Flexible Hybrid Electronics for Aerospace Applicationssemieurope.omnibooksonline.com/2016/semicon_europa/2016FLEX Europe...Flexible Hybrid Electronics for Aerospace Applications B.J

1Distribution Statement A: Approved for Public Release. Distribution is unlimited. Case # 88ABW-2016-1256.

Integrity Service Excellence

Flexible Hybrid Electronics

for Aerospace Applications

B.J. Leever, M.F. Durstock, J.D.

Berrigan, C.E. Tabor, A.T. Juhl

AFRL/RXAS

Materials & Manufacturing Directorate

Air Force Research Laboratory

Wright-Patterson AFB, OH 45433


Outline

• AF Motivation for Flexible Hybrid Electronics

• Development Strategy

• Advanced Development Projects

• Gallium Liquid Metal Alloys

• Stretchable & reconfigurable electronics

• Printed Interconnects and Capacitors

• Stretchable & resilient electronics

• Soft Packaging

• Summary & Conclusions


AFRL: Turning Science Into Capability

*Updated after PrintFY10 Funding

Driven by Service Core FunctionsVectored by Air Force Strategy + S&T Vision/Horizons + Product Center Needs + MAJCOM Needs

Initial Operating Capability Timeline

6.1

Basic

Research

6.2

Applied

Research

6.3

Advanced

Tech Demo


Space Vehicles

• Intelligence,

Surveillance &

Reconnaissance

•Responsive Space

•Space Situational

Awareness

Materials and

Manufacturing

•Materials & Processes

•Materials Applications

•Manufacturing

Technology

Sensors

•RF Sensing and

Warfare

•EO Sensing and

Warfare

•Trust in Complex

Systems

•Damage Mech Science

•Fuze Technology

•Munitions AGN&C

•Energetic Materials

•Terminal Seeker

Sciences

•Munitions System

Effects Science

Munitions

Aerospace Systems•Turbine Engines

•High-Speed/Hypersonics

•Space and Missile Prop

•Aeronautical Sciences

•Structural and Control

Sciences

Directed Energy

•Lasers

•Beam Control

•High Power

Microwaves

Information

•Computing

Architecture

• Information

Exploitation

•Command & Control

Human Performance

•Forecasting

•Training

•Decision Making

AF Office of

Scientific Research

•Aero-structure power

and control

•Physics and electronic

•Mathematics,

Information, and life

sciences

Air Force Research Laboratory

Technical Competencies


What are Flexible Hybrid Electronics?

Thin Si CMOS

POWER

Low-temperature

Manufacturing Processes

High-speed Automation

Printed Components

Integrated Array

Antenna Systems

Asset Monitoring

Systems

Human Monitoring

Systems

Soft Robotics

Manufacturing Convergence

for Application SpacesElectronics Manufacturing

Services

http://www.gizmag.com/sony-rollable-otft-driven-oled-display/15226/picture/115131/

http://www.gizmag.com/sony-rollable-otft-driven-oled-display/15226/picture/115131/

http://www.cmst.be/projects/flexible.html

http://www.cmst.be/projects/flexible.html


How could Flexible Hybrid Electronics Impact the Air Force?

Man-Machine InterfaceAirman performance limits capability in MANY military missions….and new technologies are needed to sense, assess and augment the “Airman-in-the-Loop”

• Information Overload• Missed Intelligence• Threat/Danger Missed

Embedded/Conformal Electronics for ISR/EW

Information and tracking in contested environments is foundational to decision making and force projection

Integrated & Flexible Power (Mike Durstock)Energy limits operational capabilities and mission impact for unmanned vehicles and wearable electronics

• Communication (conformal apertures)• Distributed electronics for feedback and structural health

monitoring• Reconfigurable Electronics

Survivable ElectronicsPrecision effects with smaller, low profile munitions pressing requirement for current and future platform effectiveness

• Robust electronics in extreme environments (shock, vibration, thermal)

