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Rheological properties of silver filled polymer suspensions and their effects on printing performance

Presented at the 10th Annual European Rheology Conference, AERC 2015, April 14-17 2015, Nantes, France
 
: Reinhardt, Kathrin; Eberstein, Markus; Hübner, Nancy; Saphiannikova, Marina

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Poster urn:nbn:de:0011-n-3641992 (548 KByte PDF)
MD5 Fingerprint: 49c296f9aecc840eadcef80dcdb92786
Created on: 12.11.2015


2015, 1 pp.
Annual European Rheology Conference (AERC) <10, 2015, Nantes>
English
Poster, Electronic Publication
Fraunhofer IKTS ()
paste rheology; thick film; screen printing

Abstract
Screen printing of pastes is the major structuring approach in the ceramic thick film technology by which narrow conductor, resistor and isolation layers are assembled to highly integrated sensors and microsystems. Thereby a paste is a suspension by a solvent, a polymer and an inorganic filler. Understanding the rheological properties is crucial for setting an optimal high-precision printing. Previous works have shown that the measurements of flow curves1 or the considerations of oscillation analysis2 of thick film pastes correspond to the printing behavior. However, the basic knowledge regarding correlations between therheological data and the paste recipe is still limited. For example different polymer types and their effect on the printing performance have not been studied in detail. To evaluate these parameters two polymers (ethyl cellulose (EC) & polyacrylate (PA)) were investigated, where each having a chain length variation. The polymers were solved in an organic fluid and formulated with silver powder to model thick film pastes (solids content of 40 vol%). Rotational (0.1-1000 rad/s) and capillary viscosimetry (1000-6000 /s) were carried out. A significant difference regarding viscosity and shear thinning can be observed. The PA system is more shear thinning at <100/s than the EC system and shows even a stronger deviation at >1000/s. Using time-dependent rheological experiments, relations between shear stress induced dispersion configurations were examined. The measured rheological curves were fitted with several equations to reflect a relationship between polymer, chain length and filler. Correlations are discussed in terms of polymer chain lengths, shear rate-dependent viscosities and printing resolution.

: http://publica.fraunhofer.de/documents/N-364199.html