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iNEMI Nano-Attach
iNEMI Member
Report
Nano-Attach Team
4 September 2008
Strategy Issues Graphics
Project Lead:
Project Co-Lead:
Tactics Milestones and/or Deliverables Plan Actual
Thrust Area:
Novem
ber 08TIG:
Develop low or room temperature assembly processes that have the potential to improve field reliability, streamline manufacturing and reduce costs
• Research and develop nanotechnology based dry adhesive technologies (e.g., nano-velcro or biomimetic (“gecko foot”) systems) that can be used to replace solder attach systems
• Develop techniques to integrate nanostructures with electronic components & identify cost effective implementation schemes
• Limited global suppliers of nano-materials
• Novel technology with need to develop new evaluation methods / techniques
• Phase 1 completed. Need to decide whether to continue with Phase 2.
Hope Chik (Formerly Motorola)
None
• Phase 1: Define requirements necessary to adapt nano-structure attachment schemes in electronic assembly. Identify and evaluate currently available nano-attach technologies and explore these approaches
• Phase 2: Demonstrate feasibility with proof-of-concept material evaluation (mechanical, electrical, thermal properties)
• Phase 3: Demonstrate nano-attach assembly prototype
Miniaturization
Board Assembly
Nano-Attach Project
Initiative Launched
SOW & PS Completed
Define requirements for Electronic Systems
Nano-attachment benchmarking for Electronics Sysstems
Final Project Team Slide Presentation
Final Membership Slide Presentation 3Q-08
3Q-082Q-08
3Q-073Q-07
2Q-072Q-07
1Q-071Q-07
4Q-064Q-06
1
iNEMI Nano-Attach Team Members
Page 2
Executive Summary
&
Project Outline
Nano-Attach Team
26 June 2008
Table of Contents
1. Executive Summary & Project Outline
2. Background
3. Applications – Targeted
4. Requirements & Technology Gaps
5. Phase 2 Attributes
Page 4
Nano-Attach Project Goals
Page 5
Phase 2: Evaluation and
Proof-of-Concept
– Material study
– Design guidelines
– Assembly development
Phase 3: Demonstration
and Prototype
– Build working prototype
– Develop supply chain
Go / No Go
Go / No Go
Currently at this stage
• completed Phase 1
• pre-Phase 2
Phase 1: Discovery and Concept
Development
– Define application requirements
– Benchmarking nano-attach technology
– Cost effective implementation
Phase 1: Discovery and Concept Development
Deliverables:
– Publish design targets for industrial development
– Publish design targets derived from Phase 1 findings
• Generate interest in the electronics industry
• Attract new players
• Accelerate development
– Refine project plan, deliverables, and timeline for Phase 2
– Publish summary for iNEMI members
– Recommend go/no-go for Phase 2
Gate 1: Go / No Go
Issue: Is the material technology mature enough to have a high
probability of success in Phase 2?
Page 6
Phase 2: Evaluation and Proof-of-Concept
Deliverables:
– Define and develop evaluation vehicle(s)
– Define materials characterization methods
– Performance assessment using evaluation vehicle(s)
• Assembly
• Reliability
– Develop material design guidelines
– Publish summary of test results
– Refine project plan and timeline for Phase 3
– Publish summary for iNEMI members
– Recommend go/no-go for Phase 3
Gate 2: Go / No Go
Issue: Is the technology mature enough to have a high probability of
success in Phase 3?
Page 7
Phase 3: Demonstration and Prototype
Deliverables:
– Demonstrate prototype device
– Present prototype vehicle test results
– Supply chain identified
– Publish summary for iNEMI members
– Recommend next steps
Page 8
Background
&
Motivation
Nano-Attach Team
26 June 2008
Electronic Assembly Process: Example
Page 10
Drawbacks:
• Use of elevated temperatures (mass reflow, selective soldering, conductive adhesive curing, etc.)
• Introduces thermal excursions increasing reliability risks to components and boards
• Exacerbated with even higher temperature Pb-free assembly processes
• Individualized solutions for temperature-sensitive components
Assemblies
Screen
Component Placement
Mass Reflow
Prepared
boards
Solder paste
Parts
Biomimetic Inspiration
Page 11
E. Arzt, S. Gorb, and R.
Spolenak, “From Micro to
Nano Contacts in Biological
Attachment Devices”, PNAS,
100, 10603 (2003).
