Inkjet Printing of Conductive Materials

Inkjet printing has not only become a versatile tool for graphical printing. Fur- thermore this technology is already in in use for numerous applications of selective material deposition. Inkjet printing is a digital and contacless method. By means of this technology material is deposited in an additive manner without interaction of the print head with the substrate. New materials for printing electrical conduc- tive structures are on the market. Details and experiences using these materials with microdrop print heads are reported here.

Materials Several so called nano-inks are on the market. Those inks are mostly a mixture of volatile solvents and nano sized parti- cles of metal such as , or the most common . The mechanism for establishing a reasonable conductivity is that after printing the solvents evaporate and a silver trace is left. The nano silver needs to be sintered at temperature abo- ve 150°C. Conductivities up to 10% of bulk silver are reached.

Technology microdrop Technologies is specialised in developing instrumentation and processes for inkjet printing and microdispensing. For printing nano inks the microdispen- ser heads MD-K-130 and modifications with adapted nozzle design are used. For printing structures as lines, curves and complex combinations of these elements the heads are mounted onto the Auto- drop Professional System. The integra- ted software tool allows to print imported graphical files immediately. 22844 Norderstedt /Germany Tycho-Brahe-Kehre 1 microdrop TechnologiesGmbH Inkjet PrintingofConductiveMaterials smaller structures. investigations are focussed on achieving conductivity are possible. Our proceeding down to 100µm with a reasonable good ject G1RD-CT-2002-00656). Structures ble with microdrop technology (EC pro- ted that such materials are good printa- mean size: 2.4 µm. It was demonstra - a sin with high content of silver particles; The material isbased on an epoxy re mechanical bond strength is required. good electrical conductivity also good tive adhesive (ICA) are in focus. Beyond Beside nano inksalsoisotropicconduc Conductive adhesives Kapton andothers. ing substrates: Glass, paper, silicone, we have experiences with the follow strate material. For printing nanoinks contact angle between liquid and sub- the The wetting ismainly controlled by the on dependent only interaction between both materials. is substrate the contactless The behaviour of the droplet hitting of principle can be deposited on any substrate. the dispensing the inkjet technology liquids to Due Substrates Fax: Phone: - +49 (0)4053 83-24 +49 (0)4053 83-0 - - interupted electricalconnections. pattern. This aswellminimizes the risk of with the print head following a continious by using a plotter-like printing algorithm bitmap printingisminimizedmultinozzle ved. The risk of displacement inherent to silver particles over the surface is obser an with inhomogeneousof the distribution tent. Typically a so called coffee stain effect , evaporation and material con- substrate is controlledby , terial. The behaviour of nano inks on a by defined viscosity and surface tension of the ma is process forming drop The Process www.microdrop.de [email protected] - -

04/2016-e subject to change without prior notice