Film thickness prediction in halftone screen-printing

Fox, Ian; Bohan, M. F. J.; Claypole, Tim; Gethin, D. T.

doi:10.1243/095440803322611705

Cited by 10 publications

(14 citation statements)

References 6 publications

(13 reference statements)

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“…12 However, squeegee pressure, snap-off distance (the distance between the screen and the substrate) and print speed have not demonstrated consistent trends and have been shown to vary with the rheology of the ink. [12][13][14][15][16][17][18] Yet, there has only been limited fundamental research to establish the underpinning science of screen printing. The fundamental mechanisms behind this process remain poorly understood.…”

Section: Introductionmentioning

confidence: 99%

High-speed imaging the effect of snap-off distance and squeegee speed on the ink transfer mechanism of screen-printed carbon pastes

et al. 2019

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Screen printing is the most widely used process in the production of printed electronics due to its ability to consistently transfer inks containing a wide range of functional materials onto a range of substrates. However, despite its extensive use, the mechanism by which the ink is transferred through the mesh and onto the substrate is not fully understood. Existing theories are contradictory and lack experimental validation. Therefore, high-speed imaging was used in combination with a screen-printing simulation rig that was designed to provide good optical access to study ink deposition during the screen-printing process. The variation in the four stages of ink flow through the screen, described in the theory by Messerschmitt, has been quantified with respect to changes in snap-off distance and squeegee speed. Analyses of the images were compared with measurements of the ink properties and corroborated with analyses of the prints. This has provided a better understanding of the mechanism by which the ink transfers from the mesh to the substrate and subsequently separates in screen printing. This could be used as the basis for the development of predictive algorithms, as well as to improve the understanding of how to optimize print quality and performance.

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Section: Introductionmentioning

confidence: 99%

High-speed imaging the effect of snap-off distance and squeegee speed on the ink transfer mechanism of screen-printed carbon pastes

et al. 2019

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“…Also, squeegee load has least in uence at the low open area. This is because the squeegee load is reacted to by the impermeable screen, and at the largest open areas the squeegee pressure reacts directly to force more ink through the screen [12]. However, from the parameters investigated, alteration of the squeegee pressure has least effect on density owing to the rigid nature of the roller squeegee, which will therefore have a minimal impact on the prints.…”

Section: Process Parameter Investigationmentioning

confidence: 99%

“…However, the change in snapoff with changes in roller diameter leads to an increase in contact between the roller and screen. Also under this circumstance, the hydrodynamic component may become more important, and for a given squeegee load this will result in a thicker lm and consequent increased pumping capacity [12]. …”

Section: Snap-off Studymentioning

confidence: 99%

An experimental investigation into ink transfer using a roller squeegee in high-speed screen printing

Fox

Claypole

Gethin

2003

Proceedings of the Institution of Mechanical Engineers, Part E:

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The paper describes a series of experiments on precision screen-printing with a roller squeegee. The work showed that this could only be achieved using a screen having a high mesh count, notably using a 150-34 screen, since a lower thread count offers insuf cient resistance to ow and leads to image ooding. A detailed investigation into process parameters showed that at up to 60 per cent coverage the performance of a roller squeegee in either sliding and rolling mode is identical. Above this coverage and for smaller snap-off gaps, the roller squeegee constrained to slide led to a higher ink coverage. It is suggested that the main reason for this is the viscosity reduction at the screen surface on account of the ink characteristics and the high local shear rates. This dominates the higher hydrodynamic pressure associated with the rotary motion. However, the rolling action leads to superior tonal gain characteristics. It was observed that, when the squeegee was locked, the screen adhered to the substrate, reducing the snap-off speed and increasing the contact duration. The combined effect led to an increase in ink deposit. When the snap-off gap was increased suf ciently to prevent the screen from adhering to the substrate, the rotating squeegee produced considerably higher ink deposit than the locked squeegee. Presently, this is believed to be due to the increase in hydrodynamic pressure within the squeegee nip junction which now becomes a dominating mechanism.

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“…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.…”

Section: Introductionmentioning

confidence: 99%

A Study of the Abrasion of Squeegees Used in Screen Printing and Its Effect on Performance with Application in Printed Electronics

et al. 2014

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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, OPEN ACCESSCoatings 2014, 4 357 suggesting that the wear regime designed for this study did not induce detrimental print defects such as line breakages.

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Film thickness prediction in halftone screen-printing

Cited by 10 publications

References 6 publications

High-speed imaging the effect of snap-off distance and squeegee speed on the ink transfer mechanism of screen-printed carbon pastes

High-speed imaging the effect of snap-off distance and squeegee speed on the ink transfer mechanism of screen-printed carbon pastes

An experimental investigation into ink transfer using a roller squeegee in high-speed screen printing

A Study of the Abrasion of Squeegees Used in Screen Printing and Its Effect on Performance with Application in Printed Electronics

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