Friction and wear of thin layers for MEMS

WHY

Evaluating frictional and wear characteristics of very thin nanostructured layers with macro scale tribometers, in the Newton load range, can create unrealistic conditions.  Wear phenomena are highly dependent on the contact conditions: such high loads are not relevant in the case of MEMS. The adhesive and capillary components that contribute to friction, in a micro-contact, can not be simulated with high load devices.  Therefore, there is an increasing need to use new tribological testers and procedures to obtain a better understanding of surface interactions on an appropriate scale.

HOW

The Basalt-N2 tribometer can bridge the gap between the macro-load (conventional pin-on-disk) and nano-load (atomic force microscopes AFM) tribometers. Its versatile loading system, and by selecting cantilevers or strain gauges a load range of 0.2 mN up to 100 N is possible. In the case, loads between 500 mN and 2 N were investigated. Different contact geometries (point, line, area contacts) and sliding velocities can also be used. Due to the high sensitivity of this tester the transition between different phases can be successfully recorded (e.g. sliding between coated and uncoated components).  

 

RESULT

• Conventional macro-load scale wear testers are not suitable for studying the wear behavior of thin layers, because the high initial contact pressure results in severe deformation and/or fracturing of the coating.
• Meso-load testing was useful as it allowed to record accurately the frictional behavior of the coating without damaging it, and with a minimum substrate effect.
• Thanks to the high sensitivity of this meso-load tester, surface phenomena such as oxidation and/or debris formation can be easily detected by monitoring the evolution of the coefficient of friction of the tribosystem.