Abstract
This article presents a novel method for accelerated wear of squeegees used in screen printing and describes the development of mechanical tests which allow more in-depth measurement of squeegee properties. In this study, squeegees were abraded on the screen press so that they could be used for subsequent print tests to evaluate the effect of wear on the printed product. Squeegee wear was found to vary between different squeegee types and caused increases in ink transfer and wider printed features. In production this will lead to greater ink consumption, cost per unit and a likelihood of product failure. This also has consequences for the production of functional layers, etc., used in the construction of printed electronics. While more wear generally gave greater increases in ink deposition, the effect of wear differed, depending on the squeegee. There was a correlation between the angle of the squeegee wear and ink film thickness from a worn squeegee. An ability to resist flexing gave a high wear angle and presented a sharper edge at the squeegee/screen interface thus mitigating the effect of wear. There was also a good correlation between resistance to flexing and ink film thickness for unworn squeegees, which was more effective than a comparison based on Shore A hardness. Squeegee indentation at different force levels gave more information than a standard Shore A hardness test and the apparatus used was able to reliably measure reductions in surface hardness due to solvent absorption. Increases in ink deposition gave lower resistance in printed silver lines; however, the correlation between the amount of ink deposited and the resistance, remained the same for all levels of wear, suggesting that the wear regime designed for this study did not induce detrimental print defects such as line breakages.
Highlights
As well as conventional graphics printing, screen printing is increasingly being used for a large range of functional devices where thick deposits are required; including but not limited to solar cells [1], fuel cells [2], displays [3], Organic Light Emitting Diodes (OLEDs) [4], transistors [5] as well as sensors for gases [6], humidity [7] and biological materials [8]
Squeegee 2 gave the lowest amount of solvent absorption of all the squeegees and was resistant to absorption of the solvent blend used in the carbon ink; increasing in mass by less than 1% after five hours immersion
A reliable accelerated wear test has been developed for squeegees used in screen printing
Summary
As well as conventional graphics printing, screen printing is increasingly being used for a large range of functional devices where thick deposits are required; including but not limited to solar cells [1], fuel cells [2], displays [3], Organic Light Emitting Diodes (OLEDs) [4], transistors [5] as well as sensors for gases [6], humidity [7] and biological materials [8]. The functionality of the various printed layers in terms of conductive, dielectric, insulating and light emitting properties, for example, will vary if the ink deposition is altered. Where volumes are large or the printed inks contain abrasive elements, the squeegee condition will vary over its lifetime and a decision must be made when to replace it. Research to date has focused principally on the effect of process settings [9,10,11,12] and no work has been reported to explore squeegee deterioration during printing
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
