QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY
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PRINT ISSN: 0288-4771

QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY Vol. 15 (1997), No. 1

  • CO2 Laser Welding of Aluminum Alloys (No.1)

    pp. 18-23

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    DOI:10.2207/qjjws.15.18

    Aluminum alloys were welded using 10 kW CO2 laser system. Combination of TIG or MIG arc welding with laser welding was tried in bead-on-plate welding experiments in which the molten pool formed by arc welding ran ahead of the laser beam. As the results of experiments, combination with MIG-DCEP arc welding was selected. A5083 and A6061 aluminum alloys were welded using A5356 filler wire in bead-on-plate welding in the flat position. It was concluded that combination of MIG arc welding seemed to be promising from the view point of bead formation and increase of absorption of the beam energy. But occurrence of large blow-holes or voids remained an important problem for further research.
  • Evaluation of Flashing in the Short Period before Upsetting for Monitoring of Weld Quality and Process Control

    pp. 24-30

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    DOI:10.2207/qjjws.15.24

    Influence of flashing on weld quality was investigated by analyzing the welding current in the short period before upsetting. Regression analysis proved that the integration of the flash current with an weight function could be related with the initial upset displacement and the weld interface quality. The time constant of the exponential weight function was discussed in connection with the period, flashing during which was effective to improve the weld interfece quality, and also in connection with the temperature neccessary to attain satisfactory interface quality. Process control system was proposed based upon the flash current evaluation to improve interface quality of joints.
  • Study of Electrode Wear Mechanism in Consecutive Spot Welding

    pp. 31-37

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    DOI:10.2207/qjjws.15.31

    Electrode life is of significant concern in spot weldability of coated steel sheets. The factors which dominate electrode life are still indistinct, although there has been an extensive number of investigations. One of the reason for this may be that electrode wearing process is not clarified. The purpose of this study is to define the electrode wear process and its mechanism focused on a distinction of alloying layers at electrode face during consecutive welding.
    Electrode life when consecutive spot-welding Zn-Ni electrogalvanized steel sheet is achieved over 10000 welds, whereas it is only 4000 welds for organic-silicate composite steel sheet. Electrode used on organic-silicate composite steel sheet exhibited more rapid wear than electrode used on Zn-Ni electrogalvanized steel sheet.
    In the case when welding Zn-Ni electrogalvanized steel sheet, the primary factor in electrode wear is a series of Cu (electrode material)/Zn (coating element) interaction, γCu-Zn formation on electrode face and its peeling off. Zn-Fe alloy is deposited and formed into a projection at the center of electrode face. This projection have a potential for keeping high current density when electrode wear is proceeding. This phenomenon can be thought of as one of the main factors responsible for good consecutive spot weldability.
    In the case when welding organic-silicate composite steel sheet, electrode/steel interface experiences high temperature exceeding the melting point of Cu-Zn during welding. Therefore, the principal factor of electrode wear would be a series of Cu/Zn interaction, alloying and melting. The locomotion of partial current-passed area is observed during consecutive welding. It would correspond to the movement of micro projection caused by partial current flow and melting on electrode face.
  • Fluxless Soldering of Laminated Thin Metal Plates Using Au-Sn Alloy Solder

    pp. 38-44

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    DOI:10.2207/qjjws.15.38

    Au-Sn solder has relatively high reliability because of the higher corrosion resistance and high temperature strength compared with Pb-Sn solder. It is, however, difficult to form Au-Sn alloy solder layer in the wet plating process on bonding surfaces. In this study, Au-Sn solder is provided as laminated Au-Sn-Au plating formed in a wet process on thin metal plates. Ni plating is formed prior to laminated Au-Sn-Au plating in order to improve wettability of the solder. Soldering process for thin metal plates without flux is investigated at the view point of soldering conditions and outgassing from the solder. Experimental result shows that Au plating contains larger amount of gas compared with Ni or Sn plating and the gas causes the solder layer to form voids. Forming many small holes around the specimen surface, amount of voids can be reduced. Peeling test shows that the peel strength of bonded specimen is influenced by the residual Ni thickness on the bonding interface rather than the bonding time or bonding pressure.
  • Application of He-DCEN·TIG orbital welding to aluminium piping

