What is electronic packaging?
What is electronic packaging?
What is electronic packaging?
What is electronic 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 2)
2) Signal distributionSignal distribution
3)
3) Thermal managementThermal management
4)
4) Design and testDesign and test
5)
The Key Link in the Chain
The Key Link in the Chain
Chip-to-Package
Package-to-Board
Silicon
Silicon
Ù
Ù
Package Relationship
Package Relationship
Silicon
Silicon
Ù
Ù
Package Relationship
Package Relationship
Silicon Pr oce ssor : Silicon Pr oce ssor :
Th e “br a in ” of t h e com pu t e r Th e “br a in ” of t h e com pu t e r ( ge n e r a t e s in st r u ct ion s)
( ge n e r a t e s in st r u ct ion s)
Pa ck a gin g: Pa ck a gin g:
Th e r e st of t h e body Th e r e st of t h e body
( Com m u n ica t e s in st r u ct ion s ( Com m u n ica t e s in st r u ct ion s ( Com m u n ica t e s in st r u ct ion s ( Com m u n ica t e s in st r u ct ion s t o t h e ou t side w or ld, a dds t o t h e ou t side w or ld, a dds pr ot e ct ion )
Package Assembly
Package Assembly
g
g
y
y
Die
Underfill Die bump
Substrate
Motherboard
Flip Chip Interconnect
Function of a Package: Function of a Package:
Provides housing for the Si Chip Provides circuit path from Si Chip Provides circuit path from Si Chip to Motherboard and outside w orld Manages heat generated by chip Prevents signal loss during
Package configurations
Configuration: Wirebond Configuration: Wirebond
Wire
Mold compound
Die Substrate
Adhesive
Configuration: Flip Chip
Ball
Di
Underfill Die bump
Configuration: Flip Chip
Substrate Die
Polymers in a Flip Chip Package
Polymers in a Flip Chip Package
y
y
p
p
p
p
g
g
Silicone Thermal Interface Silicone Sealant
Epoxy underfill
Die
Substrate
Die
Polymer in Wirebond Package
Polymer in Wirebond Package
Phenolic mold compound
y
g
y
g
Die
Substrate
Bismaleimide die attach
Demand For Polymer
Demand For Polymer
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
High dimensional stabilityHigh dimensional stability
Excellent thermalExcellent thermal--oxidative resistance oxidative resistance
Good chemical resistanceGood chemical resistance
Low moisture absorptionLow moisture absorption
High mechanical strengthHigh mechanical strength
Excellent stiffnessExcellent stiffness
Excellent stiffnessExcellent stiffness
High compressive strengthHigh compressive strength
What kind of polymers used for
What kind of polymers used for
electronic applications?
electronic applications?
electronic applications?
electronic applications?
What are the important
What are the important
p
p
Polymers in a Flip Chip Package
Polymers in a Flip Chip Package
y
y
p
p
p
p
g
g
Silicone Thermal Interface Silicone Sealant
Epoxy underfill
Die
Substrate
Die
Bismaleimide Triazine/Epoxy core Epoxy solder resist
Underfill; epoxy resin + low CTE filler
Thermal I nterface material; silicone rubber + high thermal conductive filler Core of the Substrate; Bismaleimide/ epoxy + woven glass fabrics
Polymer in Thermal Packaging
Polymer in Thermal Packaging
Polymer in Thermal Packaging
Polymer in Thermal Packaging
Material that thermally bonds components in an enabling assembly to Material that thermally bonds components in an enabling assembly to
ensure good heat transfer path between the die and the enabling solution. ensure good heat transfer path between the die and the enabling solution. e su e good eat t a s e pat bet ee t e d e a d t e e ab g so ut o e su e good eat t a s e pat bet ee t e d e a d t e e ab g so ut o
TI M fillsTI M fills--up the interfacial gaps between 2 components ensuring a up the interfacial gaps between 2 components ensuring a
continuous path for conduction heat transfer. continuous path for conduction heat transfer.
TI M serves two functions on flip chip packagesTI M 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 away from the chip so that the chip will
function properly. function properly.
Absorb stressAbsorb stress due to the mismatch of thermal expansion between chip, due to the mismatch of thermal expansion between chip,
TIM
substrate and the I S (integrated heat spreader). substrate and the I S (integrated heat spreader).
