Microstructure evolution during 300 °C storage of sintered Ag nanoparticles on Ag and Au substrates

Paknejad, Seyed Amir; Dumas, Guy; West, Geoff; Lewis, Gene; Mannan, Samjid H.

doi:10.1016/j.jallcom.2014.08.062

Cited by 111 publications

(29 citation statements)

References 28 publications

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“…Although the oxidation issue might be mitigated by Au or ENIG coatings on the Cu substrates, the additional processes would increase the production cost. Also, the interdiffusion between Au and porous Ag may decrease the strength [15,18]. In contrast, our Ag joints are porefree.…”

Section: Shear Test Results Fractography and Discussionmentioning

confidence: 83%

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Low-pressure solid-state bonding technology using fine-grained silver foils for high-temperature electronics

Lee

2017

J Mater Sci

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A solid-state bonding technique using fine-grained silver (Ag) foils is presented. The Ag foils are manufactured using many runs of cold rolling and subsequent annealing processes to achieve the favorable microstructure. X-ray diffraction and pole figure measurement are performed to examine the crystal structure and grain orientations. Si chips are bonded to bare Cu substrates using the Ag foil as the bonding medium at 300°C in 0.1 torr vacuum assisted by 6.9 MPa static pressure, which is much lower than that used in conventional thermal compression bonding. Cross sections prepared by focus ion beam show clear bonding interfaces with only a few voids smaller than 100 nm. The bonded structures do not crack after cooling down to room temperature, indicating that the ductile Ag layer is able to manage the strain induced by the large coefficient of thermal expansion mismatch between Si and Cu. The average shear strength of as-bonded samples is 29 MPa. High-temperature storage tests are conducted, and slight increase in strength can be observed after 300°C aging. Fracture analyses show that the breakage occurs within the Ag foil rather than on the bonding interface. Transmission electron microscopy and energydispersive spectroscopy (TEM/EDX) are conducted for Ag/Cu interface after 200-h aging, and the result shows that slight diffusion proceeds during the aging. Since Ag has the highest electrical and thermal conductivities among metals, therefore the bonded structures reported in this paper probably represent the best possible design for high-temperature and high-power electronic packaging applications.

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Section: Shear Test Results Fractography and Discussionmentioning

confidence: 83%

“…A few groups have developed coating methods on the substrates to reduce oxidation. However, the interdiffusion between metallized layers and porous silver can enlarge the pore size near the interfacial region, resulting in bonding strength degradation [15,18].…”

Section: Introductionmentioning

confidence: 99%

Low-pressure solid-state bonding technology using fine-grained silver foils for high-temperature electronics

Lee

2017

J Mater Sci

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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%

“…Therefore, we have utilized optical microscopy and a glass substrate to prevent the internal pore surfaces from oxidizing while enabling in-situ observations to take place. These microstructural changes would in most cases lead to unreliability and weakening strength [9,[17][18][19] so that these studies are an innovative technique for understanding long term mechanical reliability and strength preservation of sintered silver for applications in the range 200-400 °C.…”

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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“…Consequently, multiple percolation paths continuously emerged in the ink-jet printed electrocircuits, which was fairly pivotal to the electron transmission among AgNPs aggregate [54][55][56]. These AFM results further proved that our strategy could be explored to enable AgNPs sintered at room temperature and construct conductive AgNPs patterns directly on flexible substrates.…”

Section: A N U S C R I P Tmentioning

confidence: 60%

Controllable synthesis and sintering of silver nanoparticles for inkjet-printed flexible electronics

Zhang

Zhu

2015

Journal of Alloys and Compounds

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Microstructure evolution during 300 °C storage of sintered Ag nanoparticles on Ag and Au substrates

Cited by 111 publications

References 28 publications

Low-pressure solid-state bonding technology using fine-grained silver foils for high-temperature electronics

Low-pressure solid-state bonding technology using fine-grained silver foils for high-temperature electronics

Microstructural evolution of sintered silver at elevated temperatures

Controllable synthesis and sintering of silver nanoparticles for inkjet-printed flexible electronics

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