Issues:•Cost & Weight•Scale-up•Durability

Integrated Power harvesting, storage, and management

Today

Future

Lewis


Technology Development Strategy

• Accelerate development and transition of FHE

technologies to Air Force functional materials community

• Phased plan for FHE technology insertions

Embedded Sensors & Structural Antennas

Rugged Flexible Electronics

Human Performance

Conformal Antennas

15 16 17 18 19 20 21 22 23

Critical Pre-requisites:

• Composite Certification

• Hybrid-Materials Design

Critical Pre-requisites:

RPA Demo

AM Design Rules

• Improved Conductive

& Dielectric Inks

• Qual. Risk Reduction


Plasma Spray Direct WriteMesoScribe Technologies

Conformal & Integrated Antennas


Integrated Direct Write Electronics

PM: Ted Finnessy, AFRL/RXME

ManTech Program: Integrated Direct

Write Electronics

• Simplify fabrication by locating

electronics on vehicle exterior (vs.

inside wing).

• Demonstrate printed heaters &

thermistor for wing de-icing

• Demonstrate printed conformal

antennas

• Demonstrate flexible IC as analog-to-

digital convertor

• Complete TRL/MRL assessment

• Fabricate and test


Direct-Write Conformal Antenna on

MQ-9

Need

• Additional communications capabilities are

required on the MQ-9.

• Conventional approaches to add antennas

often requires new tooling (high cost, long

lead time) and drilling of holes in the carbon

fiber structure.

• Fuselage is crowded with apertures for

communications, leading to co-site

interference.

Technical Approach

• Retro-fit existing fleet with conformal

antennas by simply replacing existing servo

covers.

• Design and direct-write Cu antenna onto

servo cover using plasma spray technique.

• Minimize co-site interference by installing

onto unique locations of aircraft.

Phase I Results

• Indoor range data showed VSWR and

directivity comparable with COTS

components.

• Cu removal from part required a grinder.

• Significant directivity benefit in cross-

polarization performance due to location


Ford Demo: Ford Focus Console Thermoformed Silver Ink Electronics

Automotive: Printed Console Electronics

Air Force could achieve similar benefits such as elimination/reduction of wire harnesses in aircraft.


Moving Beyond Commercially Available

Human SensorsAF Mission Areas

• COTS products focus on primarily on

motion sensing, with limited cardiac

sensing

• AF needs advanced biosignatures

sensing for cognition, stress, fatigue, etc.

• Consumer products will not survive

challenging AF environments

• AF needs unobtrusive devices with

chemical and mechanical durability

Traditional electronic components and

packaging will not meet Air Force requirements.


Potential for Human Monitoring

FHE Devices

Flexible Hybrid Oral Biochemistry Sensing SystemSensing lactate as indictor for fatigue.

Numerous FHE materials & manufacturing challenges must be

overcome to enable reliable & durable wearable sensing platforms.


Flexible Materials & DevicesResearch Leader: Dr. Benji Maruyama

Developing critical Materials & Processes to enable flexible hybridelectronic systems for airman performance monitoring

……..lightweight, flex/stretch, conformal, multifunctional, robust, autonomous

Novel materials• Inherently strain-resilient• Wafer thinning• Liquid metals

Innovative packaging schemes• Flex and performance• Ensure survivability

Conformal & integrated printing approaches• Rapid design cycle• Enables retrofit• Tailored materials and

properties

AMI

Harvard

Rogers


Integration & Packaging of Human

Monitoring Components

Exposed 1-layer graphene

Single Layer Graphene Biosensor (G-FET)

16X Mag

CommPower

LogicSense A, B, …

► Flex Battery

► NFC

► Photovoltaics

► Microcontroller

► ADC chip

Challenges:

