“Soldering and Brazing” comparing with Diffusion bonding, Hot pressing, and Solid phase...

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““Soldering and Brazing” Soldering and Brazing” comparing withcomparing with 　　 Diffusion bonding, Hot pressing, Diffusion bonding, Hot pressing,

and Solid phase bondingand Solid phase bonding

Dr. Kunio TAKAHASHIDr. Kunio TAKAHASHI - Associate professor,- Associate professor,

Dept. of International Development Engineering,Dept. of International Development Engineering,Tokyo Institute of TechnologyTokyo Institute of Technology,Tokyo 152-8552, Japan,Tokyo 152-8552, JapanPhone/Fax:+81-3-5734-3915Phone/Fax:+81-3-5734-3915E-Mail:takahak@ide.titech.ac.jpE-Mail:takahak@ide.titech.ac.jphttp://www.ide.titech.ac.jp/~takahak/http://www.ide.titech.ac.jp/~takahak/

Prior to this lecture...Prior to this lecture...Activities of Japanese welding Activities of Japanese welding

communitycommunity

Organizations and their rolesOrganizations and their roles

Japanese system of education and Japanese system of education and certificationcertification

Movement around Asian Welding FederationMovement around Asian Welding Federation

About About lecturer’s ...lecturer’s ... Back groundBack ground

welding ( what is this ? )welding ( what is this ? ) Tokyo Institute of technologyTokyo Institute of technology

http://www.titech.ac.jp/http://www.titech.ac.jp/

Department of International Development Eng.Department of International Development Eng.NetworkNetwork beyondbeyond the the borderborder of of engineering fieldengineering field(community)(community) nationnationhttp://www.ide.titech.ac.jp/http://www.ide.titech.ac.jp/

Welcome to JapanWelcome to JapanAlready, you have joined to Already, you have joined to our Networkour Network..

Welding Technology, Welding Technology, as ”Inter-Field” Engineeringas ”Inter-Field” Engineering based onbased on Plasma physicsPlasma physics Electronics/Electrical Eng.Electronics/Electrical Eng. Power SourcePower Source Control Control (“self-controlled” is the best) (“self-controlled” is the best) = = Heat sourcesHeat sources Thermal Eng.Thermal Eng. Fluid dynamicsFluid dynamics Material scienceMaterial science Fracture mechanicsFracture mechanics

Physics of phenomenaPhysics of phenomena StandardStandard IndustryIndustry

roles of roles of SocietySociety

PlasmaPlasma ee---beam-beam LaserLaser Joule’s heatJoule’s heat etc…etc…

SteelsSteels(Materials)(Materials)- Making- Making- Design- Design

About this lecture “Brazing and Soldering About this lecture “Brazing and Soldering …”…”

Basic knowledgeBasic knowledge based on physics based on physics– PhenomenaPhenomena– Comparison with other welding processesComparison with other welding processes– What is and what is not clarified, theoretically ?What is and what is not clarified, theoretically ?– Recent progresses for physical understanding.Recent progresses for physical understanding.so,so,

You will understand...You will understand...– Why and How the process is used ?Why and How the process is used ? Experimental Experimental

trainingtraining– How the process can be modified ?How the process can be modified ?

Definition of brazing and solderingDefinition of brazing and soldering ExamplesExamples Comparison with other welding Comparison with other welding

processesprocesses Heat sourcesHeat sources Brazing filler metals and soldersBrazing filler metals and solders Fluxes and atmosphereFluxes and atmosphere Set up and joint shapeSet up and joint shape Phenomena in brazing and solderingPhenomena in brazing and soldering

– Wetting ( surface and interfacial tension )Wetting ( surface and interfacial tension )– Conduction of heatConduction of heat– DissolutionDissolution– FlowFlow– DiffusionDiffusion– DeformationDeformation– Oxidation - reduction reactionOxidation - reduction reaction– Solidification -> microscopic structureSolidification -> microscopic structure

ExerciseExercise

Contents Contents ofofthis lecturethis lecture

Please remember in your experimental training (Sept.19 ?)

Definition of the brazing and soldering.Definition of the brazing and soldering.

