石墨纳米片对铜电子浆料导电性的影响

Influences of graphene flake on conductivity of copper electronic pastes

为改善铜浆导电性,以表面改性的金属铜粉为主要导电相,通过添加少量导电性优异的石墨纳米片作为导电增强相制备复合电子浆料,并采用四探针测试仪、扫描电子显微镜(SEM)等分析测试方法研究了石墨纳米片的参数、添加量对铜电子浆料导电性能的影响.结果表明:选用厚度为3~5 nm,片径为5μm的石墨纳米片作为导电增强相,制得石墨纳米片—铜电子浆料,在460℃烧结后导电膜层的电阻率较小;石墨纳米片与铜粉质量比为2∶98时,测得浆料电阻率为17.14 mΩ·cm,相比纯铜浆料电阻率34.43 mΩ·cm降低了50.22%.分析电子浆料导电机理并建立导电相连接几何模型,在导电膜层中,部分折断的石墨纳米片会填充到铜颗粒之间的空隙中,较长石墨纳米片则会形成"搭桥"现象,增加导电相之间的连接,形成较紧密的微观组织和良好的导电网络,从而改善复合浆料的导电性.

To improve the conductivity of the copper pastes,the surface-treated copper powders were used as the main conductive phases,and a small amount of graphene flakes was used as the conductive reinforced phases to prepare the composite electronic pastes. The effect of the specifications and additions of graphene flakes on conductivity were characterized by four-point probe,scanning electron microscopy（SEM） and other testing methods. The results show the pastes with the graphene flakes with a thickness of 3 ～ 5 nm and a flake size of 5 μm has a smaller resistivity after sintered at 460 ℃. When the mass ratio of graphene flakes and copper powders is 2.98,the resistivity of the pastes is measured to be 17.14 mΩ·cm,50.22% lower than that of the copper pastes（34. 43 mΩ ·cm）. The conductive mechanism of the electronic pastes is revealed and geometric model of connection of the conductive phases is established. In the conductive film,the gaps between copper powders are filled by the broken graphene flakes and bridges are jointed between copper powders by longer graphenehe flakes,causing the formation of a compact microstructure and excellent conductive network. Thus the conductivity of the pastes is dramatically improved.