Characterization of Multifunctional Nanomaterials for Electronics Thermal Management and Sintering Applications
Doktorsavhandling, 2021

The science of manipulating materials at their nanoscale level is nowadays allowing endless possibilities to disrupt the current limitations on the conventional production processes and products. In electronics, the need for more capable thermal management strategies led to the exploration of advanced approaches and focus on new materials and allowed to push further the thermal dissipation capabilities of each generation of products. In this thesis, we investigate different thermal management concepts and propose new solutions based on carbon and metallic nanomaterials, while we explore the possibility to combine the size effect with the composition effect of the nanoscale materials.

Due to their high surface to volume ratio, nanoscale particles show different thermodynamics properties that led to their potential implementation in electronics fabrication processes. More specifically, silver nanoparticles (Ag NPs) have been under focus in recent years for applications to replace lead-free solder and contribute to energy saving. Due to a poor trade-off between the process parameters, the production costs, and the reliability of the silver related application, different strategies are being suggested to optimize its applications. In this present study, we investigate multiple sintering parameters of Ag NPs and use the nanoscale effect in a hybrid approach for the sintering of microscopic powder. The results of the sintering parameters are correlated to the density of the samples and their properties in terms of thermal and electrical conductivity. While the sintering of Ag NPs occurs at low temperatures and allows to obtain relatively high densities, the thermal and electrical properties are still limited and the increase in the temperature and fraction of the NPs higher than 400 degrees and 2wt.% has a much- pronounced effect to improve the physical properties of the samples.

The sintering of Ag NPs was also explored in this thesis to propose a novel approach to use graphene foam as a heat sink. While graphene is known for its outstanding physical, chemical, and mechanical properties, its integration as a practical solution in electronics is still missing. The use of Ag NPs in this work allowed to successfully attach the 3D graphene foam on its substrate and further improve both its mechanical and thermal properties by coating the graphene with Ag NPs. Also, the integration of Ag NPs as a die-attach for the 3D porous structure allowed its further use as a container for Phase Change Materials (PCM). Different amounts of PCM were introduced in the lightweight foam and the junction temperature of the hot spot was correlated to the power and the presence of the PCM. We found that graphene foam presents a real advantage for its use in thermal dissipation strategies.

2D graphene material is developed herein as a coating for micro-and nanoscale particles. Using Chemical Vapor Deposition (CVD) and Arc Discharge (AD) methods, we introduce the possibility to produce graphene coating on copper particles for application in thermal management. In addition, we explore the possibility to introduce a doping effect on the coated NPs to further study its effect on the thermal performances of NPs. The morphology and the composition of the coating were investigated and correlated with the bottom-up production process of CVD and AD. The thermal conductivity and chemical stability of the produced particles were studied for their use as fillers in thermally conductive pastes and additives water-based nanofluids. The thermal properties of the different systems were linked to the fraction of the additives and nanofillers. The graphene-coated particles were found to have a multifunctional effect. In both micro-and nanoscale particles, the graphene coating was found to act as a corrosion resistance that stabilizes the metallic core of the particles. The graphene coating also was found to act as a carbon source to reduce the microparticles in a bimodal powder at high temperatures. Finally, the encapsulation of the nanoscale powder allowed to observe a melting point depression related to the composition of the core of the nanoparticles and their nanoscale size.

In an effort to combine the size effect of the nanoparticles and their compositions, different alloyed nanoparticles were produced using AC. The morphology, the composition, and their sintering properties were compared to highlight their composition effect. The produced nanopowders were also used as a sintering aid in the spark plasma sintering approach (SPS) and the results show a positive contribution of the nanopowders in the reduction of the sintering temperature and the densification of the samples. An additional effect is also reported and arises from the possibility to use those particles to fine-tune the chemical composition of the bimodal particles.

Kollektorn, MC2 building
Opponent: Changqing Liu, Loughborough University, United Kingdom


Abdelhafid Zehri

Chalmers, Mikroteknologi och nanovetenskap (MC2), Elektronikmaterial och system

Low-Temperature Sintering Bimodal Micro Copper-Nano Silver for Electrical Power Devices

2018 7th Electronic System-Integration Technology Conference (ESTC),; (2018)

Paper i proceeding

Manufacturing Graphene-Encapsulated Copper Particles by Chemical Vapor Deposition in a Cold Wall Reactor

ChemistryOpen,; Vol. 8(2019)p. 58-63

Artikel i vetenskaplig tidskrift

Exploring Graphene Coated Copper Nanoparticles as a Multifunctional Nanofiller for Micro-Scaled Copper Paste, Zehri, A., Nilsson, T., Fu, Y., Liu, J.