Joint is Joint is heatheateded distributing distributing filler metalfiller metal between base materials, between base materials, by by capillarycapillary action action below below solidus temperaturesolidus temperature of of base materialsbase materials.. Sometimes the joint is pressed.Sometimes the joint is pressed.

example of brazing example of brazing main engine LE7A main engine LE7A H2A rocket H2A rocket

Filler metalsFiller metals

BrazingBrazingmelting point of filler metal melting point of filler metal >> 723723 K K （（ 450 450 C, C, 840 840 F F ））

SolderingSolderingmelting point of filler metal melting point of filler metal << 723723 K K （（ 450 450 C, C, 840 840 F F ））

Capillary actionCapillary action

Wetting phenomenonWetting phenomenon

Surface tensionSurface tensionor or

Surface energySurface energy

A g-C u phase diagram .

Solidus temperatureSolidus temperature

phase diagramphase diagram

– Equilibrium Equilibrium phasephase

– Lever ruleLever rule

Solidus Liquidus

exampleexample

Soldering is key technologySoldering is key technologyin micro-electronics assemblyin micro-electronics assembly

exampleexample

Soldering is key technologySoldering is key technologyin micro-electronics assemblyin micro-electronics assembly

exampleexample “flip chip” technology“flip chip” technology

A ssessed P b-Sn phase diagram.

Solders for electronicsSolders for electronicsEutectic phasEutectic phas

ee conventional solderconventional solder

– Sn-PbSn-Pb

(Sn-(Sn-3838Pb Pb 180180CC))

lead free solderslead free solders– Sn-AgSn-Ag

(Sn-3.8Ag 220(Sn-3.8Ag 220CC))– Sn-InSn-In– Sn-BiSn-Bi– Sn-ZnSn-Zn– etc...etc...

Wire bonding by Kaijo

by H.Miyazaki, S.Saito, et.al...

Pb ( lead ) problem for healthPb ( lead ) problem for health

Mental development index – age ->Mental development index – age ->

Audition handicap - Pb in bloodAudition handicap - Pb in blood Blood pressure - Pb in bloodBlood pressure - Pb in blood

(positive correlation)(positive correlation)

Solders for electronicsSolders for electronicseutectic phaeutectic pha

sese conventional solderconventional solder

– Sn-PbSn-Pb

(Sn-38Pb 180(Sn-38Pb 180CC))

(Sn-3.8Ag 220(Sn-3.8Ag 220CC))– Sn-InSn-In– Sn-BiSn-Bi– Sn-ZnSn-Zn– etc...etc...

A ssessed A g-Sn phase diagram.Solders for electronicsSolders for electronics

conventional solderconventional solder– Sn-PbSn-Pb

(Sn-38Pb 180(Sn-38Pb 180CC))

(Sn-(Sn-3.83.8Ag Ag 220220CC))– Sn-InSn-In– Sn-BiSn-Bi– Sn-ZnSn-Zn– etc...etc...

Sn-Ag-Bi-Sb-CuSn-Ag-Bi-Sb-Cu Sn-Ag-InSn-Ag-In Sn-Ag-Bi-CuSn-Ag-Bi-Cu ......

A ssessed In-Sn phase diagram.

A ssessed Sn-B i phase diagram .

A ssessed Z n-Sn phase diagram.

Problems Pb free solderProblems Pb free solder

Melting pointMelting pointproblemsproblems in processesin processes almost solve almost solve

dd ViscosityViscosity

Corrosion Corrosion still under R still under R/D/D– Heating ironHeating iron in iron solderingin iron soldering– Solder bathSolder bath in reflow solderingin reflow soldering

exampleexample Al brazingAl brazing

exampleexample Ni brazingNi brazing

exampleexample Ag brazing of Stainless and Ag brazing of Stainless and Ceramics Ceramics

The highest technology is The highest technology is never used for space never used for space development.development.

The highest technology is The highest technology is the the combinationcombination of of conventional technologies.conventional technologies.

OptimizationOptimization & & breakthroughbreakthrough are based on are based on scientific understandingscientific understanding

Comparison with other welding or joining processesComparison with other welding or joining processes

melting base materials melting base materials ex. arc welding, resistance welding, etc…ex. arc welding, resistance welding, etc…

adding molten metals between base materialsadding molten metals between base materialsex. ex. brazingbrazing,, soldering soldering, etc..., etc...

not melting base materialsnot melting base materialsex. solid phase bonding, hot pressing, etc...ex. solid phase bonding, hot pressing, etc...

