1. Ultra-High Density Magnetic Heads
Ken Gilleo – ET-Trends –
Nathan Kerrick, Cookson Electronics
MEMS & GMR
Technology
IMAPS 200 Denver
IBM MicroDrive: 351 MB
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2. OUTLINE Hard Disk Drive overview GR and GMR technology
Processing of hi-density heads
The role of temporary adhesives
HDD assembly
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3. The HDD (Hard Drive Disk)
Magnetic Disk
Positioner
Assembly
Mag. Head Assembly
Flex
Slider
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Courtesy of 3M Co

4. The HDD Head is key to Ultra-High Density
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5. HDD Technology Density increases surpass Moore’s Law.
MR and GMR are true breakthroughs.
Density records:
30 million bits/in2 December 1999 (commercial)
56 Gbits/in2 on April 2000 (lab)
Density limits have not been reached.
The technology is in the complex head.
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6. MR Head Technology I bias Magneto-Resistive Measure  as “read” signal
MR Effect: changes in electrical resistance by certain magnetically-soft when a magnetic field is turned on and off.
Shield
Shield
Soft Adjacent Layer
Contact
MR Sensing Layer
(changes resistivity)
Insulator Spacer
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7. GMR Head Technology I bias Giant Magneto-Resistive Shield Shield
GMR is a quantum effect and relies on electron spin states; >2X more sensitive than GR
Exchange Layer
Contact
Sensing Layer
Pinned Layer
(magnetically oriented)
Conducting Layer
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8. Write Head
COIL
Write Current
SLIDER
Coil
WRITE HEAD
Magnetic medium
Magnetic coil creates field that“writes” by orienting disk domain medium ON ON
Writing Current
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9. Merged Read/Write Head
Shield 2
WRITE
READ
Inductive Writing Element
Shield 1
MR or GMR Sensor
Rotating
Disk
N S
S N
N S
S N
N S
S N
READ
WRITE
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10. Building MR/GMR Head Elements
Semiconductor wafer fab
Wafer thinning
Wafer sawing
Element planing/polishing
Head assembly
Temporary
Adhesives
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11. First, some adhesive basics.
Mixing
Casting
Adhesive film
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Wafer-applied adhesive for die attach

12. POLYMERS - Engineered molecules -Tailored properties
Long-chained typically organic macromolecules made up of small repeating segments of monomers. Properties such as strength, flexibility, melting point and electrical characteristics can be ENGINEERED into the polymer.
POLYMERS
- Engineered molecules
-Tailored properties
- Highly compatible
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13. Thermoplastic Thermoset SOLID LIQUID SOLID SOLID
A polymer that is capable of softening to a flowable "liquid" when heated and hardened again when cooled.
SOLID
LIQUID
(flowable)
Thermoset
A polymer that is cross-linked so that melting does not occur under heating.
SOLID SOLID
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14. Polymer Types
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15. Thermoplastic as a temporary adhesive
Independent chain motion allows melting; debonding.
No cross-links
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16. can be dissolved or debonded without dissolving; swelling
No cross-links
Solvent Molecules
Thermoplastics
can be dissolved or debonded without dissolving; swelling
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17. Thermoplastic Adhesive FORMS
Film
sheets
rolls
Preform
any shape from disk to complex
Paste
for needle dispense
spin coat for wafer-level
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18. Resin & Filler Choices Fillers Resin bond ranges (thermoplastics):
Silver - Electrical & thermal conductivity
AlN, BeO - Thermal, but good dielectric
Unfilled - Insulating
Resin bond ranges (thermoplastics):
Low : 100oC
High :400oC
Typical: oC
Sometimes used to control static.
For Most HDD Processes
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19. -------------Thermoplastic -------------
Thermoset Adhesives
Not Temporary
Paste to
Substrate
Dispense
Place
Oven Cure
No Pressure Needed
Thermoplastic
Paste to
Substrate
Dispense
or Print
Place Part
Dry/Fuse
No Pressure Needed
Paste to
Wafer
Coat Wafer:
spin, print
Place Part
Heat & Pressure
DRY
FILM
Place Preform
Place Part
Heat & Pressure
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20. Application Processes
Liquid (paste)
Coat on wafer; spin, stencil, print; dry
Needle dispense on substrate or holder
Film
Laminate to wafer, then run processes
Preform (cut to wafer of row shape)
Bond to wafer
Bond to substrate
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21. Bonding Thermoplastics
Process Window
Viscosity
Glassy
State
Plastic State
Decomposition
Temperature Tg
Tmin
Tmax
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22. Thermoplastic PropertiesTg
Bond
Temp
Rework
Die
Shear
Thermal
Modulus
Which ones for HDD?
FILLERS C C
Cmin.
25C
WmC
PSI
none
-40
110
1700
0.2
60K
Ag, AlN
none
-25
160
2200
60K
Ag, AlN
none 45
170
2600
500K
Ag, AlN
none 98
170
3000
400K
None
145
210
150K
3800
0.22
Ag, AlN
none
180
350
4000
360K
None
280
400
4900
0.25
370K
Each row is a different polymer
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23. Bond Strength of Die Attach Adhes.
SUBSTRATE
CONDITIONING
INITIAL BOND
FINAL BOND
Ceramic
150oC, 1000 hrs.
2500 PSI
4800 PSI
Au-plated
150oC, 1000 hrs.
3100PSI
4900 PSI
Ceramic Al
150oC, 1000 hrs.
4100 PSI
4500 PSI
85%RH, 85oC,
Ceramic
2500 PSI
1800 PSI
1000 Hrs.
Au-plated
85%RH, 85oC,
3100 PSI
2600 PSI
Ceramic
1000 Hrs.
85%RH, 85oC, Al
4100 PSI
3600 PSI
1000 Hrs.
-65oC to 150oC,
Ceramic
2500 PSI
4000 PSI
500 cycles
Au-plated
-65oC to 150oC,
3100 PSI
3700 PSI
Ceramic
500 cycles
-65oC to 150oC, Al
4100 PSI
4800 PSI
500 cycles
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Bonding: 180C/ 10sec, 135g; .080" x .080" Ni/Au Kovar

24. Removal Options Heat element area Peel off parts
Immerse assembly in solvent
Remove parts
Rinse in solvent
Preferred for HDD work
SOLVENT
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25. Wafer Lapping (thinning & polishing)
Attach wafer to lava stone with temporary adhesive.
HDD Wafer
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26. Wafer Lapping Process Holder Lava Rock Wafer Grinding Media Temporary
Adhesive
Rotation
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27. Slicing Temporary adhesive 1. Heat Bond Wafer 2. Slice into Rows
3. Debond with Solvent
(sawing into rows)
Temporary adhesive
Rows formed after slicing
ROW of
Heads before
singulating
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28. Lapping & Edge Polishing
1. Dispense Adhesive
2. Mount Rows
3. Bond by heating
Adhesive
Paste
Automatic Dispenser
- Speedline
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29. Row Bonding Step Rotate 90o with cut, or rough side facing up.
(part of lapping & polishing)
Rotate 90o with cut, or rough side facing up.
Temporary Adhesive
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30. Rows are planarized/leveled/lapped
Debond in solvent
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31. Finished rows are sliced into head elements
Use temporary adhesive
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32. HDD Assembly
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33. Cheers for HDD Industry
Conclusions
HDD Beats Moore’s Law and IC industry
The breakthrough was GMR
MEMS is playing a role
Density limits have not been reached
Photonics is being added
Expect continuous density increases
73 GB
IBM
Cheers for HDD Industry
© ET-Trends LLC