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Basic Die Bonding Process & Quality. Typical Die Bonding Sequence. Epoxy dispensed on L/F. Die is bonded onto L/F. L/F. L/F index to bond position. x. x. Wafer. Die is picked up. Pad. Collet lower down to pick position. Collet at home position. Collet lower down to bond position. - PowerPoint PPT Presentation
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Basic Die Bonding Process & QualityBasic Die Bonding Process & Quality
Typical Die Bonding SequenceTypical Die Bonding Sequence
Wafer
Colletat homeposition
Die ready,Vacuum apply Ejector pin up
Collet lower down to pick position
Ejector pin back to home
Die is picked up
Die is picked up
Collet lower down to bond position
Die is bonded onto L/F
x xL/F
Epoxy dispensed on L/F
Pad
Vacuum to hold substrate
Epoxy dispensed from syringe
L/F index to bond position
Vacuum to hold substrate
Mylar delaminate from die
Typical Die Bonding SequenceTypical Die Bonding Sequence
B/A lower to pick level and position
Ejector rises up and B/A lift up the die by vacuum
B/A swings to bond level and position for bonding
Die Attach Process ElementsDie Attach Process Elements
Dispensing Materials: Epoxy, Substrate, Control system, Tools e.g.
nozzle, pin.. Process: selection of methodolgy, parameter setting for
different materials and quality requirements
Pick and Place Materials: Die, Mylar & frame, Ejector pin & cap, Collet Process: selection of tools and bonding platform
Bonding Quality Aspects: Die placement, Rotation, Tilting, Bond Line
Thickness….
PropertyAblestik
Ablebond 841-LMISR4QMI
QMI 509Hitachi
Hitachi 4730Sumitomo
Sumitomo CRM-1575CFiller Silver Silver Silver SilicaViscosity 8000 cps@25C 9000 cps@25C 89 Pa.s@25C 22 Pa.s@25CThixotropic Index 5.6 3.5 5.1 2.8Work Life 18 hours@25C 48 hours@25C N/A 48 hours@25CConductivity Conductive Conductive Conductive Non-conductiveRecommended Cure Cycle 1 hour@175C 15mins@150C 60sec@200C 3mins@150CDie Shear Strength 3500psi@25C
(for 80 sq. mils)36 kgf@25C
(for 300 sq. mils)11.39 Mpa@200C (for 80 sq. mils)
15.7RT@200C
Epoxy Type
DispensingDispensingBackground Information of EpoxyBackground Information of Epoxy
Function of epoxy Adheres the die on substrate
Commonly-used epoxy Typical Property
Paste Die Attach in Plastic Packages Adhesive Properties Handling Properties
RheologyCure Condition
Assembly PropertiesBleedOutgassingAdhesion
Reliability PropertiesVoidsThermal / Electrical ConductivityIonic ContaminationStress
Why handling is important
DispensingDispensingBackground Information of EpoxyBackground Information of Epoxy
DispensingDispensingSubstrateSubstrate
Common substrates used PCB Leadframe BGA Ceramic
Considerations Wetting properties Pad to die ratio
Dispensing MethodologyDispensing Methodology
Time-Pressure-Vacuum System Volumetric Dispensing Rotating Disc
Time-Pressure-Vacuum System A process of the application of compressed air
in a preset period for the fluid dispensingApply Vacuum for removing the
compressed airMaintain the pressurePrevent dripping & suck back
Dispensing MethodologyDispensing Methodology
Syringe with epoxy
VacuumPressure
Dispensing MethodologyDispensing Methodology
Time-Pressure-Vacuum System Draw Backs
Air compressibility Difficulty in regulating the dispensing consistently Internal pressure (Pi) changes with epoxy level
Different epoxy level changes air volume inside the syringe
Time for vacuum suction and compress air refilling is changing
Ease of dripping & sucking-in of air bubbles
Volumetric Dispensing Process Principle
