Microwave sintering of ink-jet printed copper nanoparticles

增材制造有望改变快速原型和最终消费者制造的范式，不再局限于机械部件，而不是更广泛的产品，包括通过印刷电子电路的电子产品。这种新兴技术已经达到了工业成熟度，例如，对于显示器来说，有机电子产品的卷对卷（R2R）印刷现在已经成为标准，而对于其他关键电子元件，如非易失性存储器，它仍处于起步阶段，我们的团队在2017年首次展示了完全可打印的设计。为了加速生产过程，目前的速率限制工艺步骤是烧结几个部件，虽然原则上可以用不需要烧结的替代品代替一些部件，但这种替代意味着设计或性能限制，因此作为一种选择，考虑更快的烧结方案。由于热烧结是最慢和选择性最低的选择，闪光烧结提供了一种选择性更高但成本更高的替代方案。该项目的目的是确定微波烧结的潜力，该微波烧结将联合收割机结合闪光的速度，其费用与热烧结相似，比闪光烧结便宜几个数量级。不同的参数，如金属纳米粒子油墨的吸光度作为层厚度的函数，还原剂的效果和足够强的强度的微波谐振器的设计进行了研究，并通过SEM，原子力显微镜和四点电特性验证的结果。

Additive manufacturing holds the promise for a change of paradigm in fast prototyping and end-consumer fabrication and is no longer restricted to mechanical components rather than a much broader variety products including electronics through printing of electronic circuitry. This emerging technology has already reached industrial maturity e.g. for displays where roll-to-roll (R2R) printing for organic electronics is now becoming standard while it is still in its infancy for other critical electronic components such as non-volatile memories for which our team has been the first to demonstrate a fully printable design in 2017. In order to accelerate the production process, the rate limiting process step at the moment is the sintering of several components and while it is in principle possible to replace some by alternatives that do not require sintering, such a replacement implies design or performance restrictions so that, as one option, faster sintering schemes are taken into consideration. With thermal sintering being the slowest and least selective option, flash light sintering provides a more selective yet substantially more expensive alternative. The purpose of this project is to determine the potential of microwave sintering that would combine the speed of flash light at expenses similar to thermal sintering, which is orders of magnitude more affordable than flash light sintering. Different parameters such as the absorbance of metal nanoparticle inks as a function of layer thickness, the effect of reducing agents and the design of a microwave resonator for sufficiently strong intensities are investigated and the outcome verified by means of SEM, atomic force microscopy and four-point electrical characterization.