Printed electronics are circuits that are additively manufactured using conductive pastes composed of micro-/nanoconductive metal particles. Silver-based compounds are the most widely used metals for such pastes due to their superior conductivity and oxidation stability. However, the high cost of silver (Ag) has demanded its replacement with more cost-effective and abundant metals such as copper (Cu). Despite its cost-effectiveness and abundance, Cu suffers from high oxidation tendency and sintering temperature that have limited its widespread utilization in printed electronics. In this work, we have developed a low-cost hybrid bimodal paste composed of Cu microparticles (1–5 μm) and Ag nanoparticles (20–30 nm) (CuMPs/AgNPs) via nondestructive photonic sintering. The concurrent melting of AgNPs and catalytic reduction of CuMPs allow the paste to be sintered at considerably low temperatures using an intense-pulsed light (IPL) source. The required light energy density for effective sintering of different mixing ratios of AgNPs and CuMPs was systematically measured using electrical, optical, and mechanical characterization techniques. These analyses revealed that a minimum of 16 wt % AgNPs in the bimodal CuMP/AgNP paste with an IPL irradiation energy of 10.6 J/cm² and pulse duration of 5 ms achieved a minimum sheet resistance of 0.072 Ω/□ that results from localized melting of AgNPs between adjacent CuMPs. Furthermore, the CuMP/AgNP films with a minimum of 6 wt % AgNPs showed significantly improved oxidation stability characteristics even after 7 days of incubation in accelerated oxidation conditions [70 °C and 100% relative humidity (RH)]. As a proof of concept, we demonstrated an application of the developed paste (CuMPs-6 wt % AgNPs) by directly printing a wireless resonant moisture sensor onto the interior region of a cardboard package box, which is capable of performing in situ monitoring of the moisture ranging from 30 to 85% RH with an average linear sensitivity of −3.08 % RH/MHz.

中文翻译：

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用于低成本印刷电子产品的高导电铜银双峰浆料

印刷电子产品是使用由微/纳米导电金属颗粒组成的导电浆料增材制造的电路。由于银基化合物具有优异的导电性和氧化稳定性，因此银基化合物是此类浆料中使用最广泛的金属。然而，银 (Ag) 的高成本要求用更具成本效益和丰富的金属替代它，例如铜 (Cu)。尽管具有成本效益和丰富性，但铜具有较高的氧化倾向和烧结温度，这限制了其在印刷电子产品中的广泛应用。在这项工作中，我们通过无损光子烧结开发了一种低成本的混合双峰浆料，由 Cu 微粒（1-5 μm）和 Ag 纳米颗粒（20-30 nm）（CuMPs/AgNPs）组成。AgNPs 的同时熔化和 CuMPs 的催化还原允许使用强脉冲光 (IPL) 源在相当低的温度下烧结糊状物。使用电学、光学和机械表征技术系统地测量了有效烧结不同混合比例的 AgNPs 和 CuMPs 所需的光能密度。这些分析表明，在 IPL 辐射能量为 10.6 J/cm²和 5 ms 的脉冲持续时间实现了 0.072 Ω/□ 的最小薄层电阻，这是由于相邻 CuMP 之间的 AgNP 局部熔化造成的。此外，即使在加速氧化条件 [70 °C 和 100% 相对湿度 (RH)] 下孵育 7 天后，含有最少 6 wt% AgNPs 的 CuMP/AgNP 薄膜也显示出显着改善的氧化稳定性特性。作为概念证明，我们通过将无线谐振湿度传感器直接印刷到纸板包装盒的内部区域，展示了所开发的糊剂（CuMPs-6 wt % AgNPs）的应用，该传感器能够进行原位监测湿度范围为 30 至 85% RH，平均线性灵敏度为 -3.08 % RH/MHz。