Basic die bonding process quality
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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.

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Basic die bonding process quality

Basic Die Bonding Process & Quality


Typical die bonding sequence

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

Epoxy dispensed from syringe

Die is picked up

Mylar delaminate from die

Vacuum to hold substrate

Vacuum to hold substrate

Die ready,

Vacuum apply

Ejector pin back to home

Ejector pin up


Typical die bonding sequence1

Typical 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 elements

Die 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….


Dispensing background information of epoxy

DispensingBackground Information of Epoxy

  • Function of epoxy

    • Adheres the die on substrate

  • Commonly-used epoxy

    • Typical Property


Dispensing background information of epoxy1

DispensingBackground Information of Epoxy

  • Paste Die Attach in Plastic Packages Adhesive Properties

    • Handling Properties

      • Rheology

      • Cure Condition

    • Assembly Properties

      • Bleed

      • Outgassing

      • Adhesion

    • Reliability Properties

      • Voids

      • Thermal / Electrical Conductivity

      • Ionic Contamination

      • Stress

    • Why handling is important


Dispensing substrate

DispensingSubstrate

  • Common substrates used

    • PCB

    • Leadframe

    • BGA

    • Ceramic

  • Considerations

    • Wetting properties

    • Pad to die ratio


Dispensing methodology

Dispensing Methodology

  • Time-Pressure-Vacuum System

  • Volumetric Dispensing

  • Rotating Disc


Dispensing methodology1

Dispensing Methodology

  • Time-Pressure-Vacuum System

    • A process of the application of compressed air in a preset period for the fluid dispensing

      • Apply Vacuum for removing the

        compressed air

      • Maintain the pressure

      • Prevent dripping & suck back

Vacuum

Pressure

Syringe with epoxy


Dispensing methodology2

Dispensing 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


Dispensing methodology3

Dispensing Methodology

  • Volumetric Dispensing

    • Process Principle

      Positive Displacement System

      (Piston Pump)

      • Apply compressed air

      • Pull up the piston to feed

        epoxy into the chamber

      • Switch the valve port

      • Piston is pushed to

        dispense epoxy

Syringe

Piston

Chamber

Valve


Dispensing methodology4

Dispensing 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 methodology5

Dispensing Methodology

  • Rotating Disc

    • Disc holding epoxy rotated with a stationary spreader

    • Level of epoxy thickness in disc can be adjusted

Stamping pin move in X & Z

Epoxy disc rotation


Dispensing application tools

Dispensing Application & 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 application tools1

Dispensing Application & Tools

  • Shower Head

    • Nomenclature of shower head

      • Holes

      • Hole diameter

      • Needle length

2-point stamping

4-point stamping


Dispensing application tools2

Dispensing 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)


Dispensing application tools3

Dispensing Application & Tools

  • Stamping pin

    • Nomenclature of stamping pin

      • pin tip radius

      • pin tip length

Tip radius

Stamping pin tip

Tip length


Dispensing application tools4

Dispensing Application & 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 application tools5

Dispensing Application & 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 method advantages disadvantages of different dispensing method

Effect of usage of Dispensing Method(Advantages & Disadvantages of Different Dispensing Method)

Advantages of different dispensing method

Disadvantages of different dispensing method


Effect of usage of dispensing method

Effect of usage of Dispensing Method

  • Common problems

    • Dripping

    • Tailing

    • Inconsistency

    • Void

Void Area

Photo taken by X-ray


Die attach process elements1

Die 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 place die picking tools collet

Pick & PlaceDie 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

Hi-temp Collet

Tungstein Carbide Collet

Rubber Collet

4-sided Collet

2-sided Collet


Pick place die picking tools collet1

Pick & PlaceDie 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 place die picking tools cap chuck pin

Pick & PlaceDie Picking Tools - Cap / 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 Cap

Ejector Assembly

Ejector Chuck & Pin


Pick place die picking tools cap chuck

Pick & PlaceDie Picking Tools – Cap / Chuck

  • Ejecting tools selection

    • It is base on die dimension

      • die width x die length

Definition of die dimension

Schematic diagram of chuck


Pick place die picking tools pin

Pick & PlaceDie Picking Tools - Pin

  • 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 place die picking tools pin1