    pp. 45-50

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    DOI:10.2207/qjjws.15.45

    According to the rule of high pressure gas in Japan, it is limited strictly to generate the weld defects in weld zone. In this report, on high pressure gas piping of aluminium, an automatic all position welding process without blowhole is investigated. The following results were obtained in this study.
    It was found that the quality of weld zone by using He-DCEN·TIG is better than that of Ar-AC·TIG. In He-DCEN·TIG, shielding gas flow conditions influence on generating blowhole, but back shielding gas has no effect on it. In brushing treatment of root face, many weld defects such as aluminium oxide inclusion are produced. On the other hand, in the case of mechanical treatment that the root face becomes fiine smooth, occurrence of these defects decreases.
  • Brazing of Ti in Argon Atmosphere Using Ag-based Filler Metal

    pp. 51-57

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    DOI:10.2207/qjjws.15.51

    This study was carried out to investigate the relationship between the thickness of the oxide film on a faying surface and the tensile strength of the titanium joints brazed in argon atmosphere using Ag-based filler metal, and to examine the behavior of the oxide film during the brazing process. The following results were obtained in this study.
    The specimen with a Paying surface oxidized at temperatures lower than 600°C can be easily brazed in argon atmosphere, and the joints brazed at 800°C possess the tensile strength of approximately 300 MPa. The thickness of an oxide film decreases during heating to the brazing temperature. For instance, heating to the brazing temperature of 800°C turns the oxide film of about 71 nm in thickness formed at 600°C into about 23 nm thickness.
    Copper in a molten filler metal predominantly diffuses through the thin oxide film and is enriched at the surface of titanium, and results in reacting to titanium.
    Microcracks existing in the oxide film grow larger with heating to the brazing temperature. It seems that a molten filler metal penetrates into the cracks and results in benefitting the joining process.
  • Ultrasonic Evaluation of Spot Welds by Local Immersion Method

    pp. 58-63

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    DOI:10.2207/qjjws.15.58

    In order to apply an ultrasonic testing with a focused probe to the large spot welded structures and the corrosive materials, a local immersion method was proposed. The ultrasonic testing is based upon the multiple reflections in the thin plate, and the measurement is carried out through the thin film at the bottom in the small sized tank, which is mounted on the spot welds via couplant. In this study, appropriate thin films and their combination with couplant were examined for the precise measurement of weld size and quality of spot welds.
    It was clarified from the ultrasonic measurement of spot welds with various thin films and couplants that the local immersion method was available to the nondestructive evaluation of large spot welded structures and corrosive materials, as long as the rubber and plastic films were used. These materials possess almost same acoustic impedance as water and the appropriate combination with couplant was plastic-oil which showed long film duration and good protection against the rust in the measurement. A scanning pattern with each four scanning lines in two perpendicular directions was also proposed for the short measuring time, the precision of which is almost same with the fine scanning measurement.
  • Temperature Measurement by UV Thermal Radiation

    pp. 64-69

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    DOI:10.2207/qjjws.15.64

    The accurate measurement of temperature is very important in the control of the production process. The thermocouple that requires physical contact with an object is usually used, but the radiation thermometer has made remarkable progress in various fields such as steel industry. The radiation thermometer put into practice now is one that uses infrared rays as the measuring wavelength and it is reported that the radiation thermometry has lead to noticeable error if emissivity of an object is not accurately known.
    According to Planck's law of radiation, it is evident that the effect of temperature on spectral radiance is greater at the shorter wavelength. In the present paper, the temperature measurement by UV (ultra-violet) thermal radiation has been discussed. In the experiment, stainless steel (SUS304) and iron have been melted in a reducing atmosphere by the levitation melting method, and the melting points of metals have been measured with CCD camera, image intensifier and UV-filter (spectral range : 0.35μm) .
    As a result, it is made clear that the melting point of SUS304 have been measured in error 60 K-70 K and iron in 40 K-50 K by the proposal UV thermal method, without correcting the emissivity as the infrared thermometer. UV sensor made it possible to detect the temperature thermal image and to observe the temperature distribution in melting process.
  • Low Ductility Creep Fracture in Synthetic HAZ Specimen of 2 1/4Cr-1Mo Steel and the Effect of SR Treatment

