Thermal interface materials (TIMs) used between the chip and the heat spreader play an indispensable role in effective heat removal to ensure the chip's performance and reliability. As they suffer from stresses in practical applications, TIMs need to have high toughness to resist fracture. The notch sensitivity of TIMs is considered an important parameter to evaluate its toughness. However, the notch sensitivity of TIMs is seldom mentioned, and the mechanism to enhance the toughness is still unclear. Here, using polymer-based TIMs consisting of polydimethylsiloxane/aluminum as a model, we specifically investigate notch sensitivity of TIMs and analyze the mechanical mechanism in detail from the macroscopic and microscopic scales. It was found that a transition from notch insensitive to notch sensitive will happen with a notch length of 2.0 mm, which is much higher than typical soft materials, such as hydrogels. We interpret the notch sensitivity of the TIM by finite element analysis at macroscopic scales and the Lake–Thomas theory at microcosmic scales. The relationship between the area of the strain concentration region to the notch length in finite element analysis is in good agreement with the fracture stretch ratio with different notch lengths measured in a uniaxial tensile experiment. This investigation gives an insight into designing notch-insensitivity TIM and understanding their fracture behavior.
REFERENCES
1.
S.
Xu
, T.
Cheng
, Q.
Yan
, C.
Shen
, Y.
Yu
, C. T.
Lin
, F.
Ding
, and J.
Zhang
, “Chloroform-assisted rapid growth of vertical graphene array and its application in thermal interface materials
,” Adv. Sci.
9
, 2200737
(2022
). 2.
Y.
Cui
, Z.
Qin
, H.
Wu
, M.
Li
, and Y.
Hu
, “Flexible thermal interface based on self-assembled boron arsenide for high-performance thermal management
,” Nat. Commun.
12
, 1284
(2021
). 3.
Y.
Gao
, D.
Bao
, M.
Zhang
, Y.
Cui
, F.
Xu
, X.
Shen
, Y.
Zhu
, and H.
Wang
, “Millefeuille-inspired thermal interface materials based on double self-assembly technique for efficient microelectronic cooling and electromagnetic interference shielding
,” Small
18
, 2105567
(2022
). 4.
Q.
Yan
, F. E.
Alam
, J.
Gao
, W.
Dai
, X.
Tan
, L.
Lv
, J.
Wang
, H.
Zhang
, D.
Chen
, K.
Nishimura
, L.
Wang
, J.
Yu
, J.
Lu
, R.
Sun
, R.
Xiang
, S.
Maruyama
, H.
Zhang
, S.
Wu
, N.
Jiang
, and C. T.
Lin
, “Soft and self-adhesive thermal interface materials based on vertically aligned, covalently bonded graphene nanowalls for efficient microelectronic cooling
,” Adv. Funct. Mater.
31
, 2104062
(2021
). 5.
W.
Dai
, L.
Lv
, T.
Ma
, X.
Wang
, J.
Ying
, Q.
Yan
, X.
Tan
, J.
Gao
, C.
Xue
, J.
Yu
, Y.
Yao
, Q.
Wei
, R.
Sun
, Y.
Wang
, T. H.
Liu
, T.
Chen
, R.
Xiang
, N.
Jiang
, Q.
Xue
, C. P.
Wong
, S.
Maruyama
, and C. T.
Lin
, “Multiscale structural modulation of anisotropic graphene framework for polymer composites achieving highly efficient thermal energy management
,” Adv. Sci.
8
, 2003734
(2021
). 6.
M.
Feng
, Y.
Pan
, M.
Zhang
, Q.
Gao
, C.
Liu
, C.
Shen
, and X.
Liu
, “Largely improved thermal conductivity of HDPE composites by building a 3D hybrid fillers network
,” Compos. Sci. Technol.
206
, 108666
(2021
). 7.
X.
Zeng
, X.
Zeng
, J.
Fan
, J.
Li
, Z.
Wang
, R.
Sun
, L.
Ren
, and X.
Xia
, “Ultrahigh energy-dissipation thermal interface materials through anneal-induced disentanglement
,” ACS Mater. Lett.
4
, 874
–881
(2022
). 8.
D.
He
, Z.
Wang
, X.
Zeng
, J.
Fan
, L.
Ren
, G.
Du
, R.
Sun
, and X.
Zeng
, “Interfacial coordination interaction enables soft elastomer composites high thermal conductivity and high toughness
,” ACS Appl. Mater. Interfaces
14
, 33912
–33921
(2022
). 9.
S.
Tian
, Y.
Yang
, Z.
Liu
, C.
Wang
, R.
Pan
, C.
Gu
, and J.
Li
, “Temperature-dependent Raman investigation on suspended graphene: Contribution from thermal expansion coefficient mismatch between graphene and substrate
,” Carbon
104
, 27
–32
(2016
). 10.
J.
Wieme
and V.
Van Speybroeck
, “Unravelling thermal stress due to thermal expansion mismatch in metal–organic frameworks for methane storage
,” J. Mater. Chem. A
9
, 4898
–4906
(2021
). 11.
S. Y.
Zheng
, S.
Mao
, J.
Yuan
, S.
Wang
, X.
