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ELECTRONICS MANUFACTURING PROCESSESELECTRONICS MANUFACTURING PROCESSES
Assembly Raw MaterialsAssembly Raw Materials
R. Thompson
March 2, 2000
Surface Mount AdhesivesSurface Mount Adhesives
R. Thompson
March 2, 2000
Solder Paste
Printing
Component Placement Reflow
Dispense Adhesive
Component Insertion
Adhesive Cure
Print Adhesive
Wave Soldering
Hand Soldering /
Rework
Component Insertion
TEST
THE THE ASSEMBLY ASSEMBLY PROCESSPROCESS
PCB Cleaning
(when desired)
Encapsulation
(when desired)
R. Thompson
March 2, 2000
Surface Mount for Wave SolderingSurface Mount for Wave Soldering
R. Thompson
March 2, 2000
Surface Mount AdhesivesSurface Mount Adhesives
• UseUse: : adhering chip packages and adhering chip packages and discrete devices to printed circuit discrete devices to printed circuit boards prior to wave or reflow boards prior to wave or reflow solderingsoldering
•ChemistryChemistry– EpoxyEpoxy– AcrylicAcrylic
•ApplicationApplication– Automated syringe dispenseAutomated syringe dispense– Stencil printingStencil printing– Pin transferPin transfer
•Critical requirementsCritical requirements– Rheology to control dot profile, Rheology to control dot profile,
slump, and dispense speedslump, and dispense speed– Adhesion before and after cureAdhesion before and after cure– Dielectric propertiesDielectric properties– Water absorptionWater absorption
R. Thompson
March 2, 2000
Epoxy AdhesivesEpoxy Adhesives
• AdvantagesAdvantages– Low shrinkageLow shrinkage
– High “Green Strength”High “Green Strength”
– Good adhesion to a wide Good adhesion to a wide variety of substratesvariety of substrates
– Excellent dielectricExcellent dielectric
– Good chemical resistanceGood chemical resistance
• LimitationsLimitations– Require refrigerationRequire refrigeration
– Short “Pot Life”Short “Pot Life”
R. Thompson
March 2, 2000
Acrylic AdhesivesAcrylic Adhesives
• AdvantagesAdvantages– Very high-speed dispenseVery high-speed dispense
– Low modulusLow modulus
– Fast fixturing timeFast fixturing time
– No refrigerationNo refrigeration
• LimitationsLimitations– High-temperature cureHigh-temperature cure
– UV-assisted cureUV-assisted cure
– Limited solvent resistanceLimited solvent resistance
R. Thompson
March 2, 2000
• Pressure-TimePressure-Time
• Positive DisplacementPositive Displacement– Screw (Augur)Screw (Augur)
– PistonPiston
• Effective Rate – 50k dot/hourEffective Rate – 50k dot/hour
• Adjustable – Meets Variable Production NeedsAdjustable – Meets Variable Production Needs
• Adhesive Not Exposed to Environment Prior to Adhesive Not Exposed to Environment Prior to ApplicationApplication
R. Thompson
March 2, 2000
Syringe DispenseSyringe Dispense
Syringe DispenseSyringe Dispense
STAND-OFF
PRECISIONREGULATOR
SUBSTRATE
AIR INTO MACHINE
NEEDLE
Pressure Time System
R. Thompson
March 2, 2000
Syringe DispenseSyringe Dispense
Positive Displacement Pumps
R. Thompson
March 2, 2000
Stencil PrintingStencil Printing
R. Thompson
March 2, 2000
Stencil PrintingStencil Printing
• Current Chip-shooters Place Current Chip-shooters Place Components at 80k Chips/HourComponents at 80k Chips/Hour– Current syringe-dispense rates are Current syringe-dispense rates are
<< 50k dots/hour 50k dots/hour
• A Single Board Can Be A Single Board Can Be Stencil-Stencil-printedprinted in in << 12 Seconds 12 Seconds
