Introduction to Nano-scale Mechanical Properties Testing Micro Materials Ltd. Wrexham, UK.

Outline Depth-sensing indentation The NanoTest system Case studies Nanoindentation – bond pads Nano-impact – fatigue of DLC films Polymer nanoindentation Summary

What is depth-sensing indentation? loadingunloading force, displacement and time are recorded throughout the indentation of a test sample by a diamond probe elastic and plastic properties of the sample determine the shape of the unloading curve Scanning = transverse sample movement during loading Impact = sample oscillation at constant load coating substrate

Where does depth-sensing indentation fit in? Surface/near- surface Mechanical properties of thin films and coatings Hardness Modulus Creep Depth-profiling Wear resistance Interfacial adhesion Fracture toughness Surface Friction Adhesion (local) (Wear) Topography Role of specific chemical interactions? Bulk Hardness of thick coatings and bulk materials Fracture toughness of bulk materials SPMNanoindentationMacro-hardness

Micro Materials Limited - growing market share in a fast growing market... Source: British Library on-line database. Keyword search on “nanoindentation”.

The most versatile nanomechanical property testing centre... The NanoTest system 2 loading heads: Nano -10  N mN Micro -0.1 N - 20 N 3 modules: Indentation Scanning Impact 10 options including: High temp testing Continuous compliance Pin-on-disk wear Microscopes

The NanoTest pendulum Advantages of the pendulum over vertical loading instruments include… large samples possible calibrated contact load high temperature stage sample oscillation options such as pin-on- disk wear testing and 2D levelling stage Original design - University of Lancaster, UK, Newey, Wilkins and Pollock, J Phys E, 1982, pp Micro Materials formed 1988 by Dr Jim Smith, first instruments sold 1992.

nickel plating Al pad passivation layer Si wafer Quantitative measurement of the mechanical properties of thin films Aim: determine the hardness and modulus of top layer in IC bond pad without substrate influence TechniqueApplied Force SPMnN-  N NanoTest10  N-500 mN MicroTest100 mN - 20 N HardnessN-kN Comparison of load ranges Indentation

NanoTest indentation module Techniques Nanoindentation Microindentation Load-partial-unload High temperature testing Continuous compliance Properties Hardness Elastic modulus Fracture toughness Adhesion Creep Elastic and plastic work Elastic recovery parameter Stress-strain Indentation

Depth-profiling of mechanical property variation Load-partial-unload technique 20-cycle load-partial-unload Depth controlled nm Experiment time 30 min Analysis time 30 sec rapid and quantified variation in hardness and modulus with depth Indentation

“1/10 rule” - for a hard coating on softer substrate Hardness of 5  m Ni-based top-layer of bond pad constant hardness decreasing hardness coating + substrate coating + substrate Indentation

How homogeneous is my coating? An example of nanoindentation as a QA tool rapid, automatic scheduling of arrays of indentations Indentation

Precise indent placement with a 4-objective high resolution metallurgical microscope NOTE: 1 objective can be replaced by contact/AC mode SPM Mapping variations in hardness and elasticity at the nanoscale studies of nano- and micro- scale phase separation Indentations along 10  m alloy interface between stainless steel surfaces Indentation

indentation + residual stress = coating failure Nanoindentation-induced adhesion failure Adhesion failure DLC on Si Indentation

NanoTest scanning module for… Scratch testing Nano- and micro- friction Adhesion Profilometry Acoustic Emission Fatigue wear “Nanotribometer” Scanning

Ramped load scratch testing (1) Film failure at critical normal load L c is revealed by... Depth change Acoustic Emission Friction Force Topography Scan Optical Microscopy Adhesion failure at critical load of 3.2 mN Scanning

Ramped load scratch testing (2) qualitative ranking of test coatings and multilayers at the development stage Scanning

Multi-pass sub-critical load scratch testing d plast d total Experimental parameters: 25  m Rockwell probe scratch load:- ramped to 1 mN topography load 0.1 mN scan speed 0.5  m/s Nano-scratching wear of polymer film Repeat scratches over the same wear track reveal... fatigue behaviour cohesive failure (fracture) adhesive failure (delamination) Scanning 2, 4, 6 1, 3, 5, 7

NanoTest impact module for… Impact testing Contact fatigue testing Erosive wear testing Fracture toughness Adhesion testing Dynamic hardness The only commercial nano-impact tester available Impact

Impact testing - simulating fatigue wear and failure adhesion failure fracture Impact

Impact Testing of a brittle TiN coating For bulk materials wear rates are determined from changes in probe depth For coatings, time-to-failure is related to the bonding strength to the substrate 100 mN applied load is on throughout test 80 Hz oscillation frequency Oscillation on 30 s after start Oscillation off 30 s before end Film failure after 250 s Impact

To summarise…. 1. Nanoindentation techniques are essential in the optimisation of the mechanical properties of thin films and coatings 2. The NanoTest has large range of testing techniques, and therefore offers a complete testing capability 3. These techniques are possible due to the unique pendulum design 4. The high temperature option and impact module allow testing under contact conditions that can closely simulate those in service 5. The versatility and wide range of options have resulted in the system finding applications in….

NanoTest systems are in regular use in… MIT USA Eastman Kodak USA Philips Netherlands HP Singapore Gintic Singapore Cambridge Uni UK Barcelona Uni Spain VITO Belgium NPL UK Enterprise Ireland Salford Uni UK Cranfield Uni UK Timken USA RPI NY USA AGFA DE LOT Oriel DE Paisley UK Loughborough UK TU Clausthal DE UMIST UK DERA UK Leeds Uni UK ICM Madrid Spain Trivandrum India...and many more - over 75 sites worldwide

Automotive Bearings Biomedical Devices Ceramics Composites Contact Lenses Cutting Tools Hard Coatings Laminates Magnetic Disks Microelectronics Optical Coatings Optical Disks Packaging Materials Paints Paper Coatings Pharmaceuticals Photographic Film Polymers Powders Printing Plates Semiconductors Thin Film Adhesion Turbine Blades Current NanoTest application areas include…...future application areas will be in?