    pp. 70-76

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    DOI:10.2207/qjjws.15.70

    Low-ductility fracture (LDF) occurred occasionally in the heat affected zone (HAZ) when the welded constructions of Cr-Mo steels were subjected to the long time services at high temperature. The LDF in 21/4Cr-lMo steel was reproduced in the laboratory by the creep rupture test in the temperature range of 775 to 875 K. The tests were made on synthetic HAZ specimens of the original and SR-treated conditions. SR treatment was carried out at 975 K for 2 hours. The ductility shown by the reduction in area of the specimen was discussed in relation to the time to fracture and the fracure mode.
    Two different types of LDF were recognized in HAZ specimen in the original condition. The first type of LDF appeared in the short term range of rupture producing a typical intergranular fracture (the fracture of type I). The second type appeared in the long term range of rupture, longer than a critical time period, tf, producing another type of intergranular fracture (type II). In this type of fracture, fractures occurred along grain boundaries accompanying a significant deformation of ferrite grains. A small quantity of ductile fracture of type III was usually accompanied to those fracture types.
    SR-treated specimen fractured with ductile manner in the short term range of rupture, but it lost the ductility when the time exceeded a critical time period, tsr, which was approximately the same as the time tf. The fracture of type II appeared in this time range. Those results informed that, (1) the LDF in short term range, which produced the type I fracture, disappeared after SR treatment, (2) the LDF in long term range, which produced the type II fracture, revived even after the SR treatment.
  • Solidification and Transformation Behavior of Austenitic Stainless Steel Weld Metals Solidified as Primary Austenite

    pp. 77-87

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    DOI:10.2207/qjjws.15.77

    Solidification and subsequent transformation behavior of two Fe-Cr-Ni stainless steel welds were investigated by using liquid-tin quenching method. One weld metal solidified as austenitic single phase solidification mode (A mode), and the other as austenitic-ferritic solidification mode (AF mode). In the weld metal solidified as A mode, both Cr and Ni were enriched in interdendritic regions during solidification, where the degree of enrichment of Cr was larger than that of Ni. The microstructural characteristics formed during solidification, concentration profiles of elements and crystallographic orientation, were similarly observed at room temperature. In the case of AF mode solidification, globular ferrite was formed through the eutectic reaction at cell boundaries. The ‹100›r direction of the primary austenite was found to be parallel to the ‹100›δ direction of the eutectic ferrite and the both phases were found to grow along the preferential growth directions.
  • Solidification and Transformation Behavior of Austenitic Stainless Steel Weld Metals Solidified as Primary Ferrite

    pp. 88-99

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    DOI:10.2207/qjjws.15.88

    Weld metals solidified with ferritic-austenitic solidification mode (FAmode) have dual phases of ferrite and austenite in an as-solidified condition, where ferrite exhibits different morphologies, depending on chemical composition and welding condition. The effect of solidification and transformation sequence on the formation of the final morphologies of ferrite was investigated in the present study. Austenite is formed through either eutectic reaction or peritectic reaction at dendrite boundaries after the primary formation of ferrite. In the case of the eutectic formation of austenite, ‹100›δ direction of the primary ferrite and ‹100›r direction of the eutectic austenite are parallel each other, and lie along the growth direction of primary dendrites. However, any specific relationship is not identified as to lattice planes between the two phases. Durng cooling after the solidification, austenite extends into the primary ferrite via. solid state transformation, and the final morphology of ferrite becomes vermicular without the coherent orientation relationship between the primary ferrite and the eutectic austenite. In the case of the peritectic formation of austenite, the Kurdjumov-Sachs orientation relationship is present between the primary ferrite and the peritectic austenite, while ‹100›r direction of the peritectic austenite is not parallel with the growth direction of primary dendrites. During cooling after the solidification, the primary ferrite transforms to austenite and the final morphology of ferrite becomes lathy since the primary ferrite and the peritectic austenite have the favorable coherent orientation.
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  • Effect of Various Factors on Grain Boundary Migration in the Weld Metal of an Austenitic Stainless Steel

    pp. 100-107

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    DOI:10.2207/qjjws.15.100