Positive Displacement System (Piston Pump)Apply compressed airPull up the piston to feed
epoxy into the chamberSwitch the valve portPiston is pushed to
dispense epoxy
Dispensing MethodologyDispensing Methodology
Valve
Chamber
Piston
Syringe
Dispensing MethodologyDispensing Methodology
Volumetric Dispensing Advantages
True positive displacement dispensing No dripping Inconsistency comes from piston position error and
epoxy compressibility only High accuracy
Draw Backs Slow epoxy feed-in rate Complicated design and longer time & costly
maintenance
Dispensing MethodologyDispensing Methodology
Rotating DiscDisc holding
epoxy rotated with a stationary spreader
Level of epoxy thickness in disc can be adjusted
Epoxy disc rotation
Stamping pin move in X & Z
Dispensing Dispensing Application & ToolsApplication & Tools
Shower Head Dispensing A process for
dispensing the epoxy onto the leadframe with a fixed dispensing pattern according to the shower head size
Adopted to certain range of die size (30 x 30 ~ 150 x 150 mils)
Dispensing Dispensing Application & ToolsApplication & Tools
Shower Head Nomenclature of
shower head Holes Hole diameter Needle length
4-point stamping2-point stamping
Dispensing Application & ToolsDispensing Application & Tools
Epoxy Drum Stamping A process for
dispensing the epoxy onto the leadframe with a dispensed epoxy dot according to the stamping pin size
Adopted to small die only (7 x 7 ~ 20 x 20 mils)
Stamping pin Nomenclature of stamping pin
pin tip radiuspin tip length
Dispensing Application & ToolsDispensing Application & Tools
Tip length
Tip radius
Stamping pin tip
Dispensing Dispensing Application & ToolsApplication & Tools
Writing A process for
dispensing the epoxy onto the leadframe with a selectable dispensing pattern according to the die size
Adopted to wide range of die size (30 x 30 ~ 1000 x 1000 mils)
I.D. 0.33mm I.D. 0.21mm
I.D. 0.51mm
Dispensing Dispensing Application & ToolsApplication & Tools
Writing pin Nomenclature of writing
pin writing pin length outer diameter inner diameter
Cross Double-Y-Horizontal Double-Y-Horizontal
Effect of usage of Dispensing MethodEffect of usage of Dispensing Method(Advantages & Disadvantages of Different Dispensing Method)(Advantages & Disadvantages of Different Dispensing Method)
Advantages of different dispensing methodAdvantages of different dispensing method
Disadvantages of different dispensing methodDisadvantages of different dispensing method
Higher Dispensing speed Consistent dispensed pattern Ease of BLT & die tilt control Programmable dispensed pattern Small dot dispensingEpoxy Writing Die size dependent Good Good Able UnableEpoxy Drum Stamping Able Acceptable Acceptable Unable AbleShower Head Dispensing Able Not Good Not Good Unable Unable
Ease of tailing occurrence Epoxy contamination Needle Blockage VoidEpoxy Writing Most stable No Accpetable Most stableEpoxy Drum Stamping Easy to occur Yes No NoShower Head Dispensing Acceptable (viscosity dependent) No Easy to occur Easy to occur
Effect of usage of Dispensing MethodEffect of usage of Dispensing Method
Common problems Dripping
Tailing
Inconsistency
Void
Void Area
Photo taken by X-ray
Die Attach Process ElementsDie Attach Process Elements
Dispensing Materials: Epoxy, Substrate, Control system, Tools e.g.
nozzle, pin.. Process: selection of methodolgy, parameter setting for
different materials and quality requirements
Pick and Place Materials: Die, Mylar & frame, Ejector pin & cap, Collet Process: selection of tools and bonding platform
Bonding Quality Aspects: Die placement, Rotation, Tilting, Bond Line
Thickness….