IHS
Substrate
Heat sink
Die
Types of TI M
Types of TI M
TIM
TIM
Grease
(silicone/hydrocarbon oil
Polymer Metallic
(silicone/hydrocarbon oil
Polymer
Composite Metallic
Phase change materials
Elastomer G l Hybrid Solder
Elastomer Solder
TI M Mate ials
TI M Mate ials
TI M Materials
TI M Materials
Thermal grease Thermal grease - -- - is a silicone oil containing conductive fillers is a silicone oil containing conductive fillers such as aluminum, nickel or copper.
such as aluminum, nickel or copper.
Gels Gels - -- - A crosslinked silicone polymer filled w ith a metal A crosslinked silicone polymer filled w ith a metal ( typically aluminum or silver) or w ith a ceramic ( aluminum ( typically aluminum or silver) or w ith a ceramic ( aluminum oxide or zinc oxide) particles. Gels are greases that are
oxide or zinc oxide) particles. Gels are greases that are ) p) p gg cured to prevent them from migrating out of the material. cured to prevent them from migrating out of the material.
Elastomers Elastomers –– A thermally conductive adhesive pad that can A thermally conductive adhesive pad that can be cut into desirable shape/ pattern.
be cut into desirable shape/ pattern. be cut into desirable shape/ pattern. be cut into desirable shape/ pattern.
Polymer phase change materials Polymer phase change materials - -- - Materials that undergo a Materials that undergo a transition from solid to liquid phase w hen heat is applied. transition from solid to liquid phase w hen heat is applied. They are solids at room temperatures and thick liquids
They are solids at room temperatures and thick liquids They are solids at room temperatures and thick liquids They are solids at room temperatures and thick liquids ( paste
( paste-- like) at die operating temperatures.like) at die operating temperatures.
Solder TI M Solder TI M –– Metallic preform that has excellent bulk Metallic preform that has excellent bulk thermal conductivity and low melting point metal
Polymer in Substrate
Polymer in Substrate
y
y
Core material
Made out of multi- layer glass fiber w ith resin
w ith resin
Can have various specifications for the glass fiber dimensions and
layer count
C4 bumps
SR (Solder Resist) Via
Can also specify various types of resin ( eg. BT, epoxy, etc)
Function: provide stiffness to the substrate
substrate
Core PTH
(Plated Through Hole) with
plugging material material
What is an underfill?
What is an underfill?
What is an underfill?
What is an underfill?
Underfill
Die
Bump
I n flipI n flip--chip technology, the gap between substrate and chip technology, the gap between substrate and
Substrate
Ball
Flip Chip Ball Grid Array (FCBGA)
p
p pp gy,gy, g pg p
chip is underfilled with highly filled epoxy system chip is underfilled with highly filled epoxy system
High modulus, low CTE adhesive which couples the High modulus, low CTE adhesive which couples the die and substrate
die and substrate die and substrate 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 Prevents interconnect fatigue by applying
Mechanism of UF Encapsulation
The mechanism of underfill encapsulation for solder joint protection
Die
Solder joint
li At reflow
temperature
Substrate
At room temperature Cooling
Cooling
Underfill material
Substrate and chip are interlocked by underfill The strain on joint is converted to deformation
Cooling
j
Underfill Technology Options
Underfill Technology Options
C ill U d fill (CUF)
Flow of underfill material underneath die is due to
Capillary Underfill (CUF)
underneath die is due to capillary action.
