Fractal dendrite-based electrically conductive composites for laser-scribed flexible circuits.

Cheng Yang,Ching-Ping Wong,Huan Duan,Sum Wai Chiang,Zhexu Zhang,Wei Lin,Jia Li,Feiyu Kang,Xiaoya Cui

doi:10.1038/ncomms9150

Abstract

Fractal metallic dendrites have been drawing more attentions recently, yet they have rarely been explored in electronic printing or packaging applications because of the great challenges in large-scale synthesis and limited understanding in such applications. Here we demonstrate a controllable synthesis of fractal Ag micro-dendrites at the hundred-gram scale. When used as the fillers for isotropically electrically conductive composites (ECCs), the unique three-dimensional fractal geometrical configuration and low-temperature sintering characteristic render the Ag micro dendrites with an ultra-low electrical percolation threshold of 0.97 vol% (8 wt%). The ultra-low percolation threshold and self-limited fusing ability may address some critical challenges in current interconnect technology for microelectronics. For example, only half of the laser-scribe energy is needed to pattern fine circuit lines printed using the present ECCs, showing great potential for wiring ultrathin circuits for high performance flexible electronics.

Highlights

Fractal metallic dendrites have been drawing more attentions recently, yet they have rarely been explored in electronic printing or packaging applications because of the great challenges in large-scale synthesis and limited understanding in such applications
We demonstrate that micro-structuring of the surfaces of the 3D fillers provides a new path
We introduce silver-based 3D fractal dendrites (FDs) into engineering polymer resins, and have achieved an extremely low percolation threshold of 0.97 vol% (8 wt%) of silver

Summary

Introduction

Fractal metallic dendrites have been drawing more attentions recently, yet they have rarely been explored in electronic printing or packaging applications because of the great challenges in large-scale synthesis and limited understanding in such applications. Some of the methods may add certain complexities to industry-scale formulation/preparation of ECCs that desires a large process window in mixing, easy-to-reach homogeneity, and long shelf life and so on In these regards, simple mixing of 3D metallic fillers with a polymer matrix is beneficial for process simplification, quality control, and cost reduction for ECC applications. We introduce silver-based 3D fractal dendrites (FDs) into engineering polymer resins, and have achieved an extremely low percolation threshold of 0.97 vol% (8 wt%) of silver This is attributed to the unique nano-sized rims of the metallic dendrites, which fuse with each other through a simple sintering process at low temperature, forming a conductive network at ultra-low filler loading, which can be attributable to the low-temperature sintering ability of the nano-sized silver structures[28,29]. The simulated percolation threshold using Monte Carlo computation shows good agreement with the experimental results, from both the perspectives of spatial spanning and contact probability (see Supplementary Information)

Methods

Results

Conclusion