LEAD-FREE, KISS PROCESSLEAD-FREE, KISS PROCESS(KEEP-IT-SIMPLE-SOLDERING)(KEEP-IT-SIMPLE-SOLDERING)

SUPERIOR FLUX & MFG. CO.SUPERIOR FLUX & MFG. CO.6615 Parkland Blvd.6615 Parkland Blvd.

Cleveland, OH 44139Cleveland, OH 44139

OBJECTIVE OF LEAD-FREE OBJECTIVE OF LEAD-FREE SOLDERSOLDER

WEEE/RoHS and Japanese WEEE/RoHS and Japanese regulations originally set July regulations originally set July 1, 2006 as the date when 1, 2006 as the date when electronics assembly be electronics assembly be Lead-Free. Lead-Free. Primary Reason: Landfill Lead Primary Reason: Landfill Lead

Leaching into Soil.Leaching into Soil.

ELECTRONICS USE OF ELECTRONICS USE OF LEADLEAD

Electronics assembly represents Electronics assembly represents 0.3-0.5% overall use of lead*.0.3-0.5% overall use of lead*. With such a small use of lead, why With such a small use of lead, why

is electronics targeted? is electronics targeted? Number of landfills led to this Number of landfills led to this legislation; the high profile of legislation; the high profile of electronics in ‘garbage dumps’; and the electronics in ‘garbage dumps’; and the ‘wealth’ of the highly profitable ‘wealth’ of the highly profitable electronics market.electronics market.

* Source: AlphaMetals div. of Alpha/Fry Group.* Source: AlphaMetals div. of Alpha/Fry Group.

ELECTRONIC PRODUCTSELECTRONIC PRODUCTS

Electronics targeted for Electronics targeted for addressing European legislation addressing European legislation removing lead from landfills.removing lead from landfills. A wide variety of Tin/Lead solders are A wide variety of Tin/Lead solders are

used in televisions, cell phones, used in televisions, cell phones, telephones, computers and monitors, telephones, computers and monitors, and other consumer products.and other consumer products.

Adding electronic assemblies to Adding electronic assemblies to Lead-Free list continues the Lead-Free list continues the removal of Lead from solder, that removal of Lead from solder, that is now standard for plumbing is now standard for plumbing solders.solders.

WHO HAS CONDUCTED WHO HAS CONDUCTED LEAD-FREE RESEARCH?LEAD-FREE RESEARCH?Primary American research has taken place Primary American research has taken place at the Department of Energy’s (DOE) Ames at the Department of Energy’s (DOE) Ames Laboratory at Iowa State University, under Laboratory at Iowa State University, under Dr. Iver Anderson, who has conducted Dr. Iver Anderson, who has conducted research into Tin/Lead alternatives and research into Tin/Lead alternatives and arrived at a patent for the basis of the SAC arrived at a patent for the basis of the SAC alloys. alloys. The alloy that they have patented and The alloy that they have patented and recommend is a ternary alloy combination of:recommend is a ternary alloy combination of:

Sn: 93.6%Sn: 93.6%Ag: 4.7%Ag: 4.7%Cu: 1.7%Cu: 1.7%Eutectic Melt Point: 217Eutectic Melt Point: 217ººCC

ADDITIONAL LEAD-FREE ADDITIONAL LEAD-FREE ‘SAC’ ALLOYS‘SAC’ ALLOYS

While the previous terneray ‘SAC’ alloy is the While the previous terneray ‘SAC’ alloy is the patented solder, new ‘SAC’ alloy solders have patented solder, new ‘SAC’ alloy solders have been presented to the market by a number of been presented to the market by a number of different metals/solder companies:different metals/solder companies:

11 22 33SnSn :: 96.596.5 95.595.5 95.895.8AgAg:: 3.03.0 4.04.0 3.53.5CuCu:: 0.50.5 0.50.5 0.70.7

Additional ‘SAC’ Alloy Solders are also Additional ‘SAC’ Alloy Solders are also available.available.

These different alloy combinations all claim These different alloy combinations all claim aa

‘‘Eutectic’ of 217Eutectic’ of 217ººC.C.

