Morphology and growth kinetics of intermetallic compounds in solid-state interfacial reaction of electroless Ni-P with Sn-based lead-free solders

A comparative study of solid/solid interfacial reactions of electroless Ni-P (15 at.% P) with lead-free solders, Sn-0.7Cu, Sn-3.5Ag, Sn-3.8Ag-0.7Cu, and pure Sn, was carried out by performing thermal aging at 150°C up to 1000 h. For pure Sn and Sn-3.5Ag solder, three distinctive layers, Ni3Sn4, SnNiP, and Ni3P, were observed in between the solder and electroless Ni-P; while for Sn-0.7Cu and Sn-3.8Ag-0.7Cu solders, two distinctive layers, (CuNi)6Sn5 and Ni3P, were observed. The differences in morphology and growth kinetics of the intermetallic compounds (IMCs) at the interfaces between electroless Ni-P and lead-free solders were investigated, as well as the growth kinetics of the P-enriched layers underneath the interfacial IMC layers. With increasing aging time, the coarsening of interfacial Ni3Sn4 IMC grains for pure Sn and Sn-3.5Ag solder was significantly greater than that of the interfacial (CuNi)6Sn5 IMC grains for Sn-0.7Cu and Sn-3.8Ag-0.7Cu solders. Furthermore, the Ni content in interfacial (CuNi)6Sn5 phase slightly increased during aging. A small addition of Cu (0.7 wt.%) resulted in differences in the type, morphology, and growth kinetics of interfacial IMCs. By comparing the metallurgical aspects and growth kinetics of the interfacial IMCs and the underneath P-enriched layers, the role of initial Cu and Ag in lead-free solders is better understood.

[1]  K. Tu,et al.  Six cases of reliability study of Pb-free solder joints in electronic packaging technology , 2002 .

[2]  Vesa Vuorinen,et al.  Interfacial reactions between lead-free SnAgCu solder and Ni(P) surface finish on printed circuit boards , 2002 .

[3]  Y. C. Chan,et al.  Reliability studies /spl mu/BGA solder joints-effect of Ni-Sn intermetallic compound , 2001 .

[4]  Seung-Boo Jung,et al.  Interfacial reactions and shear strengths between Sn-Ag-based Pb-free solder balls and Au/EN/Cu metallization , 2004 .

[5]  Zhong Chen,et al.  Solid state interfacial reaction of Sn–37Pb and Sn–3.5Ag solders with Ni–P under bump metallization , 2004 .

[6]  Sinn-wen Chen,et al.  Phase equilibria and solidification properties of Sn-Cu-Ni alloys , 2002 .

[7]  D. R. Frear,et al.  Morphology of interfacial reaction between lead-free solders and electroless Ni–P under bump metallization , 2000 .

[8]  Sinn-wen Chen,et al.  Interfacial reactions in the Sn-(Cu)/Ni, Sn-(Ni)/Cu, and Sn/(Cu,Ni) systems , 2003 .

[9]  J. Shang,et al.  Thermal stability of electroless-nickel/solder interface: Part B. Interfacial fatigue resistance , 2000 .

[10]  Zhong Chen,et al.  Morphology and kinetic study of the interfacial reaction between the Sn-3.5Ag solder and electroless Ni-P metallization , 2004 .

[11]  Sung K. Kang,et al.  Spalling of intermetallic compounds during the reaction between lead-free solders and electroless Ni-P metallization , 2004 .

[12]  Zhong Chen,et al.  Intermetallic compound formation between Sn–3.5Ag solder and Ni-based metallization during liquid state reaction , 2004 .

[13]  H. Reichl,et al.  A study on interfacial reactions between electroless Ni-P under bump metallization and 95.5Sn-4.0Ag-0.5Cu alloy , 2003 .

[14]  Young-Doo Jeon,et al.  Studies on Ni-Sn intermetallic compound and P-rich Ni layer at the electroless nickel UBM-solder interface and their effects on flip chip solder joint reliability , 2001, 2001 Proceedings. 51st Electronic Components and Technology Conference (Cat. No.01CH37220).

[15]  K. Paik,et al.  Interfacial reactions and bump reliability of various Pb-free solder bumps on electroless Ni-P UBMs , 2004, 2004 Proceedings. 54th Electronic Components and Technology Conference (IEEE Cat. No.04CH37546).

[16]  D. Frear,et al.  Intermetallic growth and mechanical behavior of low and high melting temperature solder alloys , 1994 .

[17]  C.M.L. Wu,et al.  Microstructural evolution of lead-free Sn-Bi-Ag-Cu SMT joints during aging , 2005, IEEE Transactions on Advanced Packaging.

[18]  H. Saka,et al.  TEM observation of interfaces in a solder joint in a semiconductor device , 2002 .

[19]  Jin Yu,et al.  Effects of phosphorus content on the reaction of electroless Ni-P with Sn and crystallization of Ni-P , 2004 .

[20]  J. Kivilahti,et al.  Intermetallic reactions between lead-free SnAgCu solder and Ni(P)/Au surface finish on PWBs , 2001, 2001 Proceedings. 51st Electronic Components and Technology Conference (Cat. No.01CH37220).

[21]  K. Suganuma,et al.  Interface microstructures between Ni-P alloy plating and Sn–Ag–(Cu) lead-free solders , 2003 .