J Fail. Anal and Preven.(2013)13: 194-201 c:edax32genesis'genmaps spc 08.Jul-2011 15: 34: 36 002.003.004005.006.007.008.00900 (b) Energy.kev ment Sn C Wt%93.512.783.72 Fig 5 EDS result of the wetting pad. The chemical reaction formula of depositing Au on nickel layer is as follows: 2Au(CN)2+Ni- 2Au Ni-+4CN.(a)The wetting pad, (b) chemical composition, and(c)weight percentage of main elem 8887 surface Incompletely protected nickel atom Fig 6 Formation of bumpy surface during immersion gold. (a)The deposition of Au on Ni, (b) bumpy surface formed Oxygen atom Bumpy surface oxygen atom bumpy surface Fig. 7 Formation of nickel oxide layer(a)Oxygen contacts the unprotected Ni(b) The unprotected nickel were oxidized within our reach there is no device could directly detect or total grain boundary area as illustrated in Fig. 10. It is the observe such little amount of organic contamination fact that energy along the grain boundary is higher than As mentioned before(Fig 3), the grain size of the that in bulk [6]. Since the atoms alone the grain bound- failed pad under inspection of SEM was relatively coarse aries were not perfectly bonded, they must have a higher and big (3-4 um). The big grain size led to the smaller tendency to engage in a chemical reaction compared withwithin our reach there is no device could directly detect or observe such little amount of organic contamination. As mentioned before (Fig. 3), the grain size of the failed pad under inspection of SEM was relatively coarse and big (3–4 lm). The big grain size led to the smaller total grain boundary area as illustrated in Fig. 10. It is the fact that energy along the grain boundary is higher than that in bulk [6]. Since the atoms alone the grain bound￾aries were not perfectly bonded, they must have a higher tendency to engage in a chemical reaction compared with Fig. 5 EDS result of the wetting pad. The chemical reaction formula of depositing Au on nickel layer is as follows: 2Au(CN)2 ? Ni ? 2Au ? Ni2??4CN. (a) The wetting pad, (b) chemical composition, and (c) weight percentage of main elements Fig. 6 Formation of bumpy surface during immersion gold. (a) The deposition of Au on Ni, (b) bumpy surface formed Fig. 7 Formation of nickel oxide layer. (a) Oxygen contacts the unprotected Ni. (b) The unprotected nickel were oxidized 198 J Fail. Anal. and Preven. (2013) 13:194–201 123