Effect of Pressure on Crystallographic,Crystallite size and Micro Strain of Sn-0.3Cu (SC) Alloy

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1 International Journal of Engineering&Technology IJET-IJENS Vol:14 No:06 56 Effect of Pressure on Crystallographic,Crystallite size and Micro Strain of Sn-0.3Cu (SC) Alloy JuliusPurnama 1,B.Soegijono 1,andM. Hikam 1 1 GraduateProgramofMaterialScience,DepartmentofPhysics,FacultyMathematicsandNaturalSciences UniversityofIndonesia,Depok16424Tel:(021) Fax:(021) *Correspondingauthor purnamajulius@gmail.com : bambangsg11@yahoo.com Abstract Tin and its alloy as solders materials is prone to whiskers growth during its application. Lead free solder materials (Sn-Cu) has been pressed to see how crystallographic parameter, micro strain, crystallite size and texture changed. X- ray diffraction pattern of the samples were obtained by means of X ray diffractometer. Rietveld refinement of the diffraction pattern show that pressure influenced crystallographic parameter, crystallite size, micro strain and texture. It is expected that by knowing which crystallographic plane affected significantly, whiskers growth through this plane. Index Term Crystallography, Crystallite size, Micro strain, Pressure, Texture, Tin. I. INTRODUCTION Tin is often used as solders materials. As tin has relatively low solubility for alloying elements, the properties of the Snbased solder matrix will be similar to the physical properties of tin. However, the mechanical properties of a joint are greatly affected by the spatial arrangement of second phase precipitates that form due to the presence of alloying elements.the most common alloying elements are Ag and Cu.[1-4] Tin whiskers commonly form on substrates coated with tin and its alloy. These are problematic, as their growth can cause shorts between current carrying lines. This problem is a consequence of Sn being in a state of compression, which results from copper diffusion into Sn, which causes a volume increase from the formation of intermetallic compounds. Grain boundaries provide fast paths that allow Sn atom flux to locations where the surface oxide is broken, so that an emerging whisker can relieve the pressure imposed by a growing intermetallic. The problem can be reduced or eliminated by preventing Cu diffusion into Sn, and managing the internal stress state so that the surface of the Sn remains in tension rather than compression. Micro strain, crystallite size and axial distribution of the crystallographic plane are also affected by the presence of internal stress.[6-7] Texture, which is preferred distribution of grains (individual crystallites) having a particular crystallographic orientation with respect to a fixed reference frame, is an important structural parameter for bulk materials and coatings. It can noticeably affect a variety of functional properties. High pressure on tin could affect the properties of Tin.[8-10] This research describes the effect of pressure and Copper on crystallographic parameter, microstrain, crystallite size and Axial distribution plane of Sn-0.3Cu. II. MATERIALS AND METHODS A. Materials Pure Tin (Merck ) and Cooper (Merck) were melted by Arc Melting method with composition Sn-0.3Cu. Five samples obtained, each with dimension 2 x 2 x2 mm. Four samples have been pressed 0, 5, 10 and 15 ton respectively and One sample was annealed at 180 o C for 3 hours. B. Methods The structure of the samples was analyzed by X-ray diffraction (XRD).Philips PW1877 X-ray diffracttometer available at Materials Science Program, Department of Physics University of Indonesia. It was used to obtain room temperature diffractograms for the samples. The X-ray diffraction data were then refined using GSAS II, which was developed by Allen C.Larson and Robert B. Von Dreele from Los Alamos National Laboratory USA, to obtained Crystallographic parameters, Crystallite size and micro strain evolution and texture. II. R ESULTS AND DISCUSSION X-ray diffraction pattern for 5 samples are shown in figure 1. It shown that peaks for the plane [2 0 0] and [1 0 1] shifted due to pressure and the samples annealed have the highest peak (Fig.2).

2 International Journal of Engineering&Technology IJET-IJENS Vol:14 No: Fig. 1..X-ray diffraction patterns of Sn-0.3Cu (SC) This shifting lead to change the crystallographic parameters, such as unit cell parameter. Fig. 4. Refinement of X-ray diffraction pattern of Sn-0.3Cu ( 5 GPa) with :a= , c= ,Rp=10.14%, Rwp=13.45%, Fig. 5..Refinement of X-ray diffraction pattern of Sn-0.3Cu ( 10 GPa) with : a=b=5.8554,c=3.1927,rp=10.12%, Rwp=12.97% Fig. 2..X-ray diffraction patterns of Sn-0.3Cu show the shifting of the peaks The Rietveld refinement of X-ray diffraction patterns of the samples are shown in figure 3 7. It show that the change in crystallographic parameter are clear due to pressure. Fig. 6.Refinement of X-ray diffraction pattern of Sn-0.3Cu (15 GPa) with: a=b=5.8228,c=3.1771,rp=8.73%, Rwp=11.90% Fig. 3. Refinement of X-ray diffraction pattern of Sn-0.3Cu (0 GPa) with : a= , c= , Rp=9.07%, Rwp=12.44% Fig. 7. Refinement of X-ray diffraction pattern of Sn-0.3Cu Anneal with : a=b=5.8096, c=3.1700, Rp=9.77%, Rwp=13.64%

