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1 [ ] w wz Kor. J. Mater. Res. Vol. 17, No. 3 (2007) Sn-3.0 Ag-0.5 Cu/OSP 무연솔더접합계면의접합강도변화에따른전자부품열충격싸이클최적화 y Á½{ *Á Á½Ÿ * t sƒ l *w wœ w wœ œw Thermal Shock Cycles Optimization of Sn-3.0 Ag-0.5 Cu/OSP Solder Joint with Bonding Strength Variation for Electronic Components Won Sik Hong, Whee Sung Kim*, Byeong Suk Song and Kwang-Bae Kim* Reliability and Failure Analysis Center, Korea Electronics Technology Institute, Gyeonggi, , Korea *Department of Materials Engineering, Hankuk Aviation University, Gyeonggi, , Korea ( , ) Abstract When the electronics are tested with thermal shock for Pb-free solder joint reliability, there are temperature conditions with use environment but number of cycles for test don't clearly exist. To obtain the long term reliability data, electronic companies have spent the cost and times. Therefore this studies show the test method and number of thermal shock cycles for evaluating the solder joint reliability of electronic components and also research bonding strength variation with formation and growth of intermetallic compounds (IMC). SMD (surface mount device) 3216 chip resistor and 44 pin QFP (quad flat package) was utilized for experiments and each components were soldered with Sn-40Pb and Sn-3.0 Ag-0.5 Cu solder on the FR-4 PCB(printed circuit board) using by reflow soldering process. To reliability evaluation, thermal shock test was conducted between 40 o C and +125 o C for 2,000 cycles, 10 minute dwell time, respectively. Also we analyzed the IMCs of solder joint using by SEM and EDX. To compare with bonding strength, resistor and QFP were tested shear strength and 45 o lead pull strength, respectively. From these results, optimized number of cycles was proposed with variation of bonding strength under thermal shock. Key words Pb-free solder, thermal shock, Sn-3.0 Ag-0.5 Cu, reliability, intermetallic compounds 1. ey t (SnPb) w. w(eu) 06 7 l ü t w û,, e, 6ƒ j 6 w e p w w e(rohs) zw. t û(pb) w (Pb-free solder) w ƒ y w.» w x yw w ƒ, t sƒ wp v w x x w w. w t sƒ w x Corresponding author wshong@keti.re.kr (W. S. Hong) x wš w yw x w y w w. x r t x t (surface mount device, SMD) QFP(quad flat package) e w»(chip resistor) Sn-40 Pb Sn- 3.0 Ag-0.5 Cu w FR-4»q v w. w s ƒ w r x(thermal shock test) 40 o C~+125 o C ƒƒ 10 w, 2,000 j x ww. x z r x (SEM) rp (EDX) w x w x yw (intermetallic compound, IMC) w, w w d w» w QFP e w» ƒƒ 45 o x x w w. w x l w sƒ w x 152

2 Sn-3.0 Ag-0.5 Cu/OSP w w y t j y 153 ww x w» w. 2. x x r SMD xk 44 pin QFP 3216 e w» w, Sn-40 Pb Sn- 3.0 Ag-0.5 Cu w FR-4(glass fiber/epoxy resin)»q t v w w. x is(coupon) w»q t Table 1, Fig. 1 t Ÿwx ƒ w v (fillet) x w. v š ƒƒ 220, 245 o C, X- q (non-destructive test, NDT) w z w (void) w w.»q x w w, x j e w» QFP w w d w, SEM, EDX w x z w x yw w. 2.1 w sƒ j Ÿw x SEM w š, w IMC x w» w EDX w w. x z w Table 1. Design conditions of test coupons for 3216 chip resistor and 44 pin QFP Classifications 3216 Chip Resistor 44 Pin QFP PCB materials FR-4(t = 1.6mm, Tg = 135 o C) Pad surface finish Cu foil(1 oz)/cu plating(25 µm)/osp Pad size of PCB 0.4Ü2.5 mm 1.6Ü1.6 mm Surface finish Ni-P/Sn Cu lead/ni-p/sn Lead pitch mm w w DAGE 4000 Bonding Tester w e w», QFP t w ƒƒ x 45 o x w. d x 45 o 167 µm/sec, e 50 µm d w, 10 t d w s³ w. 2.2 x w sƒ w e w» QFP t»q l x w x(thermal shock test) 40 o C~+125 o C ƒƒ š 10 w, ƒ y 5 ü w 2,000 j x ww. 3. š 3.1 X- q Ÿwx z w w k w» w X-ray NDT Fig. 3 ww. Sn-40 Pb w r t w w k w û ùkû, Sn- 3.0 Ag-0.5 Cu w e w» QFP w w ùkü. ù w w w w» e w. w e w, w 20% wƒ» wš. t r w, w ƒ š w» 30% ü w» w. x r, X-ray NDT w w w 10% ü wp sƒw» w ùkû. Fig. 1. Photographs of (a) 3216 chip resistor and (b) 44 pin QFP soldered on the FR-4 PCB. Fig. 2. Temperature profile of thermal shock test.