► Reliable, low-resistance interconnects

► Energy dense & flexible batteries

► Biosensor platform development

► Integration into stretchable form-factor

► Printed antennas & interconnects


In-House Additive Manufacturing Capabilities

16

Aerotech Motion Control Stage

Multiple interchangeable dispensing configurations

In-Line Multi-Material dispense point

CUSTOMIZABLE MOTION

CONTROL STAGE

VERSATILE

AEROSOL JET PRINTING

Optomec Aerosol Jet Deposition System

Fine features (≥ 10 µm)

Thin layers (≥ 100 nm)

Excellent accuracy & repeatability

Inherently clog resistant

HIGH RESOLUTION

Microfab JetLab 4xl-A

Good balance between cost and performance

Drop-on-Demand microdispensing

~10 µm minimum line width

INKJET PRINTING

LOW COST

POLYJET PRINTING

Objet Connex 3 3D Printer

Solid 3D structures

UV-curable polymers

Rigid and flexible materials

Up to 82 material characteristics in one print

3D PROTOTYPING

nTact nRad Extrusion Coating System

20 nm to 100 µm Coating Thickness

Scalable

Selected area coating capable

SLOT-DIE COATING

LARGE AREA


Gallium Liquid Metal Alloys (GaLMAs)

Gallium Alloy PropertiesMP < 0C

Viscosity ≈ WaterVapor pressure ≈ 0

Electrically conductiveNon-Toxic

Room Temperature Liquid Electronics

Reconfigurable

FlexibleStretchable

Liquid Metal encapsulated in Elastomer3D Electronics

Led by Chris Tabor in collaboration with Michael Dickey (NCSU)


On Going ProgressAcid/Base Reactions with the Surface Oxide

Concern: The spontaneous formation of the surface oxide causes residue of oxide and metal to remain in channels during fluid evacuation.

Image Courtesy of NC State Univ.; Dickey Group

Ga2O3 + 6HCl → 2GaCl3 + 3H2O

Mechanically Rigid, Continuous Surface

Individual Hydrated Metal Chlorides

HCl

React with the Oxide Modify the Oxide

OH

OH

OH

OH

OH

OH

Oxide

- H2O

Metal


GaLMA Printing and ProcessingAdditive Manufacturing with Liquid Metals

Freestanding 3-D Liquid Electronics

Aerosol Jet Printing GaLMA Inks

Filament Extrusion of GaLMAs

There are a variety of approaches being explored

to accurately print and define GaLMA structures

Cook et al. in prep.


Traditional Rigid PCBs Embedded Devices in Soft Matrix

Mass

Force Duration

AFRL, RW AFRL, RW/RX

Opportunities for Additive Manufacturing Solutions:

Passive Devices: Printed conductors & dielectrics with

device architectures insensitive to strain

Techniques: Inkjet, Aerosol, Filamentary

Packaging: Islands of varying modulus and conductivity

Technique: Filamentary

AFRL/RXAS

Soft Electronics for Survivability


Developing Printed Electronic Components

4. Printed

Electronic

Component

3. Ink Design

1. Printer Design

2. Printing Technique

Motion system

Motion controller

Interface software

Scripting language

Deposition system

Imaging

Alignment tools

Computer

…

Particulates

Reactive elements

Rheological modifiers

Solvents

Binders

Surface energy modifier

Stabilizers

…

Path planning

Loading protocol

Cleaning protocols

Alignment techniques

Stop-start compensation

…


Inks Under Investigation for Filamentary

Deposition

Metal Fillers Dielectric and Polymer Matrix

► Ag (Particles, Flakes, Wires)

► Ni Nanostrands

► ASI Carbon

► eGaIn (Liquid Metal)

► PMMA

► Polystyrene

► PVDF-HFP (various blends)

► Silicone

► Polyurethane

Close-up view of 3D printer setup (left) and optical image of

layered PVDF-HFP filaments (right). Scale: 100 μm

Material Conductivity

(S·cm-1)

Strain to

Failure

Bulk Cu 6.0·105 0.55

Bulk Ag 6.3·105 0.6

Silicone (SE1700) - 355

Ag in TPU 1.7·104 TBD

Ag in PMMA 8.0·102 TBD

Ag in SE1700 6.1·103 TBD

Ag in PVDF-HFP 2·104 TBD

Dupont (PE872) 4·103 TBD

Quantification of relationship between Ag loading, matrix and mechanical

properties currently underway.