• Evidence in nature of the use of micro- and nano-scale features as the terminal
endings of the foot hairs
• Heavier species tend to exhibit finer adhesion structures
• Efficient attachment mechanism allows the species to climb walls or hang on ceilings
What is Nano-Attach Technology?
Page 12
Double-sided Attachment Scheme:
– Two sets of nanostructures are required
– One set of nanostructure on each
surface
– Examples:
– Hook & loop
– 2 hooks
board
component
Macro-scale hook & loop
nanostructures
Single-sided Attachment Scheme:
– One set of nanostructure on one surface
– Implementation:
• On board or on component
Adhesion Mechanisms:
– van der Waals
forces
– Mechanical
adhesion
• Entanglement
• Hook and loop
Adhesion Mechanism:
– van der Waals forces
The project is focusing on the single-side attachment approach
Van der Waals Forces
Page 13
• Intermolecular forces
• Present between any and every two surfaces
• Typical forces between 10 and 1,000 nN per contact point
– Material dependent
http://en.wikipedia.org/wiki/Van_der_Waals_force
Why do two objects tend not to stick together?
Major Reason Why?
• Lack of surface contact points
Definitions: Nomenclature
Page 14
Component
Substrate
Component InterfaceIntermediate layer(s) [optional]
Substrate interface
Nanostructure Interface
Intermediate layer(s) [optional]
Definitions: Chirality of Carbon Nanotubes
Page 15
Nanotube Structure Details: Chirality
Nanotubes are created by rolling up a hexagonal lattice of carbon (graphite). Rolling the lattice at different angles creates a visible twist or spiral in the nanotube's molecular structure, though the overall shape remains cylindrical. This twist is called chirality.
Based on the rolling angle, three types of nanotubes are possible: armchair, zigzag, or chiral. A thirty degree roll (green to blue) produces an armchair pattern and a zero degree roll (green to red) makes a zigzag. Any intermediate angle produces a chiral nanotube. The names 'armchair' and 'zigzag' refer to the pattern of carbon bonds around the tube's circumference.
The nanotube's chirality, along with its diameter, determine its electrical properties. The armchair structure has metallic characteristics. Both zigzag and chiral structures produce band gaps, making these nanotubes semiconductors.
http://nanopedia.case.edu/NWPage.php?page=nanotube.chirality
What is Nanotechnology?
Page 16
“What is Nano”, Nano 101, Forbes/Wolfe 2002Human hair: 50,000 – 100,000 nm
How does nanotechnology help in adhesion?
Page 17
Why do two surfaces tend not to stick together?
• Due to surface roughness
Number of Contact Points:
1,000,000,000 /cm2
1,000,000,000,000 /cm2 ??