BINARY EUTECTIC BINARY EUTECTIC ALLOYSALLOYS

While the talk has been of While the talk has been of ternary ‘SAC’ alloy Lead-Free ternary ‘SAC’ alloy Lead-Free solders, there are binary options:solders, there are binary options:

11 22

SnSn 96.596.5 99.399.3

AgAg 3.53.5 ----

CuCu ---- 0.70.7

EutecticEutectic 221221ººCC 227227ººCC

……AND STILL MOREAND STILL MOREAdditional Lead-Free Alloys ExistAdditional Lead-Free Alloys Exist

42Sn/58Bi:42Sn/58Bi: 138138ººC EutecticC Eutectic

95Sn/5Sb:95Sn/5Sb: Plastic range 232-240Plastic range 232-240ººCC

96.2Sn/2.5Ag/0.8Cu/0.5Sb: 21896.2Sn/2.5Ag/0.8Cu/0.5Sb: 218ººC Eutectic C Eutectic (AIM Castin (AIM Castin®®

Solder)Solder)

91Tin/9Zinc: 91Tin/9Zinc: 199199ººC EutecticC Eutectic

and many more…and many more…

DEFINITION OF EUTECTICDEFINITION OF EUTECTICEutectic: Designating or of a mixture or alloy Eutectic: Designating or of a mixture or alloy with a melting point lower than that of any with a melting point lower than that of any other combination of the same components.*other combination of the same components.*Most widely used metals in electronics solders Most widely used metals in electronics solders and metal melt-points**:and metal melt-points**:

Tin (Sn): Tin (Sn): Melting PointMelting Point 232232ººCC Lead (Pb): Lead (Pb): Melting Point Melting Point 327.4327.4ººCC Silver (Ag):Silver (Ag): Melting PointMelting Point 960.5960.5ººCC Copper Cu):Copper Cu): Melting PointMelting Point 10831083ººCC Indium (In):Indium (In): Melting PointMelting Point 155155ººCC Bismuth (Bi):Bismuth (Bi): Melting PointMelting Point

271271ººCC Antimony (Sb):Antimony (Sb): Melting PointMelting Point

630630ººCC

• *Source: Webster’s New World Dictionary*Source: Webster’s New World Dictionary• ** Source: Merck Index, Twelfth Edition** Source: Merck Index, Twelfth Edition

FACTORS IN LEAD-FREE FACTORS IN LEAD-FREE SOLDER COMPOSITIONSOLDER COMPOSITION

The key factor in selecting a Lead-Free solder has The key factor in selecting a Lead-Free solder has been driven by price, cost, and temperature been driven by price, cost, and temperature requirements.requirements.Tin price, which has increased more than 100% since Tin price, which has increased more than 100% since 1/1/2003, rises from 63% of solder content to a 1/1/2003, rises from 63% of solder content to a minimum of 93.6%. minimum of 93.6%.

This raises price, cost, and temperature of Lead-This raises price, cost, and temperature of Lead-Free Solders.Free Solders.

Other alloys, such as bismuth and indium, used in Other alloys, such as bismuth and indium, used in fusible alloys, have too low a melt-point for fusible alloys, have too low a melt-point for reliability and stability of finished products; are too reliability and stability of finished products; are too weak as solder alloys and may yield unreliable field weak as solder alloys and may yield unreliable field dependability; or too expensive due to limited global dependability; or too expensive due to limited global supply.supply.Antimony, long used in industrial applications, has Antimony, long used in industrial applications, has been kept from electronics applications for many been kept from electronics applications for many years due to a high temperature requirement, and, if years due to a high temperature requirement, and, if too much antimony is used, yield a weak joint that too much antimony is used, yield a weak joint that may peel over time and cause electric failure.may peel over time and cause electric failure.

WITH SO MANY LEAD-FREE WITH SO MANY LEAD-FREE SOLDERS TO CHOOSE FROM, SOLDERS TO CHOOSE FROM,

WHY IS IT SO DIFFICULT?WHY IS IT SO DIFFICULT?The Eutectic melt-point of 63Tin/37Lead alloy is The Eutectic melt-point of 63Tin/37Lead alloy is

183183ººC.C.

The lowest melt Eutectic Lead-Free alloys used The lowest melt Eutectic Lead-Free alloys used primarily as fusible alloys, 48Sn/52In is 118primarily as fusible alloys, 48Sn/52In is 118ººC and C and 42Sn/58Bi is 13842Sn/58Bi is 138ººC, are too low for stable and C, are too low for stable and dependable life-cycle reliance use in a vast dependable life-cycle reliance use in a vast majority of applications.majority of applications.

