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Trace analysis in tin pest and pest free SnCu0.5 solder material

Trace analysis in tin pest and pest free SnCu0.5 solder material. Monika Leodolter-Dvorak and Ilse Steffan Inst. of Analytical Chemistry and Food Chemistry University of Vienna. COST 531 Meeting May 2007. Tin Pest: General Aspects and Context with Lead Free Solders based on:

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Trace analysis in tin pest and pest free SnCu0.5 solder material

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  1. Trace analysis in tin pest and pest free SnCu0.5 solder material Monika Leodolter-Dvorak and Ilse Steffan Inst. of Analytical Chemistry and Food Chemistry University of Vienna COST 531 Meeting May 2007

  2. Tin Pest: General Aspects and Context with • Lead Free Solders • based on: • W. J. Plumbridge, “Tin pest issues in lead-free electronic solders”, • J Mater Sci: Mater Electron (2007) 18:307-318 • Trace Analyses of SnCu0.5 Solder Material • Method of ICP-OES • Sample Preparation • Method Validation • Results • Comparison of the elemental composition: • “pest sample” – “pest-free sample”

  3. -Sn “grey tin” -Sn “white tin” -Sn Sn(l) 13.2°C 161°C 232°C Tin: allotropic forms: -Sn: typical metallic properties: conductor, ductile crystal structure: body centered tetragonal d = 7.29 g/cm3 -Sn: semiconductor, non-ductile crystal structure: diamond cubic d = 5.77 g/cm3

  4. Tin Pest (tin disease, tin plague, devil´s disease): first reported: 1851; responsible for the disintegration of tin dishes, organ pipes, … is the product of the conversion: -Sn  -Sn at T<13.2°C volume change leads to the total disintegration of the sample W.J.Plumbridge

  5. Factors influencing the formation • of tin pest*: • temperature • thickness of the specimen • cold work • impurities or alloyed elements • effective lower limits? *W. J. Plumbridge, “Tin pest issues in lead-free electronic solders”, J Mater Sci: Mater Electron (2007) 18:307-318

  6. Lead Free Solders and Tin Pest: • before RoHS: solder Sn/Pb (63/37) never shows • tin pest formation • lead free solders: some (e.g. SnCu0.5) show formation of • tin pest: • Can elemental analysis down to the • lower ppm-range assist clear-up? • Is a forecast possible?

  7. Tin Pest nucleation: incubation: months – years inoculation with -Sn: days growth: linear rate: 0.06 mm/d (max) at T=-40°C 0.02 mm/d at T=-18°C W.J.Plumbridge

  8. Do metallic impurities (ppm-range) influence the formation of tin pest? • Where are the limits of the method? • 3 test samples (SnCu0.5): • region without pest: 2,3 g (whole piece) • adjacent to pest wart: 0,3 g • one pest wart: 0,09 g sample preparation: digested with HCl conc. at 80°C and filled up to volume matrix concentration: up to 1 g Sn/10 mL

  9. ICP-OES: (Inductively Coupled Plasma –Optical Emission Spectrometry) excitation (Argon-Plasma, 6000°C) liquid sample introduction h polychromator aerosol detector data processing (ICPWinLab) statistical evaluation A.Schiffkowitz

  10. Criteria for the element selection: • inhibiting formation of tin pest: • Bi, Pb, Sb • promoting formation of tin pest: • Al, Mg, Zn • potential contaminants from handling • ???

  11. Instrumental Parameters: Perkin Elmer Optima 3000XL, axial view nebulizer: conespray (GemCone) spray chamber: cyclone sample uptake rate: 1.4 mL/min torch: Fassel type, Al2O3 injector Argon flows: nebulizer: 0.8mL/min outer gas: 15 mL/min inner gas: 1 mL/min RF-power: 1300 W, free running spectrometer: Echelle based detector: SCD (Segmented array Charge-coupled Device)

  12. Method validation: • spike test: • solution of pure tin shot (purity 99.999%) • spiked with: • Al, As, Bi, Cd, Fe, Ga, Ge, In, Mn, Ni, Pb, Sb, • Ta, Te, Ti, Tl, Zn • Recoveries: 98 – 103% • method of internal standard (Lanthanum): • f=1.02 ± 0.03

  13. Effects: • sample matrix causes an increase of spectral • background intensities but no influence on the net intensities: • measurement against aqueous standard solutions • numerous spectral interferences were detected • after line selection: measurement of all analytes at interference free lines

  14. Line selection: all lines 2-sided background corrected

  15. Analysis of Samples (SnCu0.5) • without tin pest • (3 different areas) 2. complete disintegrated (4 samples at random) with the same “thermal history”: stored at –18°C for several years

  16. Sample Preparation: • samples rinsed with 1 M HCl, water and methanol • 0.8 – 2.5 g dissolved in 6 M HCl at 80°C • and filled up to volume • resulting solutions were diluted prior to measurement with ICP-OES

  17. Results: *confidence interval: =0.02, n3 red: statistically significant difference of mean values

  18. Statistically significant differences

  19. Conclusion: • ICP-OES is an appropriate method for the • trace analysis in tin based alloys. • No local differences concerning trace • impurities were found. • The results could be an indication for the • influence of trace impurities on the • formation of tin pest.

  20. Thank You For Your Attention!

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