Transcript Studies

Thermal Analysis
of Sn, Cu and Ag
Nanopowders
Pavel Brož, Jiří Sopoušek, Jan Vřešťál
Masaryk University, Faculty of Science, Department of Chemistry,
Kotlářská 2, 611 37, Brno, Czech Republic
[email protected], [email protected], [email protected]
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Masaryk
University
Campus
(Brno-Bohunice)
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Outline

Introduction
- nanoparticles
- Netzsch STA 409 CD/3/403/5/G Apparatus
(thermal analysis (TA), Knudsen cell MS)
differential scanning calorimetry (heat flow DSC)

Studies
- Lead free solders
(DSC testing, CALPHAD calculations)
- Nanopowders of pure metals: Sn, Cu, Ag
(DSC, surface effects, CALPHAD calculations)

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Conclusions
Introduction
T  Tmbulk
Melting point depression
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

bulk
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 s  
2Tm

Equation
 Tm ( r )  bulk
 s   L  


Hm sr
L 



and
Sn - 0,5wt%Cu - 4wt%Ag Nano alloy particles
Diagram
showing melting
point depression
in dependence on
particle diameter
 Promising materials for lead free solders
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J. Liu (SMIT,Göteborg)
Development of Nano
Lead Free Solders –
Challenges and Future
Research Topics,
MP0602, Joint Working
Group meeting,
Brno,2007
Introduction
Laboratory of Thermal Analysis
(Dept. of Chemistry, Faculty of Science, Masaryk Univ. Brno)
Research project:
Physical and chemical properties of advanced materials and structures
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Introduction
DSC/KC/QMS Apparatus
(Netzsch STA 409 CD/3/403/5/G )
1…Furnace
(0.1 – 20 K min-1,
25-1450ºC)
2…QMS
range 1-512 amu
resolution 0,5amu
IE = 25 -100 eV
3…Turbomolecular
Pump
4…TA System
Controller (TASC)
5..Vacuum Controller,
(cca 9·10-6 mbar)
6…QMS Controller
7..Purification
Column (oxygen)
(Argon 99,999)
Mass Flow
Controller (MFC)
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Studies
Lead free solders (Ag-Cu-Sn system)

COST MP0602 Advanced Solder Materials for HighTemperature Application- their nature, design, process and
control in a multiscale domain

Example for Sn-0,7wt%Cu-3,5wt%Ag alloy (bulk)
4… liquid + BCT_A5 + ETA
liquid
liquid + Ortho
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BCT_A5 + Ortho + ETA
BCT_A5 + Ortho + Cu6Sn5_P
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Phase diagram of the
Sn - 0,7wt% Cu - Ag
system
Studies


Lead free solders (Ag-Cu-Sn system)
Detection of two phase transitions, the appearance of the first
one visible at the beginning of the peak for Sn based material
Pure Sn chosen as convenient standard
Onset
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DSC curves for ― solder Ag-Cu-Sn and ― pure Sn
Sn nanopowder
Studies
Complications
due to existence
of oxide layer
can be expected
(massive oxidation)
– melting point
temperature of Sn
232ºC
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Phase diagram of
the Sn - O system
Sn nanopowder
Studies
Sn packed
 no particle coagulation,
in oxide layer
melting point depression
heating
Flat curve  oxidized
sample
Wide low peak indicates
solidification of oxidized particles
of various distribution
Temperature decrease due to
nucleation process
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DSC curves for ― ― Sn nanopowder and ― pure Sn
cooling
Sn nanopowder
Studies
100 nm
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SEM of Sn nanoparticles before heating
Sn nanopowder
Studies
N particles
V particles / .10-3 nm3
120
100000
80000
N particles
V of particles / .10-3 nm3
80
60000
40000
40
20000
0
0
0
40
80
120
Diameter of particles / nm
160
Diameter of particles / nm
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200
0
40
80
120
Diameter of particles / nm
160
Diameter of particles / nm
Distribution of particle size before heating
200
Studies
Sn nanopowder
100 nm
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SEM of Sn nanoparticles after heating
Sn nanopowder
Studies
V particles / .10-3 nm3
NN particles
particles
V of particles / .10-3 nm3
60000
400
300
40000
200
20000
100
0
0
0
20
40
60
80
Diameter of particles / nm
100
Diameter of particles / nm
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120
0
20
40
60
80
100
Diameter of particles / nm
Diameter of particles / nm
Distribution of particle size after heating
120
Cu nanopowder
Studies
Complications
due to existence
of oxide layer
can be expected
but with more
optimal
stoichiometry
than that for Sn
(less massive)
1083ºC
– melting point
temperature of Cu
Phase diagram of
the Cu - O system
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Studies
Cu nanopowder
Flat curve  oxidized
sample
Cu packed
 no particle coagulation,
in oxide layer
melting point depression
heating
Partial coagulation thanks
to instability of oxide layer
Number of small
peaks indicates
existence of
coagulated microsized
particles. Higher
udercooling indicates
absence of nucleation
centre.
cooling
Particles coagulate  macroscopic
object forms having behaviour like
bulk material

effect of undercooling
bulk melting point - 1083 ºC
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DSC curves for ― ― Cu nanopowder
Ag nanopowder
Studies
No existence
of oxide layer
can be expected
962ºC
~200ºC
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– melting point
temperature of Ag
Phase diagram of
the Ag - O system
Ag nanopowder
Studies
– – – … first, second and third run
Deoxidation, melting
and coagulation (sintering)
(waiting for analyses)
Oxidation
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DSC curves for Ag nanopowder
Ag nanopowder
Studies
Partially
oxidized
sample
becomes
deoxidized
during the
heating and
particles
coagulate
Coagulated material
behaves like bulk
 no melting point
depression
heating
cooling
Behaviour like bulk material
 effect of undercooling
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bulk melting point - 962 ºC
DSC curves for ― ― Ag nanopowder
Conclusions






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Even oxygen traces cause formation of massive and
compact oxide cover layer which disables coagulation
of Sn nanoparticles
Concerning Cu nanoparticles the oxidation process is
less dramatic. Coagulation in liquid phase is observed.
Ag nanoparticles do not undergo oxidation at higher
temperatures and coagulation (sintering) takes place.
These facts follow from nobility of the elements.
Nanopowders are promising materials for preparation of
lead free solders applicable at higher temperatures but
there are problems with oxygen affinity for currently used
basic materials (Sn, Cu) or with coagulation (Ag).
Chemical and phase analyses on samples from the
measurements are currently performed in order to
support results of thermal analyses.
Acknowledgement:
This work has been supported by the Ministry of
Education of the Czech Republic under the project
MSM0021622410
Any cooperation is welcome
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Introduction
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Netzsch STA 409 CD/403/5/ SKIMMER
http://www.netzsch-thermal-analysis.com/en/products/detail/pid,34.html
Introduction
Knudsen effusion method coupled
with a mass spectrometer
Construction detail of DSC/KC/QMS instrument.
The instrument is not equipped with Skimmer but with a
ceramic disc with orifices of various diameters enabling or
disabling enter of effusing particles from studied sample
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Configuration of Knudsen cell and ion source.
1. Ion source, 3. shutter, 4. radiation shields,
5. particle beam, 7. sample crucible with a lid,
8. sample, 10. heating shield, 11.thermocouple
Introduction
STA 409
CD/3/403/5/G details
DSC sample carrier
Ion source
IontovýKnudsen
zdroj
cell
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