91Sn/9Zn is 19991Sn/9Zn is 199ººC, currently used in aluminum C, currently used in aluminum soldering applications, is closer to the 183soldering applications, is closer to the 183ººC base-C base-line melt-point of the current industry standard , line melt-point of the current industry standard , but the alloy is too corrosive for electronics but the alloy is too corrosive for electronics applications.applications.

WHICH FOCUSES THE WHICH FOCUSES THE ALLOY BASE TO…ALLOY BASE TO…

This leads to the Tin-Based This leads to the Tin-Based Alloys, which include:Alloys, which include: 100Sn: 100Sn: Melt-point of 232Melt-point of 232ººCC 99.3Sn/0.7Cu: 99.3Sn/0.7Cu: Eutectic of 227Eutectic of 227ººCC 96.5Sn/3.5Ag:96.5Sn/3.5Ag: Eutectic of 221Eutectic of 221ººCC ‘‘SAC’ Alloys: claim Eutectic of 218SAC’ Alloys: claim Eutectic of 218ººCC

Actual plastic phase of 218-220Actual plastic phase of 218-220ººCC AIM CastinAIM Castin®® Alloy: Eutectic of 218 Alloy: Eutectic of 218ººCC Kester SAF-A-LLOY: Plastic 219-Kester SAF-A-LLOY: Plastic 219-

235235ººCC

TIN PROPERTIESTIN PROPERTIESAll Lead-Free alloys, that meet the requirements All Lead-Free alloys, that meet the requirements for electronics applications, are high tin-content for electronics applications, are high tin-content alloys.alloys.All melt-points with these alloys are, a minimum, All melt-points with these alloys are, a minimum, of 34of 34ººC above the Eutectic Tin/Lead Solder.C above the Eutectic Tin/Lead Solder.Tin, by itself, is a corrosive metal that requires Tin, by itself, is a corrosive metal that requires changes in the solder pots or lining of solder changes in the solder pots or lining of solder baths used for wave soldering or solder dip baths used for wave soldering or solder dip applications.applications.Post-solder tin-based alloys must be watched for Post-solder tin-based alloys must be watched for “Tin Whiskers” that occur over time as the alloy “Tin Whiskers” that occur over time as the alloy ‘settles’ and forces out tin spikes from a ‘settles’ and forces out tin spikes from a previously flat surface.previously flat surface.Tin reacts with copper and creates tin/copper Tin reacts with copper and creates tin/copper Intermetallics that can cause metal cracking or Intermetallics that can cause metal cracking or embrittle the alloy.embrittle the alloy.

‘‘BACK TO THE FUTURE’BACK TO THE FUTURE’While legislation from Europe and the Far East is leading to theWhile legislation from Europe and the Far East is leading to theremoval of Lead from the electronics assembly process:removal of Lead from the electronics assembly process:

Lead-Free soldering is not new!Lead-Free soldering is not new!

When surface mount technology (SMT) reflow soldering was When surface mount technology (SMT) reflow soldering was introduced, double- sided boards were reflowed in a two step introduced, double- sided boards were reflowed in a two step process: process:

Step One: 96.5Sn/3.5Ag with 221Step One: 96.5Sn/3.5Ag with 221ººC reflow was the first C reflow was the first side. side.

Step Two: 63Sn/37Pb with 183Step Two: 63Sn/37Pb with 183ººC reflow was the second C reflow was the second side. side.

The dual alloy process was incorporated to create a 38The dual alloy process was incorporated to create a 38ººC C temperature difference between the Eutectic Melt-points of temperature difference between the Eutectic Melt-points of the solders. This included stability in alloys that allowed the the solders. This included stability in alloys that allowed the dual reflow process to take place that did not displace or dual reflow process to take place that did not displace or cause any alterations to the first process step that cause any alterations to the first process step that incorporated the Sn/Ag alloy. At the time, metallurgical incorporated the Sn/Ag alloy. At the time, metallurgical properties included an alloy that, today, can be used as a properties included an alloy that, today, can be used as a Lead-Free alloy with a proven track record.Lead-Free alloy with a proven track record.When US Mil Standards were used to establish which alloys When US Mil Standards were used to establish which alloys were acceptable in SATCOM and Aerospace applications, the were acceptable in SATCOM and Aerospace applications, the only Lead-Free alloy that was proven and, therefore, only Lead-Free alloy that was proven and, therefore, specified, was 96.5Sn/3.5Ag, meeting specification QQ-S-571.specified, was 96.5Sn/3.5Ag, meeting specification QQ-S-571.

