Flexible, Stretchable and Conformable Hybrid Electronics: Substrates and process considerations for building intelligent devices

Transcription

1 Flexible, Stretchable and Conformable Hybrid Electronics: Substrates and process considerations for building intelligent devices October 26, 2016 Jason Marsh Director of Technology America s Flexible Hybrid Electronics Manufacturing Institute

2 Agenda NextFlex Introduction From Flexible to Conformable to Stretchable Why? Conformable Why Intelligent Devices? Stretchable

3 Agenda NextFlex Introduction From Flexible to Conformable to Stretchable Why? Conformable Why Intelligent Devices? Stretchable

4 Establishment of NextFlex AU G U S T 2 8, Established 28 August 2015 Lead Hub Location Proposal Contributors Federal Funding Committed Matching Government Agencies Engaged FlexTech Alliance San Jose, California 145+ in 27 states $75 million $96 million 17 DOD & OGAs

5 Building a National Network of Institutes Network Status Flex. Hybrid Elec. San Jose, CA Smart Mfg. for Energy Efficiency Proj. Award TBD ESTABLISHED INSTITUTES Nearly $500M Federal funding catalyzed over $1.2B cost share from consortia Institutes have attracted hundreds of companies and universities as active partners from across the country Digital Mfg & Design. Chicago, IL Adv. Composites Knoxville, TN Light/Modern Metals Detroit, MI Additive Mfg. Youngstown, OH Albany & Rochester, NY Electronics Raleigh, NC Revolutionary Fibers & Textiles Boston, MA Next Up

6 MEMBERS (*Founding) Corporate Tier 1 * Tier 2 * * Tier 3 Academic / Non-Profit Tier 1 Tier 2 Tier 3 * * * * Honorary

7 TECHNOLOGY DEMONSTRATORS Human Monitoring Systems Asset Monitoring Systems Integrated Array Antenna Systems Soft Robotics 7

8 Agenda NextFlex Introduction From Flexible to Conformable to Stretchable Why? Conformable Why Intelligent Devices? Stretchable

9 FHE Device Requirements Robust ROI Product Lifecycle Considerations Unobtrusive Form Factor

10 Flex, Conform, Stretch Flexible Conformable Stretchable E Skin = 130 kpa, e ouch = 20% E Si = 130 Gpa, e frac = 1%

11 Agenda NextFlex Introduction From Flexible to Conformable to Stretchable Why? Conformable Why Intelligent Devices? Stretchable

12 Resistance Increase (Ω) Conformable: In-Mold Test Results - Elongation & Resistance Cone shape design used to check progressive stretch performance Printed tracks = 1.0mm, 0.5mm, 0.2mm Reference grid Conductor = ME602 Ag Resistance increase with progressive stretch for 1mm tracks ME602 Thermoformed Resistance vs 3D Stretch Track # A A0 A9 A8 A7 A6 A5 A4 DrawDepth mm Stretch % Stretch Values X (%) & Draw Depth Z (mm) Stretch measurements calculated from printed grid: Soft Touch controls capacitive 1D buttons, 2D sliders, 3D gesture control Antennas printed NFC (near field communication), Bluetooth/WLAN Gesture Controls Proximity sensing Circuitry flexible circuitry and wiring harness Illumunation - single/multi-color indicators, ambient lighting, logo/branding, animate Courtesy of DuPont/Tactotek Thermoformed grid Courtesy of DuPont Stretch was in 3 dimensions measured as x, y and z (draw depth) - in y direction < 5% - in x direction, progressive increase - in z direction, progressive draw depth

13 Why Is Conformability Important on Skin? Non-Conformal (NC) Skin Partially conformal (PC) Conventional Skin Fully-Conformal (FC) Epidermal Skin Jeong, et. al., Adv. Mater. 2013, 25, 6839 Conformable contact ensures Low interface impedance higher signal to noise ratio Less relative motion less motion artifacts Better heat and mass transfer Jeong, et. al., Adv. Healthcare Mater. 2014, 3,

14 Agenda NextFlex Introduction From Flexible to Conformable to Stretchable Why? Conformable Why Intelligent Devices? Stretchable

15 We don t need more data we need more decisions

16 Intelligent Devices Perishable Decision Window

17 Smart Dressing Wound Therapy for 21 st Century Sensing Chemical (ph, O2, biomarkers) Physical (moisture, temperature, strain, blood flow) Oxygen Delivery Antibiotics Growth factor Electomechanical stimulation

18 FHE Building Blocks Strain Gage CMOS Radio Printed Battery Printed Antenna Sensor Die Placement Processor Memory Stretch Power Conductor Integrated Si Die Transceiver Application Specific Package Integration & Lamination Trace Print Antenna Print Skin Contact Die on Stretch Die Thinning

19 FHE Building Blocks Strain Gage Printed Battery Printed Antenna Die Placement Trace Print CMOS Radio Integrated Si Die Stretch Conductor Integration & Lamination Antenna Print Skin Contact Die on Stretch Die Thinning

20 Multi-Functionality antenna LED strain gauge temp. sensor 0.5mm wireless power coil RF coil RF diode ECG/EMG sensor Kim*, Lu*, Ma* (*equal contribution), Rogers, et al., Science 333, 838, (2011).

