Potentials of Aerosoljet Printing for Manufacturing 3-D MID

Prof. Dr.-Ing. Joerg Franke Institute for Factory Automation and Production Systems Potentials of Aerosoljet Printing for Manufacturing 3-D MID Friedrich-Alexander-University Erlangen-Nuremberg PEP - Centre Technique de la Plasturgie, Bellignat, December 06, 2012

Contents of the presentation Potentials of Aerosoljet Printing for Manufacturing 3-D MID. 1. Aerosoljet Printing for MID 2. Printed Circuit Tracks on Thermoplastic Substrates 3. Printing on Plastic RP-Materials for MID Prototyping 4. Conclusions and Outlook J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 2

Introducing adapted printing technologies can push the limits of established process chains of Molded Interconnect Devices. 3-D Molded Interconnect Devices Integration of mechanical and electronical functions Short process chains Miniaturization / optimized installation space Few processes with high layout flexibility Often chemical processing for metallization required Only limited multilayer options Limited range of substrate materials for each structuring/metallization process Application of digital printing technologies as an innovative approach to functionalize injection molded circuit carriers Printed Electronics Current processes adapted to planar substrates Limited performance hybrid systems Long term reliability of printed structures Increased performance of printing processes Additive processing Broad range of printable (semi-)conductive and isolating/dielectric materials No specific substrates required J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 3

Line width source: Optomec From the view of automation Aerosoljet printing provides several advantages for printing functional structures on 3D substrates. Virtual impactor Pneumatic aerosol generation (alternatively ultrasonic) Carrier gas (nitrogen) Exhaust gas Sheath gas (nitrogen) Nozzle Fine (<100 µm) as well as wide (>> 1 mm) structures can be printed Broad spectrum of materials processible (particle size up to 500 nm; viscosity 0.7 1,000 mpas ) Functional ink (e. g. nanoparticle Ag) Substrate Compact geometry of the deposition head >3 mm (depending on nozzle) Nozzle Wide range of operation due to the focal length of the aerosol beam (to compensate uneven surfaces and placement errors) Distance nozzle to substrate J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 4

Contents of the presentation Potentials of Aerosoljet Printing for Manufacturing 3-D MID. 1. Aerosoljet Printing for MID 2. Printed Circuit Tracks on Thermoplastic Substrates 3. Printing on Plastic RP-Materials for MID Prototyping 4. Conclusions and Outlook J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 5

Aerosol-Jet printing on spatial injection molded substrates can be realized by applying additional handling systems. Aerosol-Jet-Printer combined with 3D handling sytem: Pneumatic atomizer Aerosoljet printer head Printing on 3D surfaces and even inside small cavities: Source: neotech Ultrasonic atomizer Grabber / workpiece carrier Printed tracks on a plastic container with circuitry on the front wall and printed capacitive sensors on side walls 6-axis-robot for substrate handling Process control module (Aerosol-Jet) J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 6

Inks containing nano-silverparticles are printed and afterwards sintered to generate conductive tracks on the molded circuit carriers. Nanoparticle inks: Metallic particles Processing: 1. Printing 2. Drying 3. Sintering Organic coating Solvents and dispersant agent y Example Cabot CSD 66 Particle material Ag Solvent Ethylene glycol Ag content 45-55 wt % Viscosity 50-100 cp Particle size < 60 nm source: Cabot source: Ohm-University Nuremberg source: Ohm-University Nuremberg Thermal processing of the inks is required Higher temperatures enhance conductivity Definition of process windows for thermoplastics J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 7

track resistance in Ω The surface quality of the molded substrates has to be considered for reproducible printing results. Printing of thin layers: Influence of the molding tool / surface quality: 60 x 60 mm² plaque height: typically 2 µm ground milled polished 8 6 4 2 tool material 0 PA6.6+ 30%-GF PA6+ 40%-MB PA6+ 20%-GF PBT/ASA +20%-GF Reduced contour defintion due to capillary action / bleeding at scratches etc. J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 8

Printed structures show acceptable results after basic long term reliability testing, but require further improvement. Thermal shock test -40 C / +125 C: 1000 cycles and Humidity heat 85% r.h. / 85 C: 504 h Four-point probe measurement to analyze the resistance of printed tracks: Average change < 10 %; in some cases post-sintering can be obtained that improves conductivity; low influence of the thermal mismatch (CTE(Ag) << CTE (substrate)) detected Cross Cut / Tape testing to determine adhesion strength: grade PA6.6+ 30%-GF PA6+ 40%-MB PA6+ 20%-GF PBT/ASA+ 20%-GF after sintering < 5% < 5% < 5% < 5% after 1000 cycles thermal-shock after 504 h humidity heat < 35% < 5% < 5% < 5% > 65% > 65% > 65% 35% percentage of the silver film pulled off in tape test Visible oxidation of printed silver layers High water absorption of polyamide grades! Research on improvement of adhesion; employment of conformal coating J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 9

