Preparation and sintering characteristics of nano-silver wrapped tin paste

Nanosilver paste, an interconnect solder is a common choice in the electronics packaging industry, however higher sintering temperatures and lower sintering strength limit its application. At present, core-shell nano-slurry has been studied and applied to chip interconnection. Based on the mechanism of heterogeneous flocculation, we have developed a new nano-silver wrapped tin paste (Sn@Ag paste), and according to the decomposition temperature of the organic dispersant in the slurry, A corresponding sintering process with a maximum temperature of 300 ° C was developed. The Sn@Ag core-shell structure makes Sn have good dispersibility and oxidation resistance, and the sintered product of the slurry is a mixture of a solid solution of Ag and an Ag 3 Sn phase. Among them, the hard and brittle phase Ag 3 Sn acts as a dispersion strengthening effect in the Ag matrix phase, and the solid solution of Ag acts as a replacement solid solution strengthening. With the increase of doping Sn content, the sintering strength is significantly improved. When the Sn content is 5%, the joint shear strength reaches the highest value of 50Mpa, which is higher than the pure nano silver paste by 10 Mpa. This new nano-silver wrapped tin paste technology has the characteristics of low temperature sintering and high temperature service, so it is expected to be widely used in semiconductor power devices.

Improvement of Sintering Performance of Nanosilver Paste by Tin Doping

Nanosilver paste, an interconnect solder, is a common choice in the electronics packaging industry. However, higher sintering temperature and lower sintering strength limit its application. At present, doped nanosilver paste has been studied for use in chip interconnection. In order to improve the sintering properties and shear strength of nanosilver paste, we have developed a new tin-doped nanosilver paste (referred to as silver tin paste), and according to the decomposition temperature of the organic dispersant in the slurry, a corresponding sintering process with a maximum temperature of 300°C was developed. The product after sintering of the silver tin paste is a mixture of a solid solution of Ag and an Ag3Sn phase. Among them, the hard and brittle phase Ag3Sn diffuse distribution in the silver matrix for strengthening, and the solid solution of Ag acts as a replacement solid solution strengthening. As the content of doped Sn increases, the sintering strength increases remarkably. When the Sn content is 5%, the joint shear strength reaches the highest value of 50 MPa. When it exceeds 5%, the sintering strength gradually decreases, which may be caused by the excessive formation of the intermetallic compound IMC as the dopant content increases. This new tin-doped nanosilver technology has the characteristics of low-temperature sintering and high-temperature service, so it is expected to be widely used in semiconductor power devices.

Welding of Silicon to Invar for Application in Synchrotron Light Instrumentation

The Double Crystal Monochromator (DCM) will be developed at the Brazilian Synchrotron Light Laboratory (LNLS) to select the desired X-Ray wavelength of Sirius, the new Brazilian fourth generation synchrotron. Components of this optical instrumentation can be obtained through welding processes, such as brazing, soldering, and diffusion bonding. The use of vacuum welding technique ensures union of silicon with FeNi alloy, Invar36 (64Fe-36Ni) from Grupo Metal and Invar39 (61Fe-39Fe) from Scientific Alloys. Union of these materials was performed with filler alloys from Nihon Superior, such as ALCONANO (nanosilver paste), SnSb (95Sn-5Sb), Sn100C (Sn-0.7Cu-0.05Ni-0.01Ge), and Sn100CV (Sn-5Bi-0.8Cu-0.05Ni). Following welding tests, microstructural and metallographic analysis of the interface region between the materials involved are performed to investigate the junction among silicon, filler alloy, and base metal. Microstructural characterization carried out by a QUANTA SEM (Scanning Electron Microscope) with EDS (Energy Dispersive Spectroscopy) technique to identify the composition, distribution, and morphology of the phases. Based on these analyses, the best parameters were Invar39/Sn100CV/Si samples using base materials coated with different depositions: one gold and the other copper. In the mechanical test, the specimen with copper film presented higher shear strength.