When the solder layer and ag 3 sn layer were selectively etched away by acetic acid solution, the cu 6 sn 5 grains (gray contrast) and some residual ag 3 sn granules (bright contrast) are clearly. To observe the top surface morphology of the cu 6 sn 5, the specimens after isothermal heat treatment were immersed in a 16.6 vol% hno 3 aqueous solution for 600 s to etch the solder matrix. subsequently, ultrasonic cleaning was conducted in ethanol for 300 s, followed by observation of the top surface of the cu 6 sn 5 using a fesem.
Abstract: this article focuses on the morphologies of primary cu 6 sn 5 and ag 3 sn intermetallics in small sn ag cu (Ø 270 μm) solder balls. the cu 6 sn 5 phase showed a large variety of different shapes and sizes, ranging from facetted hexagonal rods, to partly facetted splitting crystals and parallel growing branches, to dendritic crystals without facets. Simultaneously, the channels also promote the vertical growth of cu 6 sn 5 grains to get a smaller aspect ratio at sn 3.5ag 0.7cu(sac3507) cu interface than sn cu. (2) the growth thickness of imc during the cooling stage follows the rule of h=kt, which is the reaction control mechanism of the cu precipitation interface. Decomposition of cu 5 zn 8 produces a new intermetallic product cu 6 sn 5, which is 6 μm thick. both the separation of ag 3 sn and cu 5 zn 8 can be clearly observed, and the newly combined copper tin compound can be seen. the boundary of the imc at the interface of the solder joint is not obvious, which is due to the diffusion of cu element to. As shown in the epma results, the structure of the interfacial reaction and the phase composition of the compound can be clearly seen from top to bottom as sn, cu 6 sn 5, cu 3 sn, and cu. with the increase of reflow time, it is obvious that the grain size of interfacial cu 6 sn 5 becomes larger and the thickness of cu 3 sn layer becomes thicker.
Decomposition of cu 5 zn 8 produces a new intermetallic product cu 6 sn 5, which is 6 μm thick. both the separation of ag 3 sn and cu 5 zn 8 can be clearly observed, and the newly combined copper tin compound can be seen. the boundary of the imc at the interface of the solder joint is not obvious, which is due to the diffusion of cu element to. As shown in the epma results, the structure of the interfacial reaction and the phase composition of the compound can be clearly seen from top to bottom as sn, cu 6 sn 5, cu 3 sn, and cu. with the increase of reflow time, it is obvious that the grain size of interfacial cu 6 sn 5 becomes larger and the thickness of cu 3 sn layer becomes thicker. In a word, the ag 3 sn absorbates with pinning effect and the initially formed cu 6 sn 5 grains with the solid solution of ag atoms work together to create the orientation transformation of the cold end cu 6 sn 5 grains from the cu sn cu to the cu sn 5.0ag cu micro solder joint. The morphology of ag 3 sn was changed which was evidenced by the sem image before and after the heat treatment. significant research has focused on the formation of eutectic ag 3 sn, revealing three unique morphologies: plate like, needle like, and spherical ag 3 sn. a specific investigation has utilized controlled unidirectional solidification.
In a word, the ag 3 sn absorbates with pinning effect and the initially formed cu 6 sn 5 grains with the solid solution of ag atoms work together to create the orientation transformation of the cold end cu 6 sn 5 grains from the cu sn cu to the cu sn 5.0ag cu micro solder joint. The morphology of ag 3 sn was changed which was evidenced by the sem image before and after the heat treatment. significant research has focused on the formation of eutectic ag 3 sn, revealing three unique morphologies: plate like, needle like, and spherical ag 3 sn. a specific investigation has utilized controlled unidirectional solidification.
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