21 Agenda NextFlex Introduction From Flexible to Conformable to Stretchable Why? Conformable Why Intelligent Devices? Stretchable

22 Stretchable Challenges Axial Stretch Conductors Low Temp Substrates Serpentine Patterns Textile Compatibility

23 Die Bonding to Stretch Systems Test Die #1 Bump Tin-Lead Bump height 130 μm Bump diameter 120 μm Pitch 254 μm (10 mils) Die size 5 x 5 mm No. of bumps 64 Wafer size 5 Test Die #2 Bump Nickel-Gold Bump height 20 +/-3 μm Bump dia. 90 μm Pitch 400 μm (16 mils) Die size 10 x 10 mm Wafer size 6 No of dies ~ 132

24 Signal Integrity (Beyond Resistivity) Reflections Jitter Skew 12 micron trace in copper

25 relaxation Viscoelasticity flow Polymer chains align in flow When polymer chains relax, melt can expands in direction normal to flow Result: time-dependent reactions to Applied stress Creep Applied strain Stress relaxation Applied strain rate Stress overshoot Applied sinusoidal stress or strain Dynamic mechanical properties

26 Impact of Extension (Strain Rate) Linear viscoelastic region, h E = constant he 3h o Non-linear viscoelastic region, h E depends on polymer

27 Cyclic Strain Event 5% Stretch 10% Stretch 15% Stretch 20% Stretch 30% Stretch 50% Stretch

28 Substrate Thickness & Line Width Profound effect of substrate material and thickness Film A (more rigid): thicker film performs better Film B (less rigid): thinner film performs better

29 The Intermittent Connection? What happens when we overstrain the material? Can we live with intermittent connections?

30 Printed Ink 50% vs 100% Stretch Film B 4 mil 50% Stretch 100% Stretch 150x 150x

31 Printed Ink at 100% Stretch Film A 5 mil x80 x150 x1000 Film B 4 mil x80 x150 x1000

32 Hydrostati c compressi on We live in a 3D world Uniaxial loading Depending on the system a wearable device might experience all of the deformations to the left. Simple uniaxial stress strain measurements are not sufficient. In addition complex failure modes may result. Hydrostati c tension

33 3 Dimensional Strain

34 Flexibility and Stretchability Testing Universal Flex Tester Printed Ink Stretchability Printed Ink Coupon First cycle stretchability Test Capabilities 1.Stretchability Testing 2.Variable Radius Test 3.Sliding Plate Flexibility Test 4.Variable Angle Bend Test 5.Variable Diameter Rolling Test 6.Multi Modal Torsion Test 7.Free Arc Bend Test 8.Multi Mode Bend Test 9.Compression Crush Test Stretchability at different strains

35 ECG Biosensor Layer Thickness (mm) Finite Element Analysis for ECG Snap Sensor Fabric Encapsulation Bluetooth Module Snap button Socket Button Cap AgCI Sensor Ink Stretchable Silver Ink TPU Substrate 15 mm 3.0 mm 1.0 mm 0.5 mm 0.05 mm 0.05 mm mm mm Stretch Direction Displacement (mm) Stress (Mpa) Strain CONDITION ( At 40% Stretch) PROCESS / DESIGN IMPROVEMENT BY FEA MODELING X- DIRECTION Y- DIRECTION X - Stretch Direction 20% 30% 40% 20% 30% 40% 20% 30% 40% Simulation from 20% to 40% stretching The max stress concentrates at the location near the snap button socket at 40% stress WITHOUT BT MODULE Maximum stress decreased from 7350 to 4931MPa for x- direction and no change for y-direction Y - Stretch Direction 20% 30% 40% Simulation from 20% to 40% stretching 20% 30% 40% 20% 30% 40% The max stress concentrates at the location near the snap button socket at 40% stress Process/ Design Improvements Consideration Add chamfers on edges / Adding TPU layer on stress areas /Use a soft BT module Half model has been deployed on this FEA simulation due to symmetrical. Finite element analysis simulated for both X&Y direction. Stress/strain concentration located around the snap button at 40% stress/strain. RIGID BT MODULE SOFT BT MODULE Maximum stress decreased from 7350 to 5742MPa for x- direction and no change for y-direction Maximum stress decreased from from 7350 to 4910MPa for x-direction and no change for y-direction

36 Substrate Considerations for Stretch Bio Compatible Materials Polyurethane Silicon Direct Textile Dressing Manufacturer Base Material Telfa Medtronic PET Tegaderm 3M PET ProFore Smith & Nephew Si Dermanet DeRoyal Si Colactive Covalon Tech Biodegradeable Petrolatum Cardinal Health Cellulose Acetate ComfiTel Dermarite Si CutiCell BSN Si Meptiel One Mölnlycke Soft Si

37 Substrate Considerations for Stretch Good Adhesion Work Hardening High Cost Difficult Adhesion Many Permutations High Temp Succeptible to Creep High Strain

38 Different Types of Substrates a b c d On Tegaderm e f g h On tattoo paper i j k l On KRST Yang, et al, Adv. Mater. 27, 6423 (2015).

39 Strain Gradient Substrates TPU Printing: Carbon 3D Co-Extrusion: Multimanifold Dies

40 Test and Measurement Lab (c las s 10,000 C lean Room) Lobby Conf Conf Conf NextFlex HQ Lunch Room Board Room Conf Seminar, Training and Workforce Development Screen Exp Materials Design Lab Printing and Additive Processing Area (class 10,000 Clean Room) Cubicles Wearables Lab Product Display Materials Registry Library Die Integration and Assembly Area (c las s 10,000 C lean R oom) Conf Break Room

41 Conclusions Stretch and conformable systems are a mechanical design problem first and foremost Consider strain gradient substrate designs A functional system will have islands that flex but do not stretch Failures will typically be at transitions Keep electrical designs simple and restrict HF elements to non-stretch sections

42 More Information Contact: Jason Marsh, Director of Technology