Scratch testing of metallic nanofilms for flexible electronics

5th June 2018

Metallic nanofilms on polymer substrates are extensively used as interconnect components in various flexible electronic devices, such as antennae structures, identification tags, solar cells, electronic skin, wearables and paper-like electronic display. This is because of the inherent benefits of metallic nanofilms such as low specific weight, mechanical flexibility, ease of integration and low cost, as compared to silicon-based nanofilms.

The polymer substrate mostly endures the service loads, while the metallic nanofilm retains its function without rupturing until a relatively large amount of strain is applied. The metallic nanofilm has excellent electrical and mechanical properties, especially in electrical conductivity, yield strength and fracture toughness under the action of cyclic straining.

However, performance issues are often faced in overall reliability and durability of the flexible device and therefore, the adhesion property of a nanofilm to its substrate is crucial to prevent such issues. A poor adhesion property can contribute to a premature failure of the film and thus render the flexible electronic components ineffective. Fractures and interface delamination are the two most common failure modes of such nanofilms.

Being a reliable and relatively fast method, scratch testing can be easily implemented for inline quality control of films during production. Nevertheless, scratch tests cannot be easily performed on such flexible and thin films. The use of a nanomechanical tester for such evaluation is limited by the force range to initiate failure of the film during scratch, as their sharp tips can cut through the film without cracking and delaminating.

It is the same with nanomechanical tools, which have limited productivity because of time-consuming test preparation. One system that is specifically designed to address this issue is the Universal Scratch Test system from Bruker. The system performs faster, easier and more reliable critical load scratch failure evaluations of nanofilms.

The UMT TriboLab Scratch Test System

Built on the UMT TriboLab platform, the scratch test system provides precision control of position, load and speed. The modular design of the system ensures the flexibility to scratch test across different velocities and forces. The system uses three vital drive systems — slider, Y-stage and carriage for X-, Y- and Z-motion, respectively. The tester is a versatile, user-friendly and highly productive scratch tool, thanks to integrated “intelligent” hardware (TriboID) and software (TriboScript) interfaces.

The TriboID feature automatically detects the assortment of components connected to the system and even configures them. TriboScript provides an improved and secured scripting interface for effortless compilation of scratch test sequences from the integrated test blocks. In addition, the system is integrated with real-time control and data analysis software to guarantee high repeatability and accuracy.

Bruker’s scratch test system can be effectively used for all modes of scratch testing, including constant and progressive load conditions. The carriage drive system provides the motion along Z-direction for displacement and loading. It also accommodates the slider drive that houses an optical microscope and a force sensor. The slider offers motion along the X-direction. The test specimen is mounted and movement is provided along the Y-direction by using the linear stage.

See the complete article please download the PDF file.

Bruker Nano Surfaces





To receive the Scientist Live weekly email NewsBrief please enter your details below

Twitter Icon © Setform Limited