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

HIGHLY CONFIDENTIAL AND PRIVILEGED INFORMATION an Alent plc Company

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


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


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


Halogen Free Drivers, cont.

• NGOs like

– Continue to push OEMs to become more

environmentally friendly


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


Halogen Activity Example

• C4H6Br2O2 C4H6O2+2+2Br-1

• 4C4H6O2+2 + Sn2O4 2Sn + 4C4H6O6

Dibromobutenediol + Heat Dicarbolyxic Acid + Halide

ΔH

Reduction of Oxidized Tin


Common Lead Free Profile

175C/60S Soak 240C Peak 60S TAL

Organic Acid Formation


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


Halogens versus Halides


Group (Column) VIIA = Halogens


• 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!


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

halogenfree < 1000 ppm Br and Cl

from flame retardant, PVC

or PVC compounds


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


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


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


Performance

Comparison of

Zero Halogen and

Halogen Containing

Pastes


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


Zero Halogen HiP Resistant Paste

Good reflow at corner pads

Only one HIP Defect was

Observed after prying the BGA

from Test Vehicle


Standard Lead Free

Paste

After prying BGA from TV

Obvious HIP joint in the

center of the BGA block!


Zero Halogen Paste Can Improve

HIP Resistance

Standard Lead Free Paste Zero Halogen Paste


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


Reflow profile used for analysis

160-190C / 91 sec >220C / 53 sec


Print and Reflow Performance

190µm deposit

80µm thick stencil

After

Reflow

Before

Reflow

Halogen Containing Zero Halogen


Halogen Containing Zero Halogen

Solder ball Performance


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


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


Acknowledgements

• Jimmy Shu- Regional Marketing Manager SE

Asia

• Tom Hunsinger- Regional Product Manager-

Asia Pacific

• SGS Laboratories Singapore


For more information click the

link below:

Alpha Products

http://blog.cooksonelectronics.com/how-do-you-add-value-to-your-assembly-process/?utm_campaign=All-Products

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