He
, X.
Zhang
, C.
Du
, D.
Zhang
, Z. L.
Wu
, and J.
Yang
, “Molecularly engineered zwitterionic hydrogels with high toughness and self-healing capacity for soft electronics applications
,” Chem. Mater.
33
, 8418
–8429
(2021
). 12.
R.
Long
, C.-Y.
Hui
, J. P.
Gong
, and E.
Bouchbinder
, “The fracture of highly deformable soft materials: A tale of two length scales
,” Annu. Rev. Condens. Matter Phys.
12
, 71
–94
(2021
). 13.
M. A.
Haque
, T.
Kurokawa
, G.
Kamita
, and J. P.
Gong
, “Lamellar bilayers as reversible sacrificial bonds to toughen hydrogel: Hysteresis, self-recovery, fatigue resistance, and crack blunting
,” Macromolecules
44
, 8916
–8924
(2011
). 14.
E.
Ducrot
, Y. L.
Chen
, M.
Bulters
, R. P.
Sijbesma
, and C.
Creton
, “Toughening elastomers with sacrificial bonds and watching them break
,” Science
344
, 186
–189
(2014
). 15.
P.
Millereau
, E.
Ducrot
, J. M.
Clough
, M. E.
Wiseman
, H. R.
Brown
, R. P.
Sijbesma
, and C.
Creton
, “Mechanics of elastomeric molecular composites
,” Proc. Natl. Acad. Sci. U.S.A.
115
, 9110
–9115
(2018
). 16.
F. K.
Shi
, X. P.
Wang
, R. H.
Guo
, M.
Zhong
, and X. M.
Xie
, “Highly stretchable and super tough nanocomposite physical hydrogels facilitated by the coupling of intermolecular hydrogen bonds and analogous chemical crosslinking of nanoparticles
,” J. Mater. Chem. B
3
, 1187
–1192
(2015
). 17.
R.
Long
, M.
Lefranc
, E.
Bouchaud
, and C.-Y.
Hui
, “Large deformation effect in Mode I crack opening displacement of an Agar gel: A comparison of experiment and theory
,” Extreme Mech. Lett.
9
, 66
–73
(2016
). 18.
C.
Chen
, Z.
Wang
, and Z.
Suo
, “Flaw sensitivity of highly stretchable materials
,” Extreme Mech. Lett.
10
, 50
–57
(2017
). 19.
C.
Nelson
, J.
Galloway
, C.
Henry
, and W.
Kelley
, “Thermal performance of TIMs during compressive and tensile stress states,” in 2017 33rd Thermal Measurement, Modeling & Management Symposium (SEMI-THERM) (IEEE, 2017), pp. 261–268. 20.
A. G.
Thomas
and R. S.
Rivlin
, “Rupture of rubber. I. Characteristic energy for tearing
,” J. Polym. Sci.
10
, 291
–318
(1953
). 21.
A. A.
Griffith
, “The phenomena of rupture and flow in solids
,” Philos. Trans. R. Soc. Lond. A
221
, 163
–198
(1921
). 22.
Y.
Qi
, Z.
Zou
, J.
Xiao
, and R.
Long
, “Mapping the nonlinear crack tip deformation field in soft elastomer with a particle tracking method
,” J. Mech. Phys. Solids
125
, 326
–346
(2019
). 23.
G. J.
Lake
and A. G.
Thomas
, “The strength of highly elastic materials
,” Philos. Trans. R. Soc. Lond. A
300
, 108
–119
(1967
). 24.
J.
Tang
, J.
Li
, J. J.
Vlassak
, and Z.
Suo
, “Fatigue fracture of hydrogels
,” Extreme Mech. Lett.
10
, 24
–31
(2017
). 25.
Y.-R.
Luo
, Comprehensive Handbook of Chemical Bond Energies
(CRC Press
, 2007
).26.
H.
Gotoh
, C.
Liu
, A.
Bin Imran
, M.
Hara
, T.
Seki
, K.
Mayumi
, K.
Ito
, and Y.
Takeoka
, “Optically transparent, high-toughness elastomer using a polyrotaxane cross-linker as a molecular pulley
,” Sci. Adv.
4
, eaat7629
(2018
). 27.
W.-C.
Lin
, W.
Fan
, A.
Marcellan
, D.
Hourdet
, and C.
Creton
, “Large strain and fracture properties of poly(dimethylacrylamide)/silica hybrid hydrogels
,” Macromolecules
43
, 2554
–2563
(2010
). 28.
S.
Lin
, X.
Liu
, J.
Liu
, H.
Yuk
, H. C.
Loh
, G. A.
Parada
, C.
Settens
, J.
Song
, A.
Masic
, G. H.
McKinley
, and X.
Zhao
, “Anti-fatigue-fracture hydrogels
,” Sci. Adv.
5
, 1
(2019
). 29.
C.
Yang
, T.
Yin
, and Z.
Suo
, “Polyacrylamide hydrogels. I. Network imperfection
,” J. Mech. Phys. Solids
131
, 43
–55
(2019
). © 2022 Author(s). Published under an exclusive license by AIP Publishing.
2022
Author(s)
You do not currently have access to this content.
