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Low-temperature and pressureless silver (Ag) sintering was applied to a 1200 V/200 A silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET) power module with a Ag-finished silicon nitride active metal-brazed substrate, and the results were evaluated for applicability in electric and hybrid electric vehicles. The sintering was performed at 220–240°C, 90 min in vacuum under nitrogen gas conditions; the bonding strength, bonding layer thickness (BLT), void content, and densification of the as-sintered Ag joints were 39 MPa, 71.4 µm, 2%, and 90.5%, respectively. The shear strength, BLT, densification, and microstructure of the Ag-sintered joints were compared before and after the thermal cycling test (− 50–150°C, 1100 cycles, TCT) and high temperature storage test (200°C, 1000 h, HTST). To simultaneously compare the electrical properties of the SiC power module with lead (Pb)-free solder joints, the same SiC MOSFET power module was manufactured using a Sn-3.0Ag-0.5Cu (SAC305) Pb-free solder. The shear strength and densification after TCT and HTST were 35.5 MPa and 39.7 MPa, as well as 92.8% and 94.8%, respectively. The on-resistance and total switching efficiency of the SiC power module with the Ag-sintered joint were also compared to those of the SAC305 solder joint module, which evinced maximum values of 7.3 mΩ and 10.7 mJ that were superior to those of 8.5 mΩ and 11.3 mJ for the SAC305 solder joint, respectively. Under the same measurement conditions, the maximum generated current and voltage values are lower than those of the solder joint module, so it is envisaged that stable power module operation is realizable for long-term use. The Ag-sintered joint surpassed the SAC305 solder interconnects in terms of the electrical and mechanical reliability of the power module. When a SiC wide band gap device was used, it was discovered that Ag sintering was superior to Pb-free solder interconnects to increase the power conversion efficiency of the power module.

The reactions between Ag pastes containing two types of PbO-based glass frits and an n-type (100) Si wafer during firing in air at 800 °C were investigated in order to understand the mechanism for the formation of inverted pyramidal Ag crystallites at the Si interface as well as the effect of the PbO content of the glass frit on Ag crystallite formation. Inverted pyramidal Ag crystallites were formed by the precipitation of Ag atoms dissolved in fluidized glass during the subsequent cooling process after firing. PbO in the glass frit did not participate directly in the reaction with the Si wafer. However, its content had a strong influence on the reaction rate at the glass/Si interface and, thus, on the size and distribution of the Ag crystallites. The effect of the PbO content in the glass could be understood from the higher Ag solubility and lower viscosity of the glass at the firing temperature with increasing PbO content. Based on the experimental results, a model was proposed for the formation of Ag crystallites at the glass/Si interface during the firing process of screen-printed thick-film Ag metallization.

The interaction between Cu 6 Sn 5 particles in the bulk of a solder and a Ni substrate was examined during solid-state aging using Cu/Sn/Ni and Cu/Sn/Cu/Sn/Ni diffusion couples with initially thin Cu layers. The results clearly demonstrated that the (Cu,Ni) 6 Sn 5 particles dispersed in the bulk solder decomposed in order for a ternary (Cu 1−x Ni x ) 6 Sn 5 layer to grow at the solder/Ni interface during solid-state aging. The interaction between the (Cu,Ni) 6 Sn 5 particles and the (Cu 1−x Ni x ) 6 Sn 5 layer occurs owing to the driving force for the (Cu,Ni) 6 Sn 5 compound to become saturated with Ni. A (Ni,Cu) 3 Sn 4 layer forms at the (Cu 1−x Ni x ) 6 Sn 5 /Ni interface only after the Ni composition of the (Cu,Ni) 6 Sn 5 phase in the bulk solder approaches that of the (Cu 1−x Ni x ) 6 Sn 5 layer. Once the (Ni,Cu) 3 Sn 4 layer has formed, it grows at an exceptionally rapid rate by consuming the (Cu 1−x Ni x ) 6 Sn 5 and Sn layers, which can be problematic in solder joint reliability.