Without nanotechnology:
With nanotechnology:
1,000,000 /cm2
Surface 1
Surface 2
Surface 1
Surface 2
Example of Nano-Attach Assembly Process
Page 18
Potential benefits with nanotechnology approach:
• Room temperature process
• Streamline manufacturing
• Improve field reliability
• Simplified rework
• Reduce cost
Assemblies
Screen
Component Placement
Mass Reflow
Prepared boards
Solder paste
Parts
XXX
Targeted
Applications &
Requirements
Nano-Attach Team
4 September 2008
Library of Opportunities: Potential Applications
Page 20
Mechanical / Structural:• Replacement of glue, screws, welding of sheets
• Packaging / housings
• Opto-electronic packaging
• Plug / connectors
Thermal Connections:• Heat sinks, thermal-electric, interconnects
• Fans
Discrete Components:• Resistors, capacitors, inductors, switches, OP amps, RF shield
• Leaded devices, SMTs
IC Chips:• Memory, microprocessors, power electronics, control modules, BGAs, flip chip
• Die attach, embedded packaging, 3D packaging
Specialty Parts:• Skin / tissue attachment
Library of Opportunities:Mechanical Requirements
Page 21
Mechanical Requirements
Adhesion Strength
ElectronicComponent
Skin / Tissue
Chip / BGA
ScrewsOpto-Electronics
Glue
Structural
Mechanical ThermalElectrical
increasing
Plug / Connectors
Heat sink
Modules / Board
Fan
Weld
Solder
Tape
Epoxy
Library of Opportunities:Electrical Requirements
Page 22
Electrical Requirements
Adhesion Strength
DiscreteComponent
IC Chip / BGAModule / Board
Opto-Electronics
increasing
Mechanical ThermalElectrical
Weld
Solder
Tape
Epoxy
Library of Opportunities:Thermal Requirements
Page 23
Thermal Requirements
Adhesion Strength
Heat sink
DiscreteComponent
Weld
Solder
Tape
Epoxy
IC Chip / BGAModule / Board
Opto-Electronics
increasing
Fan
Mechanical ThermalElectrical
Proposed Applications by Team: Categorized
• Mechanical / Structural:– RF Shield Attach
– RF Shields
– RF Shield
– Flex Circuit Placement
– Electrical Connector
• Thermal Connections:– Heat Sink Attach
– Heat Sink
– Power Components with Attached Heat Sinks
– Sweat Soldering of Power Amplifier Modules
– Integrated Heat Spreader
• Temperature Sensitive:– Opto-Module Attach
– Flex Circuit to PCB Connection
– Surface Mount Flex Tab Attach
– Flex Circuit Connector
– Temperature Sensitive Components
– Lamination Process
– Photo-Sensor Flip Chip Attach
Page 24
Proposed Applications: Categorized (con’t.)
• Discrete Components:– High Voltage Transformer
– Power Components (high current density) with Attached Heat Sinks
– Daughter Board Attachment
– Surface Mount Components
– Cap Attachment
– 3D Component Attachment
• IC Chips:– Thin Area Array Devices
– QFN, DFN, LGA
– CSP, BGA, CGA
– BGA Attachment
– Repair of Balled Devices
– Gull-Winged Leaded Devices
– Flip Chip Attachment
– Photo-Sensor Flip Chip Attach
– Die Attachment
– High Frequency Die Attach
Page 25
Targeted Applications
• Mechanical / Structural:– RF Shield Attach
• Thermal Connections:– Heat Sink
• Low powered
– Power Module Heat Sinks
• Focused on those that currently require additional mechanical attachment
• Temperature Sensitive:– Components
• Examples: – Photo-Sensor Flip Chip Attach & Opto-Module
– Low Temperature Flex Components
• Surface Mount Components (Low Pitch / High Contact Area):– Discrete (Active and Passives)
– IC Chips (Fine Pitch / Low Contact Area):
• Array Devices
• Perimeter Devices
– Die Attach
Page 26
Basic attachment types include: line, area, and point attachments
Technology Gaps
&
Requirements
Nano-Attach Team
September 4, 2008
Targeted Applications:
Page 28
• RF Shield Attach
• Heat Sink
• Power Module Heat Sinks
• Temperature Sensitive SM Components
• Low Temperature Flex Components
• Discrete SM (Active and Passives)
• IC Chips (Fine Pitch / Low Contact Area):
• Array Devices
• Perimeter Devices
• Die Attach
Temperature SensitiveSM Components
Targeted Applications:Mechanical Requirements
Page 29
Low TemperatureFlex Components
Array Devices
RF Shields
Heat Sinks
Power Heat Sinks
Complexity of Attachment (ease of execution)
Contact Area
per
Attachment
Terminal
Die Attach
Discrete SM
Targeted Applications:Mechanical Requirements
Page 30
10
Low TemperatureFlex Components
Array Devices
RF Shields
weight (g) /
contact (cm2)
Temperature SensitiveSM Components
Heat Sinks
Power Heat Sinks
1
0.1
Complexity of Attachment (ease of execution)
Die Attach
DiscreteSM
Decreasing Feature Size
Temperature SensitiveSM Components
Targeted Applications:Electrical Requirements
Page 31
Low TemperatureFlex Components
Array Devices
RF Shields
Complexity of Electrical Requirements (ease of execution)
Complexity of
Mechanical
Requirements
Die Attach
Discrete SM
Temperature SensitiveSM Components
Targeted Applications:Thermal Requirements
Page 32
Heat Sinks
Power Heat Sinks
Complexity of Thermal Requirements (ease of execution)
Complexity of
Mechanical
Requirements
Die Attach
Technology Gaps
Parameters to be used in evaluation– Pull strength
• Shear / Tensile
• Peel
• Compression
– Fatigue• Mechanical degradation
• Thermal degradation
– Fracture characteristics / fracture mechanics• Creep behavior
• Izod impact test
• Shock and vibration
• Drop
(Mechanical Attachment)
Page 33
(Limited or Lack of Experimental Data Currently Available)
Technology Gaps
Properties as a function of:– Contact pressure (distribution and influence of placement force, …)
– Temperature dependencies
– Humidity
– Reattachment / repair (attachment / reattachment dependencies)
– Other environmental dependencies
(Mechanical Attachment – con’t.)
