Reconstruction and evaluation of the air permeability of a cement paste specimen with a void distribution gradient using CT images and numerical methods

Chung, Sang-Yeop; Han, Tong Seok; Kim, Se Yun

doi:10.1016/j.conbuildmat.2015.03.103

Cited by 39 publications

(9 citation statements)

References 29 publications

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“…Void ratio is also a critical factor that affects die-shear strength and thermal properties of the joints [ 32 ]. X-ray micro-tomography (μ-CT), which could identify the void distribution nondestructively based on the criterion of contrast gradient [ 39 ], was used to explore the voids in the sintered nanosilver joints of the IGBT assemblies with different sintering current.…”

Section: Discussionmentioning

confidence: 99%

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Characterizations of Rapid Sintered Nanosilver Joint for Attaching Power Chips

et al. 2016

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Sintering of nanosilver paste has been extensively studied as a lead-free die-attach solution for bonding semiconductor power chips, such as the power insulated gated bipolar transistor (IGBT). However, for the traditional method of bonding IGBT chips, an external pressure of a few MPa is reported necessary for the sintering time of ~1 h. In order to shorten the processing duration time, we developed a rapid way to sinter nanosilver paste for bonding IGBT chips in less than 5 min using pulsed current. In this way, we firstly dried as-printed paste at about 100 °C to get rid of many volatile solvents because they may result in defects or voids during the out-gassing from the paste. Then, the pre-dried paste was further heated by pulse current ranging from 1.2 kA to 2.4 kA for several seconds. The whole procedure was less than 3 min and did not require any gas protection. We could obtain robust sintered joint with shear strength of 30–35 MPa for bonding 1200-V, 25-A IGBT and superior thermal properties. Static and dynamic electrical performance of the as-bonded IGBT assemblies was also characterized to verify the feasibility of this rapid sintering method. The results indicate that the electrical performance is comparable or even partially better than that of commercial IGBT modules. The microstructure evolution of the rapid sintered joints was also studied by scanning electron microscopy (SEM). This work may benefit the wide usage of nanosilver paste for rapid bonding IGBT chips in the future.

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Section: Discussionmentioning

confidence: 99%

“…Regions with pixels below this threshold are treated as voids. The details of the methods can be found in the references [32,33,34]. Since the minimum void size that can be detected by the X-ray tomography is 10 μm, we defined a void in this work as defects that are larger than 10 μm.…”

Section: Methodsmentioning

confidence: 99%

Characterizations of Rapid Sintered Nanosilver Joint for Attaching Power Chips

et al. 2016

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“…Tortuosity used to measure the curvature of a path can also be utilized to examine the pore networks of a target sample. Furthermore, tortuosity allows for the calculation of the relative deviation from the linearity of networked void paths [55,62].…”

Section: Evaluation Of Permeability Propertiesmentioning

confidence: 99%

Effect of different expanded aggregates on durability-related characteristics of lightweight aggregate concrete

Chung

Sikora

Kim

et al. 2021

Materials Characterization

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“…For this purpose, tortuosity, an index that describes the curvature of a pore path, was adopted in this study. Tortuosity has been widely used to characterize the percolation characteristics of cement-based materials [ 30 , 31 , 32 , 33 ]. With the tortuosity investigation, the heterogeneity and connectivity of the pores within the porous specimens could be effectively described [ 34 ].…”

Section: Methodsmentioning

confidence: 99%

Mechanical and Microscopic Characteristics of Polyurethane-Based Pervious Pavement Composites

et al. 2021

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Conventional pervious pavement materials (PPM) that consist of cement and aggregate materials are known for poor durability due to their brittle behavior. Thus, to enhance the durability, we fabricated polymeric PPMs from durable and abundant polyurethane (PU) and undertook mechanical and microscopic characterizations. PU-based PPM samples with varying aggregate sizes were produced and examined to test their compressive strength and water permeability. Furthermore, X-ray micro-computed tomography (micro-CT) was implemented to analyze the samples’ pore and tortuosity characteristics. Through the micro-CT analysis, the morphological characteristics of PPM’s internal structures were identified and quantitively analyzed the correlations between the pore size distribution, connectivity, and tortuosity within the samples. Finally, the microstructures derived from micro-CT were generated as a finite element model and also numerically determined the stress distribution generated inside.

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Reconstruction and evaluation of the air permeability of a cement paste specimen with a void distribution gradient using CT images and numerical methods

Cited by 39 publications

References 29 publications

Characterizations of Rapid Sintered Nanosilver Joint for Attaching Power Chips

Characterizations of Rapid Sintered Nanosilver Joint for Attaching Power Chips

Effect of different expanded aggregates on durability-related characteristics of lightweight aggregate concrete

Mechanical and Microscopic Characteristics of Polyurethane-Based Pervious Pavement Composites

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