Quality Analysis of Welded and Soldered Joints of Cu-Nb Microcomposite Wires (original) (raw)
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Microstructural characterization of high strength high conductivity Cu-Nb microcomposite wires
Purpose: The properties and the microstructure of cold drown Cu-Nb composites have been investigated for their potential use as conductors in high field magnets. Nowadays, there is much activity in the development of such conductors all over the world. Design/methodology/approach: This study was aimed to investigate microstructure, mechanical and electrical properties of Cu-Nb15 wires. The investigated materials have been processed by vacuum furnace melting and casting, further hot forging and cold drawing. Alternatively material has been processed by one of the SPD (severe plastic deformation) method using oscillatory turning die pressing. Microstructure has been observed by optical and electron microscopy technics. Findings: The ultimate tensile strength versus cold deformation degree have been presented. These changes have been discussed in relation to the microstructure evolution. Practical implications: The obtained mechanical and electrical properties (UTS over 900 MPa and ele...
Mechanical behaviour of copper 15% volume niobium microcomposite wires
Materials Research, 2001
Cu-Nb microcomposites are attractive in magnet pulsed field technology applications due to their anomalous mechanism of mechanical strength and high electrical conductivity. In this sense, recently it was conceived the use of Cu 15% vol. Nb wires to operate as a high tensile strength cable for a diamond cutting tool (diamond wires) for marble and granite slabbing. The multifilamentary Cu 15% vol. Nb composite was obtained using a new processing route, starting with niobium bars bundled into copper tubes, without arc melting. Cold working techniques, such as swaging and wire drawing, combined with heat treatments such as sintering and annealing, and tube restacking were employed. The tensile property of the composite was measured as a function of the niobium filaments dimensions and morphology into the copper matrix, in the several processing steps. An ultimate tensile strength (UTS) of 960 MPa was obtained for an areal reduction (R = Ao/A, with Ao-initial cross section area, and A-final cross section area) of 4x10 8 X, in which the niobium filaments reached thickness less than 20 nm. The anomalous mechanical strength increase is attributed to the fact that the niobium filaments acts as a barrier to copper dislocations. Figure 6. Stress versus strain curve for the Cu 15 vol.% Nb composite.
Tehnicki vjesnik - Technical Gazette, 2018
In this work we have evaluated the feasibility of the magnetic field pressing technology for formation of Cu-Nb joints for further pulsed power applications. The electrical and mechanical properties of joints have been investigated. The structure of Cu-Nb conductors joints was investigated using optical and scanning electron microscopy. The mechanical characteristics have been evaluated using tensile tests. It has been determined that the maximum tensile strength of 350 MPa could be achieved, which is 30,4 % of a Cu-Nb wire strength. The applied pressing technology allowed minimizing the defects in the microcomposite structure due to solid-state joining process, however the resultant decrease of conductivity by 10 % influenced an increase of the Joule heating. After a 2 min 200 A current flow the difference of 54,4 °C between the conductor and the joint area was observed. It was concluded that the Cu-Nb joints formed by magnetic field pressing are applicable for pulsed magnet setups where non-destructive joints are required.
Bond strength evaluation of heat treated Cu-Al wire bonding
Journal of Mechanical Engineering and Sciences, 2018
Bond strength evaluation of wire bonding in microchips is the key study in any wire bonding mechanism. The quality of the wire bond interconnection relates very closely to the reliability of the microchip during performance of its function in any application. In many reports, concerns regarding the reliability of the microchip are raised due to formation of void at the wire-bond pad bonding interface, predominantly after high temperature storage (HTS) annealing conditions. In this report, the quality of wire bonds prepared at different conditions, specifically annealed at different HTS durations are determined by measurements of the strength of the interface between the bond wire and the bond pad. The samples are tested in pull test and bond shear test. It was observed that the higher bonding temperature as well as the longer duration of HTS increased the bond strength. This is represented through the analysis of the measurements of ball shear strength. This is due to the fact that ...
IEEE Transactions on Applied Superconductivity, 2014
The anomalous increase of the mechanical strength in copper matrix FCC-BCC composite materials caused by the specific nanoscaled microstructure formed by the heavy plastic deformation is associated mainly with the nature of the interface boundary areas. The differences in the nature of the interface areas in the Cu-Nb, Cu-V, and Cu-Fe have been discussed in connection with the parameters of crystallographic structure of three BCC elements (Nb, V, Fe). The nanostructured Cu-Nb, Cu-V, and Cu-Fe experimental high strength, high conductivity wires have been fabricated by the similar technological routes. The tensile strength and electrical conductivity for Cu-Nb, Cu-V, and Cu-Fe microcomposite wires are presented. The stability of the filamentary nanoscaled microstructure created by the large plastic deformation is investigated. We demonstrate that it is possible to maintain mechanical strength higher than 400 MPa after long time heat treatment between 250 • C and 400 • C.
