Halogen in Lead Free Solder Paste
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Transcript of Halogen in Lead Free Solder Paste
an Alent plc Company
Halogen in Lead
Free Solder Paste Dr. Michael Liberatore
Mitch Holtzer
ALPHA Metals
South Plainfield, New Jersey
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Agenda
• Halogen Overview – Drivers of Halogen-Free initiatives
– Halogen’s Impact on Solder Paste
• Halogens versus Halides
• Current standards for defining Halogen-Free
• Method for detecting halogens – In the bulk product
– Potential Ambiguity with Industry Standards
• Performance results with Halogen-Free solder paste
• Conclusions
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What is Driving the Halogen-Free
Initiative?
• RoHS guidelines recommending controls on
polycyclic aromatic halogenated compounds.
– This is the only government regulated initiative with
the goal of reducing the use of halogens
• The current Halogen-Free initiative in electronics
assembly is driven by 2 main groups
– Non Government Organizations (NGOs)
– Environmentally conscious OEMs
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Halogen Free Drivers?
• RoHS includes two common types of polycyclic
aromatic halogen flame retardants
– Polychlorinated Biphenyls
– Polybrominated Biphenyls
• By-products of their combustion are believed to
be harmful to human health and the environment
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Halogen Free Drivers, cont.
• NGOs like
– Continue to push OEMs to become more
environmentally friendly
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Halogen’s Impact in Solder Paste
• Offer inert source of heat activated organic acids
• Organic acids become available at critical point in reflow profile
• Organic acids designed to reduce oxidized metals
• Oxidized organic acids then entrapped in rosin residue are electrically inert
• Combustion products may be harmful to human health and the environment
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Halogen Activity Example
• C4H6Br2O2 C4H6O2+2+2Br-1
• 4C4H6O2+2 + Sn2O4 2Sn + 4C4H6O6
Dibromobutenediol + Heat Dicarbolyxic Acid + Halide
ΔH
Reduction of Oxidized Tin
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Common Lead Free Profile
175C/60S Soak 240C Peak 60S TAL
Organic Acid Formation
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Why is Halogen Usefull?
RMA390DH4 Flux
0
10
20
30
40
50
60
70
80
90
100
40 90 140 190 240 290 340 390 440 490 540Temp (C)
% w
t
-0.16
-0.14
-0.12
-0.1
-0.08
-0.06
-0.04
-0.02
0
0.02
Flux/Method: 20C/min; air
dw
t/dt
% w t
dw t/dt
dwt/dt max
at 343C
78.173%
at 220C
82.956%
at 183C
dwt/dt max
at 171C
Halogen Bearing Formula
Reflow
Temperature
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Halogens versus Halides
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Group (Column) VIIA = Halogens
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• Halogens – covalent bonded group
VIIA element without a net ionic charge
– primary source for Halogens in Assemblies is BFR’s in Laminates
– present a potential toxicity problem when burned
– when used in solder paste can enhance activity without reducing shelf life, stencil life or post reflow electrical reliability
• Halides
– ionic and have a charge
– added to solder pastes to
improve activity only (ROL1)
– Generally hydroscopic
causing printing/stencil life
and reliability problems
Halogens and Halides are NOT the same!
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Definition of Halogen-Free
• Zero Halogen = No Br or Cl is
intentionally added to the formulation
IPC J-STD-709
Currently a draft
standard
IPC definition of
halogen- free < 1000 ppm Br and Cl
from flame retardant, PVC
or PVC compounds
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Definition of Halogen-free • Two ways of measuring halogen content
– In the bulk of the soldering material
– In the final residue that remains on the board
• IPC J-STD-709 – Refers to reporting the halogen content in the final
residue
– It does not describe a test procedure to measure the halogen content of the residue
• OEMs – Many OEMs are defining their own level of halogen that
they will accept
– Critical to establish the halogen content that is acceptable to the OEM
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Halogen Content Test
or
Combustion Process Volumetric
Flask
Filtration Centrifuge
Ion Chromatograph
• Halogens have a neutral charge and
cannot be detected by standard IC.