Pick & PlacePick & PlaceDie Picking Tools - ColletDie Picking Tools - Collet
Pick-up tools - Collet In contact with die surface;
apply vacuum and pick up die from Mylar
Selection depends on die features e.g. size, adhesion method
Tungstein Carbide Collet
Hi-temp Collet
4-sided Collet 2-sided ColletRubber Collet
Pick & PlacePick & PlaceDie Picking Tools - ColletDie Picking Tools - Collet
Different configuration of collet rubber collet
commonly-used, for normal die bonding
2-sided & 4 sided collet for die with a special surface coating eliminate the possible contamination by the contact
between die and collet
hi-temp collet for eutectic bonding able to sustain the high temperature of leadframe
tungstein carbide collet for small die bonding (size range 20 mils below) aim to prevent the suck-back phenomenon after bonding longer lifetime
Pick & PlacePick & PlaceDie Picking Tools - Die Picking Tools - Cap / Chuck / PinCap / Chuck / Pin
Cap Act as platform
for holding the die
Holes for vacuum
Chuck Holding the pin
Pin Eject the die from
the Mylar
Ejector Chuck & Pin
Ejector Cap
Ejector Assembly
Pick & PlacePick & PlaceDie Picking Tools – Die Picking Tools – Cap / ChuckCap / Chuck
Ejecting tools selection It is base on die dimension
die width x die length
Definition of die dimension Schematic diagram of chuck
Pick & PlacePick & PlaceDie Picking Tools - Die Picking Tools - PinPin
Ejector Pin Notation Ejector pin is notated by the dimension of pin
tip radius Examples
R5 ejector pin ( for both sharp & round pin) tip radius = 0.125 mm = 5 mils
R3 ejector pin tip radius = 0.075 mm = 3 mils
R8 ejector pin tip radius = 0.200 mm = 8 mils
Pick & PlacePick & PlaceDie Picking Tools - Die Picking Tools - PinPin
Selection of ejecting tools (con’t) sharp pin & round pin
It is mainly purposed for small die (range below 20 mils) contact surface area between die and pin relatively small
compared to round tip prevent failure of pick-up
round pin It is mainly purposed for die with size greater than 20 mils able to prevent die crack since the tip is round and
pressure exerting on die back will not be too large may cause failure of pick-up
Sharp pin Round pin
Pick & PlacePick & PlaceWafer HandlingWafer Handling
Different type of wafer ring / frame / wafer cassette Wafer cassette
Disco K & S
Wafer ring Disco K & S Teflon
D company K company
Different type of wafer tape materialMylar tapeUV tapeWaffle pack
Pick & PlacePick & PlaceWafer Tape MaterialWafer Tape Material
Blue Mylar Tape
Colourless UV Tape
Pick & PlacePick & PlaceWafer Tape MaterialWafer Tape Material
Factors determine the degree of uniformity of wafer tape Die size
Large die size have a better tackiness
Surface finish of the wafer back Smooth surface of wafer back have higher tackiness
Duration of die adhesion to wafer tape The longer the die are on the tape, the more they
adhere
Pick & PlacePick & PlaceWafer Tape MaterialWafer Tape Material
Factors determine the degree of uniformity of wafer tape Exposure to UV light
The longer the exposure to UV light, the less they adhere
Storage condition It should be stored in a moderate condition
temp : 10-25 C humidity : 60-70%
Tape mounting process amount of tension should be even in both X & Y
direction
Die Attach Process ElementsDie Attach Process Elements
Dispensing Materials: Epoxy, Substrate, Control system, Tools e.g.
nozzle, pin.. Process: selection of methodolgy, parameter setting for
different materials and quality requirements
Pick and Place Materials: Die, Mylar & frame, Ejector pin & cap, Collet Process: selection of tools and bonding platform
Bonding Quality Aspects: Die placement, Rotation, Tilting, Bond Line
Thickness….
