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InMold Electronics
John Crumpton
Flexible Hybrid Electronics, MEMS and Sensors in the Automotive Industry and Related Transportation Markets Workshop 9/13/2017
Agenda
– What is InMold Electronics
– Enabling Technology
– Paste Constituents & Processing Steps
– DuPont’s Technical Approach – Collaboration
– Stretch Characterization
– Reliability Testing
2
General concept outlined:
A printed electronic circuit, which has undergone a
thermoforming and injection molding process.
The circuit remains functional as the conducting tracks
contour the 3D shape.
The circuitry may or may not have mounted components.
IME is a natural fit with existing processes - IMD/FIM (Film Insert Molding)
- Base technology from the 1990s
- Essentially combines film, graphics and electronics, in one, forming a 3D fully
integrated functional electronic device (with the option of adding components)
What is InMold Electronics (IME)?
Conventional Ag ME602 (5043)
How is this achieved:
- development of stretchable inks which can
withstand the high temperature processes
3
IME In ‘3 Easy Steps’
From paste to functional device !
(1) Printing (2) Thermoforming (3) Over-Molding
Thermoformed Conventional Ag ME602 (5043)
Enabling Technology
4
Enabling Technology - Paste Constituents & Key Features
Polymer
‘Filler’
Solvent
Elastic/Stretchable
Good adhesion to PC
Withstands high temperatures
Solubilizes polymer
Good screen print properties
Compatible with PC & graphic inks
Conductor Ag, Carbon...etc
Dielectrics different for under/over print,
cross-over
Functional Ink
Balance of conductivity & stretchability
Balance of viscosity, good printing properties
Compatibility with substrates / graphic inks /
other pastes from the IME family
5
InMold Electronics – Why the big fuss?
Why the big fuss? It’s a versatile technology which can be used in a number of
different markets, to provide various advantages, over conventionally built products
Design
Good aesthetics
Lower cost
Reliable
No movable parts
3D Electronics
Uniqueness
Simplified Builds
Thermoformable
Design aspect should not to be underestimated
Allowing novel designs for enhanced product appeal
Less space
Lighter
Automotive
Lighter
Less space
Design freedom
Reliability
Ease of assembly
Ford Overhead Console
Aviation Industry
Lower weight
Fewer cables
This technology is ideally suited for the integration of Capacitive Switches and interconnecting tracks
there are potential IME benefits for various Industries
Appliance Industry
Lower cost
Design freedom
6
7
Enabling Technology – Automobiles Past
8
Enabling Technology – Automobiles Current
Enabling Technology – Automobiles Future
9
10
Enabling Technology – Design Benefits
Broad Outline of Processing Steps
Common Process Flow
Film inmold (Film-insert molding)
Thermoforming Cut & trim Injection moldingDevice assembly Completion
PC / Other film
~ 250-350 umOven
Vacuum or high air pressure
> 150 ºC Parts
& components
PC
Drying
~ 275-325°C
Design &
Electronics
Screen printing
Ag / Functional inks Protection layer*Substrate Dry / Cure
Graphic inks
11
Processing (1) & Collaboration/Partners (2), (3)
Film inmold (Film-insert molding)
Thermoforming Cut & trim Injection moldingDevice assembly Completion
PC / Other film
~ 200-300 umOven
Vacuum or high air pressure
> 150 ºC Parts
& components
PC
Drying
~ 275-325°C
Design & Electronics
Screen printing
Ag / Functional inks Protection layer*Substrate Dry / Cure
Graphic inks
Collaboration 2
Collaboration 3
12
Processing 1
Processing 1
Multilayer Structure
Functional pastes are screen printed
on a substrate of choice, with/without
graphic inks.
- The pastes are dried to remove the solvents.
- Multilayers are fabricated by repeating the
print/dry steps
Screen Printing – guidance & details
can be obtained from the data sheets
- composition properties and processing
information is included
Drying
A critical processing parameter
- It’s important to ensure complete solvent removal
(1) Temperature < 120⁰C for PC (best 110⁰C to 120⁰C)
(2) Time - dependent on drier efficiency
(3) Air - Good airflow is essential
13
Box Oven / ‘Static’ Drying – ME60 Ag
• Looking at the spread of resistance values per drying group:
Box Oven - Drying time needed approx 20min
With fan assisted ventilation
Good drying
How to Establish the Box Oven Profile
10 parts separately printed &
dried for each drying condition
ME602
14
15
1
10
100
1000
10000
100000
1000000
10000000
0.0 20.0 40.0 60.0 80.0 100.0
Re
sist
ance
[O
hm
]
Time [s]
Time-Resistance curve all pastes @ 120°C
ME101
ME602
ME603
200528-3B
200528-3C
200528-3BC
200528-3G
200528-3H
200528-3GH
200630-3A
Belt Oven Drying ME60X Ag and R&D Samples
16
Self capacitance /
Mutual capacitance
Touch Sensing Electronics
Has been commercial for many years.