Page 34
Technology Gaps(Mechanical Attachment – con’t.)
Page 35
Where will these parameters be evaluated?
1. Substrate interface
– Substrate surface properties (contact composition [tin, gold, copper,
indium, …], etc.)
– Transferred
– Direct deposit
– Composite mixture
– What are cleanliness requirements of the mating surfaces to achieve
above properties?
2. Component interface (if needed)– Surface roughness of attachment surfaces
– Component surface properties (contact composition [tin, gold, copper,
indium, …], etc.)
Technology Gaps(Mechanical Attachment – con’t.)
Page 36
Nanotube properties that will affect these parameters
1. Properties of individual nanotubes
– Young’s Modulus
– Surface characteristics (hydrophobic, hydrophilic, )
– Operational environmental stresses (pollution, pressure [hypobaric]
sensitivity, …)
2. Properties of nanotube system
– Dependencies on nanotube interfacial area
– Density of nanotubes (attachment points)
– Patterning
– Hierarchical characteristics
Page 37
Technology Gaps
Parameters to be used in evaluation
1. Series resistance
2. Maximum current carrying capacity
3. Breakdown voltage
4. Radiation Sensitivity
– Electromagnetic radiation (RF interference, EMI, EMC, …)
– Nuclear / Atomic / Magnetic Radiation
5. EOL resistance (simulated accelerated aging)
(Electrical Contact / Conductivity )
Page 38
Technology Gaps(Electrical Contact / Conductivity – con’t.)
Properties as a function of:
1. Contact pressure (distribution and influence of placement force, …)
2. Contact area
3. Temperature
4. Humidity
5. Frequency response
6. Repeated attach/reattach cycles (attachment / reattachment
dependencies)
7. Other environmental dependencies
Page 39
Technology Gaps
Where will these parameters be evaluated?
1. Substrate interface / surface properties
– Contact composition [tin, gold, copper, indium, …]
– What are cleanliness requirements of the mating surfaces to achieve
above properties?
– Sensitivity to cleaning chemistry
2. Component interface
– Surface roughness of attachment surfaces
– Is there a limiting layer if intermediate layer(s) is(are) needed?
– Contact composition [tin, gold, copper, indium, …]
(Electrical Contact / Conductivity – con’t.)
Page 40
Technology Gaps(Electrical Contact / Conductivity – con’t.)