KISS LEAD-FREEKISS LEAD-FREE

Given the variety of different Lead-Free Given the variety of different Lead-Free Solders,Solders,Binary: 96.5Sn/3.5Ag, 99.3Sn/0.7CuBinary: 96.5Sn/3.5Ag, 99.3Sn/0.7CuTernary SAC Alloys: 93.6Sn/4.7Ag/1.7Cu, Ternary SAC Alloys: 93.6Sn/4.7Ag/1.7Cu, 96.5Sn/3.0Ag/0.5Cu, 95.8Sn/3.5Ag/0.7Cu, 96.5Sn/3.0Ag/0.5Cu, 95.8Sn/3.5Ag/0.7Cu, 95.5Sn/4.0/Ag/0.5Cu, and others.95.5Sn/4.0/Ag/0.5Cu, and others.Quad Alloys: 96.2Sn/2.5Ag/0.8Cu/0.5SbQuad Alloys: 96.2Sn/2.5Ag/0.8Cu/0.5SbFive or more alloy solders: Include Tin, Five or more alloy solders: Include Tin, Copper, Silver, Bismuth, Indium, and other Copper, Silver, Bismuth, Indium, and other combinationscombinations

A number of critical factors must be A number of critical factors must be considered,considered,

but all lead to: but all lead to:

KEEP-IT-SIMPLE-SOLDERING!!!KEEP-IT-SIMPLE-SOLDERING!!!

ARE THE ALLOYS ARE THE ALLOYS PROVEN FOR PROVEN FOR

ELECTRONICS?ELECTRONICS?The only alloy which meets military specifications The only alloy which meets military specifications and has been subjected to life tests that meet and has been subjected to life tests that meet SATCOM requirements is 96.5Sn/3.5Ag binary SATCOM requirements is 96.5Sn/3.5Ag binary Eutectic alloy of 221Eutectic alloy of 221ººC.C.

The fewer metal elements in any solder alloy The fewer metal elements in any solder alloy make for a more reliable, dependable solder make for a more reliable, dependable solder and are similar to the 63Sn/37Pb in terms of and are similar to the 63Sn/37Pb in terms of binary formulation, solder stability, and binary formulation, solder stability, and Eutectic consistency.Eutectic consistency.

The IPC, to date, has not written any The IPC, to date, has not written any specifications under the ANSI-J-STD 004, 005, 006 specifications under the ANSI-J-STD 004, 005, 006 Standards for Lead-Free alloys.Standards for Lead-Free alloys.Potential patent infringement has led to the Potential patent infringement has led to the variety of different ‘SAC’ Alloys all claiming to be variety of different ‘SAC’ Alloys all claiming to be Eutectic. This has led to a re-definition of Eutectic. This has led to a re-definition of Eutectic to include a plastic range of 218-220Eutectic to include a plastic range of 218-220ººC as C as ‘Eutectic’.‘Eutectic’.

WHAT DOES LEAD-FREE WHAT DOES LEAD-FREE SOLDER CONNECT WITH SOLDER CONNECT WITH

BEST?BEST?Silver Immersion is recommended Silver Immersion is recommended for PCB coating over HAL, Gold, for PCB coating over HAL, Gold, OSP and other PCB finishes.OSP and other PCB finishes. The Lead-Free solders that are The Lead-Free solders that are

emerging as ‘the choice’ are emerging as ‘the choice’ are generally a combination of alloys generally a combination of alloys containing Silver. Having a like-to-a-containing Silver. Having a like-to-a-like in the Silver Immersion PCBs and like in the Silver Immersion PCBs and the Solders ensures a better fusion of the Solders ensures a better fusion of solder to PCBs in assembly processes.solder to PCBs in assembly processes.

