VALIDATION AND TRACEABILITY OF XRF AND SEM-EDS ELEMENTAL ANALYSIS RESULTS FOR SOLDER IN HIGH-RELIABILITY APPLICATIONS
John R. Sieber, Adam Mortensen
A procedure and calibration samples have been developed for X-ray fluorescence spectrometry (XRF) and scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) methods of analysis of Sn and Pb mass fractions in solder and coatings in electronics. Test methods are needed by laboratories that perform Destructive Physical Analysis of high-reliability electronics. Calibrants are prepared by evaporative deposition of multiple, alternating quantities of pure Sn and pure Pb having mass per unit area values proportional to the required mass fractions of Sn and Pb in the solder being mimicked. Validation reference materials are prepared by evaporative deposition of thin films of SRM 1729 Tin Alloy (97Sn-3Pb). The films are created on high-purity Ni foil to mimic some actual electronics structures and to prevent charging during SEM EDS measurements. Maximum thickness of films prepared this way must be kept below approximately 1 m to ensure that the entire thickness is probed by the primary X-ray or electron beam and that measured, emitted X-rays come from the entire thickness of all films in these procedures. Procedures are presented in detail and method performance is characterized in this paper. The primary purpose is to create calibrations for Sn and Pb that are simple to implement and provide traceability to the SI unit of mass. The secondary purpose is to validate the calibrations using a certified reference material to prove that, for simpler structures of thin solder coatings on metal, both XRF and SEM-EDS can provide accurate results. Keeping the films thin may be unrealistic in comparison to some, if not many, electronic structures, but this approach enables a laboratory to demonstrate competence in a controlled manner.
and Mortensen, A.
VALIDATION AND TRACEABILITY OF XRF AND SEM-EDS ELEMENTAL ANALYSIS RESULTS FOR SOLDER IN HIGH-RELIABILITY APPLICATIONS, X-Ray Spectrometry, [online], https://doi.org/10.1002/xrs.2548
(Accessed December 9, 2023)