R. Thompson
March 2, 2000
Stencil PrintingStencil Printing
Typical Metal Stencil
R. Thompson
March 2, 2000
Stencil PrintingStencil Printing
• AdvantagesAdvantages– Fast cycle timeFast cycle time
– All adhesive dots All adhesive dots placed placed simultaneouslysimultaneously
– All dots are the same All dots are the same heightheight
• LimitationsLimitations– Typically limited to Typically limited to
small-standoff small-standoff componentscomponents
– Stencil cleanliness Stencil cleanliness essentialessential
– Adhesive open to Adhesive open to environmentenvironment
R. Thompson
March 2, 2000
Design CriteriaDesign Criteria
R. Thompson
March 2, 2000
Electrically Conductive AdhesivesElectrically Conductive Adhesives
R. Thompson
March 2, 2000
FunctionFunction
• Make an electrical Make an electrical connection where solder connection where solder is not feasibleis not feasible
R. Thompson
March 2, 2000
Advantages of Conductive AdhesivesAdvantages of Conductive Adhesives
• Reduced Joint StressReduced Joint Stress– Reduced thermal mismatchReduced thermal mismatch– Adhesive able to “absorb” mechanical joint stressAdhesive able to “absorb” mechanical joint stress
• Process Costs (Process Costs (notnot material costs) material costs)• Bond Non-Solderable SubstratesBond Non-Solderable Substrates• ““Low Temperature” CureLow Temperature” Cure
– Reduced stress on temperature-sensitive componentsReduced stress on temperature-sensitive components• Environmental AspectsEnvironmental Aspects
– Lead FreeLead Free
R. Thompson
March 2, 2000
Electrically Conductive AdhesivesElectrically Conductive Adhesives
• Electrically Conductive FillersElectrically Conductive Fillers
• 2 Main Adhesive Types2 Main Adhesive Types– I. I. IsotropicIsotropic
– II.II. AnisotropicAnisotropic
R. Thompson
March 2, 2000
Electrically Conductive Filler TypesElectrically Conductive Filler Types
• SilverSilver– Most commonly usedMost commonly used
– Moderate cost Moderate cost
– Best combination of thermal and electrical Best combination of thermal and electrical conductivityconductivity
• GoldGold– High Cost High Cost
– Good thermal and electrical conductivityGood thermal and electrical conductivity
R. Thompson
March 2, 2000
Electrically Conductive Filler TypesElectrically Conductive Filler Types
• NickelNickel– Low CostLow Cost– Possible corrosion after agingPossible corrosion after aging– Difficult to get high electrical conductivity at low Difficult to get high electrical conductivity at low
viscosityviscosity
• CopperCopper– Will corrode even if coated with silverWill corrode even if coated with silver
• Carbon BlackCarbon Black– Low cost, but low electrical conductivityLow cost, but low electrical conductivity
R. Thompson
March 2, 2000
Isotropic AdhesivesIsotropic Adhesives
• Conductive In All Material AxesConductive In All Material Axes
• Solder “Replacement”Solder “Replacement”
R. Thompson
March 2, 2000
Isotropic AdhesivesIsotropic Adhesives
• AdvantagesAdvantages– Low-temperature Low-temperature
curecure
– Wide compatibilityWide compatibility
– Simplified assembly Simplified assembly processprocess
– Fine-pitch capableFine-pitch capable
• LimitationsLimitations– Needs improved Needs improved
thermomechanical thermomechanical fatigue resistancefatigue resistance
