Screen printing process parameters

Zhang, Y. et. al., A study of the process parameters for yttria-stabilized zirconia electrolyte films preparcd by screen-printing, J. Power Sources 160 (2006) 1065-1073. 

Over 100 variables have been identified that affect the screen-printing process, ranging from the paste properties to the printer setup to the screen properties. Only a few of these are witiiin the control of the process engineer. Adjustments in tiiese parameters can compensate for most of the remainder. 

In the printing process it is desirable for the pattern formed on the screen to be transferred directly onto the green sheet in the medium of the paste. The printing conditions have the greatest impact on this print transfer quality, although the appropriate printing conditions vary depending on the screen and paste used so that they must be optimized on each occasion. The next section covers the various process parameters. 

Another important parameter is the size of the opening in the screen, which strongly influences the amount of paste that can be transferred during the printing process, and limits the maximum particle size of the material used to manufacture the paste. The opening is dependent on both the mesh size and the wire count as shown in Figure 5.5, and may be calculated by Equation 5.1 ... 

In the off-contact printing process, tiiis is arguably the most important parameter in the screen printer setup. If it is too large, the screen will rapidly lose tension and the print will lose definition. If it is too small, the tension on the screen during the print will not be sufficient to transfer the paste to the substrate. Referring to Figure 5.19, the magnitude of snap-off is dependent on the size of the screen, with a ratio of maximum screen dimension to snap-off of 200 1. A list of typical snap-off distances for a sample of standard-size screens is shown in Table 5.3. 

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