EBP 412 Polimer KhursusEBP 412 Polimer Khursus

What is electronic What is electronic packaging?packaging?

Electronic packaging consists of 5 key Electronic packaging consists of 5 key function in electronics;function in electronics;

1)1) Power distributionPower distribution

2)2) Signal distributionSignal distribution

3)3) Thermal managementThermal management

4)4) Design and testDesign and test

5)5) ProtectionProtection

Package-to-Board

Chip-to-Package

Board-to-System

The Key Link in the ChainThe Key Link in the Chain

Silicon Silicon Package Relationship Package Relationship

Silicon Processor:Silicon Processor:The “brain” of the The “brain” of the computercomputer(generates instructions)(generates instructions)

Packaging:Packaging:The rest of the bodyThe rest of the body(Communicates instructions (Communicates instructions to the outside world, adds to the outside world, adds protection)protection)

Package AssemblyPackage Assembly

Flip Chip Interconnect

Substrate

Die

UnderfillDie bump

Motherboard

Function of a Package:

Provides housing for the Si Chip

Provides circuit path from Si Chip to Motherboard and outside world

Manages heat generated by chip

Prevents signal loss during transmission

Package configurations

Substrate

Die

UnderfillDie bump

Ball

Configuration: Flip Chip

Configuration: Wirebond

Die

Substrate

Wire

Adhesive

Ball

Mold compound

Epoxy underfill

Polymers in a Flip Chip PackagePolymers in a Flip Chip Package

Substrate

Bismaleimide Triazine/Epoxy core Epoxy solder resist

Die

Silicone Thermal InterfaceSilicone Sealant

Phenolic mold compound

Die

Polymer in Wirebond PackagePolymer in Wirebond Package

Substrate

Bismaleimide Triazine core Epoxy solder resist

Bismaleimidedie attach

The industry needs polymers to fulfill itsThe industry needs polymers to fulfill its High reliability requirementsHigh reliability requirements Demanding environment Demanding environment

Requirements Requirements High dimensional stabilityHigh dimensional stability Excellent thermal-oxidative resistance Excellent thermal-oxidative resistance Good chemical resistanceGood chemical resistance Low moisture absorptionLow moisture absorption High mechanical strengthHigh mechanical strength Excellent stiffnessExcellent stiffness High compressive strengthHigh compressive strength

Demand For PolymerDemand For Polymer

High performance thermoset polymersHigh performance thermoset polymers

What kind of polymers used What kind of polymers used for electronic applications?for electronic applications?

What are the important What are the important properties?properties?

Epoxy underfill

Polymers in a Flip Chip PackagePolymers in a Flip Chip Package

Substrate

Bismaleimide Triazine/Epoxy core Epoxy solder resist

Die

Silicone Thermal InterfaceSilicone Sealant

Underfill; epoxy resin + low CTE fillerThermal Interface material; silicone rubber + high thermal conductive fillerCore of the Substrate; Bismaleimide/epoxy + woven glass fabrics

Polymer in Thermal PackagingPolymer in Thermal Packaging

TIM

Material that thermally bonds components in an enabling assembly to ensure good Material that thermally bonds components in an enabling assembly to ensure good heat transfer path between the die and the enabling solution. heat transfer path between the die and the enabling solution. TIM fills-up the interfacial gaps between 2 components ensuring a continuous path for TIM fills-up the interfacial gaps between 2 components ensuring a continuous path for conduction heat transfer.conduction heat transfer.TIM serves two functions on flip chip packagesTIM serves two functions on flip chip packages Maximize the Maximize the transfer of heattransfer of heat away from the chip so that the chip will function away from the chip so that the chip will function properly.properly. Absorb stressAbsorb stress due to the mismatch of thermal expansion between chip, substrate and due to the mismatch of thermal expansion between chip, substrate and the IS (integrated heat spreader).the IS (integrated heat spreader).