Distribution Statement A: Approved for Public Release. Distribution is unlimited. Case # 88ABW-2016-1256. 23

Flex Printer

• Aerotech gantry and controller

• Air bearing XY with 4 independent Z-axis

• Rotation axis option

• Multiple zoom camera

• Various tools can be attached as needed

PDMS


Polymers for Flex Cap Printing

• Thin films (<20 µm)

• Poly(propylene)

• Poly(styrene)

• Poly(methyl

methacrylate)

• Poly(vinylidene

fluoride-co-

hexafluoropropylene)

𝜀𝑟𝐸𝐵𝐷 =𝑉𝐵𝐷𝐶

𝜀0𝐴

𝐶 = 𝜀0𝜀𝑟𝐴

𝑑

Ultraflex Flex 2801

PVDF-HFP


Printing Capacitors

• Inherently a two material

system

– Dielectric

– Conductor

• Defects often propagate up

through subsequent layers

• Print and material defects

contribute to dielectric

breakdown Cross-section of PMMA cap


Control of Dielectric Film

• Printing offers good control of film thickness

• ~10 min/layer to print

• Little evidence of aging or relaxing of process-

related internal structure


Printing Process Development

Material: PVDF-HFP

Print time: 8 hours

Yield: ~10%

Capacitance : ~0.3 nF

Material: PMMA

Print time: 8 hours

Yield: ~60 %

Capacitance : 0.1 nF

Material: PMMA , Print time: 8 hours, Yield: ~100 %, Capacitance : 0.1 - 0.2 nF

Heig

ht (µ

m)

Position (mm)


Soft Electronics for Survivability

Traditional Rigid PCBs Soft Packaging Scheme

Printed Silicone

Packaging

AFRL, RW AFRL, RW/RX

Combining rigid PCBs with Soft Packaging provides interim solution…

• Printed silicone (PDMS) clearly prevents capacitor separation from PCB

• Electrical conductivity verified before and after test

• Considering stretchable conductors/interconnects to ensure electrical

connectivity during test


Next Steps

• Ink Optimization (stability, viscosity, etc.)

• Nozzle development for multiscale and multi-material

printing

• Improve parallel printing of multi-layer capacitors

• Printed Sensors and Actuators

• Integrating active electrical structures into complex mechanical structures

Schaeffer and Ruzzene, J. Appl. Phys., 2015


Summary

• AF pursuing additive manufacturing to enable numerous capabilities

including

• Human/airman performance monitoring

• Rugged/durable electronics

• Embedded electronics & optics

• Flexible Hybrid Electronics (rather than fully printed solutions) are near-term

focus

• Liquid gallium metal alloy for interconnects & reconfigurable electronics

• Printed metals and dielectrics for flexible and resilient circuit elements

• Soft packaging with stretchable interconnects

• Key Challenges

• Ink development – both metals & dielectrics

• Process enhancements – in-situ process monitoring, improved

resolution, etc.

• Multi-material print heads or print systems

• Disparate materials interfaces


Questions?


Printing vs Conventional Casting

• Some minor morphological difference were

observed but mostly higher thicknesses

• Printed films matched dielectric behavior of

cast films


Printing Faster and Better

• Multilayer Capacitors

• Capacitors in parallel

He

igh

t (µ

m)

Position (mm)

Delamination

after 2 weeks

of storage

Documents

Flexible Hybrid Electronics for Aerospace Applicationssemieurope.omnibooksonline.com/2016/semicon_europa/2016FLEX Europe...Flexible Hybrid Electronics for Aerospace Applications B.J