Pressure Induced Tin Whisker Formation on SnCu Finish by Nanoindentation Creep

Author

Shibutani, Tadahiro ; Yu, Qiang

Author_Institution

Yokohama Nat. Univ., Yokohama, Japan

fYear

2008

fDate

9-12 Dec. 2008

Firstpage

1442

Lastpage

1447

Abstract

This paper presents pressure induced tin whisker formation by means of nanoindentation creep. Bright tin-copper finish was plated on a rectangular coupon made of phosphor bronze with nickel underlayer. Applied load was from 1 mN to 80 mN. Small tin whiskers were formed along a contact edge after the dwell time of 3000 seconds with the application of more than 4 mN. Since tin whisker growth produces new surface area, there is a threshold stress to generate tin whiskers. Based on the balance of energy, the threshold stress is related to the size (or diameter) of whisker. The finite element analysis revealed that a pressure to induce whiskers is 40 MPa for observed whiskers. This threshold stress corresponds with a proposed tin whisker formation model based on a balance of energy.

Keywords

copper alloys; creep; finite element analysis; internal stresses; nanoindentation; surface finishing; tin alloys; whiskers (crystal); SnCu; bright tin-copper finish; energy balance; finite element analysis; nanoindentation creep; phosphor bronze; surface area; threshold stress; time 3000 s; whisker formation; Compressive stress; Conductors; Creep; Finite element methods; Phosphors; Residual stresses; Stress measurement; Surface finishing; Thermal stresses; Tin;

fLanguage

English

Publisher

ieee

Conference_Titel

Electronics Packaging Technology Conference, 2008. EPTC 2008. 10th

Conference_Location

Singapore

Print_ISBN

978-1-4244-2117-6

Electronic_ISBN

978-1-4244-2118-3

Type

conf

DOI

10.1109/EPTC.2008.4763634

Filename

4763634