Electrodeposition of Sn–Ag Alloys and Evaluation of Connection Reliability for Automotive Connectors

Abstract

Electrodeposition behavior of Sn-Ag alloys was investigated at current density 1-1000 AÁm À2 in both sulfate and pyrophosphate-iodide solutions at 298 K, and the contact resistance of Sn-Ag alloys deposited on a Cu connector was evaluated. In both solutions, Ag behaved as a more noble metal than Sn, showing regular codeposition. The difference in deposition potential between Ag and Sn was 0.4 V in the pyrophosphate-iodide solution and 0.2 V in a sulfate solution containing thiourea as a complexing agent for Ag þ ions. The deposits obtained from a pyrophosphate-iodide solution consisted of blocks of a few microns in size, while those from a sulfate solution exhibited grains smaller than 1 mm. The deposits containing Ag less than 45 mass% were composed of an Ag 3 Sn intermetallic compound and Sn. This is in accordance with the equilibrium phase diagram of the binary Ag-Sn system. The contact resistance of deposited Sn-Ag alloys, after heating at 433 K for 120 h, was slightly smaller at Ag content below 45 mass% than that of reflow Sn plating. The connection reliability of connectors after abrasion was better in deposited films of Sn-Ag alloys than in those with reflow Sn plating.

Corrosion Resistance of Multilayered Sn/Ag3Sn Films Electroplated on Cu Alloys for Highly Reliable Automotive Connectors

“…The multilayered Sn/Ag 3 Sn specimen consists of an Ag-Sn alloy layer with thickness of 50 nm, and a Sn layer and a Cu 6 Sn 5 layer similar to the Sn-RF specimen. It should be noted that the multilayered Sn/Ag 3 Sn film is different from conventional Sn-Ag alloy electroplating [19][20][21][22][23][24] and commercial Sn-Ag hot-dip coatings, 1,25 in which the Ag component (the former) or the Ag 3 Sn particles (the latter) are distributed the whole thickness of coatings. The multilayered Sn/Ag 3 Sn film in the present study was designed to utilize effectively the highly conductive Ag alloy film on the top layer and to minimize Ag usage by 1/40.…”

Cyclic voltammetry growth and characterization of Sn–Ag alloys of different nanomorphologies and compositions for efficient hydrogen evolution in alkaline solutions

“…This indicates that most of Ag ions are incorporated into the alloys. 17,25 The average crystallite size of the alloy is calculated using values of full width at half maximum (W) for the main three Ag/Sn peaks through Scherrer's equation; D s ¼ 0.94l/W cos q; in which q and l are the Bragg's angle and X-ray wavelength. 26,27 Also, the texture coefficients (TCs) and dislocation densities are calculated.…”

“…24 Additionally, we carried the electrochemical polarization (ECP) measurements and EC impedance spectroscopies (EISs) to evaluate the electrochemical activities of the deposits toward HERs. 25 , silver chloride (>99%), tin chloride ($99%), and methionine were obtained from Sigma-Aldrich. Also, alumina paste (Shandong Luxin Mount Tai Co., China) and dichloromethane (Merck, Darmstadt, Germany) were used.…”

Electrodeposition of a Near‐Eutectic Sn‐Ag Alloy from a Mixed Choline Chloride, Ethylene Glycol and Urea Electrolyte

“…Compositions of strongly acidic sulfate and slightly alkaline pyrophosphate solutions for the electrochemical synthesis of the SnÀ Ag alloy are known, which make it possible to obtain coatings with a silver content from 2-12 wt.% in acidic to 13-50 wt.% in alkaline solutions. [4][5][6][7] Strongly acidic solutions are much more stable than alkaline ones (up to 3-4 months of exploitation or storage). However, the hydrolysis can be completely excluded in non-aqueous solutions.…”