Contact Resistance Stability and Mechanism of Multilayered Sn/Ag Electroplating on Cu Alloys under High Temperature Circumstance

Abstract

The contact resistances of multilayered Sn/Ag electroplating with a 50 nm-thick Ag-Sn alloy film as Ag 3 Sn nano-flakes in 50-200 nm across on copper alloys were investigated after aging at ambient temperatures of 150, 175, and 200 ℃ for 120 h to 3000 h in air. The microstructures and surface characteristics of the Sn/Ag coatings after aging at different temperatures and periods were elaborated using SEM, FE-SEM, XRD, TEM, GDOES, and AES. The Sn/Ag coatings exhibited low and stable contact resistances equivalent to that of as-plated sample even after aging at 200 ℃ for 3000 h, compared to the ever-increasing contact resistances for conventional reflowed Sn coatings without Ag plating, especially at the low-load side. The excellent stability of the contact resistance of the multilayered Sn/Ag coatings can be ascribed mainly to Ag 3 Sn microparticles that are agglutinated on the coating surfaces, and to their good oxidizing resistance, irrespective of the oxidation of Cu-Sn alloys during aging. Moreover, the oxide films on the Sn/Ag coatings after aging were much thinner than those on the reflowed Sn coatings. In particular, a tiny amount of Ag was included the Cu-Sn intermetallic compounds and agglutinated at the Cu 3 Sn/Cu interface with aging. This phenomenon can be attributed to the inward Ag diffusion countered against the outward Cu diffusion from the base materials, which enhanced the anti-oxidation and adhesion characteristics of the coatings, thus leading to a high reliability under high-temperature circumstance for electrical devices in automotive applications.

Efficient Photocatalytic Removal of Contaminant by Bi3NbxTa1−xO7 Nanoparticles under Visible Light Irradiation

“…In another experiment, it was found that the addition of isopropanol, a well-known scavenger of • OH radicals, into the photoreaction system did not cause the apparent changes in the degradation rate of ARG, as shown in Figure . The results indicate that the free • OH radicals could not be the main active oxygen species in this photochemical process, which is different from TiO 2 toward photocatalytic degradation of organic pollutants. , As mentioned above, the sample shows the excellent photocatalytic activity under visible light irradiation. Therefore, it could be postulated that O 2 •− is the other pivotal active species for Bi 3 Nb 0.6 Ta 0.4 O 7 photocatalysis.…”

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

“…Through quantitative EDX analysis, the oxide films were determined to be CuO on the Sn-RF film and Cu 2 O · CuO on the Ag film, respectively. It was found in a previous study 14 that the crystalline structure of Ag 3 Sn grains was unchanged even after aging at 473 K for 3000 h in air, indicating the excellent chemical stability under the high temperature. In addition, it was also confirmed that the underlying CuSn alloy layers of Sn-RF and Sn/Ag 3 Sn specimens had transformed completely from η-Cu 6 Sn 5 to ε-Cu 3 Sn after aging at 473 K for 240 h because of the outward Cu diffusion from the base materials.…”

“…The multilayered Sn/Ag 3 Sn films demonstrated a high reliability of stable electric contact resistance at different aging temperatures, good fretting performance, and excellent resistance to the growth of Sn whiskers, thus being thought as a promising coating material for various electric connectors and terminals. [12][13][14][15] This paper focuses on evaluation of the corrosion resistance, i.e., sulfidizing resistance and oxidation resistance of the multilayered Sn/Ag 3 Sn films, compared to a commercial Ag film with 2 µm thickness and a conventional reflowed Sn film with 1 µm thickness. The surface states and microstructures of the multilayered Sn/Ag 3 Sn films before and after accelerated corrosion tests were investigated by various analysis methods and the mechanism of improved corrosion resistance was discussed.…”

Thermal Stability and Sulfidizing Resistance of High Reflective Multilayered Sn/Ag3Sn and Sn/Ag Films Electrodeposited on Cu Alloy Sheets

“…In our previous studies, we had also reported a multilayered Sn/Ag film on Cu alloys with high reliability as a promising coating material for automotive connectors and electrical contacts. It was found that the multilayered Sn/Ag 3 Sn films on Cu alloys exhibited excellent thermal stability of electric contact resistance, satisfied fretting corrosion resistance, Sn whisker-free, and good solderability [23][24][25][26][27]. Recently, we have also reported a multilayered Sn/Ag 3 Sn film on Cu alloys toward high durability LED lead frames [28], and found that the Sn/Ag 3 Sn films possessed excellent sulfidizing resistance.…”