Transactions of The Japan Institute of Electronics Packaging
Online ISSN : 1884-8028
Print ISSN : 1883-3365
ISSN-L : 1883-3365
Technical Papers
Multilayered Sn/Ag3Sn Electroplating on Cu Alloys for High Reliable Electronic/Electric Materials
Song-Zhu Kure-ChuTohru OgasawaraHitoshi YashiroRongbin YeTakuya HosokaiMichimasa UchidateEiichi SuzikiTomoyuki Naito
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2014 Volume 7 Issue 1 Pages 79-86

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Abstract

We report a multilayered Sn/Ag3Sn film electroplated on Cu alloys with high reliability as promising coating materials for LED lead-frames and for electric connectors. The multilayered Sn/Ag films consisted of an Ag-Sn alloy film with 30-80 nm-thick as Ag3Sn phase covered on a 1 μm-thick Sn film on Cu alloy substrates. The as-deposited Sn/Ag3Sn films exhibited a high specular reflectivity around 70% at the wavelengths of 480 nm, which was lower than a commercial bright Ag film with total reflectivity of 90% but much higher than a commercial bright Au film in 24% at the same wavelength. It was found through an accelerated sulfuring test that, the reflectivity of the Sn/Ag3Sn films was almost unchanged even after immersing in a 0.2% (NH4)2Sx solution for 60 min, compared to the abrupt decrease to 15% for the conventional Ag film even after immersing for 10 min. The excellent sulfuring resistance and durability of the multilayered Sn/Ag3Sn films can be attributed to the existence of a stable SnO2 film existed on the surface of Ag3Sn alloy, which was revealed by a UPS analysis in a vacuum chamber by heating at 473-673 K, thus protecting underneath Ag3Sn alloy film and inhibiting the chemical reaction of Ag and S2− ions.

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© 2014 The Japan Institute of Electronics Packaging
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