corrosion and reliability characteristics of fluxes - michalkiewicz 2013 v2.pdf

Renee Michalkiewicz,General Manager

Trace Laboratories, Inc. – BaltimoreChairman, IPC J-STD-004 Flux

Specification Task Group

Renee Michalkiewicz,General Manager

Trace Laboratories, Inc. – BaltimoreChairman, IPC J-STD-004 Flux

Specification Task Group

1

Flux Corrosion and PCA Reliability OverviewFlux Corrosion and PCA Reliability Overview

Background

Soldering Flux Qualification Tests for Corrosion

Introduction to Turbini-modified Bono Test

Assembly Process Validation Testing

Product Failures Related to Flux-Induced Corrosion

Assembly Process Improvement

Background

Soldering Flux Qualification Tests for Corrosion

Introduction to Turbini-modified Bono Test

Assembly Process Validation Testing

Product Failures Related to Flux-Induced Corrosion

Assembly Process Improvement

Copyright 2013 TraceLaboratories. All rights reserved.

BackgroundBackground

Flux Corrosion by Definition Chemical Corrosion is a process in which a solid,

especially a metal, is eaten away and changed by achemical action

Electrolytic Corrosion is an electrochemical process inwhich one metal corrodes preferentially to another whenboth metals are in electrical contact in the presence of anelectrolyte

Electromigration Video:http://www.youtube.com/user/TraceLabs

Flux Corrosion by Definition Chemical Corrosion is a process in which a solid,

especially a metal, is eaten away and changed by achemical action

Electrolytic Corrosion is an electrochemical process inwhich one metal corrodes preferentially to another whenboth metals are in electrical contact in the presence of anelectrolyte

Electromigration Video:http://www.youtube.com/user/TraceLabs



Fluxes for use in electronics have been qualifiedsince the 1950’s through MIL-F-14256, Flux,Soldering, Liquid, Paste Flux, Solder Paste andSolder-Paste Flux, (For Electronic/Electrical Use)General Specification for (1956 - 1995)Prior to Joint Standard (IPC J-STD-004), IPC-SF-818 was also in place (1988 - 1995)Flux residue activity has been measured since thebeginningFlux chemistry has changed but concernsregarding active flux residues have not

Fluxes for use in electronics have been qualifiedsince the 1950’s through MIL-F-14256, Flux,Soldering, Liquid, Paste Flux, Solder Paste andSolder-Paste Flux, (For Electronic/Electrical Use)General Specification for (1956 - 1995)Prior to Joint Standard (IPC J-STD-004), IPC-SF-818 was also in place (1988 - 1995)Flux residue activity has been measured since thebeginningFlux chemistry has changed but concernsregarding active flux residues have not



Concerns with active flux residue

Can cause degradation of copper circuit which could lead toan open circuit

Can lead to formation of dendrites which could lead to ashort circuit

Case studies are provided at the end of the presentation

Concerns with active flux residue

Can cause degradation of copper circuit which could lead toan open circuit

Can lead to formation of dendrites which could lead to ashort circuit

Case studies are provided at the end of the presentation


Soldering Flux Qualification Tests for CorrosionSoldering Flux Qualification Tests for Corrosion

IPC J-STD-004, Requirements for Soldering Fluxes

Used to classify flux activity (1995 to present)

Product qualification, not assembly process validation

Four tests to evaluate corrosive properties of flux Copper Mirror Corrosion Surface Insulation Resistance (SIR) Electrochemical Migration (ECM)

IPC J-STD-004, Requirements for Soldering Fluxes

Used to classify flux activity (1995 to present)

Product qualification, not assembly process validation

Four tests to evaluate corrosive properties of flux Copper Mirror Corrosion Surface Insulation Resistance (SIR) Electrochemical Migration (ECM)



Copper Mirror Test IPC-TM-650, Method 2.3.32 Flux is tested as-received Determines the removal effect the flux has on bright copper

mirror film deposited on glass slide

Copper Mirror Test IPC-TM-650, Method 2.3.32 Flux is tested as-received Determines the removal effect the flux has on bright copper

mirror film deposited on glass slide


L M HNo Breakthrough Less Than 50% Breakthrough Greater Than 50% Breakthrough


Corrosion Test IPC-TM-650, Method 2.6.15 Flux is tested after reflow Determines the corrosive properties of flux residues

following 10 days of 50°C / 95%RH A pellet of solder is melted in contact with the test flux on a

copper test panel

Corrosion Test IPC-TM-650, Method 2.6.15 Flux is tested after reflow Determines the corrosive properties of flux residues

following 10 days of 50°C / 95%RH A pellet of solder is melted in contact with the test flux on a

copper test panel


No CorrosionNo Corrosion Minor CorrosionMinor Corrosion Major CorrosionMajor Corrosion