Diffusion bonding, Hot pressing, Diffusion bonding, Hot pressing, and Solid phase bondingand Solid phase bonding

Samples are Samples are – heatedheated,,

and and – pressedpressed..– Sometimes Sometimes metal metal

sheetsheet is inserted. is inserted.

“filler metal” ? in brazing

Another type of equipmentsAnother type of equipments Hot Isostatic Pressing (HIP)Hot Isostatic Pressing (HIP)

ExampleExample Ni alloyNi alloy

Requirements for joiningRequirements for joining– to bring atoms near stable inter-atomic distanceto bring atoms near stable inter-atomic distance

WettingWetting Heat transfer Heat transfer DissolutionDissolution FlowFlow DiffusionDiffusion DeformationDeformation OxidationOxidation ReductionReduction SolidificationSolidification

Phenomena Phenomena

Soldering and BrazingSoldering and Brazing

and alsoand also

Diffusion bondingDiffusion bonding Hot pressingHot pressing Solid phase bondingSolid phase bonding

Heat sources for brazing and solderingHeat sources for brazing and soldering

Oxyfuelgas flameOxyfuelgas flame ::Torch brazingTorch brazing/soldering , braze weldi/soldering , braze weldingng

Arc plasmaArc plasma :Arc brazing, braze welding:Arc brazing, braze welding Joule’s heatJoule’s heat :Resistance brazing:Resistance brazing Induction heatInduction heat :Induction brazing:Induction brazing Hot iron Hot iron ::Iron solderingIron soldering Ultrasonic waveUltrasonic wave :Ultrasonic soldering:Ultrasonic soldering Infrared rayInfrared ray :Infrared soldering:Infrared soldering Laser beamLaser beam :Laser beam soldering:Laser beam soldering

etc...etc...

Other terminology Other terminology for brazing and solderingfor brazing and soldering

AtmosphereAtmosphere Atmospheric brazing/solderingAtmospheric brazing/soldering

Vacuum brazingVacuum brazing

Furnace brazingFurnace brazing

Dip brazing/solderingDip brazing/soldering ex. of dip ex. of dip solderingsoldering– Metal bath brazing/soldering Metal bath brazing/soldering (in molten solder bath)(in molten solder bath)– Salt bath brazing/solderingSalt bath brazing/soldering (in flux)(in flux)

Other terminologyOther terminology

ProcedureProcedure Abrasion tinning & re-flowAbrasion tinning & re-flow Re-flow solderingRe-flow soldering Diffusion brazing/solderingDiffusion brazing/soldering

– Transient Liquid Phase bondingTransient Liquid Phase bonding

ambiguousambiguous

Diffusion bonding ( Hot pressing ) ?Diffusion bonding ( Hot pressing ) ?– Liquid phase diffusion bondingLiquid phase diffusion bonding : : iso-thermal solidificationiso-thermal solidification– Eutectic bondingEutectic bonding : no filler metal and: no filler metal and

intent to melt base materiaintent to melt base materialsls

ex. Re-flow used in electronicsex. Re-flow used in electronics

A ssessed P b-Sn phase diagram.Brazing/Soldering temperatureBrazing/Soldering temperature

= Liquidus temp. + = Liquidus temp. + 5050~~100100 K K ( because of viscosity )( because of viscosity )

Brazing filler metals and soldersBrazing filler metals and solders Brazing filler metals in Japanese Industrial Standards (Brazing filler metals in Japanese Industrial Standards (JISJIS))

Fluxes and atmosphereFluxes and atmosphere

FluxesFluxes Shielding Shielding Reduction of surfaces Reduction of surfaces

RequirementsRequirements wettablewettable easily removableeasily removable never harmfulnever harmful

Shielding gasShielding gas

WettabilityWettability

Set up and joint shapeSet up and joint shape

Phenomena in brazing and solderingPhenomena in brazing and soldering Wetting ( Surface and interfacial tension )Wetting ( Surface and interfacial tension ) Conduction of heatConduction of heat DissolutionDissolution FlowFlow DiffusionDiffusion DeformationDeformation Oxidation - reduction reactionOxidation - reduction reaction Solidification -> microscopic structureSolidification -> microscopic structure

Wetting driven by Wetting driven by surface and interfacial tensionsurface and interfacial tension

What determines equilibrium What determines equilibrium ( contact angle, meniscus, etc… ) ?( contact angle, meniscus, etc… ) ?– surface and interfacial tensionsurface and interfacial tension

Young’s equationYoung’s equation coslis

Surface and interfacial tensionSurface and interfacial tension(Surface tension is interfacial tension between material and vacuum.)(Surface tension is interfacial tension between material and vacuum.)

