High throughput adhesion testing using a modified edge lift-off test
Jiong Liu, Martin Y. Chiang, Michael J. Fasolka, Christopher M. Stafford
The strength of an adhesively bonded joint depends on a host of factors such as surface treatment, roughness, materials properties, cure conditions and environmental variables. Therefore testing of adhesion within this large parameter space can be very time-consuming and expensive. The ability to screen candidate materials quickly remains a measurement challenge for coating manufacturers to meet rigorous adhesion requirements. It would be attractive to perform simultaneous measurements of interfacial adhesion on samples or libraries having discrete or continuous changes in two or more of these controlling factors. The modified edge lift-off test (mELT) is commonly used in the electronic packaging industry to evaluate the adhesion of interfaces with multilayer structures. This test requires a rectangular coupon of a defined substrate material to be coated with a thin film of interest. A thick polymer backing layer is coated onto the test film as a stress-generating layer. The sample is subjected to thermal quenching which leads to delamination events due to the thermal coefficient mismatch between the polymer and substrate. Previous work at NIST demonstrated a combinatorial approach to the edge lift-off test, allowing the simultaneous interfacial adhesion measurements to be performed on a single substrate possessing a combinatorial library on its surface. In the present work, we discuss the latest developments in library design and fabrication for adhesion testing via mELT. In particular, we demonstrate that this test can be used as a high-throughput tool to study the effect of processing conditions of adhesion promoters on adhesion strength of polymer/inorganic interfaces.