Die Bonding Quality IssuesDie Bonding Quality Issues Die Placement Die rotation Tilted die Epoxy build-up (fillet height) Epoxy coverage Bondline Thickness Die shear Other common errors
Lost die Cracked die Damage on die surface Skip bond unit Misorientated die Epoxy spread Epoxy outside bond area Excessive Epoxy Epoxy tailing Epoxy void
Common Problems & Possible CausesCommon Problems & Possible Causes
Die Placement
Good Placement Error Placement in X-Y direction
Die Bonding Quality Specification Die Bonding Quality Specification Bond PlacementBond Placement
Die placement Position shifted from
the target bond position
Condition of reject: (AD898 as example)
X & Y is out of the range 1 mil at Cp 1 in X or Y direction
Inspection method: Measurement using
Profile projector with 200X
Reference X axis
Reference Y axis
Target bonding position
Actual die bonded position
Y
X
Common Problems & Possible CausesCommon Problems & Possible Causes
Die Placement - con’t Too high bond level Error adjustment in 3-point alignment Too small BH Table Pick Delay Too small Bond Delay Non-leveled bond anvil block
Common Problems & Possible CausesCommon Problems & Possible Causes
Die Rotation
Good Rotation Error Rotation
Die Bonding Quality SpecificationDie Bonding Quality SpecificationDie RotationDie Rotation
Rotated die Angle rotated
reference to the target bond position
Condition of reject: (AD898 as example)
Angle is out of the range 0.5° at Cp 1.33 when viewed from above
Inspection Method: Measurement using
Profile projector with 200X
Reference X axis
Reference Y axis
= Angle of rotation viewed from above
Common Problems & Possible CausesCommon Problems & Possible Causes
Rotation - con’t Error adjustment in 3-point alignment Error adjustment in bondarm 90 degree motion Collet vacuum is not enough Too high bond level
Common Problems & Possible CausesCommon Problems & Possible Causes
Coverage
Good Coverage Inadequate Coverage Excessive Coverage
Die Bonding Quality Specification Die Bonding Quality Specification Epoxy CoverageEpoxy Coverage
Epoxy spread Condition of reject: (AD898 as
example) Epoxy is spread out of 10
mils measured from the die perimeter.
Inspection Method: Measurement using Profile
projector with 100X
Epoxy coverage Epoxy coverage area after die
bonded reference to the die area
Condition of reject: (AD898 as example) Epoxy coverage is less than
100% of die perimeter. Inspection Method:
Visual inspection using Microscope (30X)
Die
L
Epoxy
DieEpoxy not coverall the perimeter
Epoxy Spread
Epoxy Coverage
Common Problems & Possible CausesCommon Problems & Possible Causes
Coverage - con’t Inadequate coverage
Too high bond level Too short bond delay Non-leveled bond anvil block Too low bond anvil block level
Excessive coverage Too low bond level Too long bond delay Too high anvil block level
Common Problems & Possible CausesCommon Problems & Possible Causes Bondline Thickness & Fillet Height
Good BLT
Good BLT
Inadequate BLT Excessive BLT
Die Bonding Quality Specification Die Bonding Quality Specification Epoxy Build-upEpoxy Build-up
Epoxy build-up Also called Fillet
Height This is the epoxy
quantity build up onto the die
Condition of reject: (AD898 as example)
h > (1/2 T + b)
Inspection Method: Visual inspection
using Microscope (30X)
h
TDie
b
T = Die thickness h = Epoxy build-upb = Bondline thickness
Die Bonding Quality Specification Die Bonding Quality Specification Bondline ThicknessBondline Thickness
Bondline thickness Thickness of the
Epoxy -- measured from the LF to the bottom of die
Condition of reject: b out of the range 1
0.5 mil
Inspection Method: Measurement using
Hisomet microscope (200X)
Example of BLT ResultDie size: 25 mil x 25 mil
Die thickness: 9 milLeadframe: SOT 23-3L
Example of BLT ResultDie size: 25 mil x 25 mil
Die thickness: 9 milLeadframe: SOT 23-3L
Die
b
Epoxy
b = Bondline thickness under the die before curing
Common Problems & Possible CausesCommon Problems & Possible Causes
Bondline Thickness - con’t Inadequate BLT
Too high bond level Too short bond delay Too low bond anvil block
Excessive BLT Too low bond level Too long bond delay Too high anvil block level
Common Problems & Possible CausesCommon Problems & Possible Causes
