電子部品はんだ接合部の熱疲労寿命解析

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1 43 Evaluation for Thermal Fatigue Life of Solder Joints in Electronic Components Haruhiko Yamada, Kazuyoshi Ogawa 2 63Sn- 37Pb 95Pb-5Sn Si Cu Si 63Sn-37Pb Since automotive electronic components are used under severe temperature conditions, the reliability of thermal fatigue resistance of solder joints is important. In this study, a series of experimental and analytical investigations were performed to develop a method of evaluating the thermal fatigue life of solder joints. First, tensile and creep tests were carried out on two kinds of commonly used solders, 63Sn-37Pb and 95Pb-5Sn, to determine their mechanical properties. Using the measured properties, constitutive equations for the solders based on elasticity and creep were formulated. Next, a nonlinear finite element analysis was performed on structures with Si chips and Cu plates joined together with solders under thermal cycling. The validity of the analysis was verified by an experiment using a diffused type strain gauge formed on a Si chip surface. Third, the fatigue test of bulk 63Sn-37Pb solder was carried out to obtain data for fatigue life prediction. It was found that the temperature, the frequency and the strain hold had little effect on the fatigue life of solder and that the fatigue life was controlled by inelastic strain range. Finally, the thermal strain at the solder joint of a chip resistor was analyzed and the thermal fatigue life was predicted from the calculated inelastic strain range and the fatigue data of solder. Good agreement was obtained between the prediction and the thermal cycling test results in respect of the location for crack initiation and the fatigue life at the bottom of the chip. R&D Vol. 31 No. 4 ( )

2 44 ( ) ( ) (1) ( FEM ) FEM 2 Sn-Pb (2) FEM FEM (3) FEM ( ) (4) 63Sn-37Pb 95Pb-5Sn 16mm 4mm 2mm 1 63Sn- 37Pb Pbrich ( ) Sn-rich ( ) ( : 500N ) K s 1 2 R&D Vol. 31 No. 4 ( )

3 45 Scanning electron micrographs of 63Sn-37Pb solder. (a) (b) 63Sn-37Pb 95Pb-5Sn 63Sn-37Pb 95Pb-5Sn 233K 398K 63Sn-37Pb 95Pb-5Sn Tensile stress-strain curves of 63Sn-37Pb and 95Pb-5Sn solders. Relationship between creep strain rate and stress of 63Sn-37Pb and 95Pb-5Sn solders. R&D Vol. 31 No. 4 ( )

4 46 n ε = Aσ ε : σ : A : n : ε t = ε e + ε c ε t : ε e : ε c : ( 10 4 s 1 ) Fig. 2 (1) ( E A n ) FEM (a)(b) Si Cu 63Sn-37Pb 95Pb-5Sn 2 Si Si Si Elastic and creep parameters of 63Sn-37Pb and 95Pb-5Sn solders. 63Sn-37Pb 95Pb-5Sn T (K) E (GPa) A (MPa/s) n E (GPa) A (MPa/s) n Schematic diagrams of solder joint structure and diffused-type strain gauge. R&D Vol. 31 No. 4 ( )

5 K 1 13 Cu FEM 2 1/2 ( ) X Fig. 5 3 MARC Si 63Sn-37Pb 95Pb-5Sn 2 2 Material properties of solder joint structure. Material E (GPa) Poisson's ratio Coefficient of thermal expansion ( 10 6 /K ) Si Cu Sn-37Pb 26.6 Table Pb-5Sn 29.2 Temperature profile of thermal cycling test. Finite element model of solder joint structure. Comparison between finite element analysis results and experimental data of stress on silicon chip for 63Sn-37Pb solder. R&D Vol. 31 No. 4 ( )

6 48 Comparison between finite element analysis results and experimental data of stress on silicon chip for 95Pb-5Sn solder. 95Pb-5Sn 63Sn-37Pb Fig. 2 95Pb-5Sn Si Cu Fig. 8 ( ) Fig. 7 63Sn-37Pb 63Sn-37Pb 6mm 3mm 16mm 1 Fig. 1(a) ( : 5Nm ) 0 0.5Hz K 3 393K Hz 3 ( ) 393Kt r t h 30% 63Sn-37Pb 393K 0.005Hz Fig. 1(a) Pb-rich ( ) Sn-rich ( ) R&D Vol. 31 No. 4 ( )

