9 171179 2006 Sn Ag Cu Effect of Addition Elements on Creep Properties of the Sn Ag Cu Lead Free Solder Megumi NAGANO*, Noboru HIDAKA*, Hirohiko WATANABE*, Masayoshi SHIMODA* and Masahiro ONO* * 191-8502 1 * Production Technology Laboratory of Fuji Electric Advanced Technology Co., Ltd. (1 Fujimachi, Hino-shi, Tokyo, 191-8502) 40 C125 C 2 Sn Ag Cu Sn 3.5Ag 0.5Cu Ni Ge Sn 3.0Ag 0.5Cu Sn 3.5Ag 0.5Cu Ni Ge Sn 3.0Ag 0.5Cu 125 C 5MPaSn 3.5Ag 0.5Cu Ni Ge Sn 3.0Ag 0.5Cu 3 TEM Abstract Creep properties of two lead-free solder alloys, Sn 3.5Ag 0.5Cu Ni Ge and Sn 3.0Ag 0.5Cu, were investigated at temperatures between 40 C and 125 C. It is found that the creep strength of Sn 3.5Ag 0.5Cu Ni Ge solder is better than that of Sn 3.0Ag 0.5Cu solder. Especially in the low stress region at 125 C, the creep rupture time of Sn 3.5Ag 0.5Cu Ni Ge solder is about three times longer than that of Sn 3.0Ag 0.5Cu solder. Microstructure characterizations, including TEM analysis, were conducted in order to fully describe the creep properties of the lead-free solders. Key Words: Sn 3.5Ag 0.5Cu Ni Ge Solder, Lead-Free Solder, Creep Property, Microstructure, Dislocation, Stacking Fault 1. 2006 7 EU RoHS Sn Ag Cu Ni, Ge Ge Sn 1),2) Ni Ni 3) Sn Ag Cu (Ni, Ge) 2. NiGe Sn 3.5Ag 0.5Cu 0.07Ni 0.01Ge Sn 3.5Ag 0.5Cu Ni Ge JEITA Sn 3.0Ag 0.5Cu 2 Table 1 330 C SUS 14 mm 160 mm 30 Fig. 1(a)(b) 15 mm 3mm 60 C 24 Fig. 2 Table 2 3 (40 C, 75 C, 125 C) 2 Vol. 9 No. 3 (2006) 171

Table 1. Chemical composition of solder alloys Alloy No. Sn Ag Cu Ni Ge Sn 3.0Ag 0.5Cu Rem. 3.07 0.522 Sn 3.5Ag 0.5Cu Ni Ge Rem. 3.58 0.509 0.064 0.011 Fig. 3 Strength strain curve of both solders at 25 C and strain rate of 2.010 4 s 1 Fig. 1 Appearance of the test specimen Fig. 4 Strength strain curve of both solders at 125 C and strain rate of 2.010 4 s 1 Fig. 2 Miniature creep testing machine Ni X (TEM) Table 2. Creep test conditions 3. Test temp. Load stress (MPa) 40 C 14.7, 19.8 75 C 9.8, 14.7 125 C 5.0, 9.8 #2400 (0.25 mm)ph Ar (SEM) 3.1 3) 125 C Sn 3.0Ag 0.5Cu Sn 3.5Ag 0.5Cu Ni Ge 2.010 4 s 1 Fig. 3Fig. 4 Sn 3.5Ag 0.5Cu Ni Ge Sn 3.0Ag 0.5Cu 3) 125 C 172 Vol. 9 No. 3 (2006)

Fig. 5 Creep curves of the Sn 3.5Ag 0.5Cu Ni Ge solder and the Sn 3.0Ag 0.5Cu solder at 40 C Fig. 8 The creep strength of the Sn 3.5Ag 0.5Cu Ni Ge and the Sn 3.0Ag 0.5Cu solders Fig. 6 Fig. 7 Creep curves of the Sn 3.5Ag 0.5Cu Ni Ge solder and the Sn 3.0Ag 0.5Cu solder at 75 C Creep curves of the Sn 3.5Ag 0.5Cu Ni Ge solder and the Sn 3.0Ag 0.5Cu solder at 125 C 4) 3.2 Fig. 5 Fig. 7 Sn 3.0Ag 0.5Cu Sn 3.5Ag 0.5Cu Ni Ge Fig. 8 2 40 C75 C Sn 3.0Ag 0.5Cu 125 C 9.8 MPa 5MPa Sn 3.0Ag 0.5Cu Sn 3.5Ag 0.5Cu Ni Ge 3 Fig. 9Fig. 10 Norton (1) e ss As n (1) e ss s n A Fig. 11 Fig. 12 Sn 3.5Ag 0.5Cu Ni Ge Sn 3.0Ag 0.5Cu Fig. 9Fig. 10 (1)Fig. 11Fig. 12 n Table 3 n n 5 3 7 2 5),6) Table 3 40 C Sn 3.5Ag 0.5Cu Ni GeSn 3.0Ag 0.5Cu n 11 5)7) 125 C n Sn 3.0Ag 0.5Cu n 5.9 n 5 Vol. 9 No. 3 (2006) 173

