The shear strength of nano-Ag sintered joints and the use of Ag interconnects in the design and manufacture of SiGe-based thermo-electric modules

Edwards, M. J.; Brinkfeldt, K.; Rusche, Ulrich; Bukes, Tobias; Gaiser, Gerd; Silva, Manoel Ribeiro da; Andersson, Dag

doi:10.1016/j.microrel.2015.02.004

Cited by 10 publications

(1 citation statement)

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“…The high surface energy available and noble metal surface of silver also allows sintering to take place without 3 pressure being placed on the die; an added benefit for manufacturers, but one which leads to the final sintered structure containing 20-30% of pores. Although many studies have been performed on the sintering behaviour of nanoparticles [10,11], and also the mechanical properties of their sintered structures [8,9,12,13], there exists few detailed studies on the high temperature behaviour and stability of sintered silver at temperatures above 300 °C as a high temperature die attach (excepting [14][15]), while previous studies below 300 °C concentrate on bulk mechanical properties and statistical averages of microstructural properties [8,9,[16][17][18][19][20]. In the present work, we determine the nature and speed of microstructural changes in sintered silver throughout the 200-400 °C temperature range and investigate the atomic migration mechanisms that lead to these changes.…”

Section: Introductionmentioning

confidence: 99%

Microstructural evolution of sintered silver at elevated temperatures

Paknejad

Mansourian

Greenberg

et al. 2016

Microelectronics Reliability

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Reduction in the sintering temperature of metal powders by lowering particle size into the nanoparticle range has resulted in a new class of porous sintered joining materials.Especially promising are sintered silver based materials which can be used to form bonds between wide-bandgap semiconductor die and circuit boards for use in high temperature applications. This work shows that for these materials the exterior sintered silver surface oxidizes preventing surface morphology changes, while the interior pore surfaces of the porous silver remain largely oxide-free. These pore surfaces facilitate fast atomic movement resulting in grain growth and changes in the internal microstructure.Morphology changes in the temperature range 200-400 °C are presented both as statistical averages of grain size and, uniquely in this type of study, by tracking individual pores and grains. It is shown that the internal structure will undergo changes during high temperature storage in contrast to the stable outer surface. A new technique, utilizing the electromigration effect to check the relative surface mobility of atoms in the interior pores and exterior surfaces was used to support the conclusions deduced from thermal ageing 2 experiments. Finally, we speculate that the stability of the exterior surface could be reproduced in the interior if the chemistry of the paste was altered to allow formation of a passivating layer on the interior pores during the final stages of the sintering process, resulting in formation of a stable die attach material for applications of up to 400 °C, for which there is an urgent need.

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