InkjetInkjet PrintingPrinting ForFor MakingMaking FineFine ConductorsConductors andand MultiMulti••LayerLayer ElectronicsElectronics

Liisa Hakola, Research Scientist VTT –Technical Research Centre of Finland

e|5: UV & EB Technology Expo & Conference April 24th, 2006 OutlineOutline

1. VTT overview

2. Inkjet technology

3. Inkjet for making

4. Inkjet printing conductors

5. Inkjet printing multi•layer electronics

6. Summary

April 24th, 2006 Liisa Hakola 2 VTTVTT ––TechnicalTechnical ResearchResearch CentreCentre ofof FinlandFinland

n Impartial and multidisciplinary n 2,900 employees expert organisation n Turnover 220 million €, 5000 customers n Confidential research projects, STRATEGIC joint venture projects and strategic, RESEARCH self•financed research BUSINESS New SOLUTIONS enabling technologies VENTURES EXPERT VTT•wide SERVICES sales and marketing IPR, spin•offs Productive consulting services Research and development

April 24th, 2006 Liisa Hakola 3 DigitalDigital PrintingPrinting ResearchResearch atat VTTVTT 19951995••20072007

PUBLICATION: Quality Potential of Digital Photo Innovative PRINT Printing Development of Integrating INTERACT Ink Jet (NI) Printed and Dynamic Interactions and Image Electronic Media Quality in Ink Jet Printing PRINT ACCESS Business from (EPP•Programme) Microscale Publications Functional Dynamics in Applications of Printing Home Printing Ink Jet Printing High Speed IJ From Network Manufacturing Technologies Functional Inks in Based on Inkjet Inkjet Printing MANUFACTURING: ICT Surface Printable Applications Proximity Quality Assay Indicator Printable Optics and Electronics PRINTO Sustainpack Printing of On Demand Package Printing (EU IP) PACKAGING: Variable Information Communication in Consumer Packages on Packages

1995 1998 2001 2004 2007

April 24th, 2006 Liisa Hakola 4 InkjetInkjet researchresearch environmentenvironment atat VTTVTT

n State•of•the•art, industrial, piezo electric inkjet printheads ® research results upscalable for production

Water•, oil• and solvent•based inks UV•curable inks Hot melt inks and waxes Conductive and dielectric inks Biochemical and diagnostic fluids Indicator fluids

April 24th, 2006 Liisa Hakola 5 PrintingPrinting methodsmethods

Printing methods

Conventional Digital printing printing

Offset Electrophotography Inkjet

Drop•on• Flexography Dry toner Continuous demand

Binary Gravure Liquid toner Thermal deflection

Multiple Screen printing Piezo•electric deflection

Binary

Greyscale

April 24th, 2006 Liisa Hakola 6 InkjetInkjet printingprinting comparedcompared toto otherother printingprinting technologiestechnologies

Inkjet Conventional printing methods n Customisation, small series n No variable data, large volumes n Printing speed increasing (currently n Mass manufacturing with high around 1 m/s) speed (around 20 m/s) n Substrate independent n Not all substrates suitable n Ink development challenging n Ink development not so n Easy to integrate with existing challenging production lines n Integration requires space and changes in existing production lines

April 24th, 2006 Liisa Hakola 7 InkjetInkjet printingprinting technologytechnology

n Digital non•impact printing Drop•on•demand ink•jet method, additive Heater n Substrate independent Orifice n Accurate, high resolution, high speed n Possibility for mass customisation Ink Pressure n Low material consumption chamber n Inks for all kinds of applications

Continuous ink•jet

Drop generator Charge High•voltage Substrate electrode deflection plate Gutter

April 24th, 2006 Liisa Hakola 8 BenefitsBenefits ofof inkjetinkjet printingprinting inin printedprinted electronicselectronics

n Direct write of electronic components and circuits n less manufacturing steps n less material waste n cost savings n shorter turnaround times ĺ small series and customisation

printing material Inkjet printing: substrate

Photolithography: mask + expose spin• e.g. resist etching cleaning

material substrate

April 24th, 2006 Liisa Hakola 9 ApplicationApplication areasareas forfor inkjetinkjet printedprinted electronicselectronics n Not meant to replace traditional manufacturing methods n Low•cost devices n Low performance, single•use, disposable devices n New application areas n New features to printed products n Hybrid printing ĺ inkjet for customisation n Multiple material deposition with several printheads n Layering of materials ĺ 3D structures