• Must first be converted to ionic Halides - this is done in the combustion process
•Halide Control test should be preformed on
incoming standard
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Issue- False Positive Test
• ROL0 Paste < 500 ppm Halide in flux
– J-STD-004A and B
– ROL1 if Halide is >500 ppm
• Halogen Free Paste < 900 ppm Bromine
• Oxygen Bomb + Ion Chromatography
• 1400 ppm Br- Should be detected
• Is it Halogen Free? Is it Halide Free?
• Zero Halogen, Zero Halide Solves Issue
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Performance
Comparison of
Zero Halogen and
Halogen Containing
Pastes
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Viscosity stability at 35°C
Viscosity change at 35 degC
150
170
190
210
230
250
0 1 2 3 4 5
days
Pa.s
PNC0809N TLF204-93
• Both pastes
show good
viscosity stability
at 35°C for 5
days
Store in 35degC chamber
Malcom
Lot No.
Measurement 15-May 18-May 20-May 15-May 18-May 20-May
Days 0 3 5 0 3 5
3 rpm 453 478 490 379 385 389
4 360 375 386 326 326 327
5 303 314 322 294 281 288
10 182 183 190 210 194 19920 117 114 120 150 139 142
30 92 89 92 123 115 116
10 177 178 184 206 192 193
Ti 0.69 0.73 0.73 0.49 0.52 0.53
R 2.75 2.73 3.16 1.90 1.03 3.02
Change rate 0.0% 0.5% 4.4% 0.0% -7.6% -5.2%
PNC0809N
90408043P
TLF204-93
090319
150
250
1 4 7 1013 16 1922 2528 31
Zero Halogen Paste
Zero Halogen Halogen Containing
Halogen Containing Paste
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Zero Halogen HiP Resistant Paste
Good reflow at corner pads
Only one HIP Defect was
Observed after prying the BGA
from Test Vehicle
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Standard Lead Free
Paste
After prying BGA from TV
Obvious HIP joint in the
center of the BGA block!
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Zero Halogen Paste Can Improve
HIP Resistance
Standard Lead Free Paste Zero Halogen Paste
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Finest Feature Coalesced
• Benchmark for fine feature reflow yield
• Strong indicator of flux/activator survivability
• Indicator of process capability with smaller
passives (0201; 01005)
• Probable indicator of Head in Pillow Resistance
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Reflow profile used for analysis
160-190C / 91 sec >220C / 53 sec
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Print and Reflow Performance
190µm deposit
80µm thick stencil
After
Reflow
Before
Reflow
Halogen Containing Zero Halogen
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Halogen Containing Zero Halogen
Solder ball Performance
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Performance Summary
• Zero Halogen Pastes:
– Have excellent high temperature print stability
– Reduce HIP defects
– Withstand long soak profiles and have fine
feature coalescence (down to 170µ)
– Show preferred solder ball resistance
– Achieve high electrical reliability
• Pass JIS Cu Corrosion, JIS SIR, IPC SIR
and IPC EM
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Conclusions
• Current Halogen-free initiative being driven by NGOs and OEMs – The only halogens that are legislated to be removed are
polybrominated and polychlorinated biphenyls - RoHS
– Other halogens used as flame retardants are also targeted
• Halogen-free and Zero Halogen pastes have existed for many years – Soldering performance can be superior versus halogen
containing materials
– Selection of the appropriate product is driven by your process and reliability requirements, and OEM specification
• Analytical Ambiguities Removed with Zero Halogen – Prevents low value added discussions with customers
– Eliminates uncertainty of compliance with industry standards
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Acknowledgements
• Jimmy Shu- Regional Marketing Manager SE
Asia
• Tom Hunsinger- Regional Product Manager-
Asia Pacific
• SGS Laboratories Singapore
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