Silver Flakes Mixing With Silver Nanowires On Performance Of Conductive Adhesive

Generally,the melting point of bulk metals is rather high,But when the size of them reaches to nano-size,the melting point will become quite low. Thus,if the size and shape of one-dimensional nanomaterials can be controlled,they can come up to sinter as well at relatively low temperature.The diameter of silver nanowires is at nano-level,so it can appear the sintering behavior like silver nanoparticles;while the length is at micro-level,which makes the silver nanowires own the properties of long conductive path,far current transmission distance,etc.Therefore,silver nanowires are usually considered to prepare conductive adhesive in order to improve the conductive adhesive's performance.alcohothermal method was used to produce silver nanowires.By mainly investigating the dominant factors such as the molar ratio of PVP and AgNO3,control agent concentration, reaction time,etc having impact on the morphology of the product,we obtained the best process parameters of preparing the silver nanowires:molar ratio of PVP and AgNO3 was 4,concentration of FeCl3was5mmol/L,the solution was heated to 210? from room temperature,and the reaction rate was 10?/min.Under this condition,the average diameters of silver nanowires prepared are 40 nm approximately,and the average lengths are about 12?m, and the longest one is even up to ~20?m.The research showed that the product had a face-centered cubic structure of metallic silver,good crystallinity,pleasurable morphology and nice slenderness ratio.Through analysizing mass ratio of the mixed fillers and sintering behavior of the fillers,we got some conclusions as follow: as the mass ratio between the silver nanowires and the silver flakes was 1:6,the mixed fillers could overlap as a continous conductive network in matrix resin.By this time,the conductive adhesive could receive a much better electrical property.The sintering phenomenon revealed that silver flakes,formed an obvious jagged morphology in the edge at 200?,changed dramatically on surface morphology at 250?,and even fused into thick rod-like bulky grains from their original flake.However,as to mixed fillers,who began to sinter at 200?,formed a serial conductive network at about 250?,and fused into the mixture of graininess and micro-size thick flakiness,were different entirely.At last,by using the idealized model to caculate the melting point of silver nanowires and silver flakes,we found that when the size was 50 nm below,both the melting temperature of silver nanowires and silver flakes had apparent mutation.Yet compared to silver flakes,silver nanowires were more easily to mutate on melting point,which would slow down the sintering of silver flakes in mixed fillers.Silver flakes treated by glutaric acid and mixed fillers with optimum mass ratio were introduced to develop conductive adhesive.The result indicated that conductive adhesive using mixed fillers obtained better integrated properties than that of silver flakes conductive adhesive.As the fillers content was 60wt%,the two conductive adhesives had the biggest difference on properties.High temperature research showed that both the electric conductivity and the tensile shear strength of mixed fillers' conductive adhesive reached the maximum when the temperature was 250?.Yet the volume resistivity of silver flakes' conductive adhesive enlarged with the increase of temperature,and the tensile shear strength became the maximum at 200?.Compared with silver flakes conductive adhesive, the silver nanowires conductive adhesive had an more excellent property of high temperture resistance.The TGA test revealed that the existence of conductive fillers could make a contribution to the heat stability of matrix resin,and the heat stability of mixed fillers' conductive adhesive was a little better than that of silver flakes' conductive adhesive.