Intermetallic Compounds In Cu Research Articles

The growth behavior and kinetics of intermetallic compounds in Cu–Al interface at 600°C–800 °C

Due to the low production cost and light weight, copper-clad aluminum conductors show great potential value in the field of power transmission, while the phase structure and organizational changes at the Cu–Al interface in high-temperature environments have a great impact on the electrical and mechanical properties. In this paper, Cu–Al diffusion couples are prepared to study the diffusion process, microstructure, and growth kinetics of intermetallic compounds (IMCs) in Cu–Al interface during heating from 600 °C to 800 °C, and the mechanical and electrical properties of Cu–Al diffusion couples are discussed. The results show that after heat treatment, IMC layers are formed at the Cu–Al interface and the Al-side is composed of CuAl and CuAl2, in which the CuAl phase transforms from long to thick dendrites with the increase of temperature, and finally grows into a “popcorn” form. The IMCs at the Cu–Al interface from the Cu side to the Al side are in the order of Cu3Al layer, Cu9Al4 layer, Cu3Al2 layer and CuAl layer, among which the Cu3Al2 layer is the thickest (168.42 μm at 700 °C), while the Cu3Al layer is the thinnest (37.32 μm at 700 °C). The kinetic calculations show that the diffusion layer grows up rapidly, which is caused by the generation of liquid-phase during the heating process, leading to the acceleration of the diffusion of Cu and Al. The kinetic factor of the Cu3Al2 layer is the largest (n = 0.69), causing the fastest growth rate of the Cu3Al2 layer, while the Cu3Al layer shows the largest activation energy for diffusion and the smallest diffusion rate (Q = 9.48 kJ/mol, D0 = 2.06 × 10−1 m2/s), therefore its growth rate is the slowest. Based on the thermodynamic calculations and the Cu–Al phase diagram, a growth mechanism of the Cu–Al interface is proposed, the formation sequence of IMCs at the Cu–Al interface is Cu9Al4, CuAl, Cu3Al2 and Cu3Al. The formation of IMCs layer at the Cu–Al interface leads to a significant increase in the hardness of Cu–Al samples (the hardness of the Cu3Al2 is 10 times higher than that of Cu) and an obvious decrease in electrical conductivity (the electrical resistivity of Cu–Al is 5 orders of magnitude higher than that of Cu), affecting its application in the electrical industry.

Simultaneously enhanced strength and elongation capacity in Cu–15Sn-0.3Ti alloy via regulation of IMCs

Due to the technical requirements of preparing Nb3Sn superconducting wires using the bronze method, the Cu–Sn–Ti alloy with high Sn content and matching mechanical properties with pure Nb as the substrate is the key to the smooth preparation of superconducting wires. However, the high content of Sn leads to the generation of a large number of intermetallic compounds (IMCs) in Cu–Sn–Ti alloy are the main reasons for the deterioration of the elongation and strength of Cu–Sn–Ti alloy. This work uses unidirectional solidification (US) and homogenization annealing (HA) methods to regulate the volume fraction and types of IMCs in Cu–15Sn-0.3Ti alloy. The volume fraction of IMCs decreases from 20.6 % to 0.1 % after HA, and the network δ phases (Cu41Sn11) transform to fine γ phase (Cu3Sn) and CuSn3Ti5. The ultimate tensile strength (UTS) and elongation of the samples treated with HA increase by 2000 % and 94 %, respectively, and deformation twins are found in the stretched samples. The research results indicate that the elongation and UTS of Cu–15Sn-0.3Ti alloy are improved by the decrease of IMCs volume fraction and deformation twins formed during the tensile process.

Carbonate hosted intermetallic compounds in Paleoproterozoic Salumber Ghatol metallogenic belt, Aravalli Craton, Rajasthan, India

Carbonate hosted intermetallic compound in the Umarvaniyan area is localized within the intensively sheared (mylonitised) dolomite in a NW–SE shear zone (~15 km), belongs to Salumber Ghatol metallogenic belt, in Debari Group of Aravalli Craton, Rajasthan, India. It is characterized by extensive silicification and ferruginisation with hematite, goethite, magnetite and native gold specks. The intermetallic compound within the dolomite is composed of varying proportion of Cu–Zn–Ni–Os–Fe which has been detected by electron probe microanalysis (EPMA) study. The EMPA (WDS) results of the intermetallic compounds also reveal occurrences of intermetallic compounds of Cu–Zn–Ni–Os–Fe and native Au. The occurrence of these non-separable compounds is probably because these metals were formed at very high temperatures and in reducing condition during the evolving shear with low oxygen and low sulfur fugacity. The fast cooling effect thereafter probably made the geochemical environment least conducive for reaction between Cu/Zn/Ni and sulphur or oxygen.

