The effects of solder volume and Cu concentration on the consumption rate of Cu pad during reflow soldering

Abstract The combined effect of solder volume and Cu concentration in solder on the Cu consumption rate is of significant practical importance but has never been satisfactorily addressed in literature so far. In this study, lead-free solder balls of different volumes (400, 500, 760 and 960 μm in diameter) and different Cu concentrations (Sn3Ag x Cu with x  = 0, 0.3, 0.5, and 0.7 wt.%) were reflowed over Cu soldering pads in order to resolve this issue. The data obtained afforded the establishment of an empirical equation that could predict the Cu consumption during reflow. Such consumption rate information is crucial for designing the Cu conduction traces with minimum but reliable dimensions. Both the solder volume and the Cu concentration had marked effects on the morphology of the reaction product. Rationalizations for the effects on the consumption rate and the morphology are presented.

[1]  C. Kao,et al.  Minimum effective Ni addition to SnAgCu solders for retarding Cu3Sn growth , 2009 .

[2]  King-Ning Tu,et al.  Three‐dimensional morphology of a very rough interface formed in the soldering reaction between eutectic SnPb and Cu , 1995 .

[3]  C. Handwerker,et al.  Experimental and thermodynamic assessment of Sn-Ag-Cu solder alloys , 2000 .

[4]  Y. C. Chan,et al.  Comparative study of interfacial reactions of Sn-Ag-Cu and Sn-Ag solders on Cu pads during reflow soldering , 2005 .

[5]  Yee-Wen Yen,et al.  Interfacial reactions in Ag-Sn/Cu couples , 1999 .

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

[7]  Y. Chang,et al.  Reactions of solid copper with pure liquid tin and liquid tin saturated with copper , 1997 .

[8]  C. Kao.  Microstructures developed in solid-liquid reactions: using Cu-Sn reaction, Ni-Bi reaction, and Cu-In reaction as examples , 1997 .

[9]  I. Anderson,et al.  A viable tin-lead solder substitute: Sn-Ag-Cu , 1994 .

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

[11]  P. G Boswell,et al.  Crystallisation of an Mg74Zn26 glass , 1978 .

[12]  Li Wang,et al.  Intermetallic compounds growth between Sn–3.5Ag lead-free solder and Cu substrate by dipping method , 2005 .

[13]  Albert Feldman,et al.  Thermal and electrical properties of copper‐tin and nickel‐tin intermetallics , 1992 .

[14]  C. Kao,et al.  Strong Zn concentration effect on the soldering reactions between Sn-based solders and Cu , 2006 .

[15]  Xin Ma,et al.  Development of Cu-Sn intermetallic compound at Pb-free solder/Cu joint interface , 2003 .

[16]  K. N. Subramanian,et al.  Characterization of the growth of intermetallic interfacial layers of Sn-Ag and Sn-Pb eutectic solders and their composite solders on Cu substrate during isothermal long-term aging , 1999 .

[17]  L. Snugovsky,et al.  Experiments on interaction of liquid tin with solid copper , 2003 .

[18]  C. Kao,et al.  Interfacial reaction issues for lead-free electronic solders , 2006 .

[19]  Y. C. Chan,et al.  Effect of volume in interfacial reaction between eutectic Sn-3.5% Ag-0.5% Cu solder and Cu metallization in microelectronic packaging , 2005 .

[20]  Y. Chan,et al.  Effect of 0.5 wt % Cu addition in Sn–3.5%Ag solder on the dissolution rate of Cu metallization , 2003 .

[21]  Yi-Wun Wang,et al.  Kirkendall voids formation in the reaction between Ni-doped SnAg lead-free solders and different Cu substrates , 2009, Microelectron. Reliab..

[22]  Chien W. Chang,et al.  Cross-Interaction between Ni and Cu across Sn Layers with Different Thickness , 2007 .

[23]  K. Tu,et al.  Tin–lead (SnPb) solder reaction in flip chip technology , 2001 .

[24]  Won Kyoung Choi,et al.  Effect of soldering and aging time on interfacial microstructure and growth of intermetallic compounds between Sn-3.5Ag solder alloy and Cu substrate , 2000 .

[25]  K. Bae,et al.  Interdiffusion analysis of the soldering reactions in Sn-3.5Ag/Cu couples , 2001 .

[26]  Wenge Yang,et al.  The effect of soldering process variables on the microstructure and mechanical properties of eutectic Sn-Ag/Cu solder joints , 1995 .

[27]  King-Ning Tu,et al.  Rate of consumption of Cu in soldering accompanied by ripening , 1995 .

[28]  C. Kao,et al.  Effects of minor Fe, Co, and Ni additions on the reaction between SnAgCu solder and Cu , 2009 .

[29]  King-Ning Tu,et al.  Physics and materials challenges for lead-free solders , 2003 .

[30]  H. Reichl,et al.  Role of Cu in dissolution kinetics of Cu metallization in molten Sn-based solders , 2005 .