Pick & PlaceDie Picking Tools - Pin

  • 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

Round pin

Sharp pin


Pick place wafer handling

Pick & PlaceWafer Handling

  • Different type of wafer ring / frame / wafer cassette

    • Wafer cassette

      • Disco

      • K & S

    • Wafer ring

      • Disco

      • K & S

      • Teflon

D company

K company


Pick place wafer tape material

Pick & PlaceWafer Tape Material

  • Different type of wafer tape material

    • Mylar tape

    • UV tape

    • Waffle pack

Blue Mylar Tape

Colourless UV Tape


Pick place wafer tape material1

Pick & PlaceWafer 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 place wafer tape material2

Pick & PlaceWafer 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 elements2

Die 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 issues

Die 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 causes

Common Problems & Possible Causes

  • Die Placement

Good Placement

Error Placement in X-Y direction


Die bonding quality specification bond placement

Reference Y axis

Actual die bonded position

Y

Reference X axis

X

Target bonding position

Die Bonding Quality SpecificationBond 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


Common problems possible causes1

Common 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 causes2

Common Problems & Possible Causes

  • Die Rotation

Good Rotation

Error Rotation


Die bonding quality specification die rotation

Reference Y axis

Reference X axis

Die Bonding Quality SpecificationDie 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

 = Angle of rotation viewed from above


Common problems possible causes3

Common 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 causes4

Common Problems & Possible Causes

  • Coverage

Good Coverage

Inadequate Coverage

Excessive Coverage


Die bonding quality specification epoxy coverage

L

Die

Epoxy

Epoxy not cover

all the perimeter

Die

Die Bonding Quality SpecificationEpoxy 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)

Epoxy Spread

Epoxy Coverage


Common problems possible causes5

Common 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 causes6

Common Problems & Possible Causes

  • Bondline Thickness & Fillet Height

Good BLT

Good BLT

Inadequate BLT

Excessive BLT


Die bonding quality specification epoxy build up

T

h

b

Die

Die Bonding Quality SpecificationEpoxy 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)

T = Die thickness

h = Epoxy build-up

b = Bondline thickness


Die bonding quality specification bondline thickness

Die

b

Epoxy

Die Bonding Quality SpecificationBondline Thickness

Example of BLT Result

Die size: 25 mil x 25 mil

Die thickness: 9 mil

Leadframe: SOT 23-3L

  • 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)

b = Bondline thickness under the die before curing


Common problems possible causes7

Common 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 causes8

Common Problems & Possible Causes

  • Die Tilt

Die Tilt

No Die Tilt

Die Tilt


Die bonding quality specification die tilt

D

Die Bonding Quality SpecificationDie 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 = Difference between highest and lowest corner of a die


Common problems possible causes9

Common 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 shear force

Force

Die

Die Bonding Quality SpecificationDie 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

      • Deviceis accepted only when the measured die shear strength force (F) with adhesion of die attach media residue falls into the following acceptance criteria:


Die bonding quality specification other c ommon e rrors i

Crack

Scratch found on die surface

Die bottom

Die is turned over

Die is put upside down

Die Bonding Quality SpecificationOther 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)


Die bonding quality specification other c ommon e rrors ii

Lead

Epoxy on lead

Epoxy on pad

Die

Epoxy

Epoxy on die

Die

Die

Pad

Pad

Die

Pad

Die Bonding Quality SpecificationOther 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 bonding quality specification other c ommon e rrors iii

Die

T

h

b

L

Die

Die Bonding Quality SpecificationOther Common Errors III

  • Epoxy tailing

    • Condition of reject:

      • Vertical tailing :

        • h > (1/2 T + b)

      • Horizontal tailing :

        • L > 4 mils

    • Inspection Method:

      • Visual inspection usingMicroscope (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)

T = Die thickness

b = Bondline thickness

Epoxy Tailing

Double Die


Die bonding quality specification other c ommon e rrors iv

No die found on the bond unit & no mark

No die and epoxy found on the bond unit

Die

Epoxy

Die Bonding Quality SpecificationOther 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)


Die bonding quality specification other c ommon e rrors v

Die Bonding Quality SpecificationOther 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)


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