3 International Journal of Engineering&Technology IJET-IJENS Vol:14 No:06 58 MICROSTRAIN Microstrain developed due to pressure can be calculated from Scherer formula or from Rietveld Refinement using GSAS II free software. it can be shown how pressure affect microstrain, shown in Fig 8-12 Fig. 10.Microstrainof Sn-0.3Cu under 10 GPa pressure. Fig. 8.Microstrainof Sn-0.3Cu under 0 GPa pressure Fig. 11.Microstrainof Sn-0.3Cu under 15 GPa pressure Fig. 9.Microstrainof Sn-0.3Cu under 5 GPa pressure Fig. 12.Microstrainof Sn-0.3Cu Annealed

4 International Journal of Engineering&Technology IJET-IJENS Vol:14 No:06 59 Crystallite size Figure show how crystallite size are influenced by pressure. Fig. 16. Crystallite size of Sn-0.3Cu under 15 GPa pressure Fig. 13. Crystallite size of Sn-0.3Cu under 0 GPa pressure Fig. 17. Crystallite size of Sn-0.3Cu Annealed Fig. 14. Crystallite size of Sn-0.3Cu under 5 GPa pressure Beside crystallographic parameter, micro strain and crystallite size, Axial distribution of crystallographic plane are also influenced by pressure. The most influenced crystallographic plane by pressure could be the path where whisker growth. Axial distribution are shown in figure Fig. 15. Crystallite size of Sn-0.3Cu under 10 GPa pressure Fig. 18.Axial distribution of Sn-0.3Cu under 0 GPa (101) pressure

5 International Journal of Engineering&Technology IJET-IJENS Vol:14 No:06 60 Fig. 19.Axial distribution of Sn-0.3Cu under 5 GPa on (101) plane REFERENCES [1] S.K. Das,A.Sharif,Y.C.Chan,N.B.Wong,W.K.C.Yung,Influenceof small amount of Al and Cu on the microstructure,microhardness and tensile properties of Sn 9Zn binary eutectic solder alloy,j.alloys Comp.481 (2009) [2] L.C. Tsao,S.Y.Chang,Effects of Nano-TiO 2 additions on thermal analysis, microstructure and tensile properties of Sn3.5Ag0.25Cu solder,mater.des.31 (2010) S.K. [3] Yu Chi-Yang,Wei.-Yu Chen,Jeng.-Gong Duh,Suppressing the growth of Cu Sn intermetallic compounds in Ni/Sn Ag Cu/Cu Znsolder joints during thermal aging, Intermetallics 26 (2012)11 17 [4] Xiaowu Hu, Wenjing Chen, Bin Wu, Microstructure and tensile properties of Sn 1Cu lead-free solder alloy produced by directional solidification, Mater. Sci. Eng. A 556 (2012) [5] Xu Chen,GangChen,Cyclic stress strainrelationship of 63Sn37Pb solder under biaxial proportional and non-proportional loading,mater.des.28 (2007) [6] Tina Ventura, SofianeTerzi, Michel Rappaz, Aene.K. Dahle, Effects of solidification kinetics on microstructure formation in binary Sn Cu solder alloys, Acta Mater. 59 (2011) [7] TadahiroShibutani, Qiang Yu, Masaki Shiratori, Michael G. Pecht, Pressure-induced tin whisker formation, Microelectronics Reliability 48 (2008) [8] Barnett, J.D.;Bean, V.E.;Hall, H.T.X-ray diffraction studies on tin to 100 kilobars Journal of Applied Physics 37, (1966), [9] Liu, M.;Liu, M.-G.Compressions and phase transitions of tin to half a megabarhigh Temperatures-High Pressures 18, (1986), [10] El-Ashram, T.Structure and properties of rapidly solidified pure tin Radiation Effects & Defects in Solids 161, (2006), Fig. 20.Axial distribution of Sn-0.3Cu under 15 GPa on (101) plane Fig. 21.Axial distribution of Sn-0.3Cu under 15 GPa on (101) plane CONCLUSION By Rietveld refining X-ray diffraction pattern, influence of pressure on crystallographic parameter, microstrain, crystallite size and texture can be shown. The crystallographic plane where the most influenced by pressure could be the path where whiskers growth.