Nanotube properties that will affect these parameters
1. Properties of individual nanotubes
– Growth environmental parameters
» Diameter (Single-walled, multi-walled)
» Chirality - chiral angle and diameter (semiconducting or metallic)
» Surface characteristics (hydrophobic, hydrophilic, )
– Operational environmental stresses (e.g. carbon nanotubes are studied
for their chemical sensor capabilities)
2. Properties of nanotube system
– Dependencies on nanotube interfacial area and structure
– Density of nanotubes (attachment points)
Page 41
Technology Gaps(Thermal Contact / Conductivity)
Parameters to be used in evaluation
1. Thermal resistance (z direction)
2. Thermal conductivity (xy direction)
3. Thermal capacitance (transient behavior)
Properties as a function of:
1. Contact pressure (distribution and influence of placement force, …)
2. Contact area
3. Temperature
4. Humidity
5. Repeated attach/reattach cycles (attachment / reattachment
dependencies)
6. Other environmental dependencies
Parameters: Mechanical
1. Pull strength
– Shear /Tensile
– Peel
– Compression
2. Fatigue
– Mechanical degradation
– Thermal degradation
3. Fracture characteristics /
fracture mechanics
– Creep behavior
– Izod impact test
– Shock and vibration
– Drop
4. Other parameters
Page 42
A. Contact pressure (distribution and
influence of placement force, …)
B. Temperature dependencies
C. Humidity
D. Reattachment / repair (attachment
/ reattachment dependencies)
E. Other environmental
dependencies
F. As a function of others
Parameters: Electrical
1. Series resistance
2. Maximum current carrying
capacity
3. Breakdown voltage
4. Radiation sensitivity
– Electromagnetic radiation
(RF interference, EMI, EMC,
…)
– Nuclear / Atomic / Magnetic
Radiation
5. EOL resistance (simulated
accelerated aging)
6. Other parameters
Page 43
A. Contact pressure (distribution and
influence of placement force, …)
B. Contact area
C. Temperature
D. Humidity
E. Frequency response
F. Repeated attach/reattach cycles
(attachment / reattachment
dependencies)
G. Other environmental
dependencies (pressure,
atmospheric conditions, …)
H. As a function of others
Parameters: Thermal
1. Thermal resistance (z
direction)
2. Thermal conductivity (x-y
direction)
3. Thermal capacitance
(transient behavior)
4. Other parameters
Page 44
A. Contact pressure (distribution and
influence of placement force, …)
B. Contact area – surface roughness
C. Temperature
D. Humidity
E. Repeated attach/reattach cycles
(attachment / reattachment
dependencies)
F. Other environmental
dependencies
G. As a function of others
Technology
Impact
Nano-Attach Team
4 September 2008
Temperature SensitiveSM Components
Targeted Applications:Mechanical Requirements
Page 46
Low TemperatureFlex Components
Array Devices
RF Shields
Heat Sinks
Power Heat Sinks
Complexity of Attachment (ease of execution)
Contact Area
per
Attachment
Terminal
Die Attach
Discrete SM
Targeted Applications:Mechanical Requirements
Page 47
10
Low TemperatureFlex Components
Array Devices
RF Shields
weight (g) /
contact (cm2)
Temperature SensitiveSM Components
Heat Sinks
Power Heat Sinks
1
0.1
Complexity of Attachment (ease of execution)
Die Attach
DiscreteSM
Decreasing Feature Size
Temperature SensitiveSM Components
Targeted Applications:Electrical Requirements
Page 48
Low TemperatureFlex Components
Array Devices
RF Shields
Complexity of Electrical Requirements (ease of execution)
Complexity of
Mechanical
Requirements
Die Attach
Discrete SM
Temperature SensitiveSM Components
Targeted Applications:Thermal Requirements
Heat Sinks
Power Heat Sinks
Complexity of Thermal Requirements (ease of execution)
Complexity of
Mechanical
Requirements
Die Attach
Page 49
Compared to solder, using Nano-Attach Technology Would…
Simplify AssemblyEnhance / Improve
