In the actual production process, soldering is a key step in the flip-chip packaging process. The reliability of the interconnection interface of flip-chip LED chips is considered to be one of the most important reliability issues. This paper studies the influence of different soldering temperatures on the microstructure and shear behavior of the Au/Sn-3.0Ag-0.5Cu/Cu solder joints of flip-chip LED chips. The lead-free solder Sn-3.0Ag-0.5Cu was selected as the solder. The microstructure of the intermetallic compound (IMC) interface and the inferred surface of the solder joint is observed, and the microstructure evolution of the solder joint is analyzed. The void ratio of the solder joints at 250°C, 260°C, 270°C, 280°C, and 290°C soldering temperature was tested to characterize the influence of the contact area between the chip and the solder joint on the shear stress. In addition, the solder joints were aged for 1000 hours in an environment with a relative humidity of 85°C/85%, and a shear test was performed to evaluate the influence of the interface reaction on the mechanical reliability of the solder joints during the isothermal aging process. The research show that when the soldering temperature is 270°C, the Au on the bottom of the chip, and the solder and Cu on the substrate have fully reacted, and the solder joints have high shear resistance. The shear strength of the aging solder joints increases first and then decreases, because the high temperature repairs the defects in the solder layer caused by the low soldering temperature to a certain extent. With the extension of aging, cracks and voids gradually appear at the fracture interface, and the effective contact area decreases. The shear strength of the solder joint decreases, and the fracture mode becomes brittle.

在实际生产过程中，焊接是倒装芯片封装过程中的关键步骤。倒装LED芯片互连接口的可靠性被认为是最重要的可靠性问题之一。本文研究了不同焊接温度对倒装LED芯片Au/Sn-3.0Ag-0.5Cu/Cu焊点微观结构和剪切行为的影响。焊料选用无铅焊料Sn-3.0Ag-0.5Cu。观察金属间化合物（IMC）界面和焊点推断表面的微观结构，并分析焊点的微观结构演变。焊点在 250°C、260°C、270°C、280°C 时的空隙率，并测试了 290°C 的焊接温度，以表征芯片和焊点之间的接触面积对剪切应力的影响。此外，焊点在相对湿度为85℃/85%的环境中老化1000小时，并进行剪切试验，以评估界面反应对焊点机械可靠性的影响。等温老化过程。研究表明，当焊接温度为270°C时，芯片底部的Au与基板上的焊料和Cu已充分反应，焊点具有较高的抗剪切能力。老化焊点的剪切强度先增大后减小，这是因为高温在一定程度上修复了低焊接温度造成的焊层缺陷。随着时效的延长，断裂界面逐渐出现裂纹和空隙，有效接触面积减小。焊点剪切强度降低，断裂方式变脆。