Novel Bonding Processes in Electronics Assembly for High-temperature Use by In-situ Control of Reaction

本研究提出了以下几种高温电子组件连接新工艺，其连接温度低于300℃，耐热性高于260℃：1.通过焊料与镀层之间的反应来提高焊料层的熔化温度通过Sn-Ag焊料与Ni-Co之间的反应形成金属间化合物来提高焊料层的熔化温度。240℃回流过程中的Au镀覆。Ni和Co通过（Ni，Co）Sn_2反应层的快速扩散促进了金属间化合物的形成。结果表明，回流焊后可获得熔化温度高于260℃的键合层。2.金属有机银纳米粒子键合工艺作为纳米技术的一种新应用，提出了一种新型的金属有机银纳米粒子键合工艺。Ag纳米颗粒的平均尺寸约为11 nm，并且每个纳米颗粒覆盖有有机壳。通常，由于金属纳米颗粒具有较大的表面能，其团聚是不可避免的。然而，由于有机壳，这些Ag纳米颗粒单独存在，并且一旦有机壳被去除，这些Ag纳米颗粒就被活化并突然团聚。分析了其热特性，并将纳米颗粒的团聚应用于铜-铜连接，研究了连接压力、温度、保温时间等连接条件对接头强度的影响。实现了Ag与Cu之间的冶金结合，并获得了致密的烧结Ag结合层。使用纳米颗粒的接头具有与Ag相当的熔点和30-40 MPa的接头强度，其强度足以用作高温使用的电子组件。此外，得出了强度增加与上述三个参数的雅阁一致的结论。

The following novel joining processes in electronics assembly for high-temperature use that had a bonding temperature below 300℃ and a heat resistance higher than 260℃ were proposed in the present research.1.Raising melting temperature by the reaction between solder and platingThe melting temperature of the solder layer was raised by the formation of an intermetallic compound through the reaction between a Sn-Ag solder and Ni-Co/Au plating during the reflow process at 240℃. The rapid diffusion of Ni and Co through a (Ni, Co)Sn_2 reaction layer could promote formation of the intermetallic compound. As a result the bonding layer having a melting temperature higher than 260℃ could be obtained after the reflow soldering.2.Bonding process using metallo-organic Ag nanoparticlesA novel bonding process using Ag metallo-organic nanoparticles as a new application of nanotechnologies was proposed. The average size of the Ag nanoparticle is approximately 11 nm, and each nanoparticle is covered with an organic shell. Usually, the agglomeration of metallic nanoparticles is unavoidable due to its large surface energy. However, on the account of the organic shell, these Ag nanoparticles exist individually, and once the organic shell has been removed, these Ag nanoparticles turn activated and abruptly agglomerate. We analyzed its thermal characteristics, applied the agglomerating of the nanoparticles to Cu-to-Cu joining, and researched the influence of the bonding condition, such as bonding pressure, temperature or holding time, upon the joint strengths. The metallurgical bonding between Ag and Cu was achieved and a dense bonding layer of sintered Ag was realized. The joint using the nanoparticles had a melting point equivalent to that of Ag and a joint strength of 30-40 MPa, which is strong enough to be applied as an electronics assembly for high-temperature use. In addition, it came to the conclusion that the strengths increased in accord with the aforesaid three parameters.