Surface ( interfacial ) tensionSurface ( interfacial ) tension– ex. soap filmex. soap film– ex. soap bubbleex. soap bubble

Force on meniscusForce on meniscusLaplace equationLaplace equation

Effect of gravity on meniscus Effect of gravity on meniscus on shape of filleton shape of fillet– Curvature changes with height.Curvature changes with height.

Surface (interfacial) tensionSurface (interfacial) tension and Surface (interfacial) energyand Surface (interfacial) energy

Internal energy and entropyInternal energy and entropy

1st law and 2nd law of thermodynamics1st law and 2nd law of thermodynamics

For bulk,For bulk,thereforetherefore

Variables for unit area of surfaceVariables for unit area of surface

For arbitrary area of surface,For arbitrary area of surface,

Therefore,Therefore,

dApdVTdSdU btottot

sbtot UUU sbtot SSS

bbb pdVTdSdU dATdSdU ss

AUU ss ASS

0ssss TdSdUAdATSU

ss TSU ss TdSdU

TpTSTpUTp

),(),(),(

Relation betweenRelation betweenSurface (interfacial) Surface (interfacial) tensiontension and Surface (interfacial) and Surface (interfacial) energenergyy

Surface contribution of internal energy is important.Surface contribution of internal energy is important. at 0 K, at 0 K,

TpTSTpUTp

),(),(),(

Surface ( interfacial ) entropy

Surface ( interfacial ) tension

Surface ( interfacial ) energy

Theoretical approach forTheoretical approach for Electronic theory Electronic theory surface tension at surface tension at 0 K0 K (quantum (quantum mechanics)mechanics)

SCF-Jellium

Stabilized jellium

Shifted step potential

Effective electron density parameter rm (Bohr)

2 3 4 5 6

200025003000

Shifted step potentialShifted step potentialK.Takahashi, and T.Onzawa,K.Takahashi, and T.Onzawa,Physical Review B, 48, 5689 (1993)Physical Review B, 48, 5689 (1993)

Stabilized jelliumStabilized jelliumJ.P.Predew, H.Q.Tran and E.D.Smith, J.P.Predew, H.Q.Tran and E.D.Smith, Phys. Rev. B, 42, 11627 (1990).Phys. Rev. B, 42, 11627 (1990).

SCF-jelliumSCF-jelliumN.D.Lang and W.Kohn, Phys. Rev. B, 1, 4555 (1970).

comparison by K.F.Wojciechovski, Surface Science, 437, 285-288 (1999)comparison by K.F.Wojciechovski, Surface Science, 437, 285-288 (1999)

trans.phase s,phonon s,electron s,s UUUU

Temperature dependence Temperature dependence ofof surface tension surface tension

Other contributionsOther contributions( phonon, phase transformation )( phonon, phase transformation )

=0, at 0 (zero) K.

Temperature T (K)

0 500 1000 15000.0

SCF-Jellium

Stabilized jellium

Shifted step potential

Effective electron density parameter rm (Bohr)Su

2 3 4 5 6

200025003000

Experimental Experimental measurements of measurements of surface tensionsurface tension

Experimental value Experimental value which theorists which theorists have been used, have been used, is…is… “ “extrapolatedextrapolated””

Data base of Data base of Surface- and interfacial- tensionSurface- and interfacial- tension

Experimental approaches• Cleavage method• Zero creep method• Thermal grooving method• Contact angle method ( sessile drop )• Adhesion force method• ...

Theoretical approaches• Quantum mechanics • Thermodynamics• Molecular dynamics• …

!! No experimental method gives perfect information by itself.!! No experimental method gives perfect information by itself.!! No theory gives perfect information by itself.!! No theory gives perfect information by itself.

Strategy by lecturer for...Strategy by lecturer for...

