Adhesion testing of printed inks while varying the surface treatment of polymer substrates

ABSTRACT

Additive manufacturing with conductive materials enables new approaches to printed electronics that are unachievable by standard electronics manufacturing processes. In particular, electronics can be embedded directly into structural components in nearly arbitrary 3D space. While these methods incorporate many of the same materials, the new processing methods require standard test methods to compare materials, processing conditions, and determine design limits. This work demonstrates a test method to quantitatively measure the adhesion failure of printed inks deposited on a substrate without changing the ink printing conditions. The proposed method is an adaption of single lap shear testing in which the lap joint is created by bonding the second substrate to the ink after curing. It was found that the interfacial shear strengths are independent of the adhesives used to attach cured conductive ink to the second substrate. In addition, chemical surface treatments of flame and plasma and mechanical sand-blasting increase the interfacial shear strengths by ~25% and 80%, respectively, while altering the adhesive failure mode to cohesive failure for most cases. This work also shows extruded substrates with undulated features increase adhesion strength; therefore, in addition to surface treatments, the geometric freedom of additive manufacturing (AM) could be leveraged to design surface features for enhanced adhesion.

KEYWORDS:

• Additive manufacturing
• adhesion
• conductive inks
• printed electronics
• single lap shear testing
• surface treatments