IHS

Substrate

Heat sink

Die

TIM

Polymer Composite

Metallic

Grease(silicone/hydrocarbon oil

Elastomer SolderHybrid Composite

Types of TIMTypes of TIM

Gel

Phase change materials

TIM MaterialsTIM MaterialsThermal grease Thermal grease -- is a silicone oil containing conductive -- is a silicone oil containing conductive fillers such as aluminum, nickel or copper.fillers such as aluminum, nickel or copper.

Gels Gels -- A crosslinked silicone polymer filled with a -- A crosslinked silicone polymer filled with a metal (typically aluminum or silver) or with a ceramic metal (typically aluminum or silver) or with a ceramic (aluminum oxide or zinc oxide) particles. Gels are (aluminum oxide or zinc oxide) particles. Gels are greases that are cured to prevent them from greases that are cured to prevent them from migrating out of the material. migrating out of the material.

Elastomers Elastomers – A thermally conductive adhesive pad that – A thermally conductive adhesive pad that can be cut into desirable shape/pattern.can be cut into desirable shape/pattern.

Polymer phase change materials Polymer phase change materials -- Materials that -- Materials that undergo a transition from solid to liquid phase when undergo a transition from solid to liquid phase when heat is applied. They are solids at room temperatures heat is applied. They are solids at room temperatures and thick liquids (paste-like) at die operating and thick liquids (paste-like) at die operating temperatures.temperatures.

Solder TIM Solder TIM – Metallic preform that has excellent bulk – Metallic preform that has excellent bulk thermal conductivity and low melting point metalthermal conductivity and low melting point metal

Polymer in SubstratePolymer in Substrate

CorePTH(Plated

ThroughHole) withpluggingmaterial

C4 bumps

SR (Solder Resist)

Via

Ball padSolder Ball

Core materialMade out of multi-layer glass fiber with resin

Can have various specifications for the glass fiber dimensions and layer countCan also specify various types of resin (eg. BT, epoxy, etc)Function: provide stiffness to the substrate

What is an underfill?What is an underfill?

In flip-chip technology, the gap between substrate and chip is underfilled In flip-chip technology, the gap between substrate and chip is underfilled with highly filled epoxy systemwith highly filled epoxy system

High modulus, low CTE adhesive which couples the die and substrate High modulus, low CTE adhesive which couples the die and substrate Role of underfill:Role of underfill:

Provides reliability to the flip chip packageProvides reliability to the flip chip package By redistributing the stress due to CTE mismatch By redistributing the stress due to CTE mismatch Prevents interconnect fatigue by applying compressive stresses to the Prevents interconnect fatigue by applying compressive stresses to the

bumpsbumps

Underfill

Die

SubstrateBall

Bump

Flip Chip Ball Grid Array (FCBGA)

Mechanism of UF Encapsulation The mechanism of underfill encapsulation for solder joint protection

Substrate and chip are interlocked by underfill The strain on joint is converted to deformation Joint is compressed and protected by underfill

At reflow temperature

Cooling

Die

Solder joint

Substrate

Underfill material

At room temperature

Cooling

Underfill Technology OptionsUnderfill Technology Options

Flow of underfill material underneath die is due to capillary action.

Capillary Underfill (CUF)

1) Underfills are normally are premixed and supplied by supplier2) Packed in plastic syringes, frozen packed at -40ºC to prevent curing3) In shipping, these underfills need special handling4) Upon receiving the package, unpack the package, take out the syringes Quickly, and storein a freezerat temperature of -40ºC

Typical formulation and Typical formulation and it’s function it’s function

Filler, SiOFiller, SiO22 Control viscosity and CTEControl viscosity and CTE Must be small enough, so that it will not block flowMust be small enough, so that it will not block flow Approximation, particle size should not exceed 1/3 of the Approximation, particle size should not exceed 1/3 of the

gap sizegap size ResinResin

Base material and to provide interfaces adhesionBase material and to provide interfaces adhesion HardenerHardener

