Title :
Pressure Induced Tin Whisker Formation on SnCu Finish by Nanoindentation Creep
Author :
Shibutani, Tadahiro ; Yu, Qiang
Author_Institution :
Yokohama Nat. Univ., Yokohama, Japan
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;
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
DOI :
10.1109/EPTC.2008.4763634
