Academic literature on the topic 'Cu-Sn Alloy'

Copper, tin and their alloy deposits are popular for its various applications in industrial aspects like enhance corrosion resistance and provide decorative finish. This work concentrated on the fabrication of these coatings, accomplished by electrodeposition technique which allows the control of thickness and microstructure of the films. Previously these metals and alloy were electrodeposited from different aqueous electrolytes. However these baths suffer from various environmental issues and deposits suffers from H evolution and metal oxide formation. As a result solution 2 ionic liquid (IL) was proposed as an alternative. ILs are categorized as salts liquid at room temperature and consist only of cations and anions. Presently Choline chloride based IL was used due to its advantages of low cost, low melting point, low toxicity, low viscosity and high conductivity than other ILs. Physical properties of the ILs like density, viscosity and conductivity were measured with variation of temperature and concentration of added metallic salts. To determine the electrochemical properties of individual metals and alloy, voltammetry scans were carried out using various scan rates and agitation rates. For all these measurements the concentration of Cu and Sn were varied in a range of 0.01 to 0.2 M and 0.01 to 0.1 M respectively at temperature range of 25 to 55 °C using a platinum rotating disk electrode (RDE). Deposition experiments were then carried out under potentiostatic and galvanostatic conditions using a stainless steel RDE. Material properties of the deposits like crystalline structure, grain size, strain, deposit morphology and chemical composition were analyzed using x-ray diffraction (XRD), optical microscope and scanning electron microscopy (SEM). The measurement showed that density and viscosity decreases and conductivity increases with rise in operation temperature for the electrolyte with and without metal ions. The reduction of both the metal was found to be mass transfer control and limiting current for metal deposition was found. The diffusion co-efficient -7 2 -7 2 obtained for Cu and Sn in the IL system was 1.22x10 cm /s and 1.96x10 cm /s -3 respectively. For individual metal Cu and Sn, best deposits were obtained at 4.7x10 2 -3 2 A/cm and 1.6x10 A/cm respectively using RDE speed of 700 rpm at 25 °C. The Cu deposit showed face centered cubic structure of 66±10 nm grain size and that of Sn was 62±10 nm with tetragonal crystalline structure. The smooth and bright Cu-Sn alloy deposit was obtained by applying potential in the range of 0.35 to 0.36 V vs. Ag wire or -3 2 0.8 to 0.9x10 A/cm of RDE speed is 220 rpm at 25 °C. The obtained deposits showed orthorhombic CuSn structure with a grain size of 21±10 nm. On annealing the 3 crystalline structure changed to hexagonal CuSn structure and the crystalline size 103 was obtained as 77±50 nm.

Electronic equipment is facing the challenge of both miniaturisation and the need to replace lead in interconnections. In service, interconnections generally fail by thermomechanical fatigue, and this behaviour is strongly affected by the creep process. This thesis examines the creep behaviour of a popular lead-free replacement alloy, Sn-3.8wt.%Ag-0.7wt%Cu (Sn-Ag-Cu), in joint and bulk form. Experimental work involved the determination of the creep properties of this alloy at various temperatures, over a range of stresses. Over the regions tested, the creep behaviour is best described by the Norton power law constitutive equation. The stress exponent for bulk Sn-Ag-Cu ranged between 10 and 18 (at 125 to -lOoC respectively) and indicates that a dispersion-strengthened mechanism is dominant in the creep process. The activation energy for creep in the bulk Sn-Ag-Cu is approximately 120kJ/moi and falls in the region similar to that observed for the self-diffusion of tin. In joint form the stress exponent is greater than 10 at high stresses but a change in mechanism is indicated at lower stress where the creep exponent falls to 3. The activation energy for creep in Sn-Ag-Cu when used in joint form is approximately 70kJ/moi and falls in the region similar to that observed for the short-circuit diffusion of tin. Results obtained from the ternary alloy were directly compared to those from Sn- 37wt.%Pb (Sn-Pb) and other prospective lead-free alloys in bulk form. The creep resistance of the ternary lead-free alloy at 75°C is superior to the conventional Sn-Pb alloy and the possible replacement alloys (tin-copper and tin-silver). This superiority is retained when tested at similar homologous temperatures. However, the Sn-3.8Ag- O.7Cu alloy is less ductile but generally possesses strains to failure above 10 percent in comparison to the 25 to 50 percent ductility of Sn-Pb.

The most commonly used alloy in the electronics industry has been the ubiquitous tinlead alloy. As the demand for electronic devices continues to increase, there have been concerns about the continued use of lead and its long term environmental impact. In the last decade there has been a push to ban the use of lead in electronic products. Legislation from various governments around the world limiting the use of lead has given rise to the drive to find suitable lead-free alternatives. The aim of this research project was to establish a systematic approach for the selection of electrochemical parameters for the electrodeposition of tin-rich copper-tin alloys from a single electroplating bath. By studying and understanding a model system such as copper-tin, one can then use the information obtained as a basis to successfully deposit various other tin binary alloys in the future. Tin-rich deposits were enabled by employing various strategies such as maintaining a high Sn to Cu ratio in the electrolyte and by using surface active agents that have been known to facilitate alloy co-deposition. The effect of surfactants on the tin content in the deposit was initially examined with the aid of a rotating cylinder Hull cell. It was found that the presence of fluorosurfactant was crucial in eliminating metal oxide formation. Cyclic voltammetry at a rotating disk electrode showed that inclusion of surfactant in the electrolyte had no effect on the reduction potential of tin which remained at -0.45 V vs SCE. However, the reduction potential for copper shifted from approximately -0.13 to -0.18 V vs SCE, thereby facilitating alloy co-deposition. Chronoamperometry and anodic stripping voltammetry showed that current efficiency for copper-tin deposition ranged from 55-92% depending on the deposition time and deposit composition. Results from voltammetry experiments were used in the next galvanostatic electrodeposition experiments at vitreous carbon electrodes. Deposits containing up to 96 wt.% tin were obtained from both direct current and pulse plating modes. It was found that an optimal current density of 22 mA cm-2 was needed to obtain desirable deposits. For pulse plating the peak current density should be set to 100 mA cm-2 with a duty cycle of 0.2. Cu-Sn alloys obtained consisted of two phases, tetragonal tin and a hexagonal Cu6Sn5 intermetallic compound. Deposit annealing showed that the Cu3Sn intermetallic was not formed.

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