Printed Electronics
Overview of Inks, Substrates, Processes and Applications
Insulectro
Two Broad Categories
Fired On Polymer Thick Film
• Very High Temperature Processing. – Ceramic substrates
– Screening and “Tape” application of conductors and dielectrics.
– Furnace sintering @ 850°C
• Applications – RF circuits, O2 sensors,
very high temp environments.
• Polymer binder with conductive filler. – Wide range of substrates. – Flexible. – Operating temps from 50 to
260°C depending on ink and substrate.
– Very wide range of applications. • Wearables
– Printable chemical sensors.
Polymer Thick Film (PTF) Circuitry
Truly “additive” printed circuitry, where conductive material is printed onto various substrates, PET, polycarbonate, polyimide ,
fluoropolymers, and paper.
Exposed conductor Dielectric
Printed Electronics 1. Substrate acts a printing base
2. Conductors are printed
3. Dielectrics are overprinted twice
4. Conductors may be applied again
5. Dielectrics printed again as a
coverlay
• Through holes are drilled in the substrate and the right ink can make the connection.
• Conductive adhesive is used for component assembly.
Materials of Printed Electronics
Conductors & Dielectrics (Inks) Substrates
• Polyimides
• Epoxies
• Acrylics
• Thermoplastics
• Kapton (Polyimide)
• Paper
• PEEK
• PEN
• Heat Stabilized PET
• Polycarbonate
• PVC
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Thermoplastic Acrylic
• Fast drying
• Flexible
• High adhesion
• Low Temp
• Long shelf life
• Can be soldered
• Flexible
• High adhesion
• Medium Temp
• Long shelf life
Binder System Groups
Epoxy Polyimide
• High Strength
• Can be plated
• Can be soldered
• Cold limited Storage
• Flexible
• Fast drying
• Can be plated
• Can be soldered
• Long shelf life
Binder System Impacts
• Thermal Performance – Operating Temperature • Adhesion • Flexibility • Drying/cure Time and Temperature • Storage Requirements – Shelf Life • Function
Overview of Ink Families • Standard inks
• Low temperature dry/cure
• Stretchable – Wearables
– In-mold
• High operating temperature
• High conductivity
• Sensors
• Fired/sintered
Examples of DuPont Thermoplastic Inks
• Carbons – DuPont 7102, DuPont 7105, DuPont 8144
• Silvers – DuPont 5025, DuPont 5028, DuPont 5065
Silvers
• Silver/Silver Chloride – DuPont 5880, DuPont 5876, DuPont 5874
Polyimide Ink -Printed heater on FR4
DuPont KA801
Wearable Printed Sensors & Interconnects
• Fabric
• Thermoplastic Polyurethane (INTEXAR™)
• Stretchable Conductor (PE872, PE873)
• Stretchable Sensor (PE971)
• Encapsulant Overprint (PE773)
How do Conductive inks work?
• For inks that are not sintered, (thermoplastic, thermoset, UV cured) – Close inter-particle contact is necessary – This is done as the binder (polymer) shrinks
• Resistance can be increased by barrier coatings (oxides) on the particles of the conductive filler. – This is why silver is the most popular conductive particle, silver oxide is
very conductive.
As Applied Processed
SEM of Dried Ink
Thermoplastic Screenprintable Ink (Ag loading 89%)
Very dense packed Ag structure
SEM Highly Filled Silver Ink
Super dense-packed Ag particle/network
Photonically Sintered Copper
Printed Cu Antenna on FR-4 Effect of photonic sintering
• Photonically heated copper ink overcomes the challenge of copper oxidation.
• Ink is heated much faster than the substrate.
• Ink is heated much faster than the substrate.
Ink Compatibility
• Need to consider compatibility. Extremely Important, wrong product selection can lead to issues! – With Conductors, dielectrics, and substrates
– With graphic inks, and conductive adhesives
– The materials must work together.
• No re-softening (dielectric over ink)
• No change in resistance
• No adhesion issues
• No flexibility issues
Application of conductive inks
• Screen printing (most common) • Flexographic printing • Rotogravure printing • Ink Jet (New)
Rotary screen Flat-bed screen Flexography Rotogravure
Printing speed and typical tooling cost
High Speed Printing
Performance and Testing
– Resistivity measurements – Flexibility/Creasibility – Environmental performance – Adhesion/Cohesion
Application of conductive inks
• Screen printing • Flexographic printing • Rotogravure printing
Rotary screen Flat-bed screen Flexography Rotogravure
Printing speed
High Speed Printing
Screenprinting
Example: Screen Recommendations
• DuPont 5025, thermoplastic Silver, Thermally dried – 255/48 PE mesh, 5-7µm EOM, 25 Newtons, ~22° angle, use up to
50% of frame ID for image area. This will provide a dry film thickness ~ 10 microns or 0.4 mils.
• DuPont 5018, UV cured – 255/40 PE mesh, 5-7µm EOM, 25 Newtons, ~22° angle, use up to
50% of frame ID for image area. This will provide a dry film thickness ~ 19 microns or 0.75 mils, per pass, two passes are recommended
Mesh size controls print (wet) thickness
Screening is capable of fine lines
38% Ag 80% Ag
65% Ag
10 mil Line/Space
5 mil Line/Space
5 and 5 with standard screening, below with special processing
Silver content does not necessarily determine
fine line capability.
Conveyor drier
Static oven
Processing: Drying and Curing
UV-curing unit
IR Dryer
Many inks dry @ 300F
Low temp inks dry @ 200F
Sensor Inks: Ag / AgCl • Inks based on silver/silver chloride can be used for onboard
electrochemical sensors. • They can matched with chemistries to sense and measure many
different ions/compounds.
Printed Electrodes for Solution Analysis
Markets for Printed Electronic Inks
• Circuit Materials
• Medical Applications/Sensors
• High Speed Printed Electronics
• RFID Applications
• Automotive
• Display, Lighting, Windows
Markets for Printed Electronic Inks
• Printed Sensors – Homeland security applications – Blood glucose, urine, cumidin analysis
• Printed heaters – Automotive seat heaters – Printed heaters for floors and ceilings – Printed heaters for modular or integrated systems
• Solar Cell applications – Rigid – Flexible
• Many applications – Electronics everywhere (Internet of things)
• New materials/processes are continually being developed
• Many Inks that meet that meet the following needs • High conductivity
• Flexible
• High operating temperature
• Low temp processing
• Solderable
Printed Electronics
Useful Links
• Insulectro
• DuPont Microcircuit Materials
– Printed Electronics
– Wearables
– In-Mold
– Fired On (Hybrid)
– Biomedical