3 154 y Á½{ Á Á½Ÿ Fig. 3. X-ray nondestructive analysis of solder joint for 3216 chip resistor and 44 pin QFP soldered with (a), (c) Sn-3.0 Ag- 0.5 Cu and (b), (d) Sn-40 Pb, respectively. 3.2 w yw x ³ e w x yw w Fig. 4~Fig. 7 ƒƒ e w» QFP w SEM ùkü. j ƒ w x IMC d ̃ ƒ w š, w x IMC w w. e w»ù QFP»q t Cu/OSP» q, Cu Cu 6 Sn 5 ƒ x, x j ƒ Cu 6 Sn 5 Cu Cu 3 Sn x w. x IMC Cu/Sn x» IMC w x. t Ni-P/Sn QFP e w» t w (Cu,Ni) 6 Sn 5 IMCƒ x EDX mw. Ni d Cu-Sn yw x w» w Cu»q y d(diffusion barrier) w t. Ni-Sn sx k x IMC Ni 3 Sn, Ni 3 Sn 2, Ni 3 Sn 4 1) (Cu,Ni) 6 Sn 5, (Ni,Cu) 3 Sn 4 1,3-6) 5 IMCƒ x š š š. š / y Ni»q ü w Ni-Sn yw Ni 3 Sn 4 ƒ w. yw yw (channel) x Ni yw d mw y w ùƒ w m w y w. 7) yw kv(ÿh f ) 298 K ƒƒ 235.3, 192.5, kj/ mol Ni 3 Sn 4 kvƒ ƒ û. 8) Ni 3 Sn, Ni 3 Sn 2 Ni 3 Sn 4 w» w yw Ni 3 Sn 4. x Sn-3.0 Ag-0.5 Cu w Ni t (Cu,Ni) 6 Sn 5 x, Sn-40 Pb w Ni 3 Sn 4 ƒ x. w Cu w w IMC ƒ š. w IMC Ni d w (Cu,Ni) 6 Sn 5 w. Yoon 4) IMC Ni 16.05~20.59 at%, Cu 33.84~40.05 at% š Sn 34.77~40.12 at% ƒ š. Ni 20.40~ at%, Cu 33.41~35.15 at% š Sn 39.99~ at%. y Cu wš w (Cu,Ni) 6 Sn 5 w Cu ü l y. (Cu,Ni) 6 Sn 5 Cu 6 Sn 5 IMC ü Ni ƒ eyx sw ƒw. Cu-Ni 2 w w š (complete solid solution) x w. ÿw Cu Ni j» 2% ƒ ù, w FCC(facecentered cubic) ƒ š» Cu 6 Sn 5 Ni ƒ eyx y š(distortion) ù x ey. 5) (Cu,Ni) 6 Sn 5 d (Ni,Cu) 3 Sn 4 IMC d x» w. 9) (Ni,Cu) 3 Sn 4 IMC x Cu y Ni-P d x w š š š, IMC Ni 34.77~ at%, Cuƒ 6.02~10.40 at% š Sn 53.62~54.83 at% ƒ. 4-5) w Ni-P/Sn IMC Ni 3 Sn 4 NiSnP, Ni 3 Pƒ 3) x Ni 3 Pƒ (Cu,Ni) 6 Sn 5 Ni-P w w. Ni 3 Sn 4 Ni 3 P Ni-Sn-P 3 š. Suganuma 10) w Ni 3 P d w Ni 3 P Ni 3 P Ni. Ni w sw Cu-Sn IMC w ƒ. ÿw x IMC ü Ag-Sn