– Higher thermal & Higher thermal & electrical resistance electrical resistance than solderthan solder
– Not suitable for high-Not suitable for high-power applicationspower applications
R. Thompson
March 2, 2000
Anisotropic AdhesivesAnisotropic Adhesives
• ““Z-axis” ConductionZ-axis” Conduction
• Heat and Pressure CureHeat and Pressure Cure
• UV Fixture, Then HeatUV Fixture, Then Heat
• Films - Ordered ArrayFilms - Ordered Array
R. Thompson
March 2, 2000
Anisotropic AdhesivesAnisotropic Adhesives
Substrate (FR4, ITO glass or Flex)ConductivePad
Flip Chip or Flex. Circuit
Anisotropic Adhesive (Film or Paste)
Conductive Particle
Insulating Matrix
Flip Chip or Flex. Circuit
Substrate (FR4, ITO glass or Flex)
Heat + Pressure
R. Thompson
March 2, 2000
Anisotropic AdhesivesAnisotropic Adhesives
3440 Bond-line
Au bump on die
Conductive Particles
Top view
Side view
R. Thompson
March 2, 2000
Anisotropic AdhesivesAnisotropic Adhesives
• The primary limitation is that the resistance The primary limitation is that the resistance for each I/O will vary based on the for each I/O will vary based on the dispersion of the particlesdispersion of the particles
• This can be overcome with ordered This can be overcome with ordered anisotropic conductive adhesive films anisotropic conductive adhesive films (ACAF)(ACAF)
R. Thompson
March 2, 2000
Anisotropic FilmsAnisotropic Films
B e f o r e A f t e r
R. Thompson
March 2, 2000
Material TypesMaterial Types
• EpoxiesEpoxies
• SiliconesSilicones
R. Thompson
March 2, 2000
Epoxy AdhesivesEpoxy Adhesives
• BenefitsBenefits– Good adhesion to a wide variety of substratesGood adhesion to a wide variety of substrates
– High cohesive strengthHigh cohesive strength
– Low shrinkageLow shrinkage
– Good thermal and chemical resistanceGood thermal and chemical resistance
– High THigh Tgg possible possible
R. Thompson
March 2, 2000
Silicone AdhesivesSilicone Adhesives
• BenefitsBenefits– Low TLow Tgg (< -60°C) (< -60°C)
– Consistent performance over wide temp rangeConsistent performance over wide temp range
– Excellent high-temperature performanceExcellent high-temperature performance
– Low modulusLow modulus
– Good resistance to polar solventsGood resistance to polar solvents
R. Thompson
March 2, 2000
Soldering FluxSoldering Flux
R. Thompson
March 2, 2000
DipDip
• Used for Low to High VolumeUsed for Low to High Volume
• Lowest Cost for High VolumeLowest Cost for High Volume
• Complete EncapsulationComplete Encapsulation
• Masking is DifficultMasking is Difficult
R. Thompson
March 2, 2000
FluxesFluxes
• Types of FluxesTypes of Fluxes
• Flux ComponentsFlux Components
• J-STD-004 ClassificationsJ-STD-004 Classifications
• PackagingPackaging
• Application MethodsApplication Methods
• EvaluationEvaluation
R. Thompson
March 2, 2000
Types of FluxesTypes of Fluxes
• Rosin/ResinRosin/Resin – Abietic and Pimaric acidAbietic and Pimaric acid
– Relatively non-corrosiveRelatively non-corrosive
– Hard to pin testHard to pin test
• Water-solubleWater-soluble– Very corrosiveVery corrosive
• Low Solids (“No-clean”)Low Solids (“No-clean”)– Dicarboxylic acid activatorsDicarboxylic acid activators
– Easier to pin testEasier to pin test
– IPA-based and water-based (VOC-free)IPA-based and water-based (VOC-free)
R. Thompson
March 2, 2000
Flux ComponentsFlux Components
• SolventSolvent– Alcohol, water, etc.Alcohol, water, etc.