Fig. 9 Creep rate vs. normalized time for Sn 3.5Ag 0.5Cu Ni Ge solder Fig. 12 Relation between the stress and steady-state creep rate (Sn 3.0Ag 0.5Cu) Fig. 10 Creep rate vs. normalized time for Sn 3.0Ag 0.5Cu solder Fig. 13 Correlation of rupture time with Larson Miller parameter Table 3. The stress exponent of the solder alloys Alloy No. 40 C 75 C 125 C Sn 3.0Ag 0.5Cu 15.1 9.4 5.9 Sn 3.5Ag 0.5Cu Ni Ge 11.2 9.6 7.6 Fig. 11 Relation between the stress and steady-state creep rate (Sn 3.5Ag 0.5Cu Ni Ge) Larson Miller Fig. 13 C 8) 11 2 Sn 3.0Ag 0.5Cu Sn 3.5Ag 0.5Cu Ni Ge Fig. 14 Arrhenius (2) e As n exp (Q/RT) (2) R Q Fig. 14 Q Q 4950 kj/mol Sn 174 Vol. 9 No. 3 (2006)

(102 kj/mol) 1/2 Sn 5),9)12) 3.3 Fig. 15 SEM b-sn Ag 3 Sn/Cu 6 Sn 5 b-sn 13) Sn 3.0Ag 0.5Cu Sn 3.5Ag 0.5Cu Ni Ge b-sn Fig. 16 125 C 180200 Fig. 16(a)(c) Sn 3.0Ag 0.5Cu NiGe Sn 3.5Ag 0.5Cu Ni Ge Fig. 16(b)(d) 125 C 200 Fig. 14 Arrhenius plots of strain rate and reciprocal temperature Sn 3.0Ag 0.5Cu 0.5 mm mm Sn 3.5Ag 0.5Cu Ni Ge 0.5 mm 14),15) Sn 3.0Ag 0.5Cu Sn 3.5Ag 0.5Cu Ni Ge Sn 3.5Ag 0.5Cu Ni Ge (125 C)Sn 3.0Ag 0.5Cu b-sn Sn 3.5Ag 0.5Cu Ni Ge 3.4 3 Sn 3.5Ag 0.5Cu Ni Ni X Fig. 17 Ni X Ni Cu 6 Sn 5 (110) Ni 0.25% Ni 3 Sn 2 (110) Table 4 Ni 2q (3) Bragg d Fig. 15 Microstructure of the lead-free solders Vol. 9 No. 3 (2006) 175

Fig. 16 Microstructures of the Sn 3.0Ag 0.5Cu solder and the Sn 3.5Ag 0.5Cu Ni Ge solder Table 4. The plane intervals (d) calculated by measured diffraction angle (2q) Amount of Ni addition (wt%) 2q ( ) d (Å) 0 42.97 2.104 0.07 43.27 2.090 0.1 43.36 2.086 0.25 43.54 2.078 Fig. 17 Relation between amount of Ni content, and X- ray diffraction peak near to Sn (220) peak 2d sinqnl (3) l X Cu K a ; l1.54056 Åd q n Sn Ag Cu Ni Cu 6 Sn 5 (Cu,Ni) 6 Sn 5 16),17) Cu 2.556 Å Ni 2.492 Å 18) Cu 6 Sn 5 Cu Ni (TEM) Fig. 18(a)(b)Sn 3.5Ag 0.5Cu Ni Ge TEM Fig. 18(a) b- Sn 0.10.2 mm Fig. 18(b) 0.40.6 mm 176 Vol. 9 No. 3 (2006)

Fig. 18 TEM micrograph of the Sn 3.5Ag 0.5Cu Ni Ge solder Fig. 19 EDX mapping analyses of the Sn 3.5Ag 0.5Cu Ni Ge after creep test at 125 C for 550 h Fig. 19 AgSn CuNiSn 2 Fig. 20 TEM EDX Fig. 21 Ag 3 Sn Cu 6 Sn 5 JCPDS Fig. 21(b)Cu 6 Sn 5 (110) 2.09 Å 0.07%Ni X 4. 2 Sn Ag Cu Sn 3.0Ag 0.5CuSn 3.5Ag 0.5Cu Ni Ge 40 C 125 C 1) 40 C 75 C Sn 3.0Ag 0.5Cu Sn 3.5Ag 0.5Cu Ni Ge 125 C Sn 3.5Ag 0.5Cu Ni Ge 3 2) (125 C) Vol. 9 No. 3 (2006) 177

Fig. 20 The point analyses of particles in the Sn 3.5Ag 0.5Cu Ni Ge solder after creep test at 125 C for 550 h Fig. 21 Electronic diffraction pattern of the particles in the Sn 3.5Ag 0.5Cu Ni Ge solder after creep test at 125 C for 550 h 3) TEM 4) Sn Ag Cu Ni Cu Sn X Ni Cu 6 Sn 5 Cu (Cu, Ni) 6 Sn 5 2005.10.20-1) 7 pp. 491 496, 2001 2) M. Nagano, N. Hidaka, M. Shimoda and H. Watanabe: Effect of Germanium Content on Oxidation Prevention of Sn Ag Cu Lead-Free Solder, Proc. of PSEA04, pp. 256 261, 2004 3) Sn Ag Cu Ni Ge Vol. 8, No.6, pp. 495 501, 2005 4) 9 pp. 223 228, 2003 5) Vol. 8, No. 2, pp. 150 155, 2005 6) Sn 3.5Ag xbi Sn 3.5Ag xcu 6 pp. 281 286, 2000 7) p. 318, 2000 8) Sn Ag Bi In Pb 3 pp. 249 252, 1998 178 Vol. 9 No. 3 (2006)

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