Abstract
A joint assembly of lead-free solder/intermetallic layers/copper was prepared by hot-dipped solder coated on a copper substrate and then by thermal ageing at 100, 125, 150, and 170°C for 50, 100, 200, and 600 h, respectively. Results of interfacial morphologies and concentration profiles on the solder/copper joint were presented. Optical and scanning electron microscope (OM and SEM) were used to measure the thickness of intermetallic layers and then to illucidate the development of microstructure at the joint assembly. The phases of intermetallic compound were identified to be Cu3Sn and Cu6Sn5 by both X-ray mapping in electron probe micro-analysis (EPMA), and X-ray diffraction. The intermetallic layers, subtracted from the initial thickness formed by hot dipping, showed a linear dependence on the square root of ageing time at various ageing temperatures. The diffusion coefficients of intermetallic compounds are estimated by an Arrhenius equation, and the pre-exponential terms of Cu3Sn layer and Cu6Sn5 layer are 7.10×10-7cm2s-1 and 6.1×10-3cm2s-1, respectively. The associated activation energies of Cu3Sn layer and Cu6Sn5 layer are 57.03kJmol-1 and 83.76kJmol-1, respectively. A model of a diffusion-controlled mechanism is used to fit the concentration profiles of the joint assembly, and exhibits a fairly good quantitative agreement with the measured data. The initial thickness formed as soldering proceeds is also taken into account to evaluate the apparent thickness by introducing a term of corrected ageing time. ©1999 Kluwer Academic Publishers
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References
Z. Mei and J. W. Morris, Jr, J.Electron.Mater. 21 (1992) 599.
C. H. Reader, L. E. Felton, V. A. Tanzi and D. B. Knorr, J. Electron. Mater. 23 (1994) 611.
M. Mccormack and S. JIN, ibid. 23 (1994) 635.
M. Mccormack and S. Jin, ibid. 23 (1994) 687.
J. Glazer, ibid. 23 (1994) 693.
E. P. Wood and K. L. Nimmo, ibid. 23 (1994) 709.
S. K. Kang, ibid. 23 (1994) 701.
M. Mccormack and S. Jin, ibid. 23 (1994) 715.
F. Bartels and J. W. Morris, Jr, ibid. 23 (1994) 787.
D. Yao and J. K. Shang, IEEE Trans.Compon Hybrids Manuf.Technol.B. 19 (1996) 154.
L. E. Felton, C. H. Raeder and D. B. Knorr, J.Met. 45 (1993) 28.
M. Mccormack and S. Jin, ibid. 45 (1993) 36.
J. Glazer, Int.Mater.Rev. 40 (1995) 65.
H. K. Kim and K. N. Tu, Phys.Rev. B 53 (1996) 16027.
J. G. Duh, C. C. Young and Y. G. Lee, in Proceedings of the Second International Symposium on Electronic Packaging Technology, 1996, edited by K. Bi, X. Zong, S. Liu and F. Liu (Commercial Press Shanghai Plant, Shanghai, China) p. 330.
Y. G. Lee and J. G. Duh, in 1998 Proceedings Pan Pacific Microelectronics Symposium, Kona, Hawaii (Surface Mount Technology Association, Edina, Minnesota, USA) p. 501.
J. S. Huang, J. Zhang, A. Cuevas and K. N. Tu, Mater.Chem.Phys. 49 (1997) 33.
Y. Wu, J. A. Sees et. al., J.Electron.Mater. 23 (1993) 759.
P. Vianco, P. F. Hlava and A. C. Kilgo, ibid. 23 (1994) 583.
P. T. Vianco, A. C. Kilgo and R. Grant, ibid. 24 (1995) 1493.
H. K. Kim, H. K. Liou and K. N. Tu, Appl.Phys.Lett. 66 (1995) 1237.
Z. Mei, A. J. Sunwoo and J. W. Morris, JR, Metall Trans.A 23 (1992) 857.
K. Hoshino, Y. Iijima and K. I. Hirtano, Trans.Jpn.Inst.Met. 21 (1980) 674.
K. N. Tu and R. D. Thompson, Appl.Phys.Lett. 67 (1995) 2795.
K. F. Dreyer, W. K. Neils, R. R. Chromik, D. Grosman and E. J. Cotts, ibid. 67 (1995) 2795.
W. Jost, in “Diffusion in Solids, Liquids, Gases” 3rd Edn (Academic Press, New York, 1960) p. 71.
G. V. Kidson, J.Nucl.Mater. 3 (1961) 21.
P. G. Shewmon, in “Diffusion in Solids” (McGraw-Hill, 1963) p. 30.
M. G. Pecht, in “Soldering Process and Equipment” (John Wiley & Sons. New York, 1993) Ch. 2.
J. R. Manning, Phys.Rev. 16 (1960) 819.
M. Hansen, in “Constitution of Binary Alloys” (McGraw-Hill, New York, 1958) p. 633.
In “Binary Alloys Phase Diagrams” Vol. 2, 2nd Edn (ASM 1990) p. 1481.
B. D. Bastow and D. H. Kirkwood, J.Inst.Met. 100 (1972) 24.
Fon Kon et al., in “Method of Numerical Calculation” (Country Guardagainst Industrial Publish, Bejing, China, 1978) p. 154.
F. Abautret and P. Eveno, Rev.Phys.Appl. 25 (1990) 1113.
J. I. Goldstein, D. E. Newbury, P. Echlin, D. C. Joy, C. Fiori and E. Lifshin, in “Scanning Electron Microscopy and X-ray Microanalysis” (Plenum Press, New York and London, 1992) p. 109.
E. L. Erickson, P. L. Hopkins and P. T. Vianco, J.Electron.Mater. 23 (1994) p. 583.
S. Bader, W. Gust and H. Heiber, Acta.Metall.Mater. 43 (1995) 329.
J. G. Duh, PhD Thesis, Purdue University, USA (1983).
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Lee, Y.G., Duh*, J.G. Interfacial morphology and concentration profile in the unleaded solder/Cu joint assembly. Journal of Materials Science: Materials in Electronics 10, 33–43 (1999). https://doi.org/10.1023/A:1008975006706
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DOI: https://doi.org/10.1023/A:1008975006706