J Fail. Anal. and Preven. (2013)13: 194-201 nickel 8 n88 ig.8 Grand Canyon mechanism. (a) Crystalline interface cracking, (b) the diffusion of nickel atom, (e) nickel atom covered the outmost urface, and (d) nickel oxide formed covering the surface size. till now there is no direct mathematic function describing the relation between the surface energy and organic contamination grain size within our knowledge, and it is sible to observe the well-wetted golden laye consumed once wetted. This is a field whic research work to be done. Here we proposed that under permitted condition, the finer the grain the better the wetting performance Last but not least, the solder used which is pure tin also contributed to the final un-wetting failure Since pure tin is a relatively obsolete solder and has lower surface energy and higher melting point compared to prevailing solder like Sn-Ag-Cu [7], it cannot be ruled out that it was the improper choice of pure tin solder that resulted ultimate un-wetting. A discussion of the promising solder boundary area simultaneously decreased the whole e grain in manufacture of PCB would be beyond the scope of this of the golden layer. Therefore, the surface golden layer introduction of this topic in their excellent paper hensive was left in a condition of relatively low free energy. w the sample was sent for soldering, the energy provide by hot air solder leveling was not high enough to fuse the golden layer, since the latter was in an unexpected low Conclusion energy condition. This inability of smelting the golden SEM inspection and EDS analysis were both conducted layer caused by energy inadequacy manifested itself as on the normal(well-wetted) and failed (un-wetted) pac un-wetting failure mode. As for the definition of fine grai of the same sample. The topography of the two kind of Springthose inside the grain. Thus, the reduction of total grain boundary area simultaneously decreased the whole energy of the golden layer. Therefore, the surface golden layer was left in a condition of relatively low free energy. When the sample was sent for soldering, the energy provide by hot air solder leveling was not high enough to fuse the golden layer, since the latter was in an unexpected low energy condition. This inability of smelting the golden layer caused by energy inadequacy manifested itself as un-wetting failure mode. As for the definition of fine grain size, till now there is no direct mathematic function describing the relation between the surface energy and grain size within our knowledge, and it is merely impos￾sible to observe the well-wetted golden layer since it was consumed once wetted. This is a field which needs more research work to be done. Here we proposed that under permitted condition, the finer the grain the better the wetting performance. Last but not least, the solder used which is pure tin also contributed to the final un-wetting failure. Since pure tin is a relatively obsolete solder and has lower surface energy and higher melting point compared to prevailing solder like Sn–Ag–Cu [7], it cannot be ruled out that it was the improper choice of pure tin solder that resulted in the ultimate un-wetting. A discussion of the promising solder in manufacture of PCB would be beyond the scope of this paper. Abtew and Selvaduray [8] gave a comprehensive introduction of this topic in their excellent paper. Conclusion • SEM inspection and EDS analysis were both conducted on the normal (well-wetted) and failed (un-wetted) pad of the same sample. The topography of the two kind of Fig. 8 Grand Canyon mechanism. (a) Crystalline interface cracking, (b) the diffusion of nickel atom, (c) nickel atom covered the outmost surface, and (d) nickel oxide formed covering the surface Fig. 9 Organic contamination J Fail. Anal. and Preven. (2013) 13:194–201 199 123