FunctionalityEconomic Benefits
RF Shield NeutralWorse-Neutral (frequency
dependant)Worse – Neutral
Heat Sink (low power) Neutral – Better BetterNeutral – Better
(size dependant)
Power Module Heat Sinks Neutral – Better Better Better
Temperature Sensitive SM
ComponentsBetter
Worse – Better
(application dependant)Neutral – Better
Low Temperature Flex
Components
Neutral – Better
(pitch dependant)Neutral – Better Low – Moderate
Discrete SM Worse Worse – Neutral Worse – Neutral
Array DevicesWorse – Neutral
(planarity dependant)Worse – Neutral
Better
(capability to repair)
Die Attach Neutral – Better Neutral – Better Neutral – Better
Legend: Worse, Neutral, Better
Page 50
Generic Assembly Cost Model: Traditional Soldering
Page 51
Screen
Pick & Place
PWBs
solder paste components
Mass Reflow
Selective
Soldering
componentssolder
paste
Capital Investment (Equipment):
– Screen print
– Pick & Place
– Mass Reflow
– Selective Soldering
Materials:
– Solder paste
– PWBs
– Components
Page 52
Generic Assembly Cost Model: Nano-Attach
Screen
Pick & Place
PWBs
solder paste components
Mass Reflow
Selective
Soldering
componentssolder
paste
X X XX X X
Assumption: start with best case scenario, work back from there
Capital Investment (Equipment):
– Pick & Place
Materials:
– Components
– PWBs with nanostructures
Page 53
Generic Assembly Cost Model: Comparison
Transition from Traditional Solder to Nano-Attach Technology
Addition of:
Materials:
– PWBs with nanostructures
Elimination of:
Capital Investment (Equipment):
– Screen print
– Mass Reflow
– Selective Soldering
Materials:
– Solder paste
Phase 2 Attributes
Nano-Attach Team
September 4, 2008
Technology Gaps Summary
• Parameters to be used in evaluation
– Pull strength
• Shear /Tensile
• Peel
• Compression
– Fatigue
• Mechanical degradation
• Thermal degradation
– Fracture characteristics / fracture mechanics
• Creep behavior
• Izod impact test
• Shock and vibration
• Drop
• Properties as a function of:
– Contact pressure (distribution and influence
of placement force, …)
– Temperature dependencies
– Humidity
– Reattachment / repair (attachment /
reattachment dependencies)
– Other environmental dependencies
• Where will these parameters be evaluated?
– Substrate interface• Substrate surface properties (contact composition
[tin, gold, copper, indium, …], etc.)
• Transferred
• Direct deposit
• Composite mixture
• What are cleanliness requirements of the mating surfaces to achieve above properties?
– Component interface (if needed)• Surface roughness of attachment surfaces
• Component surface properties (contact composition [tin, gold, copper, indium, …], etc.)
• Nanotube properties that will affect these parameters
– Properties of individual nanotubes• Young’s Modulus
• Surface characteristics (hydrophobic, hydrophilic, )
• Operational environmental stresses (pollution, pressure [hypobaric] sensitivity, …)
– Properties of nanotube system• Dependencies on nanotube interfacial area
• Density of nanotubes (attachment points)
• Patterning
• Hierarchical characteristics
Mechanical Attachment Overview
Page 55
Technology Gaps Summary
• Parameters to be used in evaluation
1. Series resistance
2. Maximum current carrying capacity
3. Breakdown voltage
4. Radiation sensitivity
• Electromagnetic radiation (RF interference, EMI, EMC, …)
• Nuclear / Atomic / Magnetic Radiation
5. EOL resistance (simulated accelerated aging)
• Properties as a function of:
1. Contact pressure (distribution and influence of placement force, …)
2. Contact area
3. Temperature
4. Humidity
5. Frequency response
6. Repeated attach/reattach cycles (attachment / reattachment dependencies)
7. Other environmental dependencies (pressure, atmospheric conditions, …)
• Where will these parameters be evaluated?