Conduction of heat (1)Conduction of heat (1)

Fourier's LawFourier's LawHeat flux (J/mHeat flux (J/m22s)s)Thermal conductivity (J/sKm, W/Km)Thermal conductivity (J/sKm, W/Km)Temperature (K)Temperature (K)

Diffusion equationDiffusion equationLatent heat (J/kgK)Latent heat (J/kgK)Density (kg/mDensity (kg/m33))Diffusion coefficient (mDiffusion coefficient (m22/s)/s)

Diffusion equation for Cartesian coordinate system Diffusion equation for Cartesian coordinate system

T grad q

TDTcct

T grad div grad div div1

Solutions for special boundary conditionsSolutions for special boundary conditions– Steady state (t=Steady state (t=), one dimensional), one dimensional

– Steady state (t=Steady state (t=), axially symmetric ), axially symmetric

– Steady state (t=Steady state (t=), center symmetric ), center symmetric

21)( CxCxT

21 ln)( CrCrT

211)( Cr

Basic solutions of diffusion equationBasic solutions of diffusion equation– one dimensionalone dimensional area heatingarea heating

for heat input for heat input QQ Q Q ((J/mJ/m))

– two dimensionaltwo dimensional linear heatinglinear heating

Q Q ((J/mJ/m22))

– three dimensionalthree dimensional point heatingpoint heating

Q Q ((J/mJ/m33))

41 222

-20 -10 0 10 20X-AXIS

DissolutionDissolution

increasingincreasing temperaturetemperature

– heatingheating– heat conductionheat conduction

concentrationconcentration– filler metalfiller metal– diffusiondiffusion

Solubility limitSolubility limit

Phase diagramPhase diagram

FlowFlow

WettabilityWettability driving forcedriving force

ViscosityViscosity dragging forcedragging force

Approximation “Liquid is always uniform.”Approximation “Liquid is always uniform.”

DiffusionDiffusion

Fick’s 1st law, Fick’s 2nd law, and Diffusion equationFick’s 1st law, Fick’s 2nd law, and Diffusion equation

Application of basic solutionsApplication of basic solutions

wherewhere

2exp2erf d

-10 0 10X-AXIS

DiffusionDiffusion

When material P is joined with iWhen material P is joined with insert (filler) metal, change in cnsert (filler) metal, change in concentration profiles across booncentration profiles across bond interface.nd interface.

and if and if below eutectic temperature…below eutectic temperature… joint of P and Q at Tjoint of P and Q at T0 0 ,…,… joint of P and Q at <Tjoint of P and Q at <Teutectic eutectic ,…,… Q is inserted,...Q is inserted,... etc...etc...

4erf1s

DeformationDeformation : Deformation around joint: Deformation around joint

Elastic deformationElastic deformation usually negligibleusually negligible Plastic deformationPlastic deformation Creep deformationCreep deformation Diffusional deformationDiffusional deformation

( diffusional creep )( diffusional creep )– surface diffusionsurface diffusion– boundary diffusionboundary diffusion– volume diffusionvolume diffusion

Solid phase bondingSolid phase bonding

Surface

Before contact

After plastic deformation

During creep deformation

Volume diffusion

Boundary diffusion

Surface diffusion (b)

0 5 10 15 20Bonding pressure Pb (MPa)

L=10 m, h00=1 m

L=1 m, h00=0.1 m

T=1000 K

Time required for perfect contact by deformationTime required for perfect contact by deformation

800 1000 1200

Bonding temperature T (K)

Plastic deformation

Creep deformation

Boundary diffusion

Volume diffusion

L=10m, h00=1m, Pb=10MPa

Dominant mechanismDominant mechanism

Elastic deformationElastic deformation Plastic deformationPlastic deformation Creep deformationCreep deformation Diffusional deformationDiffusional deformation

– surface diffusionsurface diffusion– boundary diffusionboundary diffusion– volume diffusionvolume diffusion

Why it is called “diffusion” bonding ?

800 1000 1200

Plastic deformation

Creep deformation

Boundary diffusion

Volume diffusion

L=1m, h00=0.1m, Pb=10MPa

800 1000 1200

Plastic deformation

Creep deformation

Boundary diffusion

Volume diffusion

L=10m, h00=1m, Pb=10MPa

If you want to use If you want to use diffusion for precise diffusion for precise

joining…joining…

popular popular roughnessroughness

If carefullyIf carefullyprepared...prepared...