• ActivatorActivator– Amine hydrohalides, organic acids, basesAmine hydrohalides, organic acids, bases
– Reacts with metal oxidesReacts with metal oxides
• CarrierCarrier– Rosin/resin, polyols, high boiling solventsRosin/resin, polyols, high boiling solvents
– Coats metal surface, removes oxides & prevents Coats metal surface, removes oxides & prevents reoxidation, allows heat transferreoxidation, allows heat transfer
• AdditivesAdditives– Surfactants, thixotropes, biocide, anti-corrosion Surfactants, thixotropes, biocide, anti-corrosion
etc.etc. R. Thompson
March 2, 2000
J-STD-004 ClassificationsJ-STD-004 Classifications
• Military specifications have been replaced Military specifications have been replaced by Joint Industry Standardsby Joint Industry Standards– QQ-S-571 and MIL-F-14256 replace by QQ-S-571 and MIL-F-14256 replace by
J-STD-004, J-STD-005 and J-STD-006J-STD-004, J-STD-005 and J-STD-006
– MIL-STD-2000A replaced by J-STD-001BMIL-STD-2000A replaced by J-STD-001B
– New flux classifications:New flux classifications:
• ROROsin, sin, REREsin, sin, ORORganic and ganic and ININorganicorganic
• LLow, ow, MMedium and edium and HHigh activity levels igh activity levels
• 0 (halide-free) and 1 (halide)0 (halide-free) and 1 (halide)
R. Thompson
March 2, 2000
PackagingPackaging
• Liquid FluxLiquid Flux– Wave fluxingWave fluxing
– Spray fluxingSpray fluxing
– Foam fluxingFoam fluxing
– Hand soldering (rework)Hand soldering (rework)
• Paste Flux (without Solder)Paste Flux (without Solder)– Solder bumped chips, BGA packagesSolder bumped chips, BGA packages
• Paste Flux (with Solder)Paste Flux (with Solder)– ReflowReflow
– Paste-in-holePaste-in-hole
• Flux-core Wire SoldersFlux-core Wire SoldersR. Thompson
March 2, 2000
Spray FluxingSpray Fluxing
• UltrasonicUltrasonic
• PulsePulse
R. Thompson
March 2, 2000
Potting & Conformal CoatingPotting & Conformal Coating
• EncapsulantsEncapsulants
• ChemistryChemistry
• Cure MechanismsCure Mechanisms
• Application MethodsApplication MethodsR. Thompson
March 2, 2000
Solder Paste
Printing
Component Placement Reflow
Dispense Adhesive
Component Insertion
Adhesive Cure
Print Adhesive
Wave Soldering
Hand Soldering /
Rework
Component Insertion
TEST
THE THE ASSEMBLY ASSEMBLY PROCESSPROCESS
PCB Cleaning
(when desired)
Encapsulation
(when desired)
R. Thompson
March 2, 2000
EncapsulantsEncapsulants
• Conformal CoatingConformal Coating– Applied in a thin layer (5 to 10 mils)Applied in a thin layer (5 to 10 mils)
– Minimal stress relief and vibration dampingMinimal stress relief and vibration damping
• PottingPotting– Applied in a thick layer (over 125 mils)Applied in a thick layer (over 125 mils)
– Used for stress relief and vibration dampingUsed for stress relief and vibration damping
R. Thompson
March 2, 2000
Critical RequirementsCritical Requirements
• Electrically InsulatingElectrically Insulating– Good dielectricGood dielectric
• Thermally ConductiveThermally Conductive– ““Better than air”Better than air”
• Low-to-Moderate CTE and Low ModulusLow-to-Moderate CTE and Low Modulus– Distribute solder joint stressDistribute solder joint stress
– Necessary for fine-pitchNecessary for fine-pitch
• Good Adhesion To Each Interface MaterialGood Adhesion To Each Interface Material
R. Thompson
March 2, 2000
What They DoWhat They Do
• DielectricDielectric
• Environmental (Moisture) BarrierEnvironmental (Moisture) Barrier
• EncapsulantEncapsulant
• Conductor ProtectantConductor Protectant
• Solder Joint Stress ReliefSolder Joint Stress Relief
• Vibration DampingVibration Damping
R. Thompson
March 2, 2000
DielectricDielectric
• FunctionFunction– Prevents Arcing in Prevents Arcing in
High HumidityHigh Humidity
– Immobilizes Immobilizes ParticulatesParticulates
– Prevents Electrical Prevents Electrical ShortsShorts
– Retards CorrosionRetards Corrosion
R. Thompson
March 2, 2000
Moisture BarrierMoisture Barrier
• FunctionFunction– Breathable membraneBreathable membrane