Surface Insulation Resistance (SIR) IPC-TM-650, Method 2.6.3.7 Flux is tested after reflow Determines the corrosive properties of flux residues (as well

as leakage current development) under 40°C / 90%RHenvironment for 7 days

Surface Insulation Resistance (SIR) IPC-TM-650, Method 2.6.3.7 Flux is tested after reflow Determines the corrosive properties of flux residues (as well

as leakage current development) under 40°C / 90%RHenvironment for 7 days



Chemical corrosion and electrolytic corrosion are reasonsfor failure



Electrochemical Migration (ECM) IPC-TM-650, Method 2.6.14.1 Flux is tested after reflow Determines the corrosive properties of flux residues (as well

as IR degradation) under 65°C / 88.5%RH environment for21 days

Electrochemical Migration (ECM) IPC-TM-650, Method 2.6.14.1 Flux is tested after reflow Determines the corrosive properties of flux residues (as well

as IR degradation) under 65°C / 88.5%RH environment for21 days



Again, chemical corrosion and electrolytic corrosion arereasons for failure


Introduction to TurbiniIntroduction to Turbini--modified Bono Testmodified Bono Test

Characterizing Corrosion Effects Recently modified to better quantify and characterize the

corrosive effects of WOA flux on copper circuits WOA solutions used were abietic, succinic, glutaric, adipic and malic

acids (Experiment did not use full flux chemistry) Study found 60°C / 93%RH for 10 days to be the best to

detect differences in the WOA’s

Characterizing Corrosion Effects Recently modified to better quantify and characterize the

corrosive effects of WOA flux on copper circuits WOA solutions used were abietic, succinic, glutaric, adipic and malic

acids (Experiment did not use full flux chemistry) Study found 60°C / 93%RH for 10 days to be the best to

detect differences in the WOA’s


Soldering Process ValidationSoldering Process Validation TestingTesting

SIR testing per IPC-9202 / IPC-9203 Different from product qualification Tests all chemistries on standardly designed test vehicle

(IPC-B-52) Can use commercially available test boards or you could

have your board manufacturer / CM site produce Need to use “dummy” non-active components

SIR testing per IPC-9202 / IPC-9203 Different from product qualification Tests all chemistries on standardly designed test vehicle

(IPC-B-52) Can use commercially available test boards or you could

have your board manufacturer / CM site produce Need to use “dummy” non-active components


AssemblyAssembly Process ValidationProcess Validation TestingTesting

SIR test patterns are placed below the components The assemblies are run through an SIR environment as

mentioned in previous slides Adverse reactions between the assembly process

chemistries are assessed through electrical monitoring andvisual examination for evidence of corrosion

Allows for assessment of new assembly process prior tobuilding actual product

Drawback: Board is a test board so it cannot exactlysimulate all assembly challenges

SIR test patterns are placed below the components The assemblies are run through an SIR environment as

mentioned in previous slides Adverse reactions between the assembly process

chemistries are assessed through electrical monitoring andvisual examination for evidence of corrosion

Allows for assessment of new assembly process prior tobuilding actual product

Drawback: Board is a test board so it cannot exactlysimulate all assembly challenges


Example Case Study #1Example Case Study #1

Major auto supplier experiencing intermittentfailures in electronic system Root cause failure analysis led to investigation of materials

used in assembly process; dendritic growth was suspecteddue to black carbonized debris found between isolatedcircuits

Major auto supplier experiencing intermittentfailures in electronic system Root cause failure analysis led to investigation of materials

used in assembly process; dendritic growth was suspecteddue to black carbonized debris found between isolatedcircuits



When the flux supplier was questioned, it was revealed thatthe flux raw materials had not been tested in 15 years

Testing of the flux showed a moderate activity level per J-STD-004 – the material was being sold as a no-clean

J-STD-004 requires retesting if source of raw materialchanges, but no one is currently policing suppliers

When the flux supplier was questioned, it was revealed thatthe flux raw materials had not been tested in 15 years

Testing of the flux showed a moderate activity level per J-STD-004 – the material was being sold as a no-clean

J-STD-004 requires retesting if source of raw materialchanges, but no one is currently policing suppliers


“Qualified” Soldering Fluxes“Qualified” Soldering Fluxes

J-STD-004 Qualified Fluxes

Fluxes often qualified once and never tested again

Over the years, source of raw materials change

Activity of flux changes

In my experience, happens more often in companies that donot participate in IPC and have less of an understanding ofthe specification requirements.