Semiconductor companies have considerable
documentation, design guides and support.
- Texas Instruments
- Microchip-Atmel
- Cypress Semiconductors
- Freescale
Design & Electronics
DuPont does not participate
in the supply of electronic components or
design of the Capacitive Touch Sensors
Design guidelines for Capacitive Switches are
readily available from various Semiconductor
manufacturers
e.g. Microchip-Atmel
17
Enabling Technology – Design Benefits
Moving the user interface closer to the embedded electronics
Collaboration 2 – Bayer (Covestro) Example
Joint paper was presented at Lope-C 2012
- we investigated the capabilities of new formable Ag
- we checked various radii and shapes and
assessed performance by measuring resistance
Experimental Parameters
The substrate was Polycarbonate.
- Bayer Makrofol® DE was used.
Various advantages which include high heat
resistance, toughness, elasticity over a wide
temperature range, good stiffness and excellent
electrical insulation properties.
High Pressure Forming (HPF) method was used
- Niebling semi-automatic SAMK 400 equipment. The
film was formed at temperature of 160°C-170°C (for
8s) with compressed air pressure at 100 bar
18
Collaboration 2a – Substrates & Graphic Inks
To provide a good IME solution to the Industry, various challenges exist: - from materials and processes
to equipment used
Collaboration with technology leaders and specialized innovators is therefore essential
Substrates
Covestro (Bayer) - PC
Sabic, - PC
DuPont Teijin Films - Formable PET
Graphic Inks
Proell - mostly EU
- customer projects
Nazdar - mostly USA
19
Substrates & Graphic Inks
Courtesy of Tactotek
Working with substrates & graphic inks to resolve show-through (witness marks)
Collaboration 3 - Thermoforming
20
9
8
7
6
5
4
3
2
1
Track Before After Before After
nos Forming Forming
(Ω) (Ω) (Ω) (Ω)
9 7.0 6.8 7.0 8.1
8 5.4 7.8 5.6 11.0
7 6.8 12.1 6.7 O/C
6 6.4 14.6 6.9 20.0
5 5.2 12.8 5.5 O/C
4 6.0 5.0 6.4 6.7
3 6.6 10.1 6.7 16.8
2 5.5 10.9 5.7 28.3
1 6.2 17.4 6.3 O/C
Resistance Resistance
Sample K1 Sample K2
Forming Test Pattern
Tracks 1–9 printed over
different geometries &
radii
Tracks 1–9 – Resistance before & after thermoforming
K1- Lower resistance increase K2- 2x Open Circuits
Formech IMD600
Vacuum forming
Niebling
High pressure
forming
Niebling - Heat map demonstrating heat distribution
Example of Thermoformed Parts
High pressure forming
Applying heat & pressure
- shapes the printed film
to the 3D molding tool
Collaboration 3a – Thermoforming Example
21
ME772
Poly-Carbonate
5043
5043
ME772 ME772
Poly-Carbonate
5043170A
Various Test Areas
Cross-overs Dielectric Under-Print Dielectric Over-Print
Fine Line Printing
As-Printed ME602 Resistance
Thermoformed ME602 Resistance
Customer Sintex Tooling
- parts were thermoformed
DuPont tested at 85ºC/85%RH
Contents
– Cone Design for stretch testing
– Stretch vs Resistance measurements for improved characterisation
– New technology need reliability data
– Summary of environmental testing at 85⁰C/85%RH
& thermal cycling from -40⁰C to +85⁰C
22
Collaboration 3b – Tactotek Example
Stretch Characterization – Cone Design
Cone shape design used to check progressive stretch performance
Reference grid
Thermoformed grid
Stretch measurements calculated from printed grid:
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
Printed tracks = 1.0mm, 0.5mm, 0.2mm
23
15
10
5
DrawDepthmm
% Stretch
Cell Values
Y Direction
% Stretch
Cell Values
X Direction
Stretch Characterization - Elongation & Resistance
Cone shape design used to check progressive stretch performance
Conductor = ME602 Ag (5043)
Resistance increase with progressive stretch for 1mm tracks
Printed tracks= 1.0mm, 0.5mm, 0.2mm
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Track # A A0 A9 A8 A7 A6 A5 A4
DrawDepth mm 0 2.5 5.0 7.5 9.5 12.0 14.0 16.0
Stretch % 0 25 25 30 35 40 45 45
Res
ista
nce
Incr
ease
(Ω
)
Stretch Values X (%) & Draw Depth Z (mm)
ME602 Thermoformed Resistance vs 3D Stretch