    The grain boundary migration in the weld metal of an austenitic stainless steel SUS310S was observed. Based on the observation, the effects of the orientation relationship between grain boundaries and the segregation at the solidification boundary on the morphology of room temperature grain boundary were investigated with the correlation of the amount of grain boundary migration. The effect of strain generated during cooling stage in the weld metal on the grain boundary migration was examined using the base metal added the strain which was presumed by FEM. The following results were obtained in this study.
    The amount of grain boundary migration occurred in a weld metal is small in the case where the grain boundary energy is low or phosphorous in the solidification grain boundary is high. Except for these cases, the amount of grain boundary migration tends to he large when the solidification grain boundary shape is rough or the distance between the triple junctions of a grain boundary is short.
    In the base metal added strain during cooling stage, the serrated grain boundary was observed both in the specimen heated under synthetic thermal cycle and in the weld metal. However, it seems to be a minor factor to the grain boundary migration.
  • Effect of Bonding Conditions on the Mechanical Properties of Joint at the Elevated Temperature

    pp. 108-114

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    DOI:10.2207/qjjws.15.108

    Transient liquid phase (TLP) bonding of HP alloy was investigated employing the insert metal MBF-50. TLP-bonding was carried out at 1423-1463 K for 600s in vacuum, Ar or N2 atmosphere. Microconstituents such as Cr7 (C, B)3 were formed in the bonded layer. The amount of microconstituents decreased linearly with increasing the bonding temperature, and the microconstituents disappeared at the bonding temperature of 1463 K. The tensile properties of joint at 1273 K was improved with the bonding temperature in the range of 1423-1458 K indicating the maximum value almost same as those of the base metal at 1458 K, while the tensile properties fell down contrarily at 1463 K. The fracture of the joints bonded at 1458 K occurred in the base metal. The effects of the atmosphere on mechanical properties of joint at 1273 K were also examined. The tensile properties of joints bonded at 1458 K in Ar or N2 atmosphere were the same level as those in vacuum atmosphere. The creep rupture strength of joints bonded at 1458 K in N2 atmosphere reached nearly the minimum value of the base metal.
  • Fatigue Strength of Friction Welded Joints of Various Carbon Steels with Flash

    pp. 115-121

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    DOI:10.2207/qjjws.15.115

    The fatigue strength of friction welded joint with flash decreased remarkably with the increase in upset pressure. This is caused by stress concentration with flash, as described in the previous report. In this study, the effect of flash on prevention of decrease in fatigue strength of friction welded joints was examined by means of rotating bending fatigue test using as welded joint specimens of S15C, S35C, S45C and S55C carbon steels under various friction welding conditions.
    The following experimental results were obtained:
    (1) The reduction ratio of fatigue strength was lowered with the decrease in upset pressure. It was small in the case of high carbon steel under the same pressure.
    (2) The decrease in fatigue strength of S45C and S55C welded joints with flash was not observed when upset pressure was 64 MPa.
    (3) Hardness of toe of flash increased remarkably by a friction weld thermal cycle in the case of high carbon steel.
    (4) The stress concentration factor of welded joint with flash became large with the increase of upset pressure. It was high in the case of high carbon steel under the same pressure.
    (5) The effect of hardening on the fatigue strength was larger than that of stress concentration in the case of high carbon steel.
  • Fatigue Strength of Transvers Butt Welded Joints under Random Loading

    pp. 122-128

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    DOI:10.2207/qjjws.15.122

    The fatigue strength of transverse butt welded joints has been obtained by the tests in which the maximum stress, σmax, was kept to be the yield strength of material, σy, while the minimum stress, σmin, was changed randomly. These tests modified the stress condition of real welded structures which contains the high tensile residual stress up to the yield strength in magnitude. It was revealed from the beach marks on the fractured surfaces that the fatigue crack initiation life shared the large portion of total life. Miner's rule could be applicable except for a case in which the fatigue life was prolonged with the coaxing effect.
  • Noncontact Evaluation of Plastic Deformation in Weldment with a Crack by Infrared Thermography

    pp. 129-134

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    DOI:10.2207/qjjws.15.129