J-STD-004 Qualified Fluxes

Fluxes often qualified once and never tested again

Over the years, source of raw materials change

Activity of flux changes

In my experience, happens more often in companies that donot participate in IPC and have less of an understanding ofthe specification requirements.



How to improve your assembly reliability

Use reputable flux suppliers

Periodically request most recent qualification and lotscreening test results; ask date of testing; illicit help fromsomeone who understands flux testing results; do not rely ontechnical datasheets; this information is often many years old

IPC has initiated a pilot program to begin a QPL for fluxmaterials under Randy Cherry, IPC Director of ValidationServices; once this is available, IPC will be policing suppliers


Use reputable flux suppliers

Periodically request most recent qualification and lotscreening test results; ask date of testing; illicit help fromsomeone who understands flux testing results; do not rely ontechnical datasheets; this information is often many years old

IPC has initiated a pilot program to begin a QPL for fluxmaterials under Randy Cherry, IPC Director of ValidationServices; once this is available, IPC will be policing suppliers



Implantable medical device experiencing failuresduring in-circuit test Audit of facility showed tight control on automated assembly

process including cleanliness testing during each shift ofproduction

Review of hand soldering installation of battery revealed useof “H” level flux with no cleaning or cleanliness testingfollowing soldering

Additionally, there was no control on the volume of flux usedin this step and excessive unreacted flux was found acrossthe entire circuit surface

Implantable medical device experiencing failuresduring in-circuit test Audit of facility showed tight control on automated assembly

process including cleanliness testing during each shift ofproduction

Review of hand soldering installation of battery revealed useof “H” level flux with no cleaning or cleanliness testingfollowing soldering

Additionally, there was no control on the volume of flux usedin this step and excessive unreacted flux was found acrossthe entire circuit surface



Temperature / Humidity testing was run on actual product torecreate the failure

Photos below show dendritic growth on actual assembly With tighter control added to battery soldering, the failures

were eliminated

Temperature / Humidity testing was run on actual product torecreate the failure

Photos below show dendritic growth on actual assembly With tighter control added to battery soldering, the failures

were eliminated


Example CaseExample Case Study #2Study #2


Be sure to have controls on all stages of the solderingprocess

Verify assembly process through process validation studies


Be sure to have controls on all stages of the solderingprocess




Company that makes security systems experiencedfield failure returns of a camera correction board Excessive flux residue was observed around the BGA that

was determined to be the failure location

Company that makes security systems experiencedfield failure returns of a camera correction board Excessive flux residue was observed around the BGA that

was determined to be the failure location



Non-destructive X-ray analysis showed dendritic growthbranching from several solder balls to adjacent isolatedcircuits



The BGA component was removed for additional evaluationof dendrites bridging conductors and copper corrosion



FTIR analysis of flux showed match to specific water washtacky rework flux

Statement from technical datasheet reads:

“Meets IPC ANSI-J-STD-006 requirements for ORL0, WaterSoluble”

Does anyone know what is incorrect with this statement?

Additionally, DSC ΔTg analysis suggested that PCB wasnot fully cured; this could exacerbate issue by trappingresidues

FTIR analysis of flux showed match to specific water washtacky rework flux

Statement from technical datasheet reads:

“Meets IPC ANSI-J-STD-006 requirements for ORL0, WaterSoluble”

Does anyone know what is incorrect with this statement?