Printhead Heat UV IR Curing Curing

etc. Conductive Dielectric Resistor Conductive Semi• Protective ink ink ink ink conductive layer ink

April 24th, 2006 Liisa Hakola 10 NanoNano••particleparticle inksinks forfor makingmaking conductorsconductors n Small particle size and ink stability crucial in inkjet printing n Nano•particles provide n high metal loading with low viscosity n ink stability Curing n jetting reliability n low curing temperature n Metal nano•particle inks provide printed conductors with low resistance values n even in the range of µƙ

April 24th, 2006 Liisa Hakola 11 InkjetInkjet printingprinting finefine conductorsconductors n Lines as fine as possible and 50 µm silver continuous nano particle n conductor n Drop size and spreading define line printed at VTT on width n Print resolution defines line continuity n Substrate pre•treatment or pre• patterning 100 µm

2.4 mm

2.4 mm

April 24th, 2006 Liisa Hakola 12 InkjetInkjet printingprinting multimulti••layerlayer electronicselectronics

Dielectric n Transistors, displays, passive components n Multi•colour printing n at least one printhead for each ink Electrodes Resistor layer n color registration n Interactions between different materials n printing on substrate vs. printing on ink layer Conductor n colour bleed n Ink availability

Ferrite layer Conductor April 24th, 2006 Liisa Hakola 13 UVUV••curablecurable dielectricdielectric inkink forfor inkjetinkjet printingprinting n Printing in elevated printhead Example of capacitor

temperature 1st silver n Drying with absorption andand UVUV electrode light n Good wear resistance n High gloss n Smooth ink layer without pin 2nd silver holes electrode

Dielectric inkjet printed between electrodes

April 24th, 2006 Liisa Hakola 14 ExperimentalExperimental

10 cm n UV•curable polymer based dielectric ink (yellow) n Curing with 120 W/cm H bulb UV light source for 20 seconds n 1 or 2 ink layers n Silver nano•particle ink (black) n Curing in 120 oC for 15•30 minutes n 1 or 2 ink layers n Paper and substrate n Piezo•electric inkjet, 80 pl drop size, 630 dpi resolution

April 24th, 2006 Liisa Hakola 15 HeightHeight profileprofile ofof UVUV••curedcured dielectricdielectric inkink layerslayers onon plasticplastic substratesubstrate

70 10 ink layers, UV•curing 30 s 60 peak over scale

50 5 ink layers, UV•curing 30 s

~45µm 40 Z (µm) 30

1 ink layer, UV•curing 10 s 20 ~20µm 10 ~13µm 1 ink layer, UV•curing 30 s 0 0 200 400 600 800 1000 1200 1400 1600 1800 X (µm)

April 24th, 2006 Liisa Hakola 16 PerformancePerformance ofof multimulti••layerlayer electronicselectronics

•on paper increase in amount of dielectric 600 mƙɷ • 220 ƙɷ layers increases resistance on top of it

~1 • 200 ƙɷ 60•190 mƙɷ

> 1 Mƙɷ 1 layer dielectic and 1 layer silver on paper 190 mƙɷ Ⱥ pin holes?

April 24th, 2006 Liisa Hakola 17 SummarySummary n Inkjet printing suitable method for manufacturing electronics n Fine inkjet printed conductors possible even without substrate pre•treatment n Metal nano•particle inks produce conductive structures with low resistance n Inkjet printing suitable method for making multi•layer structures n UV•curable dielectric ink produces smooth and thick ink layers

April 24th, 2006 Liisa Hakola 18 ThankThank youyou forfor youryour attentionattention!!

Liisa Hakola, Research Scientist

VTT –Technical Research Centre of Finland Functional Printing

P.O.Box 1000, FI•02044 VTT, Finland phone: +358 20 722 7206 fax: +358 20 722 7052 e•mail: [email protected]

April 24th, 2006 Liisa Hakola 19