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Screen or stencil printing of accurate adhesive structures

: Kolbe, J.

Adhäsion. Kleben und Dichten 52 (2008), No.9, Extra: Adhesives & Sealants, pp.24-28
ISSN: 0001-8198
ISSN: 0943-1454
ISSN: 1619-1919
ISSN: 2192-8681
Journal Article
Fraunhofer IFAM ()
Fließverhalten; Klebstoff; Mikrofertigung; rheologische Eigenschaft; Schablonendruck; Scherspannung; Siebdruck; thixotropes Verhalten; Viskosität; zähflüssige Strömung; Zeitabhängigkeit

The following conclusions can be drawn from the connections between the flow behaviour of the adhesives and the results of the screen and stencil printing test: 1) Adhesives with structurally viscous behaviour are best suited to screen and stencil printing. If adhesives with thixotropic flow behaviour are used, they must be able to reconstruct their thixotropic structures within a very short period of time. 2) The viscosity of the adhesive at shear rates from 0.01 to 0.1 should be as high as possible. The current findings indicate that the viscosity should be higher than 500 Pa s. 3) A high viscosity at a low shear rate is not the only criterion which indicates the suitability of the adhesives for screen and stencil printing. For printing very detailed structures, a noticeable flow should only occur at shear stresses of 80 Pa or above, with a viscosity of 300 Pa s or greater. When testing the suitability of an adhesive for screen and stencil printing, it is important to identify first of all whether it has a time-dependent flow behaviour. If this is the case, the adhesive must be subjected to pre-shear before the measurements are made. The flow behaviour in the low shear rate range is the decisive factor. Measurements relating to shear stress up to a shear rate of 10 1/s have proved to be suitable.
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