4 Sn-3.0 Ag-0.5 Cu/OSP w w y t j y 155 Fig. 4. Cross section images of 3216 chip resistor soldered with Sn-40 Pb after thermal shock test, 1400 cycles: (a) overall shape of joint and (b) magnified view of crack tip. Fig. 5. Cross section images of 3216 chip resistor soldered with Sn-3.0 Ag-0.5 Cu after thermal shock test, 1800 cycles: (a) overall shape of joint, (b) magnified view of region A, (c) magnified view of region B, and (d) magnified view of region C. Fig. 6. Cross section images of 44 pin QFP soldered with Sn-40 Pb after thermal shock test, 2,000 cycles: (a) overall shape of solder joint, (b) magnified view of solder joint, (c) microstructure of QFP lead side and (d) microstructure of Cu pad side.

5 156 y Á½{ Á Á½Ÿ Fig. 7. Cross section images of 44 pin QFP soldered with Sn-3.0 Ag-0.5 Cu after thermal shock test, 2,000 cycles: (a) overall shape of solder joint, (b) magnified view of solder joint, (c) microstructure of QFP lead side and (d) microstructure of Cu pad side. Fig. 8. Crack propagation mechanism of solder joint for (a), (b) chip resistor and (c), and (d) QFP. IMC Ag 3 Sn x š š, Cu 6 Sn 5 IMC x š w ƒ. x IMC q (coefficient of thermal expansion, CTE)ƒ, œ w w CTE mismatch w v k ) x Sn- 40 Pb, Sn-3.0 Ag-0.5 Cu w IMC d ³, w ùkû, w ³ w w j w. Sn-40 Pb w w e w» x 1400, 1600, 1800 cycles IMC ³ w, Sn-3.0 Ag-0.5 Cu 1400, 2000 cycles ³. QFP t t Cu Ni/Sn,»q q Cu/OSP. w z»q q Cu 6 Sn 5 Cu 3 Sn x, QFP (Cu,Ni) 6 Sn 5 (Ni,Cu) 3 Sn 4 ƒ x. w Ni 3 Sn 4 ƒ x, ü Sn-3.0 Ag-0.5 Cu Cu 6 Sn 5 Ag 3 Sn x. x j

6 Sn-3.0 Ag-0.5 Cu/OSP w w y t j y 157 ƒ IMC Ì ƒw, t k IMC w x Fig. 6 Fig. 7. Sn-40 Pb, t q 20 µm w Sn-Pb œ š IMC d x ƒ š. w x ƒ š. w ³ Fig. 8 q t/ w IMC/ q š š, w xk Sn-3.0 Ag- 0.5 Cu w w ùkû. Fig. 4, Fig. 5 ³ e w» q t d IMC/ wš. Sn-3.0 Ag-0.5 Cu w xk ³ š, x Ag 3 Sn wš IMC Sn-40 Pb w ùkû. 3.3 x j 45 o x j w IMC t w e w w» w x ƒ e w» w x mw w, Fig. 9 w sƒ x z t š, x Fig. 11 ùkü. w x ƒƒ j 10 r w x s³ w. Sn-40 Pb w e w» N, asreflow r 1,000 j z 75.53N y s 3.49%. Sn-3.0 Ag-0.5 Cu e w»» 96.76N, 1,400 j z N ùkü» 22.43% y ùkþ.» 1,000 j ¾ ùkù 1,200 j l w yƒ ùkù» w. w t r» r ƒ j ùkù r s š. Sn- 3.0 Ag-0.5 Cu z ƒ ƒ Ag 3 Sn x š, w ƒ, š Ag 3 Sn y w x w ƒ. w p Fig. 5 w, x IMC j ƒ y x. Sn-40 Pb Sn-Pb œ l œ w š, Pb x ƒw Sn-rich Pb-rich w yƒ. 9) w y j, w ³ Sn Pb IMC ³ œwš Fig. 9. Photographs of 3216 chip resistor after shear strength test with thermal shock cycles. Fig. 10. Photographs of 44 pin QFPr after 45 o lead pull strength test with thermal shock cycles.