Strength and microstructure of powder metallurgy processed restacked Cu-Nb microcomposites
Metallurgical Transactions A, 1992
Powder metallurgy (PM) was used to fabricate Cu-Nb microcomposites both at the laboratory and intermediate industrial scales. Ultimate tensile strengths (UTSs) of 1.6 and 1.035 GPa were obtained for the laboratory-and intermediate-scale composites, respectively. Filament morphology and the microstructure of various microcomposites were examined with transmission electron microscopy (TEM), scanning electron microscopy (SEM), and optical microscopy. In the early stages of the fabrication process, a plain strain condition causes the Nb fibers to attain a ribbonlike shape, but in the later stages, an axially symmetric flow prevails. Beyond the Nb filament thickness of 5 to 10 nm, the overall areal reduction was observed to occur without any significant reduction in the Nb filament thickness. Effects of heat treatment and the extent of spheroidization at different temperatures were studied. Contributions of various strengthening mechanisms on PM-processed Cu-Nb composites were analyzed. Work hardening, high strength of Nb filaments, and dispersion-type hardening were the dominant factors. Our strengthening model, which involves a superposition of the different contributions, agreed with our measurements.
1998
Although Sn-Pb eutectic alloy is widely used as a joining material in the electronics industry, it has well documented environmental and toxicity issues. Sandia National Laboratories is developing alternative solder materials to replace traditional Pb-containing alloys. The alloys m based on the SnAg , SnAg -Bi and SnAg -Bi-Au systems. Prototype hybrid microcircuit (HMC) test vehicles have been developed to evaluate these Pb-fiee solders, using Au-Pt-Pd thick film metallization. Populated test vehicles with surfhce mount devices have been designed and fabricated to evaluate the reliability of surface mount solder joints, The test components consist of a variety of dummy chip capacitors and leadless ceramic chip caniers (LCCC's). Intermetallic compound (IMC) layer reaction products that form at the solder/substrate interfm have been characterized and their respective growth kinetics quantified Thicker IMC layers pose a potential reliability problem with solder joint integrity. Since the IMC layer is brittle, the likelihood of mechanical failure of a joint in service is increased. The effect of microstructure and the response of these Merent materials to wetting, aging and mechanical testing was also investigated. Solid-state reaction data for intermetallic formation yd mechanical properties of the solcler joints are reported.
Journal of Alloys and Compounds, 2020
In this study, Ni foam, Cu coated Ni foam and Cu-Ni alloy foams were used as strengthening phases for pure Sn solder. Cu-Cu joints were fabricated by soldering with these Sn-based composite solders at 260 °C for different times. The tensile strength of pure Sn solder was improved significantly by the addition of metal foams, and the Cu-Ni alloy/Sn composite solder exhibited the highest tensile strength of 50.32 MPa. The skeleton networks of the foams were gradually dissolved into the soldering seam with increasing soldering time, accompanied by the massive formation of (Cu,Ni) 6 Sn 5 phase in the joint. The dissolution rates of Ni foam, Cu coated Ni foam and Cu-Ni alloy foams into the Sn matrix increased successively during soldering. An increased dissolution rate of the metal foam leads to an increase in the Ni content in the soldering seam, which was found to be beneficial in refining the (Cu,Ni) 6 Sn 5 phase and inhibiting the formation of the Cu 3 Sn IMC layer on the Cu substrate surface. The average shear strength of the Cu joints was improved with increasing soldering time, and a shear strength of 2 61.2 MPa was obtained for Cu joints soldered with Cu-Ni alloy/Sn composite solder for 60 min.
Laser welding of copper‐niobium microcomposite wires for pulsed power applications
Materialwissenschaft und Werkstofftechnik, 2019
The laser welding of copper-niobium microcomposite wires was investigated. It was determined that the joint structure does not have welding defects, while microscopic examination of the joint cross-section showed that the microstructure of the autogenous weld consists mainly of a copper-based solid solution strengthened by niobium-rich precipitations. The weld obtained with use of filler material consists of two distinct zones, which are formed due to melting of filler wire and microcomposite wire. This structure of the joint provides an insignificant increase in electrical resistance and sufficient ultimate strength and plasticity of the joint. The tensile strength of the sample welded without filler material reaches 335 MPa, but such welded joints are very brittle due to very low ductility. However, an autogenous laser welding joint has about 1.6 times better ductility, and the tensile strength of the joint depends on the applied filler material and is equal to the tensile strength of this material.
Materials Letters, 2008
Cu-(Sn37Pb) and Cu-(Sn3.5Ag0.5Cu) solder joints were prepared at the same reflow temperature of 230°C. The microstructural observation of the solder assemblies in scanning and transmission electron microscopes confirmed the presence of η-Cu 6 Sn 5 in case of the former, and Cu 3 Sn + η-Cu 6 Sn 5 for the latter in the reaction zone. The findings are correlated with the electrical and mechanical properties of the joints. Lead free solder-Cu joint exhibited lower reaction zone thickness and improved electrical conductivity (0.28 × 10 6 Ω − 1 cm − 1 ) and shear strength ∼68MPa compared to conventional lead-tin solder-Cu joint. The latter showed electrical conductivity and shear strength of 0.22 × 10 6 Ω − 1 cm − 1 and ∼ 55 MPa, respectively. The difference in reaction zone thickness is explained on the basis of melt superheat, with Sn being the primary diffusing species in the intermetallic layer.