本研究以Fe-42 wt%Ni (Alloy 42)基材與錫層間藉由不同金屬層，探究不同多層結構對錫鬚晶生長之影響，期望能找出抑制或延緩錫鬚晶生長的最佳加工條件。將Alloy 42基材分別以電鍍銅(CuE, 1.8 μm)、無電鍍銅(CuC, 0.3 μm)、電鍍鎳(1.8 μm)與無金屬層披覆等四組實驗，而後再電鍍霧錫於其表面上；將試樣放置於-35℃ 到85℃之冷熱循環機及60 ℃烘箱中進行長時效熱處理。
實驗結果顯示，不論Alloy 42是否有鍍金屬層，其錫層厚度將會隨著電流密度的增加而呈線性關係；而鍍層結構亦為隨著不同電流密度與不同金屬墊層而有所差異。當電流密度為5.0ASD時，冷熱循環次數增加會使熱應力逐漸累積，造成試片上錫鬚晶的密度與長度隨之增加。比較各試片錫鬚晶分布密度與平均長度: Sn/Alloy42＞Sn/CuE/Alloy42 ＞ Sn/CuC/Alloy42；銅層的存在可以緩和因熱膨脹係數差異甚大所造成的熱應力。但是，Sn/Ni/Alloy 42未發現錫鬚晶的生成。其原因為錫離子擴散至鎳層，使得錫層存有張應力。此張應力能夠減緩熱應力效應。在不同電流密度條件下，電流密度與錫鬚晶平均長度成正比關係；與錫鬚晶分布密度成反比關係。在60 ℃時效熱處理500小時結果顯示，各個試樣皆未觀察到任何錫鬚晶的生成。

In this study, the multi-layer structure effect on the Sn whisker growth in the matte Sn/Fe-42 wt% Ni (Alloy 42) systems was investigated. It was expected that the optimal processing parameters to prevent the whisker growth could be found. The Alloy 42 substrates were electroplated with 1.8 m-thick of the Cu layer (CuE), electrolessplated with 0.3 m-thick Cu layer (CuC), and electroplated with 1.8 m-thick Ni layer, respectively. Thus, 4 kinds of multilayer specimens, CuE/Sn/Alloy 42, CuC/Sn/Alloy 42, Ni/Sn/Alloy 42, and Sn/Alloy 42 were prepared. Finally, thermal treatment at 60°C for 500 hours and thermal cycle tests were applied to each specimen. The thermal cycle is one hour from -35 to 85 oC.
The results indicate that the Sn layer with the thicker thickness was observed under passing the higher current density. The surface morphology was different at different metallic layers and various current densities. When current density was 5.0ASD, increasing numbers of the thermal cycle produces more thermal stress to induce the Sn whisker formation. The order of the Sn whisker length and density in each specimen is : Sn/Alloy 42 > Sn/CuE/Alloy 42 > Sn/CuC/Alloy 42. The copper layer could eliminate the thermal stress which was generated due to coefficient of thermal expansion (CTE) mismatch between Sn layer and Alloy 42 during thermal cycling. However, no Sn whiskers were formed in the Ni/Sn/Alloy 42 system. Because tin atoms diffusion to nickel layer. The tension stress built up in the tin layer. This tension stress could mitigate thermal stress. At different current density, current density and Sn whisker length were proportional. But current density and the Sn whisker density were inversely proportional. No Sn whiskers were found in each specimen after 60 oC for 500 hours.

[1] 陳信文，陳立軒，林永森，陳志銘，“電子構裝技術與材料”高立圖書 (2004)。
[2] M. L. Minges, Electronic Materials Handbook, ASM International, Materials Park, OH, vol. 1 (1989) .

[3] P. Zarrow, Circuit Assembly, vol. 10, pp. 18-20 (1999) .

[4] M. Dittes, P. Oberndorff, and L. Petit, “Tin Whisker Formation
-Results, Test Methods and Countermeasures”, Proceedings
- Electronic Components and Technology Conference, pp. 822-826
(2003) .

[5] C. Xu, Y. Zhang, C. Fan, and J. A. Abys, “Driving Force for the
Formation of Sn Whiskers: Compressive Stress-Pathways for Its
Generation and Remedies for Its Elimination and Minimization”,
IEEE Transactions on Electronics Packing Manufacturing, vol. 28,
pp. 31-35 (2003) .

[6] S. H. Liu, C. Chen, P. C. Liu, and T. Chou, “Tin Whisker Growth
Driven by Electrical Currents”, Journal of applies Physics, vol. 95,
pp. 7742-7747 (2004) .

[7] K. N. Tu and J. C. Li, “Spontaneous whisker growth on lead-free solder finishes”, Materials Science and Engineering A, vol. 409, pp. 131-139 (2005) .

[8] W. J. Choi, T. Y. Lee, K. N. Tu, N. Tamura, R. S. Celestre, A. A. MacDowell, T. T. Sheng, Y. Y. Bong, and L. Nguyen, “Structure and kinetics of Sn whisker growth on Pb-free solder finish”, 52nd Electronic Components & Technology Conference, May 28-31, San Diego, pp. 628-633, CA (2002) .

[9] I. Boguslavsky and P. Bush, “NEMI Tin Whisker test method standards”, Proceedings of the SMTA International Conference, pp. 21-25 (2003) .

[10] D. W. Romm, D. C. Abbott, S. Grenney, and M. Kan, “Whisker Evaluation of Tin-Plated Logic Component Leads”, Texas Instruments Application Report (2003) .