To provide impact toughness and final propertyTo provide impact toughness and final property CatalystCatalyst

Initiate reaction and control x-linking rateInitiate reaction and control x-linking rate ElastomerElastomer

To provide stress absorber and toughnessTo provide stress absorber and toughness Additives:Additives:

Dye/Pigment: ColorDye/Pigment: Color Surfactant: homogeneitySurfactant: homogeneity Adhesion promoter: increase interfacial adhesionAdhesion promoter: increase interfacial adhesion

Various CUF Chemistries

Epoxy Chemistries Epoxy Chemistries

Epoxy-anhydride – industry standard workhorseEpoxy-anhydride – industry standard workhorse

Epoxy-amine – offers improved toughness, Epoxy-amine – offers improved toughness,

moisture resistancemoisture resistance

Epoxy homopolymers – offers outstanding moisture Epoxy homopolymers – offers outstanding moisture

resistanceresistance

Epoxy-phenolic – offers improved toughness, Epoxy-phenolic – offers improved toughness,

flexibility, adhesionflexibility, adhesion

Key parameters to consider Key parameters to consider before selecting an before selecting an underfill materialunderfill material Flow propertiesFlow properties

Flow time/flow Flow time/flow distancedistance

RheologyRheology ViscosityViscosity

Thermal Thermal propertiesproperties CTE1/CTE2CTE1/CTE2 TTgg

Gel timeGel time Mechanical Mechanical

propertiesproperties ModulusModulus ToughnessToughness

Ionic contentsIonic contents K, Cl, NaK, Cl, Na

Environment Environment Moisture uptakeMoisture uptake

Modulating factor:

Filler loading/type

Catalyst

Resin

Toughener

How to select underfill How to select underfill materialsmaterials

1)Low CTE, can reduce thermal expansion 1)Low CTE, can reduce thermal expansion mismatch between chip/solder bump and mismatch between chip/solder bump and solder bump/substratesolder bump/substrate

2) High modulus, leads to good mechanical 2) High modulus, leads to good mechanical propertiesproperties

3) High glass transition temperature, 3) High glass transition temperature, withstand high temperature environmentwithstand high temperature environment

4) Good adhesion, improve product 4) Good adhesion, improve product lifetimelifetime

5) Low moisture absorption, extend 5) Low moisture absorption, extend shelf lifeshelf life

6) Low viscosity (fast flow)6) Low viscosity (fast flow)

7) Low curing temperature/fast curing 7) Low curing temperature/fast curing time, can reduce cost, and less time, can reduce cost, and less harmful to other componentsharmful to other components

How to select underfill How to select underfill materialsmaterials

Silicones, polyimides, epoxies, Silicones, polyimides, epoxies, phenolic, etcphenolic, etc

Thermoset PolymersThermoset Polymers

RO O

EpoxyEpoxy

OH

PhenolicPhenolic

R1

O

R2

R3

O

N

Imide/MaleimideImide/Maleimide

Performance criteriaPerformance criteria

Physical propertiesPhysical properties

Processability conditionProcessability condition

Manufacturability procedureManufacturability procedure

Reliability stress testReliability stress test

CostCost

ResinResin Typically, base resin is comprised of epoxy Typically, base resin is comprised of epoxy

systemsystem i.e. naphthalene epoxy or bisphenol Fi.e. naphthalene epoxy or bisphenol F

Posses the epoxy groups, and are convertible Posses the epoxy groups, and are convertible in 3-D structure by variety of curing reactions.in 3-D structure by variety of curing reactions.