    A Nondestructive and noncontact technique for evaluating the plastic region near a crack by using infrared thermography is proposed. The welded sheet specimen with a through-thickness center crack is used. A pre-crack is located between two welding beads and is desired to be in the compressive residual stress field parallel to the crack. A uniform tensile load perpendicular to the crack is applied to the specimen. The temperature rise of specimen surface is measured by the infrared thermography. The effect of the welding residual stress on the shape and dimensions of the heated region is examined. The heated region and the temperature rise are compared with the plastic zone and the work of plastic deformation obtained by the elastoplastic finite element analysis. The validity and the limitations of the application of infrared thermography to the evaluation of the plastic region are discussed.
  • Local Shrinkage and Rotations near the Joint by Welding in Offshore Structure and Their Influential Factors

    pp. 135-140

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    DOI:10.2207/qjjws.15.135

    Most of offshore structures for oil exploitation are composed of a deck and legs which are framed by welding many pipes. The prediction and control of the welding deformation is very important for the efficient and economical building of offshore structures. This is a basic study of the prediction and control, of which object is the offshore structure of jacket type.
    Almost all studies on the welding deformations of pipes (cylindrical drums, cylindrical shells) have been performed in relation to the local deformation by the circumferential butt welding. In this study, the welding deformation when a pipe (brace) is welded on the wall of another pipe (chord), like the welding of T-joint or Y-joint, was investigated in the actual building process of a jacket. The local deformations of the braces by welding were measured near the joints. At the same time, the influential factors, such as brace sizes, groove shapes, welding sequences, heat inputs, etc., on the local deformations were investigated.
    The correlations between the deformations and the factors were examined. As a result, it was made clear that the total heat input (the summation of heat inputs per unit length, of all welding passes) for each joint had influence on the local deformations most. The relations between the local deformations, namely, axial shrinkage, in-plane rotation, out-of-plane rotation, of the brace and the total heat input were formulated by the regression analysis. Also, the mechanisms of the increase and decrease of the deformations were discussed in detail, related to the total heat input, the welding sequence, etc. In the next report, the welding deformation of the whole structure will be simulated by the theoretical analysis, using the above relations for the local deformations.
  • Low-Cycle Fatigue Life Properties of MCrAlY Alloy Coated Systems

    pp. 141-147

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    DOI:10.2207/qjjws.15.141

    The low-pressure plasma spray coating process has been established in the field of gas turbines and is used for parts (turbine blades, duct segments, etc.) which are exposed to corrosive gases at high temperatures. Overlay coatings based on the MCrAlY alloy system (M is Ni, Co or Fe) are commonly employed as oxidation- and corrosion- resistant coatings. Mechanical properties, such as low-cycle fatigue lives, of CoCrAlY, NiCrAlY and CoNiCrAlY coated systems were investigated at high-temperature as compared with the uncoated conventional IN738LC, unidirectional solidified CM247LC and single crystal CMSX-2.
    Low-cycle fatigue properties of the MCrAlY coated superalloys at high-temperature (IN738LC : 1123 K, CM247LC, UMSX-2: 1173 K) showed only a little superior performance in comparison with the uncoated results. It was because that the low-cycle fatigue cracks initiated at casting cavities inside the substrate in any cases and the low-cycle fatigue crack initiation due to coatings could not be observed. It seems to be possible to evaluate the low-cycle fatigue lives of the MCrAlY coated superalloys at high-temperature by using the uncoated results.
  • Properties of High Arrestability Endowed Steel Plate by Refining Microstructure in Surface-layers

    pp. 148-154

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    DOI:10.2207/qjjws.15.148

