Stable and Unstable Capillary Flows of Highly-Filled Epoxy/Nickel Suspensions

Zhou, Jianyu; Sancaktar, Erol

doi:10.1163/156856108x305426

Cited by 8 publications

(3 citation statements)

References 36 publications

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“…Zhou and Sancaktar [43] observed resin migration before cure and under static pressure for (Epon 830 and Epon 815C) epoxy-based ECA's filled with 50% wt etched Ni (3 μm Ni 102 flakes, as received from AEE, Micron Metals, Inc., NJ; and etched with 10% HCl). Use of lower viscosity (5 -7 Poise) Epon 815C/Ni (etched) resulted in electrical conductivity gradients and unstable capillary flow during and after injection process.…”

Section: Methods Of Applicationmentioning

confidence: 99%

“…The flow was stabilized at 75 % wt Ni concentration, while it could be stabilized at 62.7% wt when the 170 -225 Poise viscosity Epon 830 resin was used as the binder. Stable capillary flow could also be obtained using 80 nm Ni nanopowders (Inframat Advanced Materials LLC, CT) even though filler agglomerate formation was observed [43].…”

Section: Methods Of Applicationmentioning

confidence: 99%

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Design of Electrically Conductive Adhesives and Adhesive Joints

Sancaktar¹

2023

Preprint

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Electrically conductive adhesives (ECA’s) are used widely to replace or reinforce lead soldering or conductive metal components in electronic packaging applications such as die attachment, solderless interconnections, component repair, display interconnections, and heat dissipation. Their conductive behavior as well as the associated behaviors such as heat conduction and mechanical behavior (strength, rigidity, deformation and viscoelastic behavior, which may be affected by moisture ingression) are affected by adhesive film thickness, volume fraction, size and shape of the conductive filler, as well as uncured base adhesive viscosity, substrate and filler surface treatment and the applied pressure (during bonding and during conduction). The adhesive resistivity decreases precipitously above a characteristic filler volume fraction called the percolation threshold. In general, micron-sized metal fillers mixed in an adhesive (often an epoxy) resulting with different film thicknesses exhibit thickness thresholds for transition from three-dimensional conductivity to two-dimensional conductivity with considerable increases in thickness-direction (z-axis) resistivity when the film thicknesses are smaller than these threshold values. Recently, the use of conductive nanoparticles allowed decreases in percolation threshold levels as well as increases in mechanical strength and durability of ECA’s. Most ECA’s are supplied in liquid or paste form in varying viscosities and therefore, the method of their application also affects their performance. This work intends to provide an understanding of these effects on conduction behavior in (usually high-priced) equipment in which they are used.

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Section: Methods Of Applicationmentioning

confidence: 99%

Section: Methods Of Applicationmentioning

confidence: 99%

Design of Electrically Conductive Adhesives and Adhesive Joints

Sancaktar¹

2023

Preprint

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“…These include thermal stresses caused by the coefficient of thermal expansion mismatch between the substrate and component, and by mismatch between the adhesive and adherend during temperature cycling, oxidation of the bonding surfaces and of the filler, and degradation by UV-light or corrosive gases. A better understanding of the design, reliability, material, and manufacturing characteristics of various conductive adhesive technologies must be achieved before an assessment of their application as component attachment replacement can be made [24][25][26][27][28][29][30][31][32]. In order to understand and analyze these issues, the mechanism of electrical conduction needs to be studied first.…”

Section: Introductionmentioning

confidence: 99%

Electrically Conductive Epoxy Adhesives

Sancaktar

Bai

2011

Polymers

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Abstract:Conductive adhesives are widely used in electronic packaging applications such as die attachment and solderless interconnections, component repair, display interconnections, and heat dissipation. The effects of film thickness as functions of filler volume fraction, conductive filler size, shape, as well as uncured adhesive matrix viscosity on the electrical conduction behavior of epoxy-based adhesives are presented in this work. For this purpose, epoxy-based adhesives were prepared using conductive fillers of different size, shape, and types, including Ni powder, flakes, and filaments, Ag powder, and Cu powder. The filaments were 20 μm in diameter, and 160 or 260 μm in length. HCl and H 3 PO 4 acid solutions were used to etch and remove the surface oxide layers from the fillers. The plane resistance of filled adhesive films was measured using the four-point method. In all cases of conductive filler addition, the planar resistivity levels for the composite adhesive films increased when the film thickness was reduced. The shape of resistivity-thickness curves was negative exponential decaying type and was modeled using a mathematical relation. The relationships between the conductive film resistivities and the filler volume fractions were also derived mathematically based on the experimental data. Thus, the effects of surface treatment of filler particles, the type, size, shape of fillers, and the uncured epoxy viscosity could be included empirically by using these mathematical relations based on the experimental data. By utilizing the relations we proposed to model thickness-dependent and volume fraction-dependent conduction behaviors separately, we were able to describe the combined and coupled volume fraction-film thickness relationship mathematically based on our experimental data.

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