– Prevents liquid contactPrevents liquid contact
– Prevents moisture Prevents moisture condensation at board condensation at board surfacesurface
– Provides solvent resistanceProvides solvent resistance
R. Thompson
March 2, 2000
EncapsulantEncapsulant
• FunctionFunction– Immobilized deviceImmobilized device
– Immobilizes debrisImmobilizes debris
– Supports ComponentsSupports Components
– Provides solder joints Provides solder joints stress distributionstress distribution
R. Thompson
March 2, 2000
Protects ConductorsProtects Conductors
• FunctionFunction– Insulative coatingInsulative coating
– Shields bare Shields bare conductorsconductors
– Reduces high-voltage Reduces high-voltage arcingarcing
R. Thompson
March 2, 2000
ChemistryChemistry
• AcrylicsAcrylics• EpoxyEpoxy• UrethanesUrethanes• SiliconesSilicones• Parylene (Paraxylylene)Parylene (Paraxylylene)
R. Thompson
March 2, 2000
Acrylic CoatingsAcrylic Coatings
• BenefitsBenefits– Good adhesion to Good adhesion to
many substratesmany substrates
– Good cohesive Good cohesive strengthstrength
– Wide variety of Wide variety of modulusmodulus
– Tolerant of Tolerant of hydrocarbon hydrocarbon contaminationcontamination
• LimitationsLimitations– 125°C upper 125°C upper
temperature limittemperature limit– Generally high Generally high
modulus materialsmodulus materials– Free-radical cure can Free-radical cure can
be oxygen-inhibitedbe oxygen-inhibited– Limited Solvent Limited Solvent
resistanceresistance– Typically solvent-Typically solvent-
basedbased R. Thompson
March 2, 2000
Epoxy CoatingsEpoxy Coatings
• BenefitsBenefits– Good adhesion to a Good adhesion to a
wide variety of wide variety of substratessubstrates
– High cohesive High cohesive strengthstrength
– Low shrinkageLow shrinkage
– Good thermal and Good thermal and chemical resistancechemical resistance
– High THigh Tgg possible possible
• LimitationsLimitations– Generally very rigidGenerally very rigid
– Long cure timesLong cure times
– Cure processes can be Cure processes can be cumbersomecumbersome
– Can have high Can have high chloride contentchloride content
– Not easily repairedNot easily repaired
R. Thompson
March 2, 2000
Urethane CoatingsUrethane Coatings
• BenefitsBenefits– General PurposeGeneral Purpose
– Can Be ReworkedCan Be Reworked
– Most Common Most Common CoatingsCoatings
• LimitationsLimitations– Most are solvent- Most are solvent-
basedbased
– Useful from –40°C to Useful from –40°C to +125°C+125°C
R. Thompson
March 2, 2000
Silicone CoatingsSilicone Coatings
• BenefitsBenefits– Low TLow Tgg (< -40°C) (< -40°C)
– Wide operating Wide operating temperature rangetemperature range
– Low ModulusLow Modulus
– Secondary cure Secondary cure mechanism availablemechanism available
• LimitationsLimitations– Low cohesive Low cohesive
strengthstrength
– Potential source of Potential source of contaminationcontamination
– Poor resistance to Poor resistance to some solventssome solvents
– Low abrasion Low abrasion resistanceresistance
R. Thompson
March 2, 2000
ParyleneParylene
• BenefitsBenefits– Very uniformVery uniform
– Excellent pin Excellent pin coveragecoverage
– Complete Complete encapsulationencapsulation
• LimitationsLimitations– Sensitive to Sensitive to
contaminantscontaminants
– Must be applied Must be applied under vacuumunder vacuum
– Expen$iveExpen$ive
R. Thompson
March 2, 2000
ParyleneParylene
R. Thompson
March 2, 2000
Cure MechanismsCure Mechanisms
• Air DryAir Dry– Most commonly used for aerosolsMost commonly used for aerosols
– Can take a long time Can take a long time
– Solvents/Odors (environmental concerns)Solvents/Odors (environmental concerns)
R. Thompson
March 2, 2000
Heat CureHeat Cure
• Typically High Typically High Energy Cost Energy Cost
• Most Common Form Most Common Form of Curing Solvent-of Curing Solvent-based Coatingsbased Coatings
R. Thompson
March 2, 2000
1.0E+01
1.0E+02
1.0E+03
1.0E+04
1.0E+05
1.0E+06
1.0E+07
0 20 40 60 80 100 120Time (Min.)
