| In recent years, as the emergence of the 3th generation of semiconductor represented by Si C, the development of integrated circuit exceeding the dream of Moore’s law is no longer out of reach. The 3th generation semiconductor like Si C as compared to conventional semiconductor such as Si have higher band gap width,breakdown voltage and power density, which will be more suitable for the power module and high temperature environment, so it puts forward higher requirements to the encapsulation and chip bonding materials. Cu6Sn5 has he advantages of good conductive thermal conductivity, thermal expansion coefficient matching with Cu excellently. At the same time as nano size effect of the nano material can reduce the melting point of bulk materials, it will achieve the characteristics of low temperature connection high temperature service, which makes the nano solder paste in recent years become a new subject in the field of electronic packaging. Therefore, as a kind of novel high temperature high power chip bonding material, nano Cu6Sn5 has important research significance.This paper optimizes nano Cu6Sn5 sintering joint shear strength from two aspects of formulation and process. The joint shear strength is used as evaluation index of the sintering quality. The recipe optimizing is carried out from the surfactant during nano Cu6Sn5 preparation, the flux in solder paste recipe, the adding proportion of Sn three aspects; The optimization of sintering process is undertaken at a fixed heating rate,while the sintering temperature, sintering time, sintering pressure are mainly explored to obtain the optimum technological parameters.Then Si C single chip is connected with nano Cu6Sn5 and tested its electric and thermal performance to be compared with the traditional SAC305 and sintering silver solder paste, and finally the three groups of connection of the single chip samples are used for reliability test. At the end of this research a kind of applied usually topology of half bridge module is designed and connected by nano Cu6Sn5. The output performance under different temperature and leakage current are tested.As the results shown that: The best formulated surfactant of nano Cu6Sn5 is CTAB,while the ratio of sintered material are best added 27.08% Sn both at 220℃ and 260℃.the optimum procedure parameter is sintering at 260℃/40 MPa for 20 minutes of which joints’ shear strength is 17.4MPa. The intermetallic compound Cu3 Sn generation through the morphology of the joint interface can be seen in the joint sintered at 260℃compared with 220℃ joint connector interface has compared, and most of fracture surface topography is lamellar tearing. On the other hand, nano Cu6Sn5 connectingMOSFET single-chip has good electrical properties, since its static output curve is approximate with sintering Ag and SAC305, and RDSon of Si C device connecting sample is 144.69mΩ. For the thermal performance, thermal resistance of 38μm sintered silver is significantly smaller than the other two groups, and 20μm thick nano Cu6Sn5 has similar thermal resistance with 75μm thick SAC305. High-temperature half-bridge module connected by nano Cu6Sn5 still have electric conductive performance at 200℃, an average RDSon is measured as 289.15mΩ at this temperature, at the same time conclusion of module RDSon increasing as temperature increasing has been achieved. In the end,although the reliability of nano Cu6Sn5 die bonding material is not ideal, through the initial interface morphology the nanoparticles agglomeration is suspected to lead the driving force less. It makes interface connect worse and bonding unstable so holes and other defects are in a rapid expansion of the crack under the influence of accelerated thermal stress, which makes the connection fail finally. The paper recommend that future researches on nano Cu6Sn5 die-attache material should focus on selecting anti-reunification disperser firstly, thereby improving the reliability of nano Cu6Sn5 bonding. |
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