Contents of the presentation Potentials of Aerosoljet Printing for Manufacturing 3-D MID. 1. Aerosoljet Printing for MID 2. Printed Circuit Tracks on Thermoplastic Substrates 3. Printing on Plastic RP-Materials for MID Prototyping 4. Conclusions and Outlook J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 10

Smooth surfaces and thermal stable substrate materials provide a good base for printing on parts generated by stereolithography. 1. 2. 3. 1. Liquid epoxy resin layer on the building platform, 2. Selective photopolymerization of the resin by laser radiation, 4. 6. UV 5. 3. Lowering of the building platform in correlation to the layer thickness, 4. Repeating the building process layer by layer, 5. Removal of residual liquid and supporting structures, 6. Final UV-curing of the completed physical model. Good surface quality, low roughness Building of small features and a high level of detail Heat Good resistant surface materials quality for sintering of Agink as well as reflow soldering available Fine features and high level of detail Substrate material CTE /10-4 /K Heat resistance / C Somos Nanotool Accura Bluestone 0.95-0.99 0.81-0.98 258-263 267-284 Research project: Manufacturing of functional 3D-MID prototypes by stereolithography as well as ADDIMID- and Aerosol-Jet-Printing (3A3DMID) J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 11

resistance After a plasma treatment to enhance wettability the conductor tracks printed on stereolithography materials show good reliability. Printing on STL-materials and oven sintering at 200 C Optimization of the wettability by Openair plasmatreatment of the STL-substrate surfaces: Improvement of adhesion: Without plasma treatment: disrupted traces α = 86 α = 28 With plasma treatment: clear-cut lines Cross cut and tape test passed Thermal shock test -40 C/+125 C Measurement of track resistance: Printed conductor track Substrate Printed pads for fourpoint probe measurement 30 Ω 25 20 15 10 5 0 100 500 1000 2000 cycles 1 layer 2 layers 3 layers 4 layers J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 12

Substrates produced in high throughput powder bed printing processes challenge the functionalization by Aerosol-Jetting. Research project: 3D Additive Manufacturing of Electrical and Electronic Applications (3DAMEEA) 1. 2. 3. 4. 6. 5. 1. Application of a powder coating on the building platform, 2. Selective addition of binder material (e. g. by an inkjet-printing unit), 3. Lowering of the building platform in correlation to the layer thickness, 4. Repeating application of powder and binder liquid, 5. Removal of unbound plastic powder, 6. Infiltration with additional liquids/resins and curing to enhance thermal and mechanical properties. Substrate Powder bed Powder material Polymethylmethacrylate (PMMA) Particle size /µm < 85 CTE (PMMA) /10-4 /K 1 Glass transition 100 temperature / C Binder material Polypor A (voxeljet) High potential to integrate printing head for embedded structures rough and porous surface low thermal stability of the substrates J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 13

Light beam sintering can be used to generate conductor tracks on thermal sensitive powder bed substrates. Integrated xenon light beam soldering system for sintering: Resistance < 4 Ω/cm at a line width of 500 µm Simple electronic functionality can be realized Options: Preheating of substrate Curing of electrically conductive adhesive for interconnection of discrete components Light beam sintered conductor tracks Light beam sintered silver track 500 µm Light beam cured ICA for component mounting J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 14

Contents of the presentation Potentials of Aerosoljet Printing for Manufacturing 3-D MID. 1. Aerosoljet Printing for MID 2. Printed Tracks on Thermoplastic Substrates 3. Printing on Plastic RP-Materials for MID Prototyping 4. Conclusions and Outlook J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 15

Conclusions and Outlook The combination of an Aerosol-Jet printer and 3D handling systems enables full 3D printing of circuit tracks on spatial substrates. An adapted window for sintering nanoparticle silver inks on thermoplastic substrates has to be defined for each ink substrate combination. Accelerated ageing tests show the potential to generate reliable printed structures. However further optimization is requried. Circuit tracks printed with silver inks on plasmatreated STL-materials show good reliability and adhesion and provide base for rapid manufacturing of MIDs. Selective sintering methods can be applied for local sintering of silver inks on thermal sensitive substrates (e. g. PMMA powder materials) as well as for curing of conductive adhesives. Further investigations on: Optimized selective sintering process for integrated manufacturing Integration of additonal process steps like plasmatreatment etc. Options to combine printed structures and SMT-components reliably Advanced testing to determine long term reliability J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 16

Prof. Dr.-Ing. Joerg Franke Institute for Factory Automation and Production Systems THANK YOU Friedrich-Alexander-University Erlangen-Nuremberg Egerlandstrasse 7-9 Tel.: +49.9131.8527569 D-91058 Erlangen Fax: +49.9131.302528 www.faps.uni-erlangen.de J. Hoerber, C. Goth, J. Franke Innov' Days - PEP, 06.12.2012 17