Oxidation - reduction reaction between Oxidation - reduction reaction between fluxes fluxes andand metal metal

ex. Cu joint by Pb-Sn solder with HCl fluxex. Cu joint by Pb-Sn solder with HCl flux– Reduction of base metal surfaceReduction of base metal surface

– Shield of molten metalShield of molten metal

– Assist wettabilityAssist wettability

OHCuCl2HClCuO 22

22 HSnCl2HClSn

SnCuClSnClCu 22

Oxidation - reduction reaction between Oxidation - reduction reaction between atmosphereatmosphere and and metal metal

ex. atmospheric brazing with hydrogen gasex. atmospheric brazing with hydrogen gas

depending ondepending on Material (M)Material (M) Partial pressure of HPartial pressure of H22OO Liquid NLiquid N2 2 trap, Silica gel, trap, Silica gel,

etc...etc... Partial pressure of HPartial pressure of H22 Gas controlGas control

022 OHMHOM Gnmnnm

0OH lnln

RTnKRTGGG

SolidificationSolidification

Phase diagramPhase diagram

precipitation processprecipitation process

Microscopic structureMicroscopic structure

Mechanical propertyMechanical property– materialsmaterials– cooling ratescooling rates ex. Fe-C systemex. Fe-C system

A ssessed P b-Sn phase diagram.ex. Pb-Sn solderex. Pb-Sn solder eutectic phaseeutectic phase

Ball Grid Array (BGA)Ball Grid Array (BGA)in “flip chip” technologyin “flip chip” technology

Eutectic phase can be seen.Eutectic phase can be seen.

WeaknessWeakness of of low melting point materiallow melting point materialex. Pb-Sn solderex. Pb-Sn solder

CrackingCracking

Thermal effectThermal effect

150 150 C 100 hoursC 100 hours

Brittleness Brittleness of of inter-metallic compoundinter-metallic compoundex. Fe - Alex. Fe - Al Although Al is low melting point Although Al is low melting point

material,...material,...

A ssessed F e-A l phase diagram.

ex. filler metal for Al: Low melting point ex. filler metal for Al: Low melting point precise heat precise heat controlcontrol

A ssessed A l-C u phase diagram.

A ssessed A l-Si phase diagram. A ssessed A l-M g phase diagram.

A ssessed A l-Z n phase diagram.

Weld metal Weld metal solidification cracksolidification crack

ex. Alex. Al

at the at the end of the solidificationend of the solidification,,

the liquid vanish the liquid vanish very quicklyvery quickly

lack of liquidlack of liquid crackcrack

A ssessed A l-Si phase diagram .

ex. Ti - Ti bonding with Cu filmex. Ti - Ti bonding with Cu filmA ssessed T i-C u phase diagram .

Exercise 1Exercise 1Schematically, illustrate a concentration profile at 700 Schematically, illustrate a concentration profile at 700 C C

across the interface of diffusion couple (Ag/Cu), across the interface of diffusion couple (Ag/Cu), considering phase diagram.considering phase diagram.

Exercise 2Exercise 2Cu samples are bonded using insert film of Ag by keeping Cu samples are bonded using insert film of Ag by keeping

joint at 900 joint at 900 C. After liquid metal vanished, the joint was C. After liquid metal vanished, the joint was cooled to room temperature. Schematically, illustrate a cooled to room temperature. Schematically, illustrate a change of concentration profile across the interface.change of concentration profile across the interface.

Exercise 3Exercise 3Choose a percentage of Sn in Pb-Sn solder.Choose a percentage of Sn in Pb-Sn solder.And answer a soldering temperature. And answer a soldering temperature. A ssessed P b-Sn phase diagram.

Exercise 4Exercise 4List up deformation mechanisms for solid phase bonding.List up deformation mechanisms for solid phase bonding.

fin.fin.

ボツボツ

Conduction of heatConduction of heat

Application of basic solutionsApplication of basic solutions– Step distribution in t=0.Step distribution in t=0.

– Area heatingArea heating

– Linear heatingLinear heating

– Point heatingPoint heating

Thermal conductivity, Specific heat, Mass densityThermal conductivity, Specific heat, Mass densityTemperature dependence Temperature dependence Thermal diffusion Thermal diffusion

coefficientcoefficient

Surface and interfacial tensionSurface and interfacial tension(Surface tension is interfacial tension between material and (Surface tension is interfacial tension between material and

vacuum.)vacuum.)

Meniscus between flat planeMeniscus between flat plane

“Soldering and Brazing” comparing with Diffusion bonding, Hot pressing, and Solid phase...

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