Copper Wire Bonding Interface Characteristics And Regularity Research

With the copper wire bonding as the main object in the paper, The interfacial microstructures of the Cu-wire bonding to an Al pad is observed, the composition of the bonding interface compounds is determined, he bonding interface compound formation mechanism is analyzed, and the relationship between the copper bonding process bonding temperature, bonding ultrasonic energy, chip aluminum thickness and the bonding strength is explored. Besides there is a large impact on chip cantilever bonding process in the copper wire bonding process, and the dynamic characteristics of a large rebound and low intensity of the copper wire bonding point. To solve this problem,2.8μm thickness of the aluminum chips is proposed instead of1.0μm thickness of the aluminum chip.The research work includes the following sections:Firstly, HRTEM test results show that until the copper key co-temperature rises to340℃before the compounds generated between Cu-Al interface bonding interface; X-ray diffraction analysis showed that the Cu-Al interface to generate CuAl2, Cu9A14;After Cu-Al interface compound is generated, the bonding strength and bonding success rate is significantly enhanced.Secondly, the relationship between the bonding temperature, the evolution of ultrasonic energy, the aluminum thickness and bond strength:as the bonding temperature increased to340℃, the dimple area of the bonding interface is more obvious, more fully bonded, the bonding strength higher; appropriate ultrasound energy(5mW) ultrasound energy is conducive to the formation of copper wire bonding strength, while too low or too high can lead to copper wire bonding strength; bonding chips to cover the2.8μm thick aluminum film can effectively reduce the hardness value of the chip to improve the bonding smooth to ensure that the copper wire bonding more fully to enhance the quality of copper wire bonding.Thirdly,copper wire bonding process for chip cantilever has a large impact, the dynamic characteristics of the big rebound and low intensity of the copper wire bonding point, compare the dynamic characteristics of the aluminum film thickness of the chip2.8μm and1.0μm aluminum thickness of the chip and bonding strength, the results show:the dynamic characteristics of the former is more stable, more pronounced dimple area more fully bonded, at the same time, the bonding strength of the former than the latter10g or so.