    A new type of steel plate with high crack arrestability has been developed by controlling its microstructure especially in surface layers of the plate. The microstructure of the surface layers of the plate is ultra-fine grained (so-called SUF), which provides excellent fracture toughness even at a cryogenic temperature. Crack arrestability of the plate has been further improved by the enhanced formation of side-ligaments (shear-lips) due to SUF, since unstable running crack behaviour is strongly affected by these shear-lips, which are formed in the surface layers of the plate after the unstable brittle crack has propagated in the mid-section of the plate.
    In the present report, the practical properties of the developed plate (so-called SUF plate) are investigated. Fracture tests confirm that the SUF plate possesses ultra high crack arrestability. The improved value of arrestability due to the SUF effect can be predicted by fracture mechanics.
    For practical use of the SUF plate, the damage to the surface layers in actual service should be considered, since the SUF region (surface layers) is essential for obtaining ultra high arrestability in the SUF plate. Considering corrosion loss on an un-painted surface of the plate, the SUF plate, which is prepared by cutting down one side surface to remove 'SUF', is evaluated for crack arrestability by ESSO tests. To simulate the welding damage to the SUF plate, bead-on-SUF plate specimens are tested for crack arrestability by ESSO tests. Both test results suggest that the SUF plate possesses sufficient crack arrestability even in actual service.
    Furthermore, it is also confirmed that the SUF plate has other characteristics, such as weldability and workability, which make it suitable for ship-building use, such characteristics being similar to those of a conventional-steel plate, including TMCP steel plate.
  • New Concept of Equivalent Inherent Strain for Measuring Axisymmetric Residual Stresses

    pp. 155-160

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    DOI:10.2207/qjjws.15.155

    A new concept, the equivalent inherent strain g^eq_θ, is proposed for the measurement of axisymmetric residual stresses, based on the inherent strain theory. That is combining the radial and tangential inherent strain components gr, gθ into one parameter g^eq_θ in computing the axially uniform axisymmetric residual stresses. Based on this concept, the difficulty of estimating the value of gr is overcome and stress distribution in a long cylinder can be computed by merely estimating g^eq_θ and axial inherent strain component gz from measured strains in tangential and axial directions. Stress distribution in a thin disk or ring can be simply obtained by estimating g^eq_θ from measured strain in tangential direction. The concept was verified by the experiment of measuring residual stresses in a pipe with cladding. A numerical simulation was carried out to demonstrate that the measuring method based on g^eq_θ has both the convenience of the Sachs method and the high accuracy of the inherent strain method.
  • Ultrasonic Ball Bonding with Vibration Frequency of 70, 130 and 172 kHz

    pp. 161-167

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    DOI:10.2207/qjjws.15.161

    Ultrasonic ball-bonding technology using high-frequency vibration was investigated in order to obtain high strength bonds with small deformation under low bonding temperature condition. A novel bonding machine with resonance frequencies of 130 and 172 kHz was developed. Vibration characteristics at the tip of the capillary tool in the machine were measured and compared with that of a conventional 60 kHz bonding machine. Vibration amplitude at each frequency of the developed machine was smaller than that of the conventional machine, which was 1/10 to 1/50. Using the developed machine, Au wire was ball-bonded to Al pads on Si chip at the three frequencies under different conditions of vibration amplitude, bonding static force and bonding temperature. The bondability at each frequency was evaluated by measuring deformed ball diameter and shear strength after bonding. Main results are as followed:
    (1) Minimum vibration amplitude at the tip of a bonding tool decreases, which is required for obtaining higher bond-strength than wire-strength, as vibration frequency increases.
    (2) The smallest ball deformation ratio that guarantees more than 0.3 N bond-strength decreases as vibration frequency increases, that is, increasing the frequency elevates ultrasonic ball-bondability of Au wire to Al pads.
  • Lead Break Mode and Alloy Growth of Microsoldered Layer at fine Pitch Leadframe Microjoining

    pp. 168-173

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    DOI:10.2207/qjjws.15.168

    In high temperature aging test (150°C in Air), the peel strength is weakened by intermetalic compound growth of copper and tin. This report focused on the analysis of soldered layer to understand the reasons of reduced peel strength after thermal exposure. Even if 42 alloy (Fe-42 mass%Ni), under-plated copper layer (electric copper plating) causes the Cu-Sn intermetalic growth and break from 77 layer (C6Sn5). And in case of the copper lead, Cu-Sn intermetalic layer is very thick. Because of that, copper lead bulk thickness is reduced and causing the lead bulk break befor intermetalic break. These break modes are changing through the again time, from solder bulk, lead bulk and finaly to intermetalic compound layer breaking.
  • Characteristics of Au-Sn Micro-soldered Loyer of the Combination Leadframe

    pp. 174-179

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    DOI:10.2207/qjjws.15.174