Composition and Genesis of Accessory Mineralization in Manganese Silicate Rocks of the Triassic Sikhote-Alin Chert Formation

Abstract —Manganese silicate rocks together with silicate–magnetite ores and jaspers (Late Anisian–Ladinian) form lenticular or tabular bodies in the Triassic Sikhote-Alin chert formation. The lower part of the formation (Olenekian–Early Anisian) is enriched in clayey and organic matter. Nickel and cobalt compounds and other ore minerals in the Sikhote-Alin manganese silicate rocks belong to two genetic groups including minerals of the valence and ultimately reduced Ni, Co, and other metals. Minerals of the valence species of Ni, Co (sulfoantimonides, sulfoarsenides, sulfides, antimonides, arsenides, tellurides, and silicates), and other metals (galena, sphalerite, chalcopyrite, arsenopyrite, wolframite, scheelite, molybdenite, cassiterite, stannite, cinnabar, stibnite, boulangerite, jamesonite, bournonite, löllengite, bismuthite, fahlore, altaite, native Sb and Bi, etc.) formed from the protolith material during metamorphism under the same conditions as the rock-forming minerals. The presence of minerals of ultimately reduced Ni, Co (maucherite, native Ni, Ni phosphide, Ni and Co chromides, disordered solid solutions, and intermetallic compounds of Ni with Cu, Zn, Sn, and Pb), and other metals (native Pb, Zn, Fe, Sn, Se, Au, Pt, “cupriferous gold”, and intermetallic compounds of Cu, Sn, Pb, Sb, Al, and Zn) in the manganese silicate rocks is due to the influence of the organic matter of the underlying carbonaceous silicites. During metamorphism, the most volatile components (first of all, poorly bound water and hydrocarbons) were released from the heated carbonaceous rocks; as a result, a metal-enriched fluid with highly or ultrahighly reducing properties appeared, which migrated along fractures into other rocks. The manganese silicate rocks are the products of contact metamorphism of siliceous rhodochrosite rocks formed through the diagenesis of biogenic siliceous muds enriched in Mn oxides and organic matter. Erosion of the weathering crust of islands composed of gabbroids of the Kalinovka, Vladimiro-Aleksandrovskoe, and Sergeevka complexes (in the late Middle Triassic–Late Triassic) played the leading role in the formation of metalliferous sediments. Manganese silicate rocks localized in the stratigraphic column above the carbonaceous silicites of the Triassic chert formation are enriched in Au (up to 35.38 ppm), Pt (11.27 ppm), and Pd (5.33 ppm). They contain noble-metal minerals and a wide spectrum of native elements and intermetallic compounds. The presence of Au–Pd–Pt–Ni–Co association (typomorphic for basic and ultrabasic rocks) in the Triassic protoliths of the manganese silicate rocks and carbonaceous silicites is probably due to the sorption of these elements by Mn and Fe hydroxides and organic matter during the exogenous weathering of the ancient Sikhote-Alin gabbroids.

Characterization of intermetallic compounds in Cu–Al ball bonds: Mechanical properties, interface delamination and thermal conductivity

In high power automotive electronics copper wire bonding is regarded as the most promising alternative for gold wire bonding in 1st level interconnects and therefore subjected to severe functional requirements. In the Cu–Al ball bond interface the growth of intermetallic compounds may deteriorate the physical and mechanical properties. The layer growth and properties of these intermetallic compounds are crucial in the prediction of the long term behavior. To mimic the growth of intermetallic compounds during and after copper ball bonding, diffusion couples of aluminium and copper were annealed at 225–500°C and chemically analyzed by SEM/EDS. Also five separate intermetallic compounds were melted together from the pure elements and aged in evacuated quartz ampoules for 240h at 500°C. In this work values for the indentation Young’s modulus, load independent hardness, indentation fracture toughness, volumetric densities, interface delamination and thermal conductivity are presented. It can be concluded that the Cu-rich intermetallics Cu9Al4 and Cu3Al2 are less sensitive to fracture and have lower average densities than the other intermetallic compounds. The volumetric decrease during formation causes internal stress. Interfacial delamination initiates in the Al-rich intermetallics (CuAl, CuAl2) and propagates easily into other intermetallic layers. The Cu9Al4–Cu s.s. interface is also found to be susceptible for delamination fracture. The thermal conductivity for 3 intermetallics is much lower than for pure copper or aluminium and in the range of 26–87W/m−1K−1, where Cu3Al2 layer has the lowest thermal conductivity (26–33W/m−1K−1).

