Monotonic and cyclic mechanical reliability of metallization lines on polymer substrates

TL;DR

This study compares the mechanical reliability of printed and evaporated metallization lines on polymer substrates under monotonic and cyclic loading, revealing trade-offs between ductility and cyclic stability influenced by microstructure and thickness.

Contribution

It provides new insights into how grain size and film thickness affect the cyclic and monotonic mechanical stability of metallization lines on polymers.

Findings

Evaporated lines with larger grains show good ductility but fail early in cyclic tests.

Printed lines with nanocrystalline microstructure resist cyclic cracking better.

Thinner films exhibit higher crack density after cyclic bending, consistent with shear lag model.

Abstract

Mechanical stability of Ag and Cu printed and evaporated metallization lines on polymer substrates is investigated by means of monotonic tensile and cyclic bending tests. It is shown that lines which demonstrate good performance during monotonic tests fail at lower strains during a cyclic bending tests. Evaporated lines with the grain size of several hundreds of nanometers have good ductility and consequently good stability during monotonic loading but at the same time they fail at low strains during cyclic bending. Printed lines with nanocrystalline microstructure, in contrast, demonstrate more intensive cracking during monotonic loading but higher failure strains during cyclic bending. Apart from the grain size effect, the effect of film thickness on the saturation crack density after cyclic bending is also demonstrated. Thinner films have higher crack density in accordance with the shear lag model.