7 158 y Á½{ Á Á½Ÿ. ù Sn-40 Pb œ j ƒ y j ùkû, IMC x ³ w w w yw š w. Fig. 11 x j w y ùkü š, Fig. 12» w w y ùkü. w x j ƒ» ƒ y ùkü j wš š, 1,200 j z l w y w. x w w w t y 1,200 j¾ w y w. QFP t x j 45 o x z Fig. 10 ùkü. x Sn-40 Pb w 2,000 j¾ y j, ³ w š, 14.72~17.14 N ùkü. Sn-3.0 Ag-0.5 Cu 600 j ¾ yƒ w ù 800 j wƒ j ùkù z 2,000 j¾ ³ w. e w»» Sn-40 Pb ùkù z w s j ywš, z ùkü. w IMC» w yƒ, IMC Ag 3 Sn Cu 6 Sn 5 ƒ š, /Cu q Ni w (Cu,Ni) 6 Sn 5, Ni 3 Pƒ w Fig. 6, Fig. 7. w IMC w x z 800 j z w w, Fig. 12 w y s» 39% ùkü, Sn-40 Pb y 12.9% w j ùkû. w x w QFP SMD t w sƒwš w 800 j x ww w. w Sn-3.0 Ag-0.5 Cuƒ Sn-40 Pb w asreflow z w ùkù, w j ùkù. w w y Sn-Pb œ Sn-Pb œ ù Sn-rich, Pb-rich w y wƒ ù Fig. 11. Shear strength variation of (a) 3216 chip resistor and (b) 44 pin QFP under thermal shock cycles. Fig. 12. Deviation of maximum shear strength and 45 o lead pull strength for (a) chip resistor and (b) QFP after thermal shock, 2,000 cycles. kùš, Sn-3.0 Ag-0.5 Cu x IMC y Ag 3 Sn yƒ w w w e.

8 Sn-3.0 Ag-0.5 Cu/OSP w w y t j y Sn-40 Pb, Sn-3.0 Ag-0.5 Cu w 3216 e w» 44 pin QFP w sƒ w x 2,000 j ww z w yw x w w. 1. Sn e w» Sn-3.0 Ag-0.5 Cu w Cu 6 Sn 5 Cu 3 Sn x. Ni/Sn QFP t Cu Pad e w» w Cu 6 Sn 5, Cu 3 Sn x š, t (Cu,Ni) 6 Sn 5, Cu 6 Sn 5 x. w ü Cu 6 Sn 5 Ag 3 Sn x. 2. e w» QFP x» w Sn-3.0 Ag-0.5 Cu w ƒ Sn-40 Pb ùkû, Sn-3.0 Ag-0.5 Cu Ag 3 Sn y z» w q. ù x ƒw w w ùkþ, Ag 3 Sn w w wƒ, Sn-40 Pb yƒ j ùkû. 3. x w e t SMDx QFP t w sƒw, 40 o C/10 min ~+125 o C/10 min x w q. w x w Sn-3.0 Ag-0.5 Cu w w sƒ ww, e w» t 1,200 j, SMDx QFP t 800 j x ww w. š x 1. J. W. Kim, D. G. Kim, W. S. Hong and S. B. Jung, J. Elec. Mater., 34(12), 1550 (2005). 2. J. W. Yoon, and S. B. Jung, J. Alloys and Compounds, 396, 122 (2005). 3. D. G. Kim., J. W. Kim, J. G. Lee, H. Morib, D. J. Quesnel, and S. B. Jung, J. Alloys and Compounds, 395, 80 (2005). 4. J. W. Yoon, S. W. Kim, and S. B. Jung, J. Alloys and Compounds, 392, 247 (2005). 5. J. W. Yoon, S. W. Kim, and S. B. Jung, J. Alloys and Compounds, 391, 82 (2005). 6. J. W. Yoon, D. G. Kim, and S. B. Jung, Microelectron. Reliab., 46, 535 (2006). 7. C. Gur and M. Bamberger, Acta Mater., 46(14), 4917 (1998). 8. C. J. Chen and K. L. Lin, J. Elec. Mater., 29, 1007 (2000). 9. W. S. Hong, and K. B. Kim, Kor. J. Mater. Res., 15(8), 536 (2005). 10. K. Suganuma, Lead free soldering in electronics, p.57, Marcel Dekker Inc., New York (2004). 11. JEITA, Lead Free Soldering Tech., Corona Pub. Co. Ltd., Tokyo (2003). 12. K. N. Tu, C. C. Yeh, C. Y. Liu, and C. Chen, Appl. Phys. Lett., 76, 988 (2000). 13. R. Strauss, SMT Soldering Handbook, 2nd ed., p.148, Newnes, Oxford (1998).