1. Bringing nanomechanical
measurements into the real-world
Recent Developments in Nanoscale Mechanical Property Testing High Temperature Testing and Impact Testing
Dr Krish Narain, Dr Ben Beake and Dr Jim Smith,
Micro Materials Ltd. Wrexham, UK.

2. NanoTesting techniques
Nanoindentation
Nano-scratch testing
Impact testing*
Contact fatigue testing*
Dynamic hardness testing*
High temperature testing*
* = Micro Materials techniques – Worldwide patents pending

3. Nanomechanical property testing at high temperatures
Horizontal loading configuration
has advantages for drift-free
high temperature tests
Hot stage specifications
Indentation to 500 degrees Celsius
Scratch testing to 500 degrees Celsius
Thermal drift minimal
The NanoTest high temperature stage

4. Why is high temperature testing important?
All materials exhibit temperature-dependent mechanical properties
…thermal and mechanical cycling can lead to increased
residual stresses, particularly where materials have dissimilar thermal properties
Properties of Electronic Device
and Packaging Materials
Material CTE (10-6/oC)
CVD Diamond 2.0
Beryllium Oxide 7.4
Aluminium Nitride 3.2
Silicon 3.0
Copper
Gold
testing at service temperature is necessary for optimisation
…particularly where coating-substrate CTE mismatch is an issue…

5. Higher test
temperatures
High temperature nanoindentation testing of fused silica
Thermal drift measured at
90 % unloading.
Thermal drift would be shown
by discontinuities in unloading
curves at 90 % unloading…
…minimal thermal drift

6. High temperature nanoindentation testing of fused silica
Thermal drift normally
very low – some small
drift at 300 deg. C shown
by the discontinuity at 90 %
unload
Usually thermal drift
at elevated temp is as low as
room temp (due to the
thermalisation time and the
horizontal configuration)

7. Hardness and modulus results for fused silica
FS shows increasing
Modulus with temp…
…agrees with modulus
determinations by
beam-bending methods
FS is an “anomalous glass”

8. Hardness and modulus
decrease with increasing
Temperature on
soda-lime glasses…

9. Applications
Softening parameters
Tg determination on
ultra-thin films

10. High temperature nanoindentation testing
Indentation to 50 mN on gold
Applications include...
temperature-dependent
phase changes
repeat indentations
thermal cycling
studies of creep processes
loss and storage moduli
Temp/0C H/GPa Er/GPa

11. Impact
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

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

13. Impact Testing of a brittle TiN coating
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
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

14. Contact fatigue testing
An accelerated test to mimic the mechanical fatigue cycles
which circuit boards and ME devices are subject to in service
Information obtained:
1/ time to failure (durability)
2/ type of failure
(adhesive/cohesive/mixed)
Applied
Load
test probe
piezoelectric or
pendulum
impulse
sample
oscillation
film 1
film 2/subsrate
Assess adhesion/delamination (e.g. between metal-dielectric)
Investigate fracture behaviour

15. Contact fatigue testing of conductive ITO coatings
349 nm
423 nm
more conductive ITO coating
less conductive ITO coating
the less conductive coating shows
more brittle fracture
larger change in depth

16. Pendulum impulse - DLC
AIM: to use the pendulum impulse technique to determine the effect of deposition power on impact resistance of DLC coating on Si wafers
...film thickness is
similar for all 3

17. Pendulum impulse - DLC Operating principle...
Experimental variables include:
Static Force
Impact Angle
Acceleration distance
Impact Frequency
Test probe geometry
Advantage of the impulse technique:
The energy imparted to the sample
surface can be calculated at any
given time point, since the force is known (static load applied throughout the test), and the displacement is also recorded.
Quantification of adhesion energy
Determination of total energy delivered to contact point
Dynamic hardness measurement

18. Pendulum impulse - DLC time to failure differentiate samples by...
Test conditions for all samples:-
1 mN applied load
8 repeat impact tests of 30 min each
(on different areas of the samples)
time to failure
type of failure
differentiate samples by...
Illustrative behaviour on sample deposited at 105 W RF power
105 W sample exhibited cohesive failure in only 12.5 % of tests

19. Pendulum impulse - DLC
Illustrative behaviour on sample deposited at 115 W RF power
115 W sample exhibited cohesive failure in 37.5 % of tests

20. Pendulum impulse - DLC
Illustrative behaviour on sample deposited at 125 W RF power
125 W sample exhibited cohesive failure in 62.5 % of tests

21. Calculation of energy required for failure
Pendulum impulse - DLC
Calculation of energy required for failure
(neglecting damping, rebound energy)
Energy per impact = pendulum swing x Force
Total energy = number of impacts x energy per impact

22. Summary Pendulum impulse - DLC
(1) Impact-induced coating failure is a statistical process
(2) tests are sensitive to small changes in deposition conditions
Diamond-like carbon coatings deposited at higher power have...
shorter time-to-failure
lower energy-to-failure
high probability of cohesive failure
incomplete removal (final depth is lower than thickness)
How does the impact performance of DLC compare to other brittle materials?

23. Pendulum impulse - DLC Fatigue performance of these DLC
much higher load
necessary for failure
Fatigue performance of these DLC
coatings is worse than FS and Si!
(DLC is in highly stressed state)

24. To summarise…. Bringing nanomechanical
measurements into the real-world
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….

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