Mechanism of Fillet Lifting in Sn-Bi Alloys

Published

May 1, 2002

Author(s)

William J. Boettinger, C A. Handwerker, B Newbury, TG Y. Pan, J M. Nicholson

Abstract

The probability of fillet lifting in through-hole solder joints was determined for a series of seven binary Sn-Bi solders with compositions between 2.6 and 65 mass percent Bi. A 20 pin ceramic dual inline package was soldered to printed wiring boards with three thicknesses and two pad sizes. A laboratory scale drag soldering process designed to simulate wave soldering was employed. Composition has the largest effect on failure with a peak in lift-off probability near 8 mass percent Bi. The presence of intermetallic needles of Cu(sub6)Sn(Sub5) attached to the pad side of the separation surface, but pulled from solder side indicate that fillet lifting occurs during solidification. This conclusion is further supported by real time observation of fillet lifting. The solidification of these alloys is analyzed using a Scheil analysis and the tendency for fillet lifting is related o a hot tearing criterion originally developed for castings.

Citation

Journal of Electronic Materials

Volume

31

Issue

No. 5

Pub Type

Journals

Keywords

Fillet Lifting, Pb-free, Solder, Solidification

Citation

Boettinger, W. , Handwerker, C. , Newbury, B. , Pan, T. and Nicholson, J. (2002), Mechanism of Fillet Lifting in Sn-Bi Alloys, Journal of Electronic Materials (Accessed May 10, 2025)