24
Design Incorporated Various Test Areas
Interdigitated Capacitance Design
LED’s attached with ME901
conducting adhesive
Carbon over print
Cross-overs
Under/over print
Cone
25
Test Results – 2400hrs at 85⁰C/85%RH
Printed tracks
= 1.0mm, 0.5mm, 0.2mm
ME602 Ag Conductor
- Good 85⁰C/85%RH performance through to 1500hrs
26
0
50
100
150
200
250
300
350
400
450
500
0 200 400 600 800 1000 1200 1400 1600
Re
sist
ance
(m
Ω/s
q)
Time (Hrs)
Resistance vs Time with increasing conductor stretch ME602 - 1mm track width
No Stretch/ No Draw Depth
Stretch 25% D/depth 2.5mm
Stretch 25% D/depth 5.0mm
Stretch 30% D/depth 7.5mm
Stretch 35% D/depth 9.5mm
Stretch 40% D/depth 12.0mm
Reliability Test Results - Summary
Thermal Cycling
-40⁰C to +85⁰C, Cycles
2hr cycle with 10' hold 0 100 250 400
ME602 Capacitance (pF) 1.6 1.5 1.4 1.5
ME603 Capacitance (pF) 1.6 1.5 1.3 1.5
Accelerated Environmental Ageing 85ºC/85%RH
Functional LEDs following
1500hrs at 85⁰C/85%RH27
LED’s attached with ME901
conducting adhesive
Interdigitated Capacitance Design
0
50
100
150
200
250
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Res
ista
nce
(m
Ω/s
q)
Time (Hrs)
ME602 - 1mm track width - Accelerated Ageing at 85⁰C/85%Resistance vs Time for No stretch & 25% stretch
No Stretch/ No Draw Depth
Stretch 25% D/depth 2.5mm
ME602 Ag Conductor
- Good 85⁰C/85RH performance through to 2400hrs
28
Reliability Testing - Component Attach
Customers want to attach LEDs and other components
on 2D sheets and then thermoform
Traditional conductive Adhesives have high adhesion but poor flexibility
29
12A 12D ME901TraditionalThermoset
Flex Adhesion – LEDs bent around 1 inch rod
New applications require continued development of material
Flex Testing of Conductive Adhesives
Summary / Conclusions
New stretchable ink technology, which fits well into existing IMD/IML processes, provides
the ability to create novel and fully integrated functional 3D circuitry
This technology is referred to as InMold Electronics
It’s a versatile technology, ideally suited to Capacitive Switch applications, particularly for
Automotive Surfaces and Appliances
A comprehensive suite of compatible inks have been developed which include conductors,
dielectrics, adhesives and transparent conductors
Accelerated environmental test performance at 85ºC/85%RH and thermal cycling
(from -40ºC to +85ºC) has demonstrated a robust and reliable technology
30
IME Product Portfolio
31
Product Composition Rs mΩ//25um Comments
ME602 Ag ~ 45 PC friendly & for over-printing on Graphic inks
ME603 Ag ~35 PC compatible & improved Ag show-through (on Proell inks)
ME60x New - In development
ME101 Ag 15 RFID – NFC antenna
ME10x New – In-development
ME703 Dielectric Under-print High K (improved S/N ratio for Capacitance switching)
ME772 Dielectric Over-print protection - solvent base
ME777 New over-print with UV blocking additive. In scale-up
ME774 Dielectric x-overs/multilayer, UV cure – low elongation areas > 1.2KV BDV
ME775 Dielectric x-overs, solvent base – 3-4 layers (25um), print on graphics inks
ME776 Dielectric x-overs, solvent base – 3-4 layers – improved PC compatibility & bowing
ME77x New – In-development
ME801 T/Conductor < 500 Ω/ Transparent Conductor–High LED/light transmission >90%
ME802 T/Conductor 3-4 KΩ//25um Translucent Conductor – lower cost, higher resistance
ME901 Ag Adhesive 60 1 component – stretchable
ME80x New – In-development
ME201 Carbon 100 Ω//25um Overprint – for connectors & to inhibit Ag migration
Selector Guide & Data Sheets - Inmoldelectronics.dupont.com
Example of Construction and Paste Options
32
Transparent
Conductor
ME801
Interconnecting tracks
ME602/ME603 Ag
Conducting
Adhesive
ME901
Dielectric
- over-print protection ME772
Solvent based
Dielectric
for x-overs
ME775/ME776
Translucent
Conductor
ME802
LED Attach
ME901
Dielectric
- under-print ME775/ME776
RFID – NFC
- Antenna ME101
Thank you,
John Crumpton DuPont Photovoltaic & Advanced Materials Wilmington, DE 19805