1. in tin pest and pest free Monika Leodolter-Dvorak and Ilse Steffan
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:
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. Tin: allotropic forms: -Sn 13.2°C -Sn 161°C -Sn 232°C Sn(l)
“grey tin”
13.2°C
-Sn
“white tin”
161°C
-Sn
232°C
Sn(l)
-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:

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: growth: incubation: months – years
inoculation with -Sn: days
growth:
linear rate: 0.06 mm/d (max) at T=-40°C 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: excitation liquid sample polychromator introduction detector
(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: W, free running
spectrometer: Echelle based
detector: SCD (Segmented array Charge-coupled Device)

12. Method validation: spike test:
solution of pure tin shot (purity %)
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!