Paolo Corviseri / Balver Zinn Techn. Department Certified IPC-A-610 Trainer (CIT) Paolo.corviseri@balverzinn.com Phone: +49 2375 1 915150 Mobil: +49 170 6379549 Balver Zinn Josef Jost GmbH & Co. KG SN100C : Micro alloyed lead free solder The Nickel effects
Balver Zinn Group: Briefly Foundation: 1976 Employees Germany: 80 Employees Netherlands: 28 Turnover 2007: ~70 MIO Certificates: DIN EN ISO 9001:2000 Further companies: DIN EN ISO 14001:2004 o Jost Zinn Recycling GmbH o Jost-Zinkgiesserei GmbH o BA-TI-LOY Gesellschaft für Lötmitteltechnik mbh o Cobar B.V. Netherlands 2
Balver Zinn Group: Briefly Headquarter Blintroper Weg 11 Auf dem Werenfelde 10-12 Products: o Pure tin anodes o Zinc anodes o Leaded anodes o Lead free solder wire o Solid wire Products: o Lead free solder SN100C o Lead free solder SnAgCu o Leaded Solder o Solder pastes o Fluxes o Metals development 3
Balver Zinn Group: Briefly The Netherlands Products: o Solder pastes o Fluxes o Chemistry development Cobar B.V Malaysia Products: o Lead free solder SN100C o Lead free solder SnAgCu o Solder wire BALVER ZINN (Nihon Superior Malaysia) 4
Agenda Influence of micro alloying additions on metallurgical properties of lead free alloys Basics of SN100C Micro alloyed elements Nickel Germanium How does Ni works Effect on mechanical properties Effect on metallurgical properties Effect on Reliability How does Ge works Dross formation Surface tension and flowability 5
The basis of the SN100C formulation: SnCu0.7 Tin-Copper There is a convenient eutectic in the Sn-Cu System Cu 6 Sn 5 Eutectic at 0.7Cu 6
The basis of the SN100C formulation: SnCu0.7 But the basic Sn-0.7Cu does not behave as a eutectic Sn-0.7Cu Primary tin dendrites 7
From SnCu0.7 to SN100C The behavior of Sn-Cu as a solder changes dramatically with the addition of <0.1% Ni Sn-0.7Cu Plus Ni and Ge SN100C 8
- Fluidity L Measure Length The Ragone Test Apply Vacuum Molten Solder 9
- Fluidity 1.1% difference The Ni-modified Sn-0.7Cu almost matches 63/37 10
- Fluidity Fluidity Length Unstable Effect Stable Effect 11
- Drainage 2.0 mm Ø Oxygen Free Copper Ring 20mm Flux: JIS Standard Flux A B Melting Temp.: 255 C Immersion Depth: 6mm Immersion Speed: 4mm/s Immersion Time: 20 s Withdrawal Speed: 2mm/s Solder Bath 12
- Drainage Before Dipping After Dipping Icicle Length 13
- Drainage 1000 800 600 400 200 0 65% reduction 39% reduction Icicle Length (m icrons) Sn-0.7Cu Sn-0.7Cu-0.06Ni Sn-0.7Cu-0.06Ni+Ge SN100C 14
- Drainage 1400 1200 1000 800 600 400 200 0 Icicle Length (microns) Sn-3.0Ag-0.5Cu Sn-0.7Cu-0.3Ag Sn-0.7Cu+Ag+Bi Sn-0.7Cu Sn-0.7Cu-0.06Ni Sn-0.7Cu-0.06Ni+Ge 15 85% Reduction SN100C
Copper and Nickel form Intermetallics with Copper with similar Close Packed Hexagonal Crystal Structures Cu 6 Sn 5 Ni 3 Sn 2 Almost the same crystal dimensions Lattice Constants a 0.4125nm 0.4190nm 1.6% difference c 0.5198nm 0.5086nm 2.2% difference Melting Point 415 C 1246 C 16
Ni selectively incorporates in Cu 6 Sn 5 No Ni in the tin matrix (Cu,Ni) 6 Sn 5 20μm Ni No Ni 17
- Microstructural Stability Tin-Copper Phase Diagram Phase transformation from hexagonal Cu 6 Sn 5 to monoclinic Cu 6 Sn 5 with volume change Nickel stabilizes the hexagonal close packed form of the Cu 6 Sn 5 ensuring the integrity of the intermetallic layer 18