SHEAR STRENGTH VS. SHEAR STRENGTH VS. DUCTILITYDUCTILITY

In all tests conducted to prove a Lead-Free Solder In all tests conducted to prove a Lead-Free Solder can be used to replace Sn/Pb, the ‘strength’ of the can be used to replace Sn/Pb, the ‘strength’ of the solder, defined by Shear Strength, is the factor solder, defined by Shear Strength, is the factor employed to determine how reliable a solder will employed to determine how reliable a solder will be.be.Tin/Lead solder will always lose to the Lead-Free Tin/Lead solder will always lose to the Lead-Free alloys, which have greater shear strength.alloys, which have greater shear strength.

However, the ductility, or ability to be However, the ductility, or ability to be forgiving, is overlooked as the true strength for forgiving, is overlooked as the true strength for the Tin/Lead solders that have been the the Tin/Lead solders that have been the industry standard for more than 50 years.industry standard for more than 50 years.

The Lead-Free Alloys, with high tin-content are The Lead-Free Alloys, with high tin-content are more prone to:more prone to:

Cracking than tin/lead, due to the tensile Cracking than tin/lead, due to the tensile strength and lower ductility.strength and lower ductility.Tin Whiskers in the event that the alloy-Tin Whiskers in the event that the alloy-balance is altered by metals content and balance is altered by metals content and fluctuation over time.fluctuation over time.Tin/Copper Intermetallics developing Tin/Copper Intermetallics developing between the tin and copper reaction.between the tin and copper reaction.

PCB ASSEMBLY PROCESSPCB ASSEMBLY PROCESSSMT Reflow (Recommended alloys: 96.5Sn/3.5Ag, SAC Alloys)SMT Reflow (Recommended alloys: 96.5Sn/3.5Ag, SAC Alloys)

Higher temperature and longer time profiles are necessary Higher temperature and longer time profiles are necessary to accommodate the higher melt-point of Lead-Free alloys.to accommodate the higher melt-point of Lead-Free alloys.Components, sensitive to high temperatures, must be Components, sensitive to high temperatures, must be carefully monitored to ensure that over-heating does not carefully monitored to ensure that over-heating does not affect reliability.affect reliability.Once established, thermal profiling must be strictly Once established, thermal profiling must be strictly adhered to, to ensure consistent PCB outputadhered to, to ensure consistent PCB output

Wave Soldering (Recommended Alloy: 99.3Sn/0.7Cu*)Wave Soldering (Recommended Alloy: 99.3Sn/0.7Cu*)Solder pots formulated for Tin/Lead solders must be Solder pots formulated for Tin/Lead solders must be replaced or retrofit with a special lining to ensure that the replaced or retrofit with a special lining to ensure that the tin does not corrode, or ‘eat-away’, at the metal-lining of tin does not corrode, or ‘eat-away’, at the metal-lining of the pot and corrupt the solder.the pot and corrupt the solder.Solder temperature must be raised from 235-250Solder temperature must be raised from 235-250ººC to 260-C to 260-290290ººC (or higher) to create similar flow action to the C (or higher) to create similar flow action to the tin/lead solder onto, and up into, the PCB leads and joints.tin/lead solder onto, and up into, the PCB leads and joints.Higher solder temperatures create greater dross than the Higher solder temperatures create greater dross than the lower temperature of the Tin/Lead solders.lower temperature of the Tin/Lead solders.The use of nitrogen on the solder bath can greatly improve The use of nitrogen on the solder bath can greatly improve flow and reduce dross content on the solders.flow and reduce dross content on the solders.

*Ask Superior Flux about this alloy vs. SAC and other alloy recommendations.*Ask Superior Flux about this alloy vs. SAC and other alloy recommendations.

SOLDER PASTES AND SOLDER PASTES AND FLUXESFLUXESSMT REFLOWSMT REFLOW

Conventional solder paste mediums can, and should be Conventional solder paste mediums can, and should be used, for all Lead-Free solder alloys and provide:used, for all Lead-Free solder alloys and provide:

No slumping.No slumping. No tomb-stoning No tomb-stoning No white residues on PCBs No white residues on PCBs Non-halide Activation systemNon-halide Activation system Consistent rheology, thixotropy, and viscosity.Consistent rheology, thixotropy, and viscosity. Clear, pin-testable residues with all No-Cleans.Clear, pin-testable residues with all No-Cleans.

