Venkatesh Sivasubramaniam - COST 531 Final Meeting, Vienna,17-05-2007 1 Particle reinforced lead-free solders A Comparative study on reinforcing Sn-4Ag-0.5Cu solder with nano and micron sized Cu particles V.Sivasubramaniam 1, 2 , J.Janczak-Rusch 1 , J.Botsis 2 , J.Cugnoni 2 1 -Laboratory of Joining and Interface Technology, EMPA Material Science and Technology, Dübendorf, Switzerland 2 -Laboratory of Applied Mechanics and Reliability, EPFL, Lausanne, Switzerland COST 531 Final Meeting, Vienna,17-05-2007
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Venkatesh Sivasubramaniam - COST 531 Final Meeting, Vienna,17-05-2007 1 Particle reinforced lead-free solders A Comparative study on reinforcing Sn-4Ag-0.5Cu.
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Venkatesh Sivasubramaniam - COST 531 Final Meeting, Vienna,17-05-2007
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Particle reinforced lead-free solders
A Comparative study on reinforcing Sn-4Ag-0.5Cu solder with
Venkatesh Sivasubramaniam - COST 531 Final Meeting, Vienna,17-05-2007
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Results from previous tests (old temp. profile)
Venkatesh Sivasubramaniam - COST 531 Final Meeting, Vienna,17-05-2007
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• The driving force of the moving of the Cu from substrate is due to the concentration difference in solders and substrate
• Ni and Cu have similar chemical characteristics,thus their diffusion in Sn is expected to be similar but due to the simultaneus presence of Cu,Ni in Ni reinforced Sn3.5Ag which apparently accelerates formation of (Cu-Ni-Sn) IMC
• However since there is not much growth of interfacial layer in Ni reinforced Sn3.5Ag below 100C its quite suitable for applications such as computers where the service conditions are below 100C
• Cu6Sn5 particles inhibits the growth of interfacial IMC by increasing the activation energy from 0.8eV to 1.23eV in SnPb
• It appears that creep resistance FeSn2 > Ni3Sn4 > Cu6Sn5 > Eutectic SnAg
Literature review - Consolidated inferences
Venkatesh Sivasubramaniam - COST 531 Final Meeting, Vienna,17-05-2007
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Microstructural analysis of composite solder joint ‘before’ ageing
SAC405+2wt% ultra fine Cu2O
SAC405+2wt% micron-Cu
10microns
10microns
Venkatesh Sivasubramaniam - COST 531 Final Meeting, Vienna,17-05-2007
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Microstructural analysis of composite solder joint ‘after’ ageing
SAC405+2wt% nano Cu SAC405+2wt% micron-Cu
Venkatesh Sivasubramaniam - COST 531 Final Meeting, Vienna,17-05-2007
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nano Cu2O particles
Disperse in SAC405 paste
Strong flux(OM338)
Reflowed at 240°C
SAC405 reinforced with CuSn(IMC)
Cu2O Cu
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Venkatesh Sivasubramaniam - COST 531 Final Meeting, Vienna,17-05-2007
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Venkatesh Sivasubramaniam - COST 531 Final Meeting, Vienna,17-05-2007
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Quality control of joints-X-ray Radiography
Step gage from SAC405 cast X-ray image of step gage