银包铜核壳微/纳米焊料的制备、烧结连接机理及其电迁移可靠性研究

The way to achieve industrial transformation and upgrading is to develop high-tech industries. So, it is necessary to realize independent research and produce of electronic devices, especially the third-generation semiconductors, as it is the future of electronic devices. The connection materials are indispensable in the manufacture of electronic devices, however, the traditional connection materials cannot meet the requirements of third-generation semiconductors. Due to the low-temperature sintering high-temperature service characteristics, nanoparticle pastes are most likely to be the connection materials for the third-generation semiconductors. But, it is easily to be electromigrated in sintered silver and oxidized for the copper nanoparticle paste, which limits their applications. Besides, the connection layer formed by the nanoparticle paste often has a large number of voids. Therefore, it is significance to overcome these shortcomings in the development of nanoparticle paste. Based on this, we are intending to prepare silver-coated copper core-shell (Cu@Ag) micro/nano hybrid paste, investigate the sintering mechanism of heterogeneous scale and dissimilar metal particles and identify its ability of reducing porosity, oxidation and electromigration, so as to provide technological reserve and basic theory for the nanoparticle paste.

发展高新技术产业是我国实现产业转型升级的必由之路，其中电子器件的自主研发和生产是重中之重，特别是针对下一代电子器件的核心——第三代半导体。电子器件制造中封装连接材料必不可少，而传统的连接材料无法满足第三代半导体的需求，纳米焊料以其低温烧结、高温服役的特点成为最有可能的替代材料。然而，铜纳米焊料的易氧化、烧结银易的电迁移、烧结层的高孔隙率等问题限制了他们的应用，因此，在纳米焊料的研发中同时克服这三个缺点成为其迈向应用层面的关键所在。基于此，本项目拟制备银包铜(Cu@Ag)核壳微/纳米混合焊料，研究异种尺度下异种金属核壳颗粒的烧结融合机理，以及由其烧结所得焊点的电迁移可靠性，探究其是否同时具备抗氧化、抗电迁移、降低孔隙率的能力，为第三代半导体封装连接材料的研发提供技术储备和理论基础。

高温封装材料是第三代半导体(SiC/GaN)制造过程中的关键材料之一，而传统的连接材料无法满足其高温环境下的使用需求。纳米焊料以其低温烧结、高温服役的特点成为最有可能的替代材料。然而，铜纳米焊料的易氧化、烧结银的易电迁移、烧结层的孔隙率较高等问题限制了他们的应用，因此，在纳米焊料的研发中同时克服这三个缺点成为其迈向应用层面的关键所在。基于此，本项目通过工艺探索，制备了三种不同类型的银包铜颗粒，由于银层的包覆，三种类型颗粒具有良好的抗氧化性和大气环境下室温贮存能力。微纳米银包铜颗粒(Cu@Ag MNPs)所制备的焊膏具有更高的连接强度(300℃，大气环境条件下，裸铜键合可达到21.5MPa)和更低的孔隙率(孔隙率是单一尺度颗粒的三分之一)。TEM下加热Cu@Ag MNPs，发现其在烧结过程中Cu核依然被Ag层包覆，证明其具有良好的抗氧化性。采用水滴实验，研究了Cu@Ag MNPs焊膏的电化学迁移行为，其抗电化学迁移能力是是银的2倍。通过本项目的研究，开发一种更性能更加优良的、适用于高温封装的微纳米银包铜颗粒。

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