WAVE SOLDERINGWAVE SOLDERINGFluxesFluxes

When going Lead-Free, consider a VOC-Free/Lead-Free When going Lead-Free, consider a VOC-Free/Lead-Free operation for workplace and environmental safety.operation for workplace and environmental safety.

No-Clean fluxes require more activity to meet the higher No-Clean fluxes require more activity to meet the higher temperature requirements of the Lead-Free Solder temperature requirements of the Lead-Free Solder process.process.

Water-Soluble fluxes, with higher solids contents and Water-Soluble fluxes, with higher solids contents and activity levels, can be used as drop-in fluxes.activity levels, can be used as drop-in fluxes.

VOC-Free and Alcohol-based fluxes all meet the process VOC-Free and Alcohol-based fluxes all meet the process and performance requirements for Lead-Free applications and performance requirements for Lead-Free applications in water-soluble and No-Clean formulations.in water-soluble and No-Clean formulations.

REFLOW OPTIONSREFLOW OPTIONS

Vapor PhaseVapor Phase Can use a fixed temperature of Can use a fixed temperature of

230230ººC with the Lead-Free Alloys, but C with the Lead-Free Alloys, but must maintain consistent process must maintain consistent process time at temperature phases.time at temperature phases.

ConvectionConvection Recommended temperature is 245-Recommended temperature is 245-

250250ººC and must maintain 45-60 C and must maintain 45-60 seconds at temperature.seconds at temperature.

LEAD-FREE REFLOW LEAD-FREE REFLOW PROFILEPROFILE

44ººC does not make a difference in C does not make a difference in Reflow Reflow

Profiles for the Lead-Free alloys.Profiles for the Lead-Free alloys.

PRICE OF SOLDER AND PRICE OF SOLDER AND COST OF OPERATIONSCOST OF OPERATIONS

Question anyone who tells you that the Lead-Free Question anyone who tells you that the Lead-Free conversion only costs ‘tenths of a penny per PCB joint’. conversion only costs ‘tenths of a penny per PCB joint’. Lead-Free alloys are more expensive than Tin/Lead and Lead-Free alloys are more expensive than Tin/Lead and the costs of the joints add up. But this is not the sole the costs of the joints add up. But this is not the sole cost added in the conversion:cost added in the conversion:

Engineering costs and the time invested in Engineering costs and the time invested in establishing and developing a consistent process establishing and developing a consistent process adds rapidly.adds rapidly.

Higher melt point of solders require hotter ovens and Higher melt point of solders require hotter ovens and solder pots, which increase capital equipment solder pots, which increase capital equipment operations and maintenance costs.operations and maintenance costs.

Potential for using nitrogen, an additional Potential for using nitrogen, an additional consumable, increases in Lead-Free wave solder consumable, increases in Lead-Free wave solder applications to reduce dross and extend solder life.applications to reduce dross and extend solder life.

Capital equipment costs, such as hotter ovens for Capital equipment costs, such as hotter ovens for reflow and retrofitted or new solder baths for wave reflow and retrofitted or new solder baths for wave soldering add-up.soldering add-up.

Rework and repair will likely increase at the outset of Rework and repair will likely increase at the outset of any operation/process change.any operation/process change.

SUMMARY OF LEAD-FREE SUMMARY OF LEAD-FREE SOLDERINGSOLDERING

The new Lead-Free solders are meeting legislation, The new Lead-Free solders are meeting legislation, not metallurgical/scientific discovery.not metallurgical/scientific discovery.If Lead-Free soldering offers so many advantages, If Lead-Free soldering offers so many advantages, and Lead-Free solders have been used in many and Lead-Free solders have been used in many applications for many years, why was it not chosen applications for many years, why was it not chosen as the base alloy until legislation forced it upon the as the base alloy until legislation forced it upon the electronics industry?electronics industry?All Lead-Free alloys will be more costly than the All Lead-Free alloys will be more costly than the Tin/Lead solder, as will operation and process costs.Tin/Lead solder, as will operation and process costs.All Lead-Free alloys that are being touted as the All Lead-Free alloys that are being touted as the ‘best choice’ have a higher melt point than ‘best choice’ have a higher melt point than 63Sn/37Pb solder.63Sn/37Pb solder.Higher solder temperature will push the Higher solder temperature will push the semiconductors and components to the edge of semiconductors and components to the edge of performance.performance.Multiple alloys are developing as the standard for Multiple alloys are developing as the standard for SMT and Wave Soldering, but the industry, as a SMT and Wave Soldering, but the industry, as a whole, have not formulated a global standard for the whole, have not formulated a global standard for the solder alloys and performance characteristics.solder alloys and performance characteristics.