1) Underfills are normally are premixed and supplied by supplier
2) Packed in plastic syringes, frozen packed at -40º C to prevent curing 3) I n shipping, these underfills need special handling) pp g, p g
Typical formulation and it’s
Typical formulation and it’s
function
function
function
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 flowg ,g ,
Approximation, particle size should not exceed 1/ 3 of the gap sizeApproximation, particle size should not exceed 1/ 3 of the gap size
ResinResin
Base material and to provide interfaces adhesionBase material and to provide interfaces adhesion
Hardener Hardener
HardenerHardener
To provide impact toughness and final propertyTo provide impact toughness and final property
CatalystCatalyst
I nitiate reaction and control xI nitiate reaction and control x--linking ratelinking rategg
ElastomerElastomer
To provide stress absorber and toughnessTo provide stress absorber and toughness
Additives:Additives:
Dye/ Pigment: Color Dye/ Pigment: Color
Dye/ Pigment: ColorDye/ Pigment: Color
Surfactant: homogeneitySurfactant: homogeneity
Various CUF Chemistries
Epoxy Chemistries Epoxy Chemistries
Epoxy
Epoxy--anhydride anhydride –– industry standard workhorseindustry standard workhorse Epoxy
Epoxy amineamine offers improved toughnessoffers improved toughness Epoxy
Epoxy--amine amine –– offers improved toughness, offers improved toughness, moisture resistance
moisture resistance Epoxy homopolymers
Epoxy homopolymers –– offers outstanding moistureoffers outstanding moisture Epoxy homopolymers
Epoxy homopolymers offers outstanding moisture offers outstanding moisture resistance
resistance Epoxy
Epoxy--phenolic phenolic –– offers improved toughness, offers improved toughness, flexibility, adhesion
Key parameters to consider
Key parameters to consider
before selecting an underfill
before selecting an underfill
before selecting an underfill
before selecting an underfill
material
material
Flow propertiesFlow properties
Flow time/ flow Flow time/ flow
di t di t
distance distance
RheologyRheology
ViscosityViscosity
Thermal propertiesThermal properties
Modulating factor:
Filler loading/type
Thermal propertiesThermal properties
CTE1/ CTE2CTE1/ CTE2
TTgg
Gel timeGel time
Catalyst
Resin
Mechanical Mechanical
properties properties
ModulusModulus
T h T h
Resin
Toughener
ToughnessToughness
I onic contentsI onic contents
K, Cl, NaK, Cl, Na
EnvironmentEnvironment
Environment Environment
Ho
to select
nde fill mate ials
Ho
to select
nde fill mate ials
How to select underfill materials
How to select underfill materials
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 p/p/ pp solder bump/ substrate
solder bump/ substrate
2) High modulus leads to good mechanical 2) High modulus leads to good mechanical 2) High modulus, leads to good mechanical 2) High modulus, leads to good mechanical
properties properties
3) High glass transition temperature 3) High glass transition temperature 3) High glass transition temperature, 3) High glass transition temperature,
Ho
to select
nde fill mate ials
Ho
to select
nde fill mate ials
How to select underfill materials
How to select underfill materials
4) Good adhesion, improve product lifetime 4) Good adhesion, improve product lifetime 5) Low moisture absorption extend shelf life 5) Low moisture absorption extend shelf life 5) Low moisture absorption, extend shelf life 5) Low moisture absorption, extend shelf life 6) Low viscosity (fast flow)
6) Low viscosity (fast flow)
7) L i t t / f t i ti
7) L i t t / f t i ti
7) Low curing temperature/ fast curing time, 7) Low curing temperature/ fast curing time, can reduce cost, and less harmful to other can reduce cost, and less harmful to other
Thermoset Polymers
Thermoset Polymers
Silicones, polyimides, epoxies, phenolic, etc Silicones, polyimides, epoxies, phenolic, etc
R
O O
OH
Performance criteria
Performance criteria O O
Epoxy Epoxy Phenolic Phenolic Performance criteria Performance criteria Physical properties Physical properties R1 O Processability condition Processability condition Manufacturability procedure Manufacturability procedure R2 R3 O N y p y p
Reliability stress test Reliability stress test
C t
C t O
Imide/Maleimide Imide/Maleimide
Resin
Resin
Typically base resin is comprised of epoxy systemTypically base resin is comprised of epoxy system
Typically, base resin is comprised of epoxy systemTypically, base resin is comprised of epoxy system
i.e. naphthalene epoxy or bisphenol Fi.e. naphthalene epoxy or bisphenol F
Posses the epoxy groups, and are convertible in 3Posses the epoxy groups, and are convertible in 3--D pp y gy g p ,p , D
structure by variety of curing reactions. structure by variety of curing reactions.
