DURABLE CONDUCTIVE MATERIALS

FOR ROBUST WEARABLE ELECTRONICS

Leonard Allison – Engineered Materials Systems

Div Nagase & Co.

PTF CIRCUITRY – OUR CHALLENGE !

PCB

Cu Flex

PTF

$56 Bn market per IPC

PTF CIRCUITRY ADVANTAGES

• Lower cost

• Environmentally friendly

• Various functional inks

• Flexible

• Ease of integration into end use device

WHY HAS PTF CIRCUITRY ADVANCED?

• Improved materials

• Improved processes

• Standards development (SGIA/PEMS/ASTM)

• Replacing copper circuitry in harsh environments

WHAT HOLDS PTF CIRCUITRY BACK?

• Ability to attach or integrate IC chips

• Solder vs. silver adhesives

• Conductivity of copper vs. silver

• Finer lines, density with copper

• PTF ink deposit variation

• Silver migration / oxidation

• Durable SMT attachment of passives and LED

DURABLE ADVANCEMENTS ON TRADITIONAL PET FILM

Multiple crease cycles on PET film

SMT withstands mandrel test

Insulation resistance 85/85 5VDC bias

INSULATOR MUST WITHSTAND CREASING ASTM F1683-09

SURFACE ROUGHNESS

Product Measured Ra Value

DI-7542 0.5793µm

Competitor A 1.4479µm

Competitor B 2.0644µm

• Better printing and self-levelling of insulator

• Less defects and pin holes

• Better deposit of silver jumpers

HOW TO TEST INSULATION EFFECTIVENESS

• ASTM F1996 - 06 Standard Test Method for Silver Migration for Membrane Switch

Circuitry

• IPC TM-650 2.6.3.3 Surface Insulation Resistance

• ASTM F1662 - 10 Standard Test Method for Verifying the Specified Dielectric

Withstand Voltage and Determining the Dielectric Breakdown Voltage of a

Membrane Switch

• EMS’ Accelerated Tests

• 85°C / 85% RH testing under 5V bias

• Evaluate migration/oxidation/V breakdown and adhesion

55⁰C / 85% RH for 10 days

non-condensing, < 2mA

25-55⁰C cycling / 90% RH

6.66 days 50 VDC

TEST SAMPLE PREPARATION

COUPONS UNDER TEST

AFTER 500 HOURS 85/85 5 VDC BIAS

FAILURE MECHANISMS

• Loss of dielectric strength

• Discoloration, stress

• Adhesion

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

1000V

1750V

2000V

2500V

2750V

3000V

3500V

4000V

4500V

Dielectric Witstanding Voltageby Insulation Type

H

G

F

E

D

C

B

A

DYNAMIC MANDREL TEST ASTM F 3147-15

ROBUST SMT JOINT

STRETCHABLE ON TPU AND TRANSFER INKS

Mimo Baby motion/heat sensor

Conductive Transfer Ink SystemEasily laminated onto fabric

Stretchable on TPU

STRETCH STRAIGHT LINE

0

20

40

60

80

100

120

140

160

0.00% 10.00% 20.00% 30.00% 40.00% 50.00% 60.00% 70.00%

Resi

stanc

e (Ω)

% Stretch

Impact of Resistance as Substrate is Stretched

Line 1

Line 2

Substrate

American Polyfilm

Substrate

Thickness 10 Mil

Grade VLM 4001

Product CI-1036

Test Method

Motorized

Elongation Test

• Line 1

• Line 2

STRETCH RECOVERY ONE CYCLE

0

100

200

300

400

500

600

700

800

900

1000

0 200 400 600 800 1000 1200 1400

Resi

stanc

e (Ω

)

% Stretch

CI-1036 Hysteresis

Line 1

Line 2

• Material stretched from 0% to 100% to 0%

• Actual Length of stretch is 6”

• Line 1

• Line 2

STRETCH 20% - CYCLES TO FAIL

ANCILLARY STRETCHABLE CONDUCTIVE INKS

CI-2051 CARBONCI-4040 SILVER CHLORIDEDI-7540 UV-CURE INSULATOR

Printed carbon resistorsInsulation top-coat

Carbon top-coatInsulation for multi-layer

STRETCH RECOVERY SILVER AND INSULATOR

• CI-1036 on VLM 4001• DI-7540 on CI-1036 and VLM-4001

• Stretch properties maintained

with the addition of DI-7540

• Excellent hysteresis

CONCLUSION

• PTF Circuitry has made advancements leading to the replacement of copper

circuitry

• Silver migration can be prevented

• Silver/insulator should pass multiple crease cycles ASTM F1683-09

• SMT attachments should pass ASTM F3147-17

• New material durability enables New Form Factor Printed Electronics

• New ASTM standards development underway for ‘stretchable’