| Silver-based conductive adhesive is a packaging material with great potential for use in flexible electronic devices.However,there are still challenges in its application in the field of flexible electronics,such as the difficulty of achieving compatibility between mechanical and electrical properties,as well as poor adhesion between the adhesive layer and substrate during low-temperature curing.Therefore,it is crucial to explore a simple,efficient,and low-temperature curing process that can enable the conductive silver adhesive to have both electrical and mechanical properties.This work constructs three-dimensional conductive micro-nano materials（MXene@Ag）from the perspective of conductive fillers to improve the comprehensive performance of conductive adhesives.It studies sheet-like silver powder and organic carriers suitable for UV/thermal dual curing and combines screen printing technology to verify the application potential of three-dimensional conductive micro-nano materials doped with conductive adhesives in flexible printed circuits.The specific research content is as follows:（1）Sheet-like silver powder was prepared by combining liquid-phase reduction method and ball milling method.The morphology and particle size of sheet-like silver powder could be controlled by changing the ball milling parameters to determine the optimal preparation process of sheet-like silver powder.Polyurethane acrylate and thermoplastic elastomer were used as the resin matrix of UV/thermal dual-curing conductive adhesive,and sheet-like silver powder was used as the conductive filler to explore the optimal ratio of each component of organic carrier in conductive silver glue.Conductive silver glue prepared under optimized process shows good curing shrinkage performance on flexible substrate after dual curing without deformation and bending of substrate.（2）A highly conductive composite material MXene@Ag dendrite was synthesized by a simple and mild liquid-phase reduction method.The electrical and antioxidant properties of MXene@Ag dendrite were tested to ensure its practicality and rationality as a conductive filler.The effect of MXene@Ag dendrite doping content on the electrical properties of dual-curing conductive adhesive was systematically studied.When the content of silver sheet powder was 60 wt%,the content of MXene@Ag dendrite material was 3.5wt%,and the total content of conductive filler was 63.5 wt%,where the dual-curing conductive adhesive prepared had a resistance rate of 9.62×10-7Ω·m after UV curing for 30 s and thermal curing at 80℃for 4 h,which was reduced by 86.98%compared with that of pure silver film.（3）The deformation stability and environmental stability of conductive adhesive doped with MXene@Ag dendrite were investigated.After thousands of bending and twisting,the conductive adhesive still maintained stable electrical properties.Through the analysis of the fatigue fracture mechanism of dual-curing conductive adhesive,it was found that large-sized flexible MXene sheets in the dual-curing conductive adhesive acted as connecting bases to keep the entire conductive circuit completely broken when bent,and silver dendrites established bridges with silver sheet powder at the crack to form a conductive path.The synergistic effect of both makes the dual-curing conductive adhesive have stable conductivity under microcracks.In addition,flexible printed circuits showed excellent environmental stability without significant changes in 8 days under 98%RH salt spray test at 50℃. |
PDF Full Text Request