Study on high temperature bonding reliability of sintered nano-silver joint on bare copper plate

Zhao, Su-Yan; Li, Xin; Mei, Yunhui; Lü, Gongxuan

doi:10.1016/j.microrel.2015.10.017

Cited by 56 publications

(13 citation statements)

References 18 publications

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“…Figure 14 shows the comparison of our data and HTS results available in the literature so far [16,17]. It can be seen that the sintered silver can produce strong joints at the initial state.…”

Section: Shear Test Results Fractography and Discussionmentioning

confidence: 78%

“…Despite large CTE mismatch between Si and Cu, the Si/Ag/Cu structures did not break after cooling down to room temperature, indicating that the ductile Ag joint could manage the induced shear strains. conducted the aging at 250°C) [16,17].…”

Section: Resultsmentioning

confidence: 99%

“…A fundamental challenge of sintered Ag process is the pores that cannot be eliminated. In high-temperature reliability tests, many research groups had reported the penetration of oxygen through the pores within the Ag to reach Cu substrates, producing an oxide layer which becomes the weak region [16,17]. A few groups have developed coating methods on the substrates to reduce oxidation.…”

Section: Introductionmentioning

confidence: 99%

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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: 78%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…Extensive research in the area of developing high temperature Pb free solder is in progress, there is still no solder alloy which can completely replace Pb based high temperature solders [4]. Several prospective candidates, such as Au based alloys, Bi based alloys and Ag based alloys have been reported [5][6][7][8][9][10][11][12][13][14]. Currently, Zn based alloys have been emerged as potential candidate in substituting health hazardous Pb containing solders.…”

Section: Introductionmentioning

confidence: 99%

Study of off-eutectic Zn–xMg high temperature solder alloys

Galib

Hasan

Sharif

2016

J Mater Sci: Mater Electron

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Researchers have been working for some times to develop a Pb-free substitute for high-Pb containing solders in electronics. In this study the effect of Mg content on microstructure, melting behavior, thermal, electrical and mechanical properties of a new high-temperature Pb-free solder based on binary Zn-Mg alloy were investigated. The nominal compositions of Zn-xMg (x = 0.5-6.0) alloys were synthesized by conventional melting and casting route. The microstructures of the solders changed significantly on adding Mg content. Higher Mg containing alloys were found rich in intermetallic phases. The formation of the Mg 2 Zn 11 and metastable MgZn 2 intermetallic phases were identified and were also quantified by X-ray diffraction analysis. The presence of higher amount of intermetallic compounds in hypereutectic Zn-Mg systems deteriorated the tensile properties of the binary alloy. The results of electrical resistivity test indicated that the Mg could elevate the resistivity of newly developed Zn-Mg alloys. The melting behavior of the solder alloys studied by differential thermal analysis (DTA) analysis revealed that the melting temperature range of the solder alloys narrowed with Mg addition. Thermal mechanical analysis (TMA) analysis revealed that the co-efficient of thermal expansion (CTE) decreased on increasing Mg content.

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“…Most of these pores are connected. Oxygen can easily penetrate through these pores to reach the substrate surface such as Cu and oxidize it at elevated temperature, thus largely weakening the joint strength [8,9]. …”

Section: Introductionmentioning

confidence: 99%

Solid-state bonding of silicon chips to copper substrates with graded circular micro-trenches

Lee

2018

J Mater Sci: Mater Electron

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Silicon (Si) chips of 5 mm × 5 mm were bonded directly to copper (Cu) substrates using solid-state process at 300 °C without using any die-attach materials. A static pressure of 6.9 MPa was applied. To deal with the large mismatch in coefficient of thermal expansion (CTE) between Si and Cu, graded circular micro-trenches were fabricated on the Cu substrates. The micro-trenches provide space for Cu material to move into during the bonding process where the Cu surface incurs plastic deformation to conform to Si bottom surface for intimate contact. The micro-trenches also help relax stresses on the bonding interface caused by the fact that Cu contracts significantly more than Si during cooling down. The results obtained are encouraging, implying that the concept of using micro-trenches work. Scanning electron microscopy (SEM) images on cross sections of bonded structures show that Si chips were well bonded to Cu substrates without voids or defects on the interface and without any cracks on Si chip. Shear test were performed on six samples. It turned out that, of all six samples, the Si chip fractured first and the entire Si bottom surface was stilled well bonded to the Cu substrate. The average breakage force of Si chips on six samples is 13.5 Kgf. The breakage force of the joint cannot be determined but is certainly higher than 13.5 Kgf, which is more than twice of the specification American Military Standard. The new chip bonding structure with solid-state process reported in this paper eliminates the use of die-attach materials and the thermal resistance associated with the dieattach. It also removes the operating temperature limit constrained by the melting temperature of die-attach materials. We except this new bonding structure design to be a valuable alternative to high power and high temperature devices.

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Study on high temperature bonding reliability of sintered nano-silver joint on bare copper plate

Cited by 56 publications

References 18 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

Study of off-eutectic Zn–xMg high temperature solder alloys

Solid-state bonding of silicon chips to copper substrates with graded circular micro-trenches

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