Dip coating of dielectric and solder mask epoxy polymer layers for build-up purposes

Polymer coatings used as build-up layers in advanced printed circuit boards (PCBs) are usually applied through curtain coating or lamination for industrial purposes. Dip coating can be used as an easier and cheaper way of applying a build-up layer, in particular for research purposes, because of the relative high viscosity of liquid polymer solutions used for build-up layers or solder mask layers. The thickness of the deposited layer is examined on different substrates and can be varied with great ease and small variance by changing the pull-out speed. The experimental thickness of the coated layer is compared to various models existing in literature. The deposited polymer layers show a thickening effect in comparison to the Landau and Levich theory. This thickening effect depends on the properties of the polymer solution and the substrate on which the polymer layer is applied. The coated thickness of polymer solutions is influenced by a number of phenomena, such as normal stresses, non-Newtonian viscosity effects and influences of gravity. More practical empirical thickness models are developed and fitted. Polymer solutions containing inorganic filler particles show a different coating behavior in comparison to polymer solutions containing no filler particles.