- Microstructural Stability Transformation from hexagonal to monoclinic at 186 C 2.15% volume increase Fewer deformation modes available Hexagonal Monoclinic 19
- Microstructural Stability η - η Cu 6 Sn 5, Heated/cooled at 1 C/min* η-hexagonal stabilised (Cu,Ni) 6 Sn 5, Heated/cooled at 1 C/min** *Fig4 (b) from G. Ghosh and M. Asta: Journal of Materials Research, 20(2005) 3102-3117. ** (Cu,Ni) 6 Sn 5 taken from Sn0.7Cu0.05Ni alloy, DSC by Nihon Superior Co. Ltd. 20
- Microstructural Stability 500 μm 21
Sn-0.7Cu Cu 6 Sn 5 Cu 6 Sn 5 Cu 22
Cu 6 Sn 5 Sn-3Ag-0.5Cu Cu 6 Sn 5 Cu 23
~ 3 at% Ni in (Cu,Ni) 6 Sn 5 Sn-0.7Cu-0.05Ni (Cu,Ni) 6 Sn 5 Cu 24
- Microstructural Stability SnAg3Cu0,5 Sn0.7Cu Sn0.7Cu0.05Ni Cu 6 Sn 5 Cu 6 Sn 5 (Cu,Ni) 6 Sn 5 Cu 6 Sn 5 Cu 6 Sn 5 ~ 3 at% Ni in (Cu,Ni) 6 Sn 5 25 25
Microstructural Stability SN100C OSP Substrate After 2 reflow cycles and 500 hour @ 125 C Crack-free IMC stabilized by Ni SAC305 Cracking of IMC due to phase change on cooling 26
Microstructural Stability ~9% Ni Transmission Electron Micrograph Electron Diffraction Pattern Transmission Electron Micrograph Electron Diffraction Pattern 27
- Microstructural Stability Measure total crack length 28
- Microstructural Stability 0.5 (No.or Length of Cracks) /(IMC Length) 0.4 0.3 0.2 0.1 Normalised Crack Numbers Normalised Crack Length 29 0 Sn07Cu Sn3Ag07Cu Sn07Cu005Ni BGA Alloys
- IMC Morphology Slower Growth of Ni-stablized (Cu,Ni) 6 Sn 5 30
- IMC Morphology More Uniform Morphology of Ni-stablized (Cu,Ni) 6 Sn 5 Morphology, (y/x) Periodical triangle pattern model x y h 0 31
- Intermetallic Growth Intermetallic layer in SN100C is initially the thickest but after ageing is the thinnest IM C Growth on OSP Finish Intermetallic Thickness (microns) 32 4 3 2 1 0 SnPb SnAgCu SnCu SN100C SnCuNi Solder Alloy Initial IMC Thickness IMC Thickness After Therm al Cycling (-40C - +125C 4000 cycles)
- Intermetallic Growth 33
- Copper Erosion Rate The stabilized (Cu,Ni) 6 Sn 5 dissolves in solder more slowly Nominal Cu Loss of Extended Contact with SAC305 and Sn-Cu-Ni 60 50 % Cu Loss 40 30 20 10 SAC305 Sn-Cu-Ni 0 1.5 fpm 3.0 fpm 4.5 fpm Conveyor Speed Effect of Contact Time on Lead-Free Wave Solder Jim Morris & Richard Szyanowski Speedline Technologies APEX 2008 34
Intermetallic Growth The nickel in the intermetallic has the effect of suppressing columnar morphology, stabilizing the hexagonal close packed form of the Cu6Sn5 and slowing its growth SN100C SAC305 35
BALVER ZINN: The Germanium - Effect - Oxidation Resistance The Ge acts as an antioxidant and surface active agent SnCuNi SN100C SnCuNi+Ge 15 minute Ramp to 340 C 30 minute cool Sn-0.7Cu-0.05Ni Sn-0.7Cu-0.05Ni+Ge K Watling, A Chandler, K Nogita. A Dahle, University of Queensland, Submitted for publication 36 36
BALVER ZINN: Summary Addition of < 0.1 Ni in SnCu changes the behaviour of SnCu dramatically Ni increases the flowability of SN100C Ni decreases the copper dissolution of SN100C Ni stabilised the IMC of SN100C SN100C has initially the thickest IMC SN100C shows the slowest growth of IMC during aging The thinnest IMC after aging Less dross formation by Ge 37 37
BALVER ZINN: Summary Thank you for your Attention! 38