The technology of EPMA (Electron Probe Micro-Analyzer) has been believed the completed technology in general. However, several technical problems, such as the inconvenience when one wishes to switch the mode of system from SEM mode to X-ray analysis mode for example, still exist. This problem has limited the practical spatial resolution. For these problems, we developed a new-model FE-EPMA, which is equipped with a field emission electron gun with a wavelength-dispersive X-ray spectrometer (WDS) [1]. This new FE-WDS-EPMA enables a much smaller probe diameter and shorter measurement times than a conventional W-WDS-EPMA[2]. And, usability and convenience of operation was dramatically improved. In this report, one of the typical applications will be presented.
The element distribution in several material structures can be analyzed using X-ray mapping data with this FE-WDS-EPMA, but it is difficult to execute accurate analysis of the grain boundary and joining boundary, because these interfaces has such a narrow width and a very small amount of segregation. And, we also used scatter diagram method to evaluate materials structure from the X-ray mapping data. The analysis with the combination of FE-WDS-EPMA and scatter diagram method gives us important information of materials such as distribution of elements in complex compounds.
We have applied this method for the study of the bonding interface between Ni-P electroless plate and lead-free Sn-Ag-Cu solder. From the result of the analysis, we found the coarse (CuNi)6Sn5 and Ni depletion layer at the bonding interface. The existence P-rich region, as Ni depletion layer, at the edge of solder side in the Ni-P electroless plate is confirmed. And, the P-rich region is separated two layers, at the solder side of it was diffused small amount of Sn from solder.
These results are regarded to show us that the combination of FE-WDS-EPMA and scatter diagram method is widely applicable and has been useful in many respects.
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