Formation and Growth of Intermetallic Compounds in Cu–Au and Au–Al Systems for Copper on Gold Bonding

Copper (Cu) ball on gold (Au) bump (COG) bonding is developed as a practicable approach to solving the challenges posed by Cu wire bonding on large integrated circuit devices. In the COG bonding, there are two different interfaces, Cu-Au and Au-Al couples, which is totally different from either Cu or Au wire bonding. In this paper, the COG bonding was studied on a typical experimental chip of 69-μm bond pad opening and four-layer central via pattern design with current wire bonders. Tests of wire pull, ball shear, and crater were adopted in investigating the bonding strength at the interfaces and the potential damage of the underlying metals of bond pads after the COG bonding. The intermetallic compounds (IMCs) formation at the two interfaces, Cu-Au and Au-Al couples, were studied in detail on the cross-sectioned assembled samples. Two reliability tests, high-temperature baking (HTB) and temperature cycle (TC) were also used to investigate the IMC change and growth. The results showed that qualified bonding strength on all of bond pads existed and no damage such as crack and crater was observed on the underlying metals of the bond pads after removing Al metallization. At the Au-Al interface, a comparable Au-Al IMC was formed on as-bonded samples, and it gradually grew thick after the reliability tests and its corresponding content also changed along with temperature and time. At the Cu-Au interface, there was no observable formation of Cu-Al IMC on as-bonded samples. Undergoing 1008 hours HTB at 175°C, only a very thin Cu-Au IMC appeared at the Cu-Au interface. After all, the Cu-Au IMC appearance hardly affects the IC's mechanical performance.

Thermodynamic modeling of the Cu–Si system

The thermodynamic description of the Cu–Si system has been updated with first-principles calculations of the ϵ-Cu 15Si 4 phase and solid solution phases. Calculated enthalpy of formation for the ϵ -phase indicates that enthalpies of formation for intermetallic compounds in Cu–Si must be negative, which were evaluated as positive in the previous thermodynamic modelings. Enthalpies of mixing for the solid solution phases, bcc, fcc, and hcp, are also calculated from first-principles study of Special Quasirandom Structures (SQS) and all the solution phases exhibit similar mixing behavior. It is concluded that first-principles calculations of solid phases including solution phases can supplement scarce experimental data and be readily used in thermodynamic modelings.

Microstructure and adhesion strength of Sn–9Zn–1.5Ag–xBi (x=0wt% and 2wt%)/Cu after electrochemical polarization in a 3.5wt% NaCl solution

Abstract The microstructure and adhesion strength of the Sn–9Zn–1.5Ag– x Bi ( x = 0 wt% and 2 wt%)/Cu interface after electrochemical polarization have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and pull-off testing. The equilibrium potentials of Sn–9Zn–1.5Ag/Cu and Sn–9Zn–1.5Ag–2Bi/Cu are −1.31 V sce and −1.22 V sce , respectively, indicating that Sn–9Zn–1.5Ag–2Bi/Cu has a better corrosion resistance than that of Sn–9Zn–1.5Ag/Cu. The intermetallic compounds of Cu 6 Sn 5 , Cu 5 Zn 8 and Ag 3 Sn are formed at the soldered interface between the Sn–9Zn–1.5Ag– x Bi solder alloy and the Cu substrate. The scallop-shaped Cu 6 Sn 5 is close to the Cu substrate and the scallop-shaped Cu 5 Zn 8 is found at the interface in the solder matrix after soldering at 250 °C for 10 s. The corrosion products are ZnCl 2 , SnCl 2 and ZnO. On the other hand, pits are also formed on the surface of both solder alloys. The interfacial adhesion strength of the Sn–9Zn–1.5Ag/Cu and Sn–9Zn–1.5Ag–2Bi/Cu decreases from 8.27 ± 0.56 MPa and 12.67 ± 0.45 MPa to 4.78 ± 0.45 MPa and 8.14 ± 0.38 MPa, respectively, after electrochemical polarization in a 3.5 wt% NaCl solution. The fracture path of the Sn–9Zn–1.5Ag–2Bi/Cu is along the solder alloy/ZnO and solder/Cu 6 Sn 5 interfaces.