Interfacial reactions between lead-free SnAgCu solder and Ni(P) surface finish on printed circuit boards

Author

Zeng, Kejun ; Vuorinen, Vesa ; Kivilahti, Jorma K.

Author_Institution

Lab. of Electron. Production Technol., Helsinki Univ. of Technol., Finland

Volume

25

Issue

3

fYear

2002

fDate

7/1/2002 12:00:00 AM

Firstpage

162

Lastpage

167

Abstract

Transmission electron microscopy and scanning electron microscopy were employed to analyze the interfacial microstructure between Sn-Ag-Cu solder alloys and Ni(P)/Au metallizations. The intermetallic compound Cu₆Sn₅, containing a small amount of dissolved Ni, was found to form preferentially on the Ni coating. This compound layer served as a barrier for direct reaction of Sn with the Ni(P) coating. On the Ni(P) side, a nickel phosphide was identified. Thermodynamic evaluation of the Cu-Ni-Sn system was carried out to rationalize the enrichment of Cu at the solder/finish interface. Effects of the interfacial reactions on joint reliability are discussed.

Keywords

assembling; circuit reliability; copper alloys; gold; interface phenomena; nickel compounds; printed circuit manufacture; scanning electron microscopy; silver alloys; soldering; tin alloys; transmission electron microscopy; Cu-Ni-Sn system; Cu₆Sn₅; Cu₆Sn₅ intermetallic compound; Ni coating; Ni(P) surface finish; Ni(P)/Au metallizations; PCBs; Pb-free SnAgCu solder; SEM; SnAgCu-NiP-Au; TEM; interfacial microstructure analysis; interfacial reaction; printed circuit boards; scanning electron microscopy; solder joint reliability; solder/finish interface; thermodynamic evaluation; transmission electron microscopy; Coatings; Environmentally friendly manufacturing techniques; Lead; Microstructure; Nickel; Printed circuits; Scanning electron microscopy; Surface finishing; Tin; Transmission electron microscopy;

fLanguage

English

Journal_Title

Electronics Packaging Manufacturing, IEEE Transactions on

Publisher

ieee

ISSN

1521-334X

Type

jour

DOI

10.1109/TEPM.2002.801648

Filename

1158826