1. Substrate interface / surface properties
2. Contact composition [tin, gold, copper, indium, …]
3. What are cleanliness requirements of the mating surfaces to achieve above properties?
4. Sensitivity to cleaning chemistry
5. Component interface
6. Surface roughness of attachment surfaces
7. Is there a limiting layer if intermediate layer(s) is(are) needed?
8. Contact composition [tin, gold, copper, indium, …]
• Nanotube properties that will affect these
parameters
1. Properties of individual nanotubes
2. Growth environmental parameters
• Diameter (Single-walled, multi-walled)
• Chirality - chiral angle and diameter (semiconducting or metallic)
• Surface characteristics (hydrophobic, hydrophilic, )
3. Operational environmental stresses (e.g. carbon nanotubes are studied for their chemical sensor capabilities)
4. Properties of nanotube system
5. Dependencies on nanotube interfacial area and structure
6. Density of nanotubes (attachment points)
Electrical Contact / Conductivity Overview
Page 56
Technology Gaps Summary
• Parameters to be used in evaluation1. Thermal resistance (z direction)
2. Thermal conductivity (x-y direction)
3. Thermal capacitance (transient behavior)
• Properties as a function of:1. Contact pressure (distribution and influence of
placement force, …)
2. Contact area – surface roughness
3. Temperature
4. Humidity
5. Repeated attach/reattach cycles (attachment / reattachment dependencies)
6. Other environmental dependencies
• Where will these parameters be evaluated?1. Substrate interface / surface properties
• Contact composition / surface material [tin, gold, copper, indium, …]
• Cleanliness requirements of the mating surfaces to achieve above properties
• Sensitivity to cleaning chemistry
2. Component interface
• Surface roughness of attachment surfaces
• Is there a limiting layer if intermediate layer(s) is(are) needed?
• Contact composition / surface material [tin, gold, copper, indium, …]
• Nanotube properties that will affect these
parameters
1. Properties of individual nanotubes
• Diameter (Single-walled, multi-walled)
• Chirality - chiral angle and diameter (semiconducting or metallic)
• Surface characteristics (hydrophobic, hydrophilic, )
• Operational environmental stresses (e.g. carbon nanotubes are studied for their chemical sensor capabilities)
2. Properties of nanotube system
• Dependencies on nanotube interfacial area and structure
• Density of nanotubes (attachment points)
• Dependency on nanotube mix (semiconducting vs. metallic)
• Density of conductive particles (dispersion uniformity)
Thermal Contact / Conductivity Overview
Page 57
Information Needed to Develop Evaluation Vehicle
Nano-material Structure (Nanostructure Level)– Identify available material systems (i.e. carbon nanotube based, polymer
based, composite, etc.)
– Which material system(s) should we choose to explore / evaluate?
– Application spaces [prioritized listing]• Mechanical attachment (component to board) (essential)
• Electrical contact / conductivity (interfacial resistivity)
• Thermal contact / conductivity (interfacial resistance)
• Electromechanical (e.g. resettable / programmable fuse, electrically actuated contact, etc …)
• Both electrical and thermal (possible interactions, positive and/or negative)
Page 58
Information Needed to Develop Evaluation Vehicle
Layer Structure (System Level)
– Investigating material layer structures in Phase 2 is essential in developing the device prototypes for Phase 3 where the nanostructures will need to be incorporated into the component/board pads
– Is an intermediate layer necessary and for what material systems?
• Consider the deposition or formation on a pre-existing contact structure (mechanical, electrical, and/or thermal) – implies no intermediate layer
• If the nanostructures need an intermediate layer (carrier), characterizing the nanostructure and the intermediate layer as an unit will be critical (single and/or double sided nano-structures)
• How does layer structure affect the performance (i.e. electrical, thermal, mechanical) of the nanostructure system?
– Investigating interfacial performance of mechanical, thermal, and electrical behavior of joint structures with common electronic packaging materials
Page 59
Relative Performance of Materials
PolymersCarbon
Nanotubes
Embedded
Polymers
Semiconductor / Metallic
Nanowires
Mechanical strength low - moderate high low - moderate moderate
Electrical conductivity low high moderate moderate - high
Thermal conductivity low - moderate high moderate moderate - high
Density low - moderate high low - moderate moderate - high
Ease of fabrication moderate moderatedifficult /
researchmoderate - difficult
Page 60
Electronic assembly
• Carbon nanotubes (CNTs) may provide best path
Baseline Material Properties Comparison
Page 61
Common Material Systems
Performance Carbon Nanotubes
Tensile StrengthHigh-strength steel alloys
~2 GPa~63 GPa [1]
Current Carrying Capacity
Copper wires
~1 x 106 A/cm2up to 1 x 1010 A/cm2 [2]
ThermalDiamond
3,320 W/m*Kup to 6,000 W/m*K [3]
[1] M.F. Yu, O. Lourie, M.J. Dyer, K. Moloni, T.F. Kelly, R.S. Ruoff, “Strength and Breaking Mechanism of
Multiwalled Carbon Nanotubes Under Tensile Load”, Science, 287, 637 (2000).
