Overcoming the trade-off between curing temperature and conductivity for high-performance conductive silver pastes

Abstract

The demand for low-temperature cured conductive silver pastes increases rapidly due to the development of advanced electronic fields, such as flexible electronics. Lowering curing temperatures of conductive silver pastes is generally realized using low-boiling-point solvents. However, such solvents have a low viscosity, leading to the sedimentation of the conductive phase. Increasing the content of the highly viscous binder phase helps solve this issue, but it will lower the electric conductivity. Herein, the trade-off between curing temperature and conductivity of conductive silver pastes was overcome by applying nano-silver particles as the sedimentation inhibitor while bifunctional epoxidized cardol (E-Cardol), with flexible C₁₅ side chains that can significantly enhance the toughness, as the binder. Experiments were performed to determine chemical compositions, reveal morphologies, and measure conductive resistivity values. Conductive silver pastes with a curing temperature of 140 °C and a silver content of 65 wt.% were fabricated, exhibiting a resistivity of 3.10 × 10⁻⁵ Ω·cm, comparable to that of conventional low-temperature cured silver pastes with the silver content of 80 wt.%. Moreover, this silver paste also exhibited excellent adhesion performance and enhanced anti-folding property.

Graphical abstract

Keywords

low-temperature cured conductive silver paste / electrical resistivity / flexibility / epoxidized cardol / anti-sedimentation

References

[1] Hu A, Guo J Y, Alarifi H, . Low temperature sintering of Ag nanoparticles for flexible electronics packaging.Applied Physics Letters, 2010, 97(15): 153117

[2] Zhang R, Moon K, Lin W, . A simple, low-cost approach to prepare flexible highly conductive polymer composites by in situ reduction of silver carboxylate for flexible electronic applications.Composites Science and Technology, 2011, 71(4): 528–534

[3] Li Z, Zhang R, Moon K S, . Highly conductive, flexible, polyurethane-based adhesives for flexible and printed electronics.Advanced Functional Materials, 2013, 23(11): 1459–1465

[4] Hu Y, Zhao T, Zhu P, . Low cost and highly conductive elastic composites for flexible and printable electronics.Journal of Materials Chemistry C: Materials for Optical and Electronic Devices, 2016, 4(24): 5839–5848

[5] Paknejad S A, Mannan S H . Review of silver nanoparticle based die attach materials for high power/temperature applications.Microelectronics and Reliability, 2017, 70: 1–11

[6] Suhir E, Lee Y C, Wong C P, eds. Micro- and Opto-Electronic Materials and Structures: Physics, Mechanics, Design, Reliability, Packaging. San Francisco: Springer, 2007

[7] Hu P A, O’Neil W, Hu Q . Synthesis of 10 nm Ag nanoparticle polymer composite pastes for low temperature production of high conductivity films.Applied Surface Science, 2010, 257(3): 680–685

[8] Zhang R, Moon K, Lin W, . Preparation of highly conductive polymer nanocomposites by low temperature sintering of silver nanoparticles.Journal of Materials Chemistry, 2010, 20(10): 2018–2023

[9] Fu S C, Zhao M, Shan H, . Fabrication of large-area interconnects by sintering of micron Ag paste.Materials Letters, 2018, 226: 26–29

[10] Bell N B, DiAntonio C B, Dimos D B . Development of conductivity in low conversion temperature silver pastes via addition of nanoparticles.Journal of Materials Research, 2002, 17(9): 2423–2432

[11] Chen D, Qiao X, Qiu X, . Effect of silver nanostructures on the resistivity of electrically conductive adhesives composed of silver flakes.Journal of Materials Science: Materials in Electronics, 2010, 21(5): 486–490

[12] Liu J, Li X, Zeng X. Silver nanoparticles prepared by chemical reduction-protection method, and their application in electrically conductive silver nanopaste. Journal of Alloys and Compounds, 2010, 494(1–2): 84–87

[13] Guo G, Gan W, Xiang F, . Effect of dispersibility of silver powders in conductive paste on microstructure of screen-printed front contacts and electrical performance of crystalline silicon solar cells.Journal of Materials Science: Materials in Electronics, 2011, 22(5): 527–530

[14] Faddoul R, Reverdy-Bruas N, Bourel J . Silver content effect on rheological and electrical properties of silver pastes.Journal of Materials Science: Materials in Electronics, 2012, 23(7): 1415–1426

[15] Mo L, Zhang Y, Zhao L, . Effect of sub-micrometer sized silver particle on the performance of the front Ag paste for c-Si solar cells.Journal of Alloys and Compounds, 2018, 742: 256–262

[16] Li J, Wan X, Li N, . Preparation of micron-sized plate-like silver powders used in silver paste by wet-chemical reduction method.Journal of Materials Science: Materials in Electronics, 2022, 33(17): 14021–14031

