Rate effects in metal-ceramic interface sliding from the periodic film cracking technique

et al. 2010

Exp Mech

Chromium (Cr) films are widely used as interlayers to promote the adhesion of copper or gold to substrates. However, the Cr interlayer usually fractures at lower strains than the ductile metal films. In this paper, the cracking and buckling behavior of Cr films on polyethylene terephthalate (PET) substrates were studied in situ under tensile loading with the Atomic Force Microscope (AFM) and optical microscope imaging. Cr films with three nominal thicknesses of 15, 70 and 140 nm were studied. The depth and width of the cracks, as well as the height and width of the buckles, were measured from AFM images acquired at incremental loading steps. The buckle shapes at different strain levels were carefully examined using AFM line profile. It was found that at large strain levels the measured buckle shapes usually deviated from the elastic buckling mode shapes. Further in situ AFM imaging of the buckles at a smaller scan area revealed that in some cases the buckles were cracked at the apex. These in situ nanoscale measurements provided experimental observations and data for further model development and more accurate measurement of the interfacial fracture energy at the Cr-PET interface.

Section: Introductionmentioning

confidence: 99%

In situ Study of Cracking and Buckling of Chromium Films on PET Substrates

Jin

et al. 2010

Exp Mech

“…It is easily included, as shown by Andersons and Leterrier et al [13][14][15] Similar shear lag analyses have been performed with SiO 2 -PET film systems as well as SiN x -Kapton film systems. [13][14][15] However, some differences are found between the preceding approach and others, [17,18] but both are based on the shear lag analysis of Kelly and Tyson. [26] In-situ tensile tests performed inside a scanning electron microscope (SEM) allow one to determine the system's fracture strain, where cracks first initiate, as well as any subsequent buckling and delamination that may occur.…”

Section: Introductionmentioning

confidence: 99%

“…[1] Failure of the films by cleavage fracture is similar to previous studies of ceramic films on metal substrates pulled in tension. [17][18][19] With the periodic cracking method that is based on a shear lag analysis, [17,18,20,21] the maximum shear traction that is supported by the interface can be calculated. The periodic cracking method was first developed to study the shear properties of metal-ceramic interfaces, [17] with similar periodic cracking of other material systems having also been studied.…”

Section: Introductionmentioning

confidence: 99%

Fracture and Delamination of Chromium Thin Films on Polymer Substrates

Taylor

Schalko

et al. 2009

Metall Mater Trans A

New emerging technologies in the field of flexible electronic devices require that metal films adhere well and flex with polymer substrates. Common thin film materials used for these applications include copper (Cu) with an adhesion interlayer of chromium (Cr). Copper can be quite ductile and easily move with the polymer substrate. However, Cr is more brittle and fractures at lower strains than Cu. This study aims to examine the fracture and subsequent buckling and delamination of strained Cr films on polyimide (PI). In-situ scanning electron microscope (SEM) straining is used to systematically study the influence of film thickness on fracture and buckling strains. Film fracture and delamination depend on film thickness, and increases in crack and buckle density with decreasing thickness are explored by a shear lag model.

“…The fragmentation test is a method that can be easily implemented to examine substrate effects and testing conditions, utilizing uniaxial tensile straining to cause fracture and delamination of brittle films on compliant substrates [6][7][8][9][10]. The technique has been employed to study interfacial shear stresses with the interfacial yield model [11] for ceramic films on metal substrates [9,12] as well as metal and ceramic films on various polymer substrates [6,7,[13][14][15]. Of possible substrate materials, polyethylene terephthalate (PET) is considered a viable substrate material due to its cost effectiveness and continuous processing capabilities.…”

Section: Introductionmentioning

confidence: 99%

Robust mechanical performance of chromium-coated polyethylene terephthalate over a broad range of conditions

Taylor

Berger

et al. 2012

Philosophical Magazine

Mechanical properties of metal films on polymer substrates are normally studied in terms of the fracture and adhesion of the film, while the properties of the polymer substrate and testing conditions are overlooked. Substrate orientation and thickness, as well as strain rate and temperature effects, are examined using Cr films deposited onto polyethylene terephthalate substrates. A faster strain rate affects only the initial fracture strain of the Cr film and not the crack and buckle spacings in the high strain condition. The substrate orientation slightly changes the average crack spacing while the substrate thickness has little effect on the cracking and buckling behaviour. Straining experiments at high temperature increased the average crack spacing and led to a change in buckling mode. The lack of sizeable changes in the mechanical behaviour over the large range of testing procedures leads to a resilient material system for flexible applications.