248
Y. Dai and C. S. Tan
micro
1:3
1:1
3:1
6:1
9:1
nano
crack
Porosity: : 27.8%
crack
Porosity: 22.1%
Porosity: 13.6%
Porosity: 19.9%
Porosity: 25%
100µm
100µm
100µm
100µm
100µm
100µm
100µm
(a)
(b)
(c)
(d)
(e)
(f)
(g)
Fig. 9.18 SEM images (top-view) of micro-, nano- paste and mixed paste with different ratios
that is similar to the micro-particles paste. The 3:1 mixed paste is most compact
with only 13.6% porosity. The porosity results are consistent with those of the sheet
resistance results.
The nano-particles in the 9:1 paste is likely not sufficient to fill in the interstitials and this leads to high porosity and low packing density. The particles are
not connected well with each other so the electrical conductivity is not as good as
other mixed pastes. From the SEM images characterizations, it is concluded that the
micro—and nano—particles should remain in a suitable range to ensure the microparticles can prohibit cracking in nano-paste and nano-particles are sufficient to fill
the interstitials.
9.3.3 Discussion on Simulation and Experiment Results
The experimental results reveal that the mixed paste with the 3:1 ratio provides
improved properties compared to other mixing ratios. Although it is not consistent
with the modelling results (which predicted a 6:1 ratio), the deviation could arise
from several possible reasons list below.
Y. Dai and C. S. Tan
micro
1:3
1:1
3:1
6:1
9:1
nano
crack
Porosity: : 27.8%
crack
Porosity: 22.1%
Porosity: 13.6%
Porosity: 19.9%
Porosity: 25%
100µm
100µm
100µm
100µm
100µm
100µm
100µm
(a)
(b)
(c)
(d)
(e)
(f)
(g)
Fig. 9.18 SEM images (top-view) of micro-, nano- paste and mixed paste with different ratios
that is similar to the micro-particles paste. The 3:1 mixed paste is most compact
with only 13.6% porosity. The porosity results are consistent with those of the sheet
resistance results.
The nano-particles in the 9:1 paste is likely not sufficient to fill in the interstitials and this leads to high porosity and low packing density. The particles are
not connected well with each other so the electrical conductivity is not as good as
other mixed pastes. From the SEM images characterizations, it is concluded that the
micro—and nano—particles should remain in a suitable range to ensure the microparticles can prohibit cracking in nano-paste and nano-particles are sufficient to fill
the interstitials.
9.3.3 Discussion on Simulation and Experiment Results
The experimental results reveal that the mixed paste with the 3:1 ratio provides
improved properties compared to other mixing ratios. Although it is not consistent
with the modelling results (which predicted a 6:1 ratio), the deviation could arise
from several possible reasons list below.