[11] http://www.kson.com.tw/chinese/study_11_1.htm

[12] G. W. Stupian, “Tin whiskers in Electronic Circuits”, Aerospace Technical Report, pp.1-21 (1992) .

[13] M. Dittes, P. Oberndorff and L. Petit, “Tin Whisker Formation –
Results, Test Methods and Countermeasures”, 53rd Proceedings
- Electronic Components and Technology Conference, pp. 822-826 (2003) .

[14] B. D. Dunn, “A Laboratory Study of Tin Whisker Growth”, European Space Agency Journal, pp. 1-50 (1987) .

[15] Y. Hada, O. Morikawa, H. Togami, ”Study of Tin Whiskers on Electromagnetic Relay Parts”,26th Annual National Relay Conference, pp. 9.1-9.15 (1978) .

[16] B. D. Dunn, “Mechanical and Electrical Characteristics of Tin Whiskers with Special Reference to Spacecraft Systems”, European Space Agency Journal, pp. 1-17 (1988) .

[17] K. N. Tu, “Irreversible Processes of Spontaneous Whisker Growth in Bimetallic Cu-Sn Thin-film Reaction”, Physical Review B, vol. 49, pp. 2030-2034 (1994) .

[18] W. J. Choi, T. Y. Lee, and K. N. Tu, “Structure and Kinetics of Sn
Whisker Growth on Pb-free Solder Finish” , Proc. IEEE Elect.
Comp. Technol. Conf., pp. 628-633 (2002) .

[19] HP EL-MF-864-00: Testing and plating process control requirement 120 foe Tin based plating on lead-free component, (2005) .

[20] Y. Zhang, C. Fan, C. Xu, O. Khaselev, and J. A. Abys: “Tin Whisker Growth-Substrate Effect Understanding CTE mismatch and IMC formation”, Circuit Tree Magazine , pp. 70-82 (2004) .

[21] B. Z. Lee and D. N. Lee, “Spontaneous Growth Mechanism of Tin Whiskers”, Acta Materialia, vol. 46, pp. 3701-3714 (1998) .

[22] Y. Zhang, C. Fan, C. Xu, O., J. A. Abys, and A. Vysotskaya, “Understanding Whisker Phenomenon, Whisker Index and Tin/Copper, Tin/Nickel Interface”, Proc. IPC SMEMA Council Apex (2002) .

[23] Jay A. Brusse, Gary J. Ewall, and Jocelyn P. Siplon, “Tin Whiskers: Attributes and Mitigation”, Capacitor and Resistor Technology Symposium (CARTS), New Orleans, Louisiana, March, pp.221-233 (2002) .

[24] C. W. Hwang , K. Suganuma, J. G. Lee, and H. Mori, “Interface microstructure between Fe-42Ni alloy and pure Sn”, Journal of Materials Research, vol. 18, pp. 1202-1210 (2003) .

[25] K. N. Tu and R. D. Thompson, “Kinetics of Interfacial Reaction in Bimetallic Copper-tin Thin Films”, Acta Materialia, vol. 30, pp. 947-952 (1982) .

[26] K. N. Tu, “Cu/Sn Interfacial Reactions: Thin-film Case versus Bulk Case”, Materials Chemistry & Physics, vol. 46, pp. 217-223 (1996) .

[27] F. Bartels, J. w. Morris, Jr, G. Dalke, and W. Gust, “ Intermetallic Phase Formation in Tin Solid-liquid Diffusion Couples”, Journal of Electronic Materials, vol. 23, pp. 787-790 (1994) .

[28] W. J. Tomlinson and H. G. Rhodes, “Kinnetics of Intermetallic Compound Growth Between Nickel, Electroless Ni-B and Tin at 453 to 493 K”, Journal of Materials Science, vol. 22, pp. 1769-1772 (1987) .

[29] J. Haimovich, “Intermetallic Compound Growth in Tin and Tin-lead Platings over Nickl and its Effects on Solderability”, Welding Research Supplement, vol. 68, pp. 102-111 (1898) .

[30] S. Bader, W. Gust, H Hieber, “ Rapid Formation of Intermetallic Compounds by Interdiffusion in Cu-Cn and Ni-Sn System”, Acta Materialia, vol. 43, pp. 329-337 (1995) .

[31] S. W. Chen, C. M. Chen, and W. C. Liu, “ The Electric Current Effects upon The Sn/Cu and Sn/Ni Interfacial Reactions”, Journal of Electronic Materials , vol. 27, pp. 1196-1198 (1998) .

[32] J. A. Van Beek, S. A. Stolk, and F. J. Jvan Loo, Zeitschrift Fur Meatlkunde, vol. 73, pp. 439-4449 (19852) .

[33] C. M. Liu, and M. S. Thesis, National Central University, Taiwan (2000) .

[34] C. Xu, Y. Zhang, C. Fan, and J. A. Abys, “Understanding Whisker
Phenomenon: Driving Force for Whisker Formation”, Circuit Tree Magazine, pp. 94-105 (2002) .

[35] J. H. Lau, S. H. Pan, and C. Xu, “3D Large Deformation and Nonlinear Stress Analyses of Tin Whisker Initiation and Growth on Lead-Free Components,” 53rd Proceedings- Electronic Components
and Technology Conference, pp. 692-697 (2003) .

[36] S. C. Britton, “Spontaneous Growth of Whiskers on Tin Coatings:
20 Years of Observation”, Trans. of the Institute of Metal
Finishing, vol. 52, pp. 95-102 (1974) .