The interaction between Cu6Sn5 particles in the bulk of a solder and a Ni substrate was examined during solid-state aging using Cu/Sn/Ni and Cu/Sn/Cu/Sn/Ni diffusion couples with initially thin Cu layers. The results clearly demonstrated that the (Cu,Ni)6Sn5 particles dispersed in the bulk solder decomposed in order for a ternary (Cu1-xNix)6Sn5 layer to grow at the solder/Ni interlace during solid-state aging. The interaction between the (Cu,Ni)6Sn5 particles and the (Cui-xNix)6Sn5 layer occurs owing to the driving force for the (Cu,Ni)6Sn5 compound to become saturated with Ni. A (Ni,Cu)3Sn4 layer forms at the (Cu1-xNix)6Sn5/Ni interface only after the Ni composition of the (Cu,Ni)6Sn5 phase in the bulk solder approaches that of the (Cu1-xNix)6Sn5 layer. Once the (Ni,Cu)3Sn4 layer has formed, it grows at an exceptionally rapid rate by consuming the (Cu1-xMx)6Sn5 and Sn layers, which can be problematic in solder joint reliability.

The interaction between Cu sub(6)Sn sub(5) particles in the bulk of a solder and a Ni substrate was examined during solid-state aging using Cu/Sn/Ni and Cu/Sn/Cu/Sn/Ni diffusion couples with initially thin Cu layers. The results clearly demonstrated that the (Cu,Ni) sub(6)Sn sub(5) particles dispersed in the bulk solder decomposed in order for a ternary (Cu sub(1-x)Ni sub(x)) sub(6)Sn sub(5) layer to grow at the solder/Ni interface during solid-state aging. The interaction between the (Cu,Ni) sub(6)Sn sub(5) particles and the (Cu sub(1-x)Ni sub(x)) sub(6)Sn sub(5) layer occurs owing to the driving force for the (Cu,Ni) sub(6)Sn sub(5) compound to become saturated with Ni. A (Ni,Cu) sub(3)Sn sub(4) layer forms at the (Cu sub(1-x)Ni sub(x)) sub(6)Sn sub(5)/Ni interface only after the Ni composition of the (Cu,Ni) sub(6)Sn sub(5) phase in the bulk solder approaches that of the (Cu sub(1-x)Ni sub(x)) sub(6)Sn sub(5) layer. Once the (Ni,Cu) sub(3)Sn sub(4) layer has formed, it grows at an exceptionally rapid rate by consuming the (Cu sub(1-x)Ni sub(x)) sub(6)Sn sub(5) and Sn layers, which can be problematic in solder joint reliability.

We characterized the electrical and chemical properties of Cu-doped In sub(2)O sub(3)(CIO) (2.5 nm thick)/Sb-doped SnO sub(2)(ATO) (250 nm thick) contacts to p-type GaN by means of current-voltage measurement, scanning transmission electron microscope (STEM) and x-ray photoemission spectroscopy (XPS). The CIO/ATO contacts show ohmic behaviors, when annealed at 530 and 630 degree C. The effective Schottky barrier heights on diodes made with Ni (5 nm)/Au (5 nm) contacts decrease with increasing annealing temperature. STEM/energy dispersive x-ray (EDX) profiling results exhibit the formation of interfacial In-Ga-Sn-Cu-oxide. XPS results show a shift of the surface Fermi level toward the lower binding energy side upon annealing. Based on the STEM and XPS results, the ohmic formation mechanisms are described and discussed.

We characterized the electrical and chemical properties of Cu-doped In 2 O 3 (CIO) (2.5 nm thick)/Sb-doped SnO 2 (ATO) (250 nm thick) contacts to p-type GaN by means of current-voltage measurement, scanning transmission electron microscope (STEM) and x-ray photoemission spectroscopy (XPS). The CIO/ATO contacts show ohmic behaviors, when annealed at 530 and 630°C. The effective Schottky barrier heights on diodes made with Ni (5 nm)/Au (5 nm) contacts decrease with increasing annealing temperature. STEM/energy dispersive x-ray (EDX) profiling results exhibit the formation of interfacial In-Ga-Sn-Cu-oxide. XPS results show a shift of the surface Fermi level toward the lower binding energy side upon annealing. Based on the STEM and XPS results, the ohmic formation mechanisms are described and discussed.