Abstract
Recently, nanosilver pastes have emerged as one of the most promising high temperature bonding materials for high frequency and high power applications, which provide an effective lead-free electronic packaging solution instead of high-lead and gold-based solders. Although nanosilver pastes can be sintered at lower temperature compared to bulk silver, applications of nanosilver pastes are limited by long-term sintering time (20–30 min), relative high sintering temperature (>250 °C), and applied external pressure, which may damage chips and electronic components. Therefore, low temperature rapid sintering processes that can obtain excellent nanosilver joints are anticipated. In this regard, we present a review of recent progress in the rapid sintering of nanosilver pastes. Preparation of nanosilver particles and pastes, mechanisms of nanopastes sintering, and different rapid sintering processes are discussed. Emphasis is placed on the properties of sintered joints obtained by different sintering processes such as electric current assisted sintering, spark plasma sintering, and laser sintering, etc. Although the research on rapid sintering processes for nanosilver pastes has made a great breakthrough over the past few decades, investigations on mechanisms of rapid sintering, and the performance of joints fabricated by pastes with different compositions and morphologies are still far from enough.
Highlights
Die-attach materials play a key role in ensuring the performance and reliability of electronic devices [1,2,3,4], such as in thermal [5,6,7,8] and electrical management [9,10] for high power devices
Die-attach materials are generally classified as conductive adhesives, solder alloys, glasses, metal films, and metal pastes [5]
These materials are only suitable for low-temperature range applications due to a low value of performance index, M (0.1–1.8 × 106 W/m, M = K/α, where K is the thermal conductivity, and α is the coefficient of thermal expansion) [5], and low melting points (
Summary
Die-attach materials play a key role in ensuring the performance and reliability of electronic devices [1,2,3,4], such as in thermal [5,6,7,8] and electrical management [9,10] for high power devices. Traditional hot-pressing sintering processes for nanosilver pastes needs to apply external pressure and complicated temperature profiles, and the processes are usually time-consuming and sometimes require an inert gas atmosphere [33], which severely limit the applications of nanosilver pastes [34] In this regard, many rapid sintering processes have been proposed to overcome the drawbacks of the hot-pressing sintering processes, such as in-situ formation of nanoparticles and joints, spark plasma sintering (SPS), laser sintering, and current assisted sintering process. Through a SPS process, joints with shear strength of 50 MPa can be obtained when the sintering temperature is 200 ◦C and the sintering time is as short as 1 min [36]. Emphasis was placed on the properties of sintered joints obtained by different sintering processes
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