Graphene-coated copper nanoparticles for thermal conductivity enhancement in water-based nanofluid

2019 22nd European Microelectronics and Packaging Conference and Exhibition, EMPC 2019,; (2019)

Paper i proceeding

Graphene Oxide and Nitrogen-Doped Graphene Coated Copper Nanoparticles in Water-Based Nanofluids for Thermal Management in Electronics, Zehri A., Nylander, A., Nilsson, T., Ye, L., Fu, Y., Liu, J.

Characterisation of Nanosized Low Carbon Steel Alloy Based Nanopowder As a Sintering Aid For Spark Plasma Sintering process, Zehri A., Zhang Y., Aboulfadl H., Cao Y., Sögaard C., Ye L., Palmqvist A., A., Nyborg L., Nilsson T.M.J., Fu F., Liu J.

It is common in many studies that treat the field of nanoscale materials and technologies to introduce nanomaterials with the example of the division of the bulk gold. A large gold piece is periodically cut into smaller parts and each division is said to occur without changing its core value until it reaches a point where the small pieces start behaving in a way that differs from the initial bulk material. These new extremely tiny pieces have a completely different set of properties where materials have an extraordinary set of physical, chemical and mechanical properties, but also melt and can be processed at much lower temperatures.
In this work, we bridge the nanoscale world with the reality of the modern processing and manufacturing context where sustainability is at its core. The concept of equality moved from an intra-generational issue to an inter-generational ethical topic, where finite resources should be exploited wisely. In such a context, the combination of the size of the nanoparticles and their compositions can become a game-changer. Throughout this work, we exploit the low processing temperatures of nanoparticles to propose new methods to produce multifunctional materials used in heat dissipation strategies in
electronic and low-temperature manufacturing. We put an effort to connect the top-down method to the bottom-up energy- and materials-efficient production strategy, where we explore the arc discharge process to produce new alloy-based nanoparticles that are used as a sintering aid for
spark plasma sintering. Using the same production route, we also report on new types of materials that have the potential to be integrated into advanced thermal management solutions.

At the beginning of this thesis, we asked three fundamental questions that are related to the integration of nanomaterials in heat management in electronics and low-temperature sintering:

- Can nanoscale materials be integrated further into the heat dissipation of modern electronics?
- How can graphene-based materials benefit from new structures of fillers and is it possible to use
modern production solutions to manufacture even more advanced graphene fillers?
- How can non-conventional manufacturing processes benefit from the use of nanoscale materials
and their?

To answer these questions, we conducted a set of experiments and explored new approaches where we show the potential of using nanomaterials in modern processing and manufacturing. To the question on whether the nanoscale can be further implemented in the heat dissipation strategies,
we answer yes, and in many ways! The nanoscale effect that originates from the high surface energy of the particles can be used in modern electronics in the fabrication of components and interconnections but also to integrate other heat transfer solutions that bring further enhancement
into the thermal capability of the electronic package. To the question on how new structured graphene-based powders can further be used in the service of advanced heat dissipation solutions, we answer that the supported graphene on the spherical substrate allows an optimal orientation to the heat transfer and might result in a continuous increase in the thermal conductivity of thermally conductive adhesive and waterbased nanofluids, but that will depend largely on the right condition on the structure and stability of the core/shell spherical particles. To the question of how modern sintering technics can exploit the nanoscale materials, we answer that the key is to dare to explore the variation of the chemical composition of the nanoparticles to take
full control of the potential of the nanoscale material in the future of electronics and beyond.

Nanoteknikstödd tillverkning av högpresterande sinterstål

Stiftelsen för Strategisk forskning (SSF) (GMT14-0045), 2016-01-01 -- 2020-12-31.

Förbättrade cementbaserad ytskydd/reparation materialer med utnyttjande av två-dimensionella material

Formas (FR-2017/0009), 2018-01-01 -- 2020-12-31.


Hållbar utveckling


Nanovetenskap och nanoteknik (SO 2010-2017, EI 2018-)







Chalmers materialanalyslaboratorium




Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5057


Chalmers tekniska högskola

Kollektorn, MC2 building

Opponent: Changqing Liu, Loughborough University, United Kingdom

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