    This report considered the low melting point Au-Sn micro-soldering (connection heat tool temp. 523 K) which is applied to the combination leadframe assembling. This method is performed by heat and press tool connection of tin spot plated leads and gold plated interposer with non flux. Au-Sn micro-soldered layer has the high thermal resistance of 556 K and the high reliability in 423 K storage and the 358 K×85%RH electro-migration test (applied DC bias). And the organic polyimide base film is not damaged at micro-soldering temperature because of short connection time (5 second at 523 K).
  • Au-Sn Eutectic Bonding Technology for LSI Package

    pp. 180-186

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    DOI:10.2207/qjjws.15.180

    The Au-Sn eutectic bonding process was developed by applying micro bonding process for LSI package. The Sn-plated Cu sheet was bonded by heat-press with the bonding tool on the Au-plated Cu foil.
    When the bonding, which was made under a pressure of 100 MPa using Au plating with a thickness of 1.2 μm and Sn plating with that of 3 μm, the bonding strength which was obtained by the 90° peel test was 0.5 N/mm at 250°C. With increasing the bonding temperature, the strength became up to 3.5 N/mm at 300°C. By reducing the bonding pressure from 100 MPa and using Au plating with a thickness of 0.6μm, the strengths were reduced rapidly. For example, the bonding strength which was obtained by bonding at 50 MPa was 2.5 N/mm.
    The brittle intermetallic compounds as AuSn, AuSn2 and AuSn4, were formed in the bonding layer. When the bonding was made at low temperature, the Au-Sn intermetallic compound layer was formed in a thickness of 2 μm. This cross-sectional structure demonstrated that fracture occured through the thick Au-Sn layer. With the high temperature bonding above 300°C the Au-Sn-Cu layer was formed due to diffusion of Cu. The Au-Sn intermetallic conpounds existed like islands in the bonding layer at high bonding temperature. When the bonding made with Au thin plating like a thickness of 0.6μm, the Au-Sn intermetallic compound layer was formed in the bonding layer. On the case of bonding at low pressure it was found that the Au-Sn layer was formed in the bonding layer. It is assumed that the high bonding strength is achieved by eliminating the Au-Sn layer and forming Au-Sn-Cu layer contained a little Au-Sn intermetallic compound.
  • Friction Characteristics of Thermal Sprayed Coatings and its Application on High-strength Bolted Joints

    pp. 187-192

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    DOI:10.2207/qjjws.15.187

    The sliding friction between solids is a problem related to the material surface and its neighborhood. It is very important to control and adjust it in engineering. In this research, the characteristics of sliding friction between thermal sprayed surfaces have been studied. Materials sprayed were aluminum (Al), zinc-5% aluminum alloy (Zn-A1), and alumina (Al2O3) and sliding pairs were either of the same material or of different materials. Further, it also has been studied from the standpoint of applying thermal spraying to the surface treatment for high-strength bolted joints. In the experiments, frictional force was recorded as a function of sliding distance. It was found that force-distance curves of as-coated specimens could be classified into two types; one is periodical oscillation with the stick-slip such as for the sliding pair of Zn-Al/Zn-Al and the other is with random fluctuation for the sliding pairs of Al/Al and Al2O3/Al2O3. The coefficient of friction was biggest for sliding pair of Al/Al, which is about 2 times as high as that of the shot-blasted surface of mild steel substrate (for Al/Al and Zn-Al/Zn-Al). It has been confirmed also that Amontons law is applicable in any of the sprayed sliding pairs tested. Especially, it has be shown that aluminum-sprayed coating and zinc-sprayed coating will be expected to apply to high-strength bolted joints, because of having big coefficient of friction and strong corrosion resistivity.
  • 平成9年度春季全国大会シンポジウム

    pp. 193-227

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    DOI:10.2207/qjjws.15.193

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