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的新型连接工艺：键合温度低于300℃，耐热性高于260℃。1.通过焊料与电镀之间的反应提高熔化温度。在240℃的回流焊过程中，锡银焊料与Ni-Co/Au电镀反应生成金属间化合物，从而提高了焊料层的熔化温度。Ni和Co通过(Ni，Co)Sn2反应层的快速扩散可促进金属间化合物的形成。结果表明，再流焊后可获得熔化温度高于260℃的粘结层。2.金属有机银纳米颗粒键合工艺提出了一种新型的银金属有机纳米颗粒键合工艺，作为纳米技术的新应用。银纳米颗粒的平均尺寸约为11 nm，每个纳米颗粒上覆盖着一个有机壳层。通常情况下，金属纳米颗粒由于其较大的表面能，其团聚是不可避免的。然而，由于有机壳层的原因，这些银纳米颗粒单独存在，一旦有机壳层被移除，这些银纳米颗粒就会被激活并突然聚集在一起。分析了纳米颗粒的热特性，将纳米颗粒的团聚应用于铜-铜连接，研究了键合压力、温度、保温时间等键合条件对接头强度的影响。实现了银与铜的冶金结合，实现了致密的烧结银结合层。使用纳米颗粒的接头熔点相当于银的熔点，接头强度为30-40兆帕，足够强，可以用作高温电子组件。此外，还得出了强度随上述三个参数的增大而增大的结论。

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.