Cu-Ni-Si合金薄板的直接粉末轧制及其强度与导电性匹配的调控机制

In order to meet the demand of lead frame with multi- and fine-pith pins used for advanced integrated current (IC), it is necessary not only to further improve strength and electrical conductivity of Cu-Ni-Si alloys, but also to overcome the complexity and high cost of the current method used to produce Cu-Ni-Si alloys sheet. In this proposal, experimental investigation and finite element simulation will be used to study the effect of several complex physicomechanical and geometrical parameters on the density and strength of rolled compacts, such as morphology, particle size, hardness, compressibility and fluidity of powder materials as well as roll diameter and roll gap of rolling machine. Then the deformation behavior of powders during direct rolling will be discussed. On the other hand, differential scanning calorimeter (DSC), in-situ resistance measuring together with synchronized water-quenching equipment and in-situ transmission electron microscopy (TEM) will be used to obtain the information of phase transformation, such as thermal effect, variation of electrical conductivity, microstructural evolutions and so on. Then the precipitation mechanism of δ-Ni2Si phase will be discussed according to experimental results and theoretical calculations using Šesták-Berggren (SB) model and Johnson-Mehl-Avrami (JMA) equation. By clarifying these elemental scientific problems, the control on shaping quality of powder-rolled compact and adjustment of strength and electrical conductivity of Cu-Ni-Si alloys sheet will be achieved. The results of this proposal are expected to provide guidance for the industrial production of Cu-Ni-Si alloys sheet with high strength and high electrical conductivity as well as its applications as IC lead frame.

进一步优化和改善Cu-Ni-Si合金的强度和导电性，解决当前“熔铸+锻造+轧制”方法制备Cu-Ni-Si合金薄板的工艺复杂性和高成本，是应对未来超高集成电路“多引脚和小节距”引线框架生产和应用的迫切需求。本项目拟结合轧制实验和有限元模拟系统研究粉末物性参数(形貌、粒度、硬度、压缩性和流动性等)和设备几何因数(轧辊转速和间隙等)对轧制生坯成型质量的影响，利用同步热分析、原位电阻测试与同步水淬装置和原位透射电镜等多种实验手段结合SB模型和JMA方程进行理论计算，进而揭示粉末在轧制过程中的变形行为和应力诱导下沉淀相δ-Ni2Si的析出行为与机制等两方面的关键科学问题。在此基础上，探索直接粉末轧制工艺和强度与导电性匹配的调控机制，为IC引线框架用高强度高导电性Cu-Ni-Si合金薄板的低成本、短流程和高效率的工业化生产及其工程应用提供理论和实验依据。

随着集成电路向“多引脚和小节距”的方向发展，兼具高强度和高导电性的引线框架材料引起了广泛研究，其中Cu-Ni-Si合金因无磁性和焦耳热效应被认为是潜在的候选材料。然而，目前Cu-Ni-Si合金尚未能满足实际工程应用需求，且主流的“熔铸+锻造+轧制”制备方法工艺性复杂、成本高。为解决这一问题，本项目提出了一种低成本、短流程、高效率和适用于工业化生产的粉末轧制法，以期直接制备高强度高导电性Cu-Ni-Si合金薄板。项目执行过程中，首先以纯Cu粉末为研究对象，通过实验研究获取粉末体系变形行为与变形参数，基于ABAQUS平台建立了粉末直接轧制过程的3D有限元模型，探讨了轧辊间隙、轧制速度和粉末粒径轧制工艺参数对粉末成型质量的影响，确定了最佳的轧制工艺参数和适宜的粉末特征，模拟和实验结果趋势吻合，证实了模拟方案的可靠性；其次以Cu、Ni和Si单质粉末为原料，基于粉末轧制研究结果和所确定的模拟方案，确定了最佳的粉末轧制工艺，并采用正交实验系统研究了烧结温度和烧结时间对薄板表观性能和显微组织的影响，揭示了单质混合粉末体系在烧结过程中的相变与组织演化行为，进而获得了直接粉末轧制+烧结的最佳工艺参数，成功制备了致密度超过99%的Cu-Ni-Si合金薄板；随后，对所制备的Cu-Ni-Si合金薄板进行不同程度的冷变形以及不同温度的时效处理，研究时效过程中显微组织、硬度和导电率的变化规律，结合相变动力学方程探讨应力诱导下δ-Ni2Si 析出行为，建立了相变的动力学方程，确定了沉淀相的形核机制；最后，采用冷变形与热处理相结合的方式，探讨了不同工艺参数对强度和导电性的影响规律，找出了强度和导电性匹配调控的关键所在，获得了兼具较高强度和较好导电性的Cu-Ni-Si合金薄板的直接粉末轧制制备和后处理工艺参数，所制备的Cu-Ni-Si合金薄板的硬度超过700MPa、导电率超过40%IACS。本项目的研究结果可为IC引线框架用高强度高导电性的高效制备及其工程应用提供理论和实验依据。