Additionally, DSC ΔTg analysis suggested that PCB wasnot fully cured; this could exacerbate issue by trappingresidues




Control process steps that are not part of normal process –i.e. rework

Rework flux must see full heat to be fully activated

Look for “red flags” on product datasheets that flux supplierdoes not have understanding of product specifications



Control process steps that are not part of normal process –i.e. rework

Rework flux must see full heat to be fully activated

Look for “red flags” on product datasheets that flux supplierdoes not have understanding of product specifications




Military OEM had Field Failure Return;Circuit on Assembly Measuring Open; Neededto determine Root Cause Microsection was taken in area of open circuit Missing copper in tented via led to conclusion that flux and

cleaning solutions had been trapped within via

Military OEM had Field Failure Return;Circuit on Assembly Measuring Open; Neededto determine Root Cause Microsection was taken in area of open circuit Missing copper in tented via led to conclusion that flux and

cleaning solutions had been trapped within via


C.HillmanC.Hillman



Do not tent via on one side of board

Make sure vias are completely tented; no solder mask voids


Do not tent via on one side of board

Make sure vias are completely tented; no solder mask voids


Summary of RecommendationsSummary of Recommendations

Use reputable flux suppliers Periodically request most recent qualification and lot

screening test results Be sure to have controls on all stages of the soldering

process Verify assembly process through process validation studies Control process steps that are not part of normal process –

i.e. rework Rework flux must see full heat to be fully activated Look for “red flags” on product datasheets that flux supplier

does not have understanding of product specifications Do not tent via on one side of board Make sure vias are completely tented; no solder mask voids

Use reputable flux suppliers Periodically request most recent qualification and lot

screening test results Be sure to have controls on all stages of the soldering

process Verify assembly process through process validation studies Control process steps that are not part of normal process –

i.e. rework Rework flux must see full heat to be fully activated Look for “red flags” on product datasheets that flux supplier

does not have understanding of product specifications Do not tent via on one side of board Make sure vias are completely tented; no solder mask voids


ACKNOWLEDGEMENTACKNOWLEDGEMENT

Thanks go out to the following Trace managersand test engineers for providing case studyinformation, photographs and video:Keith SellersMichael AllisonDaniel PhillipsDaniel Olsen

Thanks go out to the following Trace managersand test engineers for providing case studyinformation, photographs and video:Keith SellersMichael AllisonDaniel PhillipsDaniel Olsen


REFERENCE ACKNOWLEDGEMENTREFERENCE ACKNOWLEDGEMENT

MIL-F-14256, Flux, Soldering, Liquid, PasteFlux, Solder Paste and Solder-Paste Flux, (ForElectronic/Electrical Use) General Specificationfor (1956)

IPC-SF-818, General Requirement for ElectronicSoldering Fluxes

IPC J-STD-004B, Requirements for SolderingFluxes (2008)

Zhou, et al. - Characterizing Corrosion Effects ofWeak Organic Acids Using a Modified Bono Test(2013)

MIL-F-14256, Flux, Soldering, Liquid, PasteFlux, Solder Paste and Solder-Paste Flux, (ForElectronic/Electrical Use) General Specificationfor (1956)

IPC-SF-818, General Requirement for ElectronicSoldering Fluxes

IPC J-STD-004B, Requirements for SolderingFluxes (2008)

Zhou, et al. - Characterizing Corrosion Effects ofWeak Organic Acids Using a Modified Bono Test(2013)


REFERENCE ACKNOWLEDGEMENTREFERENCE ACKNOWLEDGEMENT

IPC-9202, Material and ProcessCharacterization / Qualification (2011)

IPC-9203, Users Guide to IPC-9202 and theIPC-B-52 Standard Test Vehicle (2012)

C. Hillman, Improved Methodologies forIdentifying Root-Cause of Printed Board Failures(2005)

IPC-9202, Material and ProcessCharacterization / Qualification (2011)

IPC-9203, Users Guide to IPC-9202 and theIPC-B-52 Standard Test Vehicle (2012)

C. Hillman, Improved Methodologies forIdentifying Root-Cause of Printed Board Failures(2005)


Renee Michalkiewicz410-229-4360

[email protected]

Renee Michalkiewicz410-229-4360

[email protected]

Copyright 2013 Trace Laboratories. All rightsreserved.

35

Live Video of Dendritic GrowthLive Video of Dendritic Growth


corrosion and reliability characteristics of fluxes - michalkiewicz 2013 v2.pdf

Documents

flux residue activity

corrosion introduction

definition chemical

joint standard ipc jstd

degradation of copper

toan open circuit

solder paste andsolder

ashort circuit case