[17] Li W, Yu C, Wang Y, . Experimental investigation of effect of flake silver powder content on sintering structure and properties of front silver paste of silicon solar cell.Materials, 2022, 15(20): 7142

[18] Stratton R . Theory of field emission from semiconductors.Physical Review, 1962, 125(1): 67–82

[19] Kirkpatrick S . Percolation and conduction.Reviews of Modern Physics, 1973, 45(4): 574–588

[20] Ruschau G R, Yoshikawa S, Newnham R E . Resistivities of conductive composites.Journal of Applied Physics, 1992, 72(3): 953–959

[21] Fang Z, Lin Z, Zhang P . Preparation and characterization of low temperature curing conductive silver paste for screen printing.AIP Conference Proceedings, 2018, 1995: 020020

[22] Hsu C P, Guo R H, Hua C C, . Effect of polymer binders in screen printing technique of silver pastes.Journal of Polymer Research, 2013, 20(10): 277

[23] Aradhana R, Mohanty S, Nayak S K . A review on epoxy-based electrically conductive adhesives.International Journal of Adhesion and Adhesives, 2020, 99: 102596

[24] Derakhshankhah H, Mohammad-Rezaei R, Massoumi B, . Conducting polymer-based electrically conductive adhesive materials: design, fabrication, properties, and applications.Journal of Materials Science: Materials in Electronics, 2020, 31(14): 10947–10961

[25] Liu X, Wu S, Chen B, . Tuning the electrical resistivity of conductive silver paste prepared by blending multi-morphologies and micro-nanometers silver powder.Journal of Materials Science: Materials in Electronics, 2021, 32(10): 13777–13786

[26] Zhan H, Guo J, Shen J, . Synthesis of silver flakes and their application as conductive filler for low-curing-temperature silver pastes.Journal of Electronic Materials, 2019, 48(5): 2745–2753

[27] Wang T, Chen X, Lu G Q, . Low-temperature sintering with nano-silver paste in die-attached interconnection.Journal of Electronic Materials, 2007, 36(10): 1333–1340

[28] Lim H S, Kim S N, Lim J A, . Low temperature-cured electrically conductive pastes for interconnection on electronic devices.Journal of Materials Chemistry, 2012, 22(38): 20529–20534

[29] Jiu J, Zhang H, Nagao S, . Die-attaching silver paste based on a novel solvent for high-power semiconductor devices.Journal of Materials Science, 2016, 51(7): 3422–3430

[30] Zhang P, Jiang X, Yuan P, . Silver nanopaste: synthesis, reinforcements and application.International Journal of Heat and Mass Transfer, 2018, 127: 1048–1069

[31] Scenev V, Szalapak J, Werft L, . Low-temperature processible highly conducting pastes for printed electronics applications.Advanced Engineering Materials, 2022, 24(9): 2101752

[32] Li C M, Sun Y, Sun M, . Novel cocklebur-like nano silver oxide for low-temperature curing pastes with dense conductive paths.Journal of Materials Science: Materials in Electronics, 2023, 34: 1856

[33] Siow K S . Mechanical properties of nano-silver joints as die attach materials.Journal of Alloys and Compounds, 2012, 514: 6–19

[34] Mariani P, Vesce L, Di Carlo A . The role of printing techniques for large-area dye sensitized solar cells.Semiconductor Science and Technology, 2015, 30(10): 104003

[35] Ma H, Li Z, Tian X, . Silver flakes and silver dendrites for hybrid electrically conductive adhesives with enhanced conductivity.Journal of Electronic Materials, 2018, 47(5): 2929–2939

[36] Wang X Q, Gan W P, Zhou J, . Effect of silver powders on a low curing temperature silver conductive adhesive.Journal of Materials Science: Materials in Electronics, 2018, 29(21): 18547–18552

[37] Li C F, Li W, Zhang H, . Highly conductive ag paste for recoverable wiring and reliable bonding used in stretchable electronics.ACS Applied Materials & Interfaces, 2019, 11(3): 3231–3240

[38] Wen J, Tian Y, Hao C, . Fabrication of high performance printed flexible conductors by doping of polyaniline nanomaterials into silver paste.Journal of Materials Chemistry C: Materials for Optical and Electronic Devices, 2019, 7(5): 1188–1197

[39] Zhao H, Shao L, Chen J F . High-gravity process intensification technology and application.Chemical Engineering Journal, 2010, 156(3): 588–593

[40] You F, Zhao X, Yue Q, . A review on solidification of alloys under hypergravity.Progress in Natural Science, 2023, 33(3): 279–294

RIGHTS & PERMISSIONS

Higher Education Press