Tiny Bubbles: Determining the Cause of Blisters in a Screen Printed Elastomeric Ink

When an ink is screen printed, air is inevitably worked into the printed bead.  How quickly this entrapped air is able to escape from the bead determines whether or not a blister will form when the ink is dried and cured.  Good and bad lots of ink were studied to determine the source of blisters.  Following an overview of the ink manufacturing process, we will outline the physical properties that influence bubble formation and escape: namely, surface tension and rheology.  Next, a comparison of these two key properties for good and bad lots will be offered with a focus on rheology.   Molecular weight distribution of the elastomer and particle size distribution of the filler are then contrasted, leading to the proposal of a hypothesis.  Particle size distribution of the ground filler plays a key role in the rheology of the coating and subsequent blister formation.