高导电抗氧化银包铜粉的化学镀制备与性能

Preparation and properties of highly conductive and oxidation-resistant silver-coated copper powder by electroless plating

摘要

[目的]为解决纯银粉价格高和纯铜粉易氧化的应用瓶颈，开发一种兼具高导电性、优异抗氧化性的银包铜粉，以替代纯银粉在电子浆料中的应用。[方法]先采用液相还原法制备微米级类球形高纯铜粉，然后通过低温置换镀+高温还原两步法制备银包铜粉。研究了还原镀银的还原剂类型(包括酒石酸钾钠、甲醛、抗坏血酸和水合肼)及反应温度(50 ~ 80 °C)对包覆效果的影响。采用扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)、激光粒度仪、热重分析仪(TGA)和粉末电阻测试仪对粉体的形貌、成分、结构、粒径分布、抗氧化性及导电性进行表征。[结果]采用酒石酸钾钠为还原剂，在70 °C下还原镀银时，可获得表面光滑、包覆致密的银包铜粉。所得银包铜粉(Ag质量分数为25%)粒径分布均匀，无氧化物杂质。其抗氧化温度为280 °C，在30 MPa压力下的电阻率低至3.45 × 10 ⁻⁵ Ω·cm，与纯银的电阻率非常接近。[结论]本工艺制备的银包铜粉兼具优异的热稳定性和高导电性，能够有效解决铜粉易氧化和银粉成本高的问题，满足电子浆料对导电填料的性能要求。

Abstract

[Objective] To address the high cost of pure silver powder and the susceptibility of pure copper powder to oxidation, a silver-coated copper powder with high conductivity and excellent oxidation resistance as a substitute for pure silver powder in electronic pastes was developed. [Method] Micron-sized, spherical high-purity copper powder was firstly prepared by liquid-phase reduction. And then silver-coated copper powder was prepared via a two-step process involving low-temperature displacement plating followed by high-temperature reduction plating. The effects of reductant (i.e. potassium sodium tartrate, formaldehyde, ascorbic acid, and hydrazine hydrate) and reaction temperature (50-80 °C) during reduction plating on the coating effectiveness were studied. The morphology, composition, structure, particle size distribution, oxidation resistance, and electrical conductivity of the obtained powder were characterized using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), laser particle size analysis, thermogravimetric analysis (TGA), and powder resistivity testing. [Result] Using potassium sodium tartrate as the reducing agent at 70 °C yielded silver-coated copper powder with a smooth surface and compact coating. The resulting powder (25% Ag by mass) exhibited a uniform particle size distribution and was free of oxide impurities. It demonstrated an oxidation resistance temperature of 280 °C and a low resistivity of 3.45 × 10 ⁻⁵ Ω·cm at 30 MPa, which was very close to that of pure silver. [Conclusion] The silver-coated copper powder prepared by this process combines excellent thermal stability and high electrical conductivity. It effectively addresses the oxidation issue of copper powder and the high cost of silver powder, meeting the performance requirements for conductive fillers in electronic pastes.

关键词

银包铜粉 / 两步化学镀法 / 抗氧化性 / 导电性

Key words

silver-coated copper powder / two-step electroless plating / oxidation resistance / electrical conductivity

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