Low Temperature Sintered Silver Nanoflake Paste for Power Device Packaging and Its Anisotropic Sintering Mechanism

Abstract

Sintered silver pastes have emerged as a kind of packaging material for wide-bandgap (WBG) power devices because of their superior electrical and thermal conductivity. Herein, silver pastes containing monodisperse triangular silver nanoflakes with a size distribution of 40−260 nm were prepared. The sintered silver joints exhibited a significant high shear strength of 49.8 MPa, larger than that of traditional silver paste, and with a relatively low porosity of 5.1%. These remarkable properties were attributed to the special anisotropic sintering process and bridging effect of the silver nanoflakes. Anisotropic sintering of the silver nanoflakes refers to the successive deformation of the corners, edges, and surfaces during sintering. Especially, the deformation of surfaces provides large diffusion paths for the silver atoms, resulting in a denser sintered silver joint. The bridging effect results from two separate silver nanoflakes that are linked by a single silver nanoflake, which increases the connection between the silver nanoflakes and thus improves the mechanical property of the sintered silver joints. This anisotropic sintering mechanism and bridging effect should inspire other researchers to investigate the sintering mechanism of other materials and optimize the performance of the corresponding pastes of these materials.

Effects of Cu/SnAgCu Powder Fraction and Sintering Time on Microstructure and Mechanical Properties of Transient Liquid Phase Sintered Joints

“…This indicated the weak strength of those joints under thermal cycling, as shown in Figure 6b,d. In addition, the shear strength of the joints was compared with that of the sintered joints reported in recent studies [60][61][62][63][64][65][66][67][68][69]. Clearly, the joints showed a high shear strength and good reliability, showing their potential for packaging applications.…”

Solvothermal Preparation of Crystal Seeds and Anisotropy-Controlled Growth of Silver Nanoplates

“…This Ag nanoplates were produced by the solvothermal method and then employed as the seeds for subsequent growth. ,− In a typical synthesis process, 12 g of PVP was first completely dissolved in 70 mL of DMF solution, and 0.37 g of AgNO 3 was then added to the mixture and stirred for 30 min at room temperature. The mixed solution was transferred to a three-necked flask and heated at 110 °C for 3 h under oil bath conditions.…”

“…At the same time, the vertical size of as-prepared nanoplates can be controlled at the level of several nanometers, and its sharp corner has high free energy, so that it has a large driving force for sintering. Therefore, its sintering temperature can be much lower than the melting point of bulk silver, which might be used for flexible circuit printing, biosensors, micronano chip packaging, etc. − …”

Study on Low-Temperature Conductive Silver Pastes Containing Bi-Based Glass for MgTiO3 Electronic Power Devices

“…Nowadays, most of the glass powders available on the market which have the outstanding performance of silver pastes are leaded glass powders. However, due to detrimental effects on human health and the environment, many countries have banned the production of electronic components containing toxic substances, such as lead and mercury [ 11 ]. Therefore, soda lime glass as an eco-friendly glass powder has been used in some works, but its glass transition temperature is too high (>1000 °C) for large-scale fabrication.…”