微型柔性器件作为未来电子器件的重大发展趋势，需要印刷电子技术的进一步革新，因此印刷技术与印刷材料是亟待发展的关键突破口。三维分枝型结构的银粉因其独特的三维纳米结构而具有显著的低温烧结特性，以其制得的激光蚀刻银浆具有低成本、高粘附力、高图案分辨率、高耐候性、长寿命、适用于柔性基板等优点，因此受到相关学者的广泛关注。 基于此，本文提出了一种可千克级批量制备、形貌可控、尺寸均匀的亚微米银花合成技术。利用SEM、TEM、XRD、UV-vis等形貌结构表征先进手段优化银粉合成条件、探究银粉生长机制与低温烧结熔缩机制。银花的尺寸可调控至400nm~1.1μm，表面具有丰富的纳米片层结构，特征尺寸在10nm左右；银花的生长过程在柠檬酸钠的选择性吸附与诱导作用下，沿着（111）面取向生长；银花于60℃开始烧结，于200℃时发生结构熔缩。 结合前期已开发的银粉表面修饰技术（碘处理），制备所得的花状银粉银浆具有较低的渗流阈值，银含量降低至25wt%时，电阻率仍能保持在6.094×10-3Ω·cm。并且基于银花银浆的低温烧结固化特性，可实现低功率激光快速烧结固化。此外，还通过工业标准的测试手段（包括85℃/85%RH可靠性测试、冷热循环冲击测试、力学弯曲测试）进行分析判定银浆的综合实际应用性能，测试结果说明，银花银浆具有较高的高温高湿可靠性与抗冷热冲击性能，并且小曲率直径弯折后电阻变化率都在可接受的范围内，不仅能满足目前实际器件的使用要求，未来亦有望广泛应用于超薄柔性印刷电子领域。基于高性能花状银粉银浆与低功率激光烧蚀技术，可实现线宽18μm，线距15μm的精细布线，并且可适用于目前实际大规模生产的触控屏边框引线制备工艺。基于高性能花状银粉银浆与低功率快速激光固化烧结技术，制得与皮肤兼容性与贴合性良好的皮肤电子模型与灵敏较高的的触控电容器。总之，基于高性能银花银浆的全激光工艺在超精细布线、超薄触控、印刷电容与柔性指纹锁等电子元器件有很好的应用前景。
As a major trend in the development of electronic devices in the future, micro-flexible devices require further innovations in printed electronic technology. Therefore, the development and research of printing technique and printed materials are critical for obtaining ultrathin flexible devices. Current research shows that the three dimensional (3-D) silver particle has remarkable low-temperature sintering behavior which result from its unique three-dimensional nanostructure. 3-D Ag particle-based laser-etched paste have been drawing more attentions in broad research fields due to its low-cost, high adhesion, high pattern resolution, high weather resistance, long life and compatibility with flexible substrate. Based on above discussion, we introduce a facile and controllable synthetic method of monodispersed submicron flower-like silver particles (Ag SMFs) which is about 400 nm~1.1 μm in size. More importantly, the maximum amount of Ag SMFs synthesized in one batch was about 1000 g in this study. What’s more, using some advanced morphological characterization methods (SEM, TEM, XRD, UV-vis, etc) to optimize synthesis process of Ag SMFs, explore silver growth mechanism and low-temperature sintering and fusing mechanism. By tuning the reaction condition, a series of submicron silver particles with acute branches were obtained, and the feature size of each branch is about 10 nm. The citrate molecules preferentially bind to (111) plane of face-centered cubic (fcc) structure of silver. This promoted anisotropic growth maximizing the surface area of (111) plane of Ag SMFs. The sintering and fusing temperature of Ag SMFs were about 60 °C and 200 °C, respectively. Ag SMFs with surface modification (iodine treatment) paste has a lower percolation threshold, and the resistivity can still be maintained at 6.094×10-3 Ω·cm when the silver content was reduced to 25 wt%. In addition, Ag SMFs paste can be quickly sintered and cured by low-power laser due to its low-temperature sintering and curing behavior. To determine the comprehensive practical performance of silver paste, we conducted some industry standard test methods (85 °C/85% RH reliability test, thermal shock test, bending test), and test results show that Ag SMFs paste has a sufficient reliability under high temperature and high humidity condition and thermal shock resistance. Moreover, the resistance variation of Ag SMFs paste after bending test (small curvature diameter) was within an acceptable range. With above intriguing and excellent performance mentioned, Ag SMFs paste not only can meet the requirements of current practical device, but also is expected to be widely used in ultrathin flexible printed electronics. Based on the high-performance Ag SMFs paste and low-power laser ablation technology, the conductive circuit line width and distance was controlled to be 18 μm and 15 μm, respectively. And Ag SMFs paste can be applied to the manufacturing process of touch panels for mass production. Based on high-performance Ag SMFs paste and low-power fast laser curing/sintering technology, a skin electronic model with good skin compatibility and a sensitive touch capacitor were manufactured. In short, the All-laser process based on high-performance Ag SMFs paste has extensive application prospect in electronic components such as ultrafine circuits, ultrathin touch screen, printed capacitors and flexible fingerprint locks.
