Trace analysisTrace analysisin tin pest and pest freein tin pest and pest freeSnCu0.5 solder materialSnCu0.5 solder material
Monika Leodolter-Dvorak and Ilse Steffan
Inst. of Analytical Chemistry and Food ChemistryUniversity of Vienna
COST 531 MeetingMay 2007
1.1. Tin Pest: General Aspects and Context withTin Pest: General Aspects and Context withLead Free SoldersLead Free Solders
based on: W. J. Plumbridge, “Tin pest issues in lead-free electronic solders”, J Mater Sci: Mater Electron (2007) 18:307-318
2.2. Trace Analyses of SnCu0.5 Solder MaterialTrace Analyses of SnCu0.5 Solder Material
• Method of ICP-OES• Sample Preparation• Method Validation• ResultsResults
Comparison of the elemental composition:Comparison of the elemental composition:““pest sample” – “pest-free sample”pest sample” – “pest-free sample”
Tin:Tin:
allotropic forms:
-Sn“grey tin”13.2°C
-Sn“white tin”161°C -Sn 232°C Sn(l)
-Sn: typical metallic properties: conductor, ductilecrystal structure: body centered tetragonald = 7.29 g/cm3
-Sn: semiconductor, non-ductilecrystal structure: diamond cubicd = 5.77 g/cm3
Tin PestTin 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
Factors influencing the formation Factors influencing the formation of tin pestof tin pest**::
•temperature
•thickness of the specimen
•cold work
•impurities or alloyed elementseffective lower limits?
*W. J. Plumbridge, “Tin pest issues in lead-free electronic solders”, J Mater Sci: Mater Electron (2007) 18:307-318
Lead Free Solders and Tin Pest:Lead Free Solders and Tin Pest:
• before RoHS: solder Sn/Pb (63/37) never showstin pest formation
• lead free solders: some (e.g. SnCu0.5) show formation oftin pest:
• Can elemental analysis down to the lower ppm-range assist clear-up?
• Is a forecast possible?
nucleation:incubation: months – years
inoculation with -Sn: daysgrowth:
linear rate: 0.06 mm/d (max) at T=-40°C 0.02 mm/d at T=-18°C
Tin PestTin Pest
W.J.Plumbridge
Do metallic impurities (ppm-Do metallic impurities (ppm-range) influence the formation of range) influence the formation of tin pest?tin pest?
Where are the limits of the method?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 andfilled up to volumematrix concentration: up to 1 g Sn/10 mL
ICP-OES:ICP-OES:(Inductively Coupled Plasma –Optical Emission Spectrometry)
liquid sampleintroduction
excitation(Argon-Plasma,
6000°C)aerosol h polychromat
or
detector
data processing(ICPWinLab)
A.Schiffkowitz
statistical evaluation
Criteria for the element selection: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
• ???
Instrumental Parameters:Instrumental Parameters:
Perkin Elmer Optima 3000XL, axial view
nebulizer: conespray (GemCone)spray chamber: cyclonesample uptake rate: 1.4 mL/min
torch: Fassel type, Al2O3 injectorArgon flows: nebulizer: 0.8mL/min
outer gas: 15 mL/mininner gas: 1 mL/min
RF-power: 1300 W, free running
spectrometer: Echelle baseddetector: SCD (Segmented array Charge-coupled Device)
Method validationMethod 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, ZnRecoveries: 98 – 103%
•method of internal standard (Lanthanum):f=1.02 ± 0.03
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
Effects:Effects:
Line selection:
all lines 2-sided background corrected
analyte line [nm] analyte line [nm]Ag 328.068; 338.289 Ge 303.906Al 396.152 In 325.609As 193.696; 197.197 Mn 257.610; 294.920Au 242.795 Mo 202.030Bi 223.061 Ni 221.647; 231.604Cd 214.438; 226.502 Pb 216.418; 220.353Co 230.786; 238.892 Sb 217.581; 231.147Cr 267.716 Ta 226.230; 240.063Cu 221.458; 224.700 Te 214.281; 238.578
324.754; 327.396 Tl 276.787Fe 238.204; 259.940 W 207.911Ga 294.364; 417.206 Zn 206.191
Analysis of Samples (SnCu0.5)Analysis of Samples (SnCu0.5)
1. 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
Sample Preparation:Sample Preparation:
•samples rinsed with 1 M HCl, water and methanol
•0.8 – 2.5 g dissolved in 6 M HCl at 80°Cand filled up to volume
•resulting solutions were diluted prior to measurement with ICP-OES
*confidence interval: =0.02, n3red: statistically significant difference of mean values
conc [µg/g] c i *[µg/g] conc [µg/g] c i *[µg/g]Pb 431 18 283 12Bi 155,8 6,4 27,8 3,2In 96,5 8,8 14,2 0,8Fe 35,7 2,6 29,7 2,2Ge 23,7 2,5 <10Ni 23,0 1,7 5,8 1,6Tl 10,0 0,9 7,5 1,4Ag 9,1 1,1 1,3 0,1Co 7,3 0,5 1,3 0,3Cu [mg/g] 4,8 0,4 4,6 0,2Al 2,8 1,9 2,0 0,5Cd 2,1 0,2 0,9 0,1Cr 0,4 0,2 0,2 0,0Sb 0,34 0,02 0,14 0,01Mn 0,31 0,03 0,26 0,01
pest-free samples pest samples Results:Results:
Sb Cd Co Ag
pest free
pest0
2
4
6
8
10
µg/g
ultra trace elements 0.00001 - 0.001 m%
Pb Bi In Ge Ni
pest freepest0
100
200
300
400
500
µg
/g
trace elements 0.001 - 0.04 m%
Statistically significant differencesStatistically significant differences
Conclusion:Conclusion:
1. ICP-OES is an appropriate method for thetrace analysis in tin based alloys.
2. No local differences concerning traceimpurities were found.
3. The results could be an indication for theinfluence of trace impurities on the formation of tin pest.
Thank You Thank You For Your Attention!For Your Attention!