I t provides good adhesion to the chip and substrate I t provides good adhesion to the chip and substrate
interfaces interfaces interfaces interfaces
Bisphenol resin is the most commonly used epoxy Bisphenol resin is the most commonly used epoxy
resin due to attractive properties; fluidity, low resin due to attractive properties; fluidity, low pp pp ;; y,y, shrinkage during cure & ease of processing shrinkage during cure & ease of processing
O O O O O O O O
Epoxies
Epoxies
Epoxies
Epoxies
Advantages Advantages
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
Disadvantages Disadvantages
l & k
l & k
Brittle & poor resistance to crack propagation Brittle & poor resistance to crack propagation
(therefore catalysts/ blend hardeners & reactive diluents are (therefore catalysts/ blend hardeners & reactive diluents are
Types of epoxy resins
Types of epoxy resins
Bisphenol, commercial epoxy Bisphenol, commercial epoxy Novolac (Phenol
Novolac (Phenol--formaldehyde)formaldehyde)-- PhenolicPhenolic Novolac (Phenol
Novolac (Phenol formaldehyde)formaldehyde) Phenolic Phenolic groups in a polymer are linked by a
groups in a polymer are linked by a
methylene bridge, provide highly cross methylene bridge, provide highly cross--methylene bridge, provide highly cross methylene bridge, provide highly cross
linked system, for high temp and excellent linked system, for high temp and excellent chemical resistance
chemical resistance chemical resistance chemical resistance Resole (base
Resole (base--catalyzed phenolcatalyzed
phenol--formaldehyde) high temp curing and formaldehyde) high temp curing and formaldehyde), high temp. curing, and formaldehyde), high temp. curing, and excellent chemical resistance
Crosslinking agents
Crosslinking agents
Crosslinking agents
Crosslinking agents
To provide a 3To provide a 3--D network system to enhance D network system to enhance
th t h f th d fill t i l th t h f th d fill t i l the toughness of the underfill material the toughness of the underfill material
i.e. amines, anhydrides, dicyanodiamides, etc.i.e. amines, anhydrides, dicyanodiamides, etc.
Plays an important role in determining the Plays an important role in determining the
properties of final cured epoxy properties of final cured epoxy
I t ff t th i it d ti it f th I t ff t th i it d ti it f th
I t effects the viscosity and reactivity of the I t effects the viscosity and reactivity of the
formulation, determined types of chemical bonds formulation, determined types of chemical bonds formed and degree of cross linking that will
formed and degree of cross linking that will formed and degree of cross linking that will formed and degree of cross linking that will occur (thus effect the Tg)
Effect of curing agent on the Tg of
Effect of curing agent on the Tg of
g g
g g
g
g
Polyimides
Polyimides
Polyimides
Polyimides
-- Superior thermal stability (up to 500º C)Superior thermal stability (up to 500º C)
E ll t l t i t
E ll t l t i t
-- Excellent solvent resistanceExcellent solvent resistance
-- Ease of applicationEase of application
-- Excellent mechanical propertiesExcellent mechanical properties
Disadvantages Disadvantagesgg
-- Affinity for moisture absorption due to Affinity for moisture absorption due to carbonyl polar groups of polyimide
carbonyl polar groups of polyimidey py p gg pp p yp y
-- High temp. cureHigh temp. cure
Pol imides
Pol imides
Polyimides
Polyimides
Polyimides are formed by a 2Polyimides are formed by a 2--stage processstage process
The first stage involves polycondensation of an The first stage involves polycondensation of an gg p yp y
aromatic dianhydride and aromatic diamine to aromatic dianhydride and aromatic diamine to form an intermediate poly(amic acid).
form an intermediate poly(amic acid).
Dehydradition of poly(amic acid) at elevated Dehydradition of poly(amic acid) at elevated
Bis
Bis maleimide T ia ine (BT)
maleimide T ia ine (BT)
Bis
Bis--maleimide Triazine (BT)
maleimide Triazine (BT)
Mainly produced by Mitshubishi Chemicals Mainly produced by Mitshubishi Chemicals
in Japan in Japanpp
High Tg (> 230High Tg (> 230º C)º C)
Good thermal
Good thermal mechanical propertiesmechanical properties
Good thermalGood thermal--mechanical propertiesmechanical properties
Silicones
Silicones
Silicones
Silicones
-- High thermal stabilityHigh thermal stability
-- Superior electrical, physical and chemical Superior electrical, physical and chemical
properties properties
p p
p p
-- Non corrosiveNon corrosive
Low level of ionic contamination (ionic Low level of ionic contamination (ionic
-- Low level of ionic contamination (ionic Low level of ionic contamination (ionic
contamination effect the electrical contamination effect the electrical reliability of the device