It provides good adhesion to the chip and It provides good adhesion to the chip and substrate interfacessubstrate interfaces

Bisphenol resin is the most commonly used Bisphenol resin is the most commonly used epoxy resin due to attractive properties; epoxy resin due to attractive properties; fluidity, low shrinkage during cure & ease of fluidity, low shrinkage during cure & ease of processingprocessing

DGE of 1,6-dihydroxynaphthalene

OO OO

Bisphenol F

O

O

O

O

EpoxiesEpoxiesAdvantagesAdvantages excellent chemical and corrosion resistance excellent chemical and corrosion resistance superior mechanical propertiessuperior mechanical properties Excellent adhesionExcellent adhesion Low shrinkageLow shrinkage Reasonable material costReasonable material cost

DisadvantagesDisadvantagesBrittle & poor resistance to crack propagationBrittle & poor resistance to crack propagation

(therefore catalysts/blend hardeners & reactive (therefore catalysts/blend hardeners & reactive diluents are added into the foemula)diluents are added into the foemula)

Types of epoxy resinsTypes of epoxy resins

Bisphenol, commercial epoxyBisphenol, commercial epoxy

Novolac (Phenol-formaldehyde)- Novolac (Phenol-formaldehyde)- Phenolic groups in a polymer are Phenolic groups in a polymer are linked by a methylene bridge, linked by a methylene bridge, provide highly cross-linked system, provide highly cross-linked system, for high temp and excellent chemical for high temp and excellent chemical resistanceresistance

Resole (base-catalyzed phenol-Resole (base-catalyzed phenol-formaldehyde), high temp. curing, formaldehyde), high temp. curing, and excellent chemical resistanceand excellent chemical resistance

Crosslinking agentsCrosslinking agents To provide a 3-D network system to To provide a 3-D network system to

enhance the toughness of the underfill enhance the toughness of the underfill materialmaterial

i.e. amines, anhydrides, dicyanodiamides, i.e. amines, anhydrides, dicyanodiamides, etc.etc.

Plays an important role in determining the Plays an important role in determining the properties of final cured epoxyproperties of final cured epoxy

It effects the viscosity and reactivity of the It effects the viscosity and reactivity of the formulation, determined types of chemical formulation, determined types of chemical bonds formed and degree of cross linking bonds formed and degree of cross linking that will occur (thus effect the Tg)that will occur (thus effect the Tg)

Effect of curing agent on the Effect of curing agent on the Tg of epoxy resinTg of epoxy resin

PolyimidesPolyimides- Superior thermal stability (up to 500ºC)- Superior thermal stability (up to 500ºC)- Excellent solvent resistanceExcellent solvent resistance- Ease of applicationEase of application- Excellent mechanical propertiesExcellent mechanical propertiesDisadvantagesDisadvantages- Affinity for moisture absorption due to - Affinity for moisture absorption due to

carbonyl polar groups of polyimidecarbonyl polar groups of polyimide- High temp. cureHigh temp. cure- High cost High cost

Polyimides are formed by a 2-stage Polyimides are formed by a 2-stage processprocess

The first stage involves polycondensation The first stage involves polycondensation of an aromatic dianhydride and aromatic of an aromatic dianhydride and aromatic diamine to form an intermediate poly(amic diamine to form an intermediate poly(amic acid).acid).

Dehydradition of poly(amic acid) at Dehydradition of poly(amic acid) at elevated temp. yialds the polyimide (PI) elevated temp. yialds the polyimide (PI) structurestructure

PolyimidesPolyimides

Polymerization of a Polymerization of a polyimidepolyimide

Bis-maleimide Triazine (BT)Bis-maleimide Triazine (BT)

Mainly produced by Mitshubishi Mainly produced by Mitshubishi Chemicals in JapanChemicals in Japan

High Tg (> 230High Tg (> 230ºC)ºC) Good thermal-mechanical propertiesGood thermal-mechanical properties Good toughnessGood toughness

SiliconesSilicones- High thermal stabilityHigh thermal stability- Superior electrical, physical and Superior electrical, physical and

chemical propertieschemical properties- Non corrosiveNon corrosive- Low level of ionic contamination Low level of ionic contamination

(ionic contamination effect the (ionic contamination effect the electrical reliability of the deviceelectrical reliability of the device