Search

Ag-alloy wire has been recognized to be a good candidate for interconnect in light-emitting diode (LED) technology. This study employed fine Ag-alloy wires bonded on Al-Si pad to investigate their failure mechanism under current stressing of 8×10 4 A/cm 2 at ambient temperature of 150 °C and 175 °C, respectively. We report a novel polarity effect that the spontaneous whisker growth of Ag near bonded area only happens when electrons flowed from Al to Ag, while surface of bond joints remains intact with electrons flowed from Ag to Al, suggesting that the nucleation and growth of Ag whisker is strongly affected by the direction of electron flow. We proposed that the different behaviors on the whisker growth is because compressive stress caused by current crowding effect only builds up with electrons flowed from Al to Ag. [ABSTRACT FROM AUTHOR]

In this research, thousands of 20-\mum pitch microbumps with a diameter of 10 \mum and a structure of a pure Sn cap on a Cu pillar were electroplated on 8-inch wafers, and those wafers were then respectively singularized as a top chip and bottom Si interposer for stacking. Two methods, namely conventional reflow and solid–liquid interdiffusion (SLID) bonding, were adopted to interconnect the microbumps. In the former case, the as-plated Sn caps were fluxed, and the chip was then placed on the Si interposer. Afterward, the Sn caps on the chip and on the Si interposer were melted and interconnected at a peak temperature of 250^\circC. The flux residues were cleaned after reflow, and the microgap between the chip and the Si interposer was fully sealed by a capillary underfill. In the SLID bonding process, the oxides on the as-plated Sn caps were removed by a plasma etcher first, and then the chip was placed on the interposer with a bonder as well, subsequently, the Sn caps were heated to 260^\circC to react with the Cu pillar to form Cu6Sn5. In the final step, the intermetallic microjoints were protected by the same capillary underfill. After assembly, the Joint Electron Devices Engineering Council preconditioning test was used to screen the test vehicles for reliability assessment, and then a temperature cycling test was performed to predict the lifespan of the microjoints. The test results showed that the microjoints formed by SLID bonding provided a superior reliability performance to those assembled by reflow. The fracture of the microjoints was caused by the volume contraction induced by the growth of Cu6Sn5, but the failure mechanisms of those two microjoints were quite different. [ABSTRACT FROM AUTHOR]

The combination of excellent electrical conductivity and low cost makes copper a good selection for interconnect materials. However, rapid oxidation of Cu nanoparticles especially at high temperatures is a fatal demerit. To improve the oxidation resistance and realized mass production, Cu@Ag core-shell submicron particles were prepared using commercial copper oxide particles through a low temperature reduction method and subsequent electroless-plating to form Ag shells. Thermal analytical results suggest that Ag coated Cu particles show improved anti-oxidation ability. Mixed with Ag submicron particles obtained from thermal spray pyrolysis, the electrical resistivity of the sintered Cu-Ag composite pastes reaches 10.4 μΩ cm under a reductive atmosphere. Under the bonding pressure of 10 MPa at 275 °C for 30 min, robust Cu to Cu bonding can be achieved with the Cu-Ag composite pastes, for which the shear strength of the joints reaches 32.7 MPa, and it remains 28.2 MPa as the bonding pressure is reduced to 5 MPa. It was also demonstrated that the joints thus formed have superior elevated temperature strength, and excellent reliability subjected to high temperature storage at 250 °C as well as thermal cycling ranged from −65 °C to 150 °C. [ABSTRACT FROM AUTHOR]

Highlights: [•] Serious warpage of IGBT power module is induced from assembly processes. [•] A pre-bending substrate with a curve opposite the warp is proposed. [•] Design is validated by FEA and related actual measurements. [•] Increasing DBC thickness of Al2O3 layer reduces warps and bonded solder stresses. [•] A thicker base plate is suggested to reduce warping of the entire packaging structure. [ABSTRACT FROM AUTHOR]

A high-power packaging device composed of 600 V/450 A insulated gate bipolar transistor (IGBT) module is presented. Thermal dissipation is improved, and the temperature of junction declines after Ag paste sintering is applied instead of conventional soldering. A 100 μm-thick sintered Ag preform is utilized to assemble two IGBTs and two diodes on Al 2 O 3 direct bonded copper (DBC) substrate during reflow in a vacuum oven. Three DBCs are attached on a copper baseplate to construct a power module. After a thermal cycling test is conducted for up to 2000 cycles, the die shear strength of the sintered Ag is as high as 24.8 MPa. Lowering the induced stress to fracture failure by using finite element simulation is carefully suggested. Furthermore, the measured thermal resistance is reduced by approximately 22%, and the noise during the electrical performance is eliminated by using Ag sintering. This research reveals the successful application of Ag paste sintering in 600 V/450 A IGBT module. • A 600 V/450 A insulated gate bipolar transistor module is presented. • Thermal and electrical properties of silver paste sintering are measured. • Die shear strength of the sintered Ag is as high as 24.8 MPa is acquired. • Scaling diode and preform thicknesses has a good advantage in releasing thermal stress. • Lowering fracture failure is suggested using finite element simulation. [ABSTRACT FROM AUTHOR]