Interfacial Reactions of Sn-3.0Ag-0.5Cu Solder with Cu-Mn UBM During Aging

Cu under bump metallurgy (UBM) has been widely used in flip-chip technology. The major disadvantages of Cu UBM are fast consumption of copper, rapid growth of intermetallic compounds (IMCs), and easy formation of Kirkendall voids. In this study we added two different contents of Mn (2 at.% and 10 at.%) to Cu UBM by sputtering to modify the conventional Cu metallization. For the higher Mn concentration in the Cu-Mn UBM, a new Sn-rich phase formed between Cu6Sn5 and the Cu-Mn UBM, and cracks formed after aging. For the lower Mn concentration, growth of Cu3Sn and Kirkendall voids was significantly suppressed after thermal aging. Kinetic analysis and x-ray elemental mapping provided evidence that Mn diffusion into Cu3Sn slowed diffusion of Cu in the Cu3Sn layer. The Mn-enriched Cu3Sn layer may serve as a diffusion barrier to reduce the interfacial reaction rate and Kirkendall void formation. These results suggest that Cu-Mn UBM with low Mn concentration is beneficial in terms of retarding Cu pad consumption in solder joints.

[1]  Jenq-Gong Duh,et al.  Interfacial Reaction of Sn and Cu-xZn Substrates After Reflow and Thermal Aging , 2010 .

[2]  Weiqun Peng,et al.  Effect of thermal aging on the interfacial structure of SnAgCu solder joints on Cu , 2007, Microelectron. Reliab..

[3]  Young-Ho Kim,et al.  A new solder wetting layer for Pb-free solders , 2009 .

[4]  T. Laurila,et al.  Formation of Intermetallic Compounds Between Liquid Sn and Various CuNix Metallizations , 2008 .

[5]  Kim,et al.  Kinetic analysis of the soldering reaction between eutectic SnPb alloy and Cu accompanied by ripening. , 1996, Physical review. B, Condensed matter.

[6]  Guido Schmitz,et al.  On the mechanism of the binary Cu/Sn solder reaction , 2005 .

[7]  Seung-Boo Jung,et al.  Growth of an intermetallic compound layer with Sn-3.5Ag-5Bi on Cu and Ni-P/Cu during aging treatment , 2003 .

[8]  Ning-Cheng Lee,et al.  The effects of additives to SnAgCu alloys on microstructure and drop impact reliability of solder joints , 2007 .

[9]  D. Frear,et al.  Pb-free solders for flip-chip interconnects , 2001 .

[10]  Chang-Da Tsai,et al.  A study on the reaction between Cu and Sn3.5Ag solder doped with small amounts of Ni , 2003 .

[11]  Hwa-Teng Lee,et al.  Shear strength and interfacial microstructure of Sn–Ag–xNi/Cu single shear lap solder joints , 2007 .

[12]  M. Abtew,et al.  Lead-free Solders in Microelectronics , 2000 .

[13]  H. J. Yang,et al.  Morphologies, orientation relationships and evolution of Cu6Sn5 grains formed between molten Sn and Cu single crystals , 2008 .

[14]  T. Laurila,et al.  Solid-State Reactions between Cu(Ni) Alloys and Sn , 2007 .

[15]  Tomi Laurila,et al.  Interfacial reactions between lead-free solders and common base materials , 2005 .

[16]  Li-Wei Lin,et al.  Alloying modification of Sn-Ag-Cu solders by manganese and titanium , 2009, Microelectron. Reliab..

[17]  Robert W. Messler,et al.  Microstructure evolution of eutectic Sn-Ag solder joints , 1994 .

[18]  Swapan Das,et al.  Aging Characteristics of Sn-Ag Eutectic Solder Alloy with the Addition of Cu, In, and Mn , 2009 .

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

[20]  Hwa-Teng Lee,et al.  Effect of adding Sb on microstructure and adhesive strength of Sn-Ag solder joints , 2004 .

[21]  Fu Guo,et al.  Evaluation of creep behavior of near-eutectic Sn–Ag solders containing small amount of alloy additions , 2003 .

[22]  Hyuck-Mo Lee,et al.  Wettability and interfacial reactions of Sn-based Pb-free solders with Cu–xZn alloy under bump metallurgies , 2009 .