. 696-705

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    A dyeing machine part made of type 304 stainless steel was severely attacked in contact with 0.1mol/l sulfamic acid (amidosulfuric acid, H2NSO3H) solution of pH 1.2 contaminated with hydrosulfito (Na2S2O4) at 60°C. This study was conducted at 30°C and succeeded to reproduce the enhanced attack with corrosion rates up to 5.4mm per year under added Na2S2O4 concentrations between 0.1 and 5mmol/l at pHs lower than 2.2. The steel dissolved at active potentials with deposition of black corrosion products and generation of H2S gas on its surface. Such high rates of corrosion was attributed to the effects of Na2S2O4 which increased both anodic dissolution of the steel and cathodic current for reduction of S0 to H2S. When the Na2 S2O4 concentration increased over 7mmol/l, the increased cathodic current passivated the steel by exceeding the anodic one which was inhibited by protective surface film consisting mainly of S0 and NiS.
  • Corrosion Behavior of Sintered Silicon Carbide in Water Vapor at 300°C

    pp. 706-709

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    The corrosion behavior of sintered silicon carbide (SiC) was examined in saturated water vapor at 300°C and the results were compared with those in 300°C water environment. Significant intergranular corrosion occured in the water vapor. The weight loss of the samples exposed to the water vapor was larger than that in the water. In the water vapor environment, scales, such as amorphous SiO2, did not form on the surface. This fact suggestes that volatile species, such as Si(OH)4 were produced. The flexural strength of the samples exposed to both the environments for 10 days reduced to about 80% of the initial strength.

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