[2] B.Q. Wei, R. Vajtai, and P.M. Ajayan, “Reliability and Current Carrying Capacity of Carbon
Nanotubes”, Appl. Phys. Lett., 79, 1172 (2001).
[3] J. Hone, M. Whitney, C. Piskoti, and A. Zettl, “Thermal Conductivity of Single-Walled Carbon
Nanotubes”, Phys. Rev. B, 59, R2514 (1999).
Evaluation Vehicle Assumptions
Evaluation Vehicle A (Direct Growth)– Carbon nanotube based system
– Vertically aligned nanostructures
– Nanostructures directly grown on surface• Substrates: Si and Cu
– Single-sided adhesion scheme (i.e. Gecko like)
– Adhesion requires only a preload force
– Sample sizes cover spectrum of dimensions
– Need repeatable contact area application
– Need strong adhesion between growth substrate and nanostructures
Page 62
Evaluation Vehicle Assumptions (con’t.)
Evaluation Vehicle B (Transfer)– Carbon nanotube based system
– Vertically aligned nanostructures
– Nanostructures grown in a separate process (growth substrate irrelevant)
– Nanostructures transferred onto contact (i.e. stamping process)
– Single-sided adhesion scheme (i.e. Gecko like)
– Adhesion requires only a preload force
– Sample sizes cover spectrum of dimensions
– Need repeatable contact area application
– Need something easy to peel (substrate irrelevant), to separate from growth substrate
Page 63
Transfer Technology Papers[1] A. Kamar, V.L. Pushparaj, S. Kar, O. Nalamasu, P.M. Ajayan, R. Baskaran, “Contact Transfer of
Aligned Carbon Nanotube Arrays onto Conducting Substrates”, Appl. Phys. Lett., 89, 163120 (2006).
[2] L. Zhu, J. Xu, Y. Xiu, D.W. Hess, and C.P. Wong, “Controlled Growth of Well-Aligned Carbon Nanotubes and Thier Assembly”, Adv. Pack. Mat. Int. Sym., 123 (2006).
Test Coupon: Mechanical
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2”
1”
Mounting hole
Test Material
Nanostructure material:
• Evaluation Vehicle A: CNTs grown on substrate
• Evaluation Vehicle B: CNTs transferred onto dummy substrate
Test pad materials:
• flash gold, Cu, intentionally oxidized Cu, Cu (OSP coating), Si, printed conductor
(AgPt, AgPd) on ceramic, Al (heatsinks), and anodized Al.
Substrate
Nanostructure
material
Stack-up ViewTop View
Test Coupon: Electrical
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2”
1”
Mounting hole
Test Material
Top View
Substrate
Nanostructure
material
Stack-up View
Measurement
Evaluation Module Design Parameters: Electrical
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Coupon Size:
– Feature sizes (device dependence)
• Suggest coupon as initial test vehicle
• Coupon size: 1” x 2” maximum
– Use two coupons per attachment (asymmetrical design)
Pad:
– Need one pad on coupon for nano attach material and one trace to a continuity pad/via.
– Design coupons in an array with various pad diameters
– May need a thermal via in test pad area
Pad Material: (depends on temperature of nano attach)
– 1st choice if FR4
– 2nd choice is Alumina (ceramic hybrid material)
Surface finish:
– ENIG, Im-Sn or OSP depending on nano material requirements
– Alumina would use PbAg pads or be plated with NiAu
Test Coupon: Thermal
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Nanostructure Material8 mm
• Total thickness is 2mm + 2mm = 4 mm
• Different materials substrates can be used
if the thermal conductivity is known.
8 mm
Substrate
Nanostructure
material
Top View Stack-up View
Laser Beam
Thermal Conductivity Measurement: Using Laser Flash
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Tem
pera
ture
Measuring thermal diffusivity () and calculate thermal conductivity: k = *Cp*
Sample size: 8mm x 8mm about 2mm thick
Page 69
Thermal Conductivity Measurement: One Example
Laser flash is useful for quantifying
effects of voiding on thermal impedance
TIM = tot – (x/k)top - (x/k)bottom