CONCLUSION CONCLUSION KEEP-IT-SIMPLE- KEEP-IT-SIMPLE-

SOLDERINGSOLDERINGSMT ReflowSMT Reflow

The sole long proven alloy that meets Lead-Free requirements The sole long proven alloy that meets Lead-Free requirements is 96.5Sn/3.5Ag. It is a binary alloy with a true Eutectic of is 96.5Sn/3.5Ag. It is a binary alloy with a true Eutectic of 221221ººC.C.If a SAC Alloy is the specification that must be met, the If a SAC Alloy is the specification that must be met, the closest alloy to the Tin/Silver Eutectic is 96.5Sn/3.0Ag/0.5Cu. closest alloy to the Tin/Silver Eutectic is 96.5Sn/3.0Ag/0.5Cu. The melt point falls in the 218-220The melt point falls in the 218-220ººC range and is not C range and is not different, in terms of setting process guidelines, than the different, in terms of setting process guidelines, than the Tin/Silver. However, with copper as part of the solder, Tin/Silver. However, with copper as part of the solder, potential tin/copper Intermetallics and/or whiskers must be potential tin/copper Intermetallics and/or whiskers must be investigated.investigated.

Wave SolderingWave Soldering

A 99.3Sn/0.7Cu, due to cost and a wider process window A 99.3Sn/0.7Cu, due to cost and a wider process window available in this process, make this 227available in this process, make this 227ººC Eutectic alloy the C Eutectic alloy the preferred choice. However, with copper as part of the solder, preferred choice. However, with copper as part of the solder, potential tin/copper Intermetallics and/or whiskers must be potential tin/copper Intermetallics and/or whiskers must be investigated.investigated.Again, if a SAC alloy is specified, the 96.5Sn/3.0Ag/0.5Cu is Again, if a SAC alloy is specified, the 96.5Sn/3.0Ag/0.5Cu is recommended to maintain consistency of boards used in recommended to maintain consistency of boards used in Reflow and Wave soldering. With copper as part of the solder, Reflow and Wave soldering. With copper as part of the solder, potential tin/copper Intermetallics and/or whiskers must be potential tin/copper Intermetallics and/or whiskers must be investigated.investigated.

CONCLUSION CONCLUSION KEEP-IT-SIMPLE- KEEP-IT-SIMPLE-

SOLDERINGSOLDERINGSMT Reflow and Wave applications actually show that SMT Reflow and Wave applications actually show that there may be alloys that meet the specific Lead-Free there may be alloys that meet the specific Lead-Free soldering processes, while maintaining a simple soldering processes, while maintaining a simple process approach to the Lead-Free conversion. process approach to the Lead-Free conversion. The assembly processes must be evaluated from a The assembly processes must be evaluated from a number of different angles, and the final process must number of different angles, and the final process must bring these elements together. This includes:bring these elements together. This includes:

MetallurgicalMetallurgical ChemicalChemical TemperaturesTemperatures TimingTiming Acceptable output levelsAcceptable output levels How to minimize rework and repair How to minimize rework and repair

All PCBs must be given extended time, after initial All PCBs must be given extended time, after initial process evaluations have been conducted, to ensure process evaluations have been conducted, to ensure stability, long-life, and dependability of the PCBs that stability, long-life, and dependability of the PCBs that have been converted to the Lead-Free alloys.have been converted to the Lead-Free alloys.

LEAD-FREE, KISS PROCESSLEAD-FREE, KISS PROCESS(KEEP-IT-SIMPLE-(KEEP-IT-SIMPLE-

SOLDERING) SOLDERING) SUPERIOR FLUX & MFG. Co.SUPERIOR FLUX & MFG. Co.

6615 Parkland Blvd.6615 Parkland Blvd.Cleveland, OH 44139Cleveland, OH 44139