摘要
利用一步化学还原法合成具有粒径双峰分布的铜纳米颗粒,并制备可在低温无压条件下烧结的纳米铜膏。铜纳米颗粒由平均粒径160 nm的大颗粒及其被平均粒径9 nm小颗粒包围的团聚体构成;采用乳酸基复合包覆剂不仅能有效防止铜颗粒氧化,还对纳米颗粒烧结过程有促进作用。280℃下无压烧结后的铜膏烧结接头剪切强度高达65 MPa,究其原因主要是烧结过程中形成的大尺寸块体铜颗粒的强化作用,以及铜膏烧结基体与上、下基板界面间形成了致密无缺陷的牢固冶金互连。铜膏烧结接头的形成主要由“颗粒-颗粒”间纳连接及“颗粒-基板”界面的纳连接而实现,前者以表面活性能高的小尺寸铜纳米颗粒为“桥梁”将大尺寸铜颗粒连接成致密块体铜,而后者借助乳酸铜高温下分解得到的铜纳米颗粒与基板间的互扩散和自扩散最终在界面形成连续且致密的纳连接层。烧结接头在空气中250℃时效1000 h后,铜膏烧结基体与界面处虽出现空洞,但仍具有高强度(大于56 MPa),表明铜膏烧结接头有较好的抗高温热氧化性能。
Bimodal-sized Cu nanoparticles(NPs)with a conformation of NPs(~9 nm)capping on large ones(~160 nm)are synthesized through a one-step chemical reduction method,which are then used to prepare the Cu paste capable of pressureless sintering at low temperature.The lactic acid based capping agents show both effective oxidation protection and sintering enhancing effects for Cu NPs.Cu paste joints after pressureless sintering at 280℃have high shear strength up to 65 MPa,which is underpinned by the strengthening effect of bulk Cu particles and the formation of nearly defect-free and dense interfaces joined metallurgically between sintered Cu paste matrix and substrates.The sintered Cu paste joint is formed by means of two nano-joining processes,i.e.,nano-joining between Cu NPs and Cu NPs via bridging under the driving force from their high specific surface energy,as well as nano-joining between Cu NPs and substrates through formation of continuous yet dense diffusion layers at interfaces of sintered particles and substrates due to the enhanced self-and inter-diffusion of Cu NPs produced from decomposition of Cu lactate.Despite formation of some voids at the interface of sintered Cu paste/Cu substrate after high temperature storage at 250℃for 1000 h,Cu paste joints still show relatively high strength(>56 MPa).
作者
黄海军
周敏波
吴雪
张新平
HUANG Haijun;ZHOU Minbo;WU Xue;ZHANG Xinping(School of Materials Science and Engineering,South China University of Technology,Guangzhou 510640;Guangdong Provincial Engineering Technology R&D Center of Electronic Packaging Materials and Reliability,South China University of Technology,Guangzhou 510640)
出处
《机械工程学报》
EI
CAS
CSCD
北大核心
2022年第2期58-65,共8页
Journal of Mechanical Engineering
基金
国家自然科学基金(51775195)
广州市科技计划(201807010028)资助项目。
关键词
纳米铜膏
双峰分布
无压烧结
纳连接
可靠性
Cu nanoparticle paste
bimodal distribution
pressureless sintering
nano-joining
reliability