7 49 ( Fig. 9 ) t r 1s t h t r 50s Fig. 11 t r 63Sn-37Pb Fig. 9 ( Coffin-Manson ) N f = ( 73.8 / γ i ) 2.09 γ i : (%) N f : ( ) Scanning electron micrographs of cross section of 63Sn-37Pb solder specimen tested at 393K, 0.005Hz. Effects of temperature and frequency on fatigue life of 63Sn-37Pb solder. Effect of strain hold on fatigue life of 63Sn-37Pb solder. R&D Vol. 31 No. 4 ( )

8 50 Mises (3) ε i = γ i / ε i : (%) (4) (3) N f = ( 42.6 / ε i ) 2.09 FEM Al 2 O 3 ( FR-4 ) 63Sn-37Pb 2 1/2 X Y Mises 2 A ( ) B C Mises Material properties of chip resistor component. Material E (GPa) Poisson's ratio Coefficient of thermal expansion ( 10 6 /K ) Al 2 O Cu Sn-37Pb Table FR ( x-direction ) 45.0 ( y-direction ) Chip resistor component. Equivalent creep strain range distribution in solder joint at 2nd thermal cycle. R&D Vol. 31 No. 4 ( )

9 Fig. 13 A C Table 4 (5) A 300 AB 1% 2000 C 1% Fig. 13 Table (5) Mises Equivalent creep strain range and predicted fatigue life of solder joint. Location Equivalent creep Predicted strain range fatigue life ε c (%) N f ( cycles ) A B C Equivalent stress-creep strain hysteresis loops of solder joint at 2nd thermal cycle. Scanning electron micrograph of cross section of chip resistor solder joint after 3000 thermal cycles. R&D Vol. 31 No. 4 ( )

10 52 1/2 1/ (1) 63Sn-37Pb 95Pb-5Sn (2) Si Cu Si (3) 63Sn-37Pb (4) 1), :, 44-11(1990), 6 2) Cole, M. and Caulfield, T. : Scripta Met. Mater., 27-7(1992), 903 3) Savage, E. I., et al. : ISHM'90 Proc., (1990), 669 4) Yamada, H., et al. : FATIGUE'96, (1996), ) Pan, T. Y. : IEEE Trans. Comp., Hybrids, Manuf. Technol., 14-4(1991), 824 6), 3 : 4, (1991), 223 7), 2 :, (1991), 15 8) Pao, Y. H., et al. : Trans. ASME J. Electron. Packaging, 115-1(1993), 1 9) Sarihan, V. : Trans. ASME J. Electron. Packaging, 115-1(1993), 16 10), 2 :, (1996), ), 2 :, (1981), ) Vaynman, S., et al. : FATIGUE'87, (1987), ), 2 :, (1988), ) Solomon, H. D. : Trans. ASME J. Electron. Packaging, 111-2(1989), 75 15), 2 :, (1992), ), 2 :, (1994), ), :, 48-8(1994), 44 18) Yagi, Y., et al. : Proc. ASME/JSME Advances in Electronic Packaging, Vol.2(1992), ) Cortez, R, et al. : Proc. Electron. Compon. Technol. Conf., 42(1992), R&D Vol. 31 No. 4 ( )

Fig. 4. Configuration of fatigue test specimen. Table I. Mechanical property of test materials. Table II. Full scale fatigue test conditions and test

Fig. 4. Configuration of fatigue test specimen. Table I. Mechanical property of test materials. Table II. Full scale fatigue test conditions and test (J. Soc. Mat. Sci., Japan), Vol. 52, No. 11, pp. 1351-1356, Nov. 2003 Fatigue Life Prediction of Coiled Tubing by Takanori KATO*, Miyuki YAMAMOTO*, Isao SAWAGUCHI** and Tetsuo YONEZAWA*** Coiled tubings,