*
(po
ise) 100°C150°C
70°C
85°C
UV CureUV Cure
• High Speed / Very High Speed / Very EfficientEfficient
• Must Have Effective Must Have Effective Secondary Cure for Secondary Cure for Shadowed AreasShadowed Areas
• Are Typically More Are Typically More ExpensiveExpensive
R. Thompson
March 2, 2000
Cure MechanismsCure Mechanisms
• MoistureMoisture– Uses ambient or forced moisture to initiate the cure Uses ambient or forced moisture to initiate the cure
reactionreaction
– Most commonly found in silicone family as primary Most commonly found in silicone family as primary or secondary mechanismor secondary mechanism
R. Thompson
March 2, 2000
Application MethodsApplication Methods
• PottingPotting– Automated meter-mixAutomated meter-mix
– Hand-mix with vacuum de-airHand-mix with vacuum de-air
• Conformal CoatingConformal Coating– Manual sprayManual spray
– Automated sprayAutomated spray
– DipDip
– Chemical vapor deposition (CVD)Chemical vapor deposition (CVD)
R. Thompson
March 2, 2000
Automated Meter-MixAutomated Meter-Mix
R. Thompson
March 2, 2000
Manual SprayManual Spray
• Medium Volume ProductionMedium Volume Production• Low to Moderate Cost for High Low to Moderate Cost for High
VolumeVolume• Does Not Coat Under ComponentsDoes Not Coat Under Components• Masking Easier Than Dip CoatMasking Easier Than Dip Coat• Slightly More Maintenance Than Slightly More Maintenance Than
Dip CoatDip Coat• Parameters Affecting ThicknessParameters Affecting Thickness
– Feed systemFeed system– Line speed Line speed – Atomization pressureAtomization pressure– Material temperatureMaterial temperature
R. Thompson
March 2, 2000
Automated SprayAutomated Spray
• Moderate to High VolumeModerate to High Volume
• Often Eliminates Often Eliminates MaskingMasking
• Most Expensive Most Expensive Equipment for High Equipment for High VolumeVolume
• Higher Maintenance Higher Maintenance Than Dip or SprayThan Dip or Spray
R. Thompson
March 2, 2000
ThermalThermal ManagementManagement
R. Thompson
March 2, 2000
Why is it Needed?Why is it Needed?
• Packaging ReductionPackaging Reduction– Smaller componentsSmaller components– More powerMore power– Tighter spacingTighter spacing
• Heat Transfer EfficiencyHeat Transfer Efficiency– Improve heat dissipationImprove heat dissipation– Decrease thermal resistanceDecrease thermal resistance
• Component EffectivenessComponent Effectiveness– More efficient component outputMore efficient component output– Longer working life, increased reliabilityLonger working life, increased reliability
R. Thompson
March 2, 2000
• Mechanical FastenersMechanical Fasteners
• Thermal PadsThermal Pads– With mechanical fastenersWith mechanical fasteners
– With adhesivesWith adhesives
• GreaseGrease– With mechanical fastenersWith mechanical fasteners
• AdhesivesAdhesives
Methods to Dissipate HeatMethods to Dissipate Heat
R. Thompson
March 2, 2000
• DisadvantagesDisadvantages– Insufficient surface-Insufficient surface-
to-surface contactto-surface contact
– No electrical isolationNo electrical isolation
– Potential for Potential for looseningloosening
– Difficult to automateDifficult to automate
– Additional assembly Additional assembly processprocess
Mechanical FastenersMechanical Fasteners
• AdvantagesAdvantages– FastFast
– Simple to installSimple to install
R. Thompson
March 2, 2000
R. Thompson
March 2, 2000
Thermal PadsThermal Pads
• AdvantagesAdvantages– Fairly good Fairly good