Die Tilt
No Die Tilt Die Tilt
Die Tilt
Die Bonding Quality Specification Die Bonding Quality Specification Die TiltDie Tilt
Die Tilt Tilt up of the die
horizontal surface Condition of reject:
(AD898 as example)
D > 0.6 mil
Inspection Method: Visual inspection
using Hisomet Microscope (200X)
D
D = Difference between highest and lowest corner of a die
Common Problems & Possible CausesCommon Problems & Possible Causes
Die Tilt Non-leveled bondarm Uneven flatness of substrate & collet surface Non-leveled bond anvil block Error adjustment in 3-point alignment Inadequate suck bond & bond delay Dispensing position accuracy Dispensing pattern Measurement tools
Die Bonding Quality Specification Die Bonding Quality Specification Die Shear ForceDie Shear Force
Die Shear Force The minimum force requirement
to shear a die Depends on the die size area
Shear Strength A force sufficient to shear the die
from its mounting or equal to twice the minimum specified shear strength shall be applied to the die using appropriate apparatus
AD898 as example Die area < 6250 mils2
Minimum die shear strength (Fm) = 0.4 gf/mils2 x Die area (A) mils2 , where A = length x width
Die area ≥ 6250 mils2
Fm = 2500gf Acceptance Criteria
Device is accepted only when the measured die shear strength force (F) with adhesion of die attach media residue falls into the following acceptance criteria:
Die
Force
Die attach media residue
Acceptance criteria
Less than 10 % Measured die shear strength (F) 2 x Fm
Between 10% and 50%
Measured die shear strength (F) 1.25 x Fm
Larger than 50% Measured die shear strength (F) Fm
Die Bonding Quality Specification Die Bonding Quality Specification Other Common Errors IOther Common Errors I
Cracked Die Broken die Condition of reject:
Any kind of crack seen on surface Side penetrating the inner portion of die
Inspection Method: Visual inspection using Microscope (30X)
Damage on die surface Caused mark on die surface Condition of reject:
Any physical damage, such as scratch, found on die surface caused by die bonder.
Inspection Method: Visual inspection using Microscope (30X)
Mis-orientated die Condition of reject:
A bonded die is turned over. A bonded die is put upside down.
Inspection Method: Visual inspection using Microscope (30X)
Crack
Scratch found on die surface
Die is turned over Die is put upside down
Die bottom
Epoxy on lead
Lead
Pad
Die
Epoxy on die
Die
Pad
Epoxy on pad
Die
Die
Pad
Epoxy
Die Bonding Quality Specification Die Bonding Quality Specification Other Common Errors IIOther Common Errors II
Epoxy outside bond area Epoxy on die / lead / pad Condition of reject:
Epoxy is found outside bond area
Inspection Method: Visual inspection using
Microscope (30X)
Excessive Epoxy Condition of reject:
Excessive epoxy is found on the bond area.
Inspection Method: Visual inspection using
Microscope (30X)
Epoxy Outside Bond Area
Excessive Epoxy
Die
L
DieT hb
T = Die thicknessb = Bondline thickness
Die Bonding Quality Specification Die Bonding Quality Specification Other Common Errors IIIOther Common Errors III
Epoxy tailing Condition of reject:
Vertical tailing : h > (1/2 T + b)
Horizontal tailing : L > 4 mils
Inspection Method: Visual inspection using
Microscope (30X)
Double Die Condition of reject:
Two dice are bonded at the same bonding position with one stack on the other one.
Inspection Method: Visual inspection using
Microscope (30X)
Epoxy Tailing
Double Die
Die Bonding Quality Specification Die Bonding Quality Specification Other Common Errors IVOther Common Errors IV
Skip bond unit Condition of reject:
No die and epoxy is found on a bond unit
No die is present on the epoxy and no mark of die is observed.
Inspection Method: Visual inspection
using Microscope (30X)
No die found on the bond unit & no mark
No die and epoxy found on the bond
unit
Die
Epoxy
Die Bonding Quality Specification Die Bonding Quality Specification Other Common Errors VOther Common Errors V
Lost die Condition of reject:
No die is present on the epoxy but a mark of die is observed.
Inspection Method: Visual inspection
using Microscope (30X)
No die found but mark of die observed
Die
Epoxy
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