Abstract
By using the low loading of the conductor filler to achieve high conductivity is a challenge associated with electrically conductive adhesion. In this study, we show an assembling of nickel-coated polystyrene (Ni@PS) microspheres into 3-dimensional network within the epoxy resin with the assistance of an electric field. The morphology evolution of the microspheres was observed with optical microscopy and scanning electron microscopy (SEM). The response speed of Ni@PS microsphere to the electric field were investigated by measuring the viscosity and shear stress variation of the suspension at a low shear rate with an electrorheological instrument. The SEM results revealed that the Ni@PS microspheres aligned into a pearl-alike structure. The AC impedance spectroscopy confirmed that the conductivity of this pearl-alike alignment was significantly enhanced when compared to the pristine one. The maximum enhancement in conductivity is achieved at 15 wt. % of Ni@PS microspheres with the aligned composites about 3 orders of magnitude as much as unaligned one, typically from ~10−5 S/m to ~10−2 S/m.
Highlights
Accepted: 3 November 2021Electrically conductive adhesives have widely applied in electronic devices such as die attachment, solderless interconnection, semiconductor packaging [1,2], interconnection of solar cells [3,4] and touch screens [5]
The response time, tres demonstrates the speed of the chain buildup, which plotted as functions of the nickelcoated polystyrene (Ni@PS) content, as shown in the Figure 6b. the tres decreases as Ni@PS content increasing
Of Ni@PS, as marked in red in the Figure 8a, which is different from the image under optical microscopy that chains are continuous along the electric field direction in the suspension containing 5 wt.% Ni@PS (Figure 5)
Summary
Conductive adhesives have widely applied in electronic devices such as die attachment, solderless interconnection, semiconductor packaging [1,2], interconnection of solar cells [3,4] and touch screens [5]. Ag-migration, poor interface adhesion with the polymer matrix and easy to form Ag2 O in the air atmosphere, whereas nickel with outstanding combination property such as its high chemical stability, lower density than gold and silver, and easy to be coated on the surface of polymer core by electroless plating, is continuously to be of great interest as a conductive filler in epoxy resin. To achieve a high electric conductivity of composites at a conductive filler loading as low as possible, applying magnetic field [20–23] or electric field [24,25] to assemble particles into ordered structure have proven to be an efficient approach Such an assembly might produce the continuous conductive pathway at a lower filler loading. The enhancement of electric conductivity of aligned composites was demonstrated with the AC impedance spectroscopy
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