conductivityconductivity
– Minimal void Minimal void formationformation
• DisadvantagesDisadvantages– Fasteners requiredFasteners required
– Release film removal Release film removal requiredrequired
– Pad relaxationPad relaxation
– Labor intensiveLabor intensive
R. Thompson
March 2, 2000
R. Thompson
March 2, 2000
Thermal GreaseThermal Grease
• AdvantagesAdvantages– Good conductivityGood conductivity
– Minimal void Minimal void formationformation
• DisadvantagesDisadvantages– Fasteners requiredFasteners required
– Poor electrical Poor electrical isolationisolation
– Collects debrisCollects debris
– Matrix migrationMatrix migration
– Labor intensiveLabor intensive
R. Thompson
March 2, 2000
R. Thompson
March 2, 2000
AdhesivesAdhesives
• AdvantagesAdvantages– Good conductivityGood conductivity
– Good electrical Good electrical isolationisolation
– Eliminates fastenersEliminates fasteners
• DisadvantagesDisadvantages– Accurate dispense Accurate dispense
requiredrequired
– Cure process requiredCure process required
– Material storage Material storage requiredrequired
R. Thompson
March 2, 2000
R. Thompson
March 2, 2000
R. Thompson
March 2, 2000
Curing MethodsCuring Methods• Activator CureActivator Cure
– Fast fixture strengthFast fixture strength– Thick sectionsThick sections
• UV CureUV Cure– Rapid cureRapid cure– On-demand cureOn-demand cure
• Activator and UVActivator and UV– Rapid cureRapid cure
• HeatHeat– Complete polymer cross-linkingComplete polymer cross-linking
• Activator, Heat, and UVActivator, Heat, and UV– Rapid fixture strengthRapid fixture strength– Rapid cureRapid cure
Material EvaluationMaterial Evaluation
R. Thompson
March 2, 2000
Material EvaluationMaterial Evaluation
• CharacterizationCharacterization
• CompatibilityCompatibility
R. Thompson
March 2, 2000
CharacterizationCharacterization
• Electrical PropertiesElectrical Properties– Surface Insulation Resistance (SIR)Surface Insulation Resistance (SIR)– Electromigration (Dendritic growth)Electromigration (Dendritic growth)
• Mechanical PropertiesMechanical Properties– Bond strength (Peel, Shear)Bond strength (Peel, Shear)– Modulus of Elasticity (Young’s Modulus)Modulus of Elasticity (Young’s Modulus)– Coefficient of Thermal Expansion (CTE)Coefficient of Thermal Expansion (CTE)
• Performance CharacteristicsPerformance Characteristics– Out-gassingOut-gassing– Moisture uptakeMoisture uptake
R. Thompson
March 2, 2000
CompatibilityCompatibility
• Flux ResidueFlux Residue
• Solder Mask (if present)Solder Mask (if present)
• Component Mold-release MaterialComponent Mold-release Material
• Solder Materials (Sn/Pb, No-lead, etc.)Solder Materials (Sn/Pb, No-lead, etc.)
R. Thompson
March 2, 2000
Testing MethodsTesting Methods
R. Thompson
March 2, 2000
Failure ModesFailure Modes
• Adhesion Depends On Surface Wettability and ConditionAdhesion Depends On Surface Wettability and Condition
• Two Failure ModesTwo Failure Modes
R. Thompson
March 2, 2000
Surface Insulation ResistanceSurface Insulation Resistance
• BellcoreBellcore– 25 mil lines25 mil lines
– 50 mil spaces50 mil spaces
– ~ 100 squares/comb~ 100 squares/comb
• IPCIPC– B-25 combB-25 comb– 12.5 mil lines and spaces12.5 mil lines and spaces– ~ 500 squares/comb~ 500 squares/comb
R. Thompson
March 2, 2000
Electromigration (Dendritic Growth)Electromigration (Dendritic Growth)
R. Thompson
March 2, 2000
Wetting BalanceWetting Balance
R. Thompson
March 2, 2000
