| 1. |
- Hansson, Josef, 1991, et al.
(författare)
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A review of recent progress of thermal interface materials: from research to industrial applications
- 2016
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Ingår i: IMAPS Nordic Annual Conference 2016 Proceedings; Tonsberg; Norway; 5 - 7 June 2016. - 9781510827226
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Konferensbidrag (refereegranskat)abstract
- The increasing trend of further scaling down electronic components put an increasing demand for more efficient cooling. A significant part of the thermal resistance from source to ambient occurs at the interface between materials, and thermal interface materials are crucial for efficient heat transfer. Recent years have seen a significant amount of progress various types of thermal interface materials. In this review, the field of thermal interface materials (TIMs) development is summarized and analyzed, focusing on three topics which have received attention at a research level, and their road towards market applicability. The first topic is development in particle laden polymers, which uses thermally conductive filler particles in a polymer matrix. New development is focused on novel fillers such as h-BN or carbon based fillers, and hybrid filler combinations. The next topic is continuous metal phase TIMs, which includes solder and liquid metal TIMs. The thermal performance is already very good, and development is largely focused on improving the mechanical properties. Finally, the last topic is carbon nanotube array TIMs, which used chemical vapor deposition-grown carbon nanotube arrays as bridging material. The concept has promise for great performance in both handling, mechanical stability and thermal performance, but is still at a research stage. In addition to these topics, a quantitative study on the progress of thermal interface materials development is made, both in terms of research papers published and in terms of patents filed. The study shows a stable trend of continuous development on all levels and concludes that significant improvements can be expected to continue in the future.
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| 2. |
- Hansson, Josef, 1991, et al.
(författare)
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Effect of Fiber Concentration on Mechanical and Thermal Properties of a Solder Matrix Fiber Composite Thermal Interface Material
- 2019
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Ingår i: IEEE Transactions on Components, Packaging and Manufacturing Technology. - 2156-3985 .- 2156-3950. ; 9:6, s. 1045-1053
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Tidskriftsartikel (refereegranskat)abstract
- Increased demand on the mechanical and thermal properties on the thermal interface and die attach material creates a demand for materials with tailored material properties. Solder matrix fiber composites (SMFCs) have been shown to address these challenges, but have, so far, required complicated procedures and components. In this paper, we present the fabrication of a new type of SMFC based on commercially available fiber networks infiltrated with Sn-Ag-Cu alloy (SAC305) or indium using equipment for large-volume production. The composite material exhibits similar thermal properties compared to pure solder, and mechanical properties that can be tailored toward specific applications. We also show that the handling properties of the SMFC allows it to be used in process flows where multiple reflow cycles are required and can achieve a well-defined bond line thickness (BLT) and good bonding using fluxless reflow under pressure.
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| 3. |
- Hansson, Josef, 1991, et al.
(författare)
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Fabrication and characterization of a carbon fiber solder composite thermal interface material
- 2017
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Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging (NordPac). - 9781538630556 ; , s. 97-100
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Konferensbidrag (refereegranskat)abstract
- One of the significant bottlenecks in thermal management is to develop thermal interface materials (TIMs) with lower thermal interface resistance while retaining good reliability, mechanical properties and handling capabilities. Recently, the combination of electrospun polymer fibers and solder matrix has gathered interest, combining the excellent thermal properties of metal with the mechanical properties of polymers. Carbon fibers are increasingly common as reinforcement in composites, owing to their high strength and thermal conductivity. Utilizing carbon fibers in a similar composite could allow for the fabrication of TIMs with so far unexplored properties such as increased thermal conductivity, strength and tunable CTE. In this work, we have fabricated and characterized a TIM based on a carbon fiber network infiltrated by an alloy of Sn-Ag-Cu, (CF-TIM). Commercially available carbon fibers are coated with a thin layer of Ag and infiltrated by molten alloy under high pressure. The result is a preform TIM, easy to handle and compatible with standard SMT assembly. A thermal interface resistance lower than 2 Kmm2/W between two ENIG coated Cu substrates was measured with laser flash. Comparing total thermal interface resistance to bond line thickness indicates a very low contact resistance consistent with good metallurgical bonding and a bulk thermal conductivity of 24 W/mK for the TIM. X-ray inspection and SEM of cross section of the assembled structure indicates good adhesion between fiber and matrix, and a very low degree of voiding. To demonstrate the handling capabilities of CF-TIM, a variety of reflow conditions were investigated. A consistent bond line thickness (BLT) of 45±5μm was achieved independent on applied pressure during reflow, and decreased less than 20% after 10 additional reflow cycles, without additional material leakage. This demonstrates the possibility of CF-TIM use in assembly line processes requiring additional reflow steps. Solder preforms are common in industry, and due to similar handling characteristics of the CF-TIM, it should be easily integrated into existing electronics assembly lines. The usage of commercial fibers not reliant on slow and expensive processes such as electrospinning further opens up the potential for mass production.
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| 4. |
- Hansson, Josef, 1991, et al.
(författare)
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Novel nanostructured thermal interface materials: a review
- 2018
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Ingår i: International Materials Reviews. - : Informa UK Limited. - 0950-6608 .- 1743-2804. ; 63:1, s. 22-45
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Forskningsöversikt (refereegranskat)abstract
- The trend of continuing miniaturisation of microelectronics leads to new thermal management challenges. A key point in the heat removal process development is to improve the heat conduction across interfaces through improved thermal interface materials (TIMs). We identify the key areas for state-of-the art TIM research and investigate the current state of the field together with possible future advances.
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| 5. |
- Hansson, Josef, 1991, et al.
(författare)
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Review of Current Progress of Thermal Interface Materials for Electronics Thermal Management Applications
- 2016
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Ingår i: 2016 Ieee 16th International Conference on Nanotechnology (Ieee-Nano). - 9781509014934 ; , s. 371-374
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Konferensbidrag (refereegranskat)abstract
- Increasing power densities within microelectronic systems place an ever increasing demand on the thermal management. Thermal interface materials (TIMs) are used to fill air gaps at the interface between two materials, greatly increasing the thermal conductance when solid surface are attached together. The last decade has provided significant development on high-performing TIMs, and this paper makes a summarized review on recent progress on the topic. Current state of the art commercial TIM types are presented, and discussed in regards to their advantages and disadvantages. Two main categories of TIMs with high interest are then reviewed: continuous metal phase TIMs and carbon nanotube array TIMs.
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| 6. |
- Hansson, Josef, 1991, et al.
(författare)
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Synthesis of a Graphene Carbon Nanotube Hybrid Film by Joule Self-heating CVD for Thermal Applications
- 2018
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Ingår i: Proceedings - Electronic Components and Technology Conference. - 0569-5503. ; 2018-May
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Konferensbidrag (refereegranskat)abstract
- Hybrid films based on vertically aligned carbon nanotubes (CNTs) on graphene or graphite sheets have been proposed for application as thermal interface materials and micro heat sinks. However, the fabrication of these materials are limited to small scale, expensive and complicated chemical vapor deposition (CVD) for CNT synthesis. We present a new method for direct growth of CNTs on one or both sides of a thin graphene film (GF) using joule self-heating of the graphene film to provide the necessary heat for the thermal breakdown of carbon feedstock in a CVD process. The resulting CNT forests show good density and alignment consistent with regular CVD synthesis processes on silicon surfaces. The resulting double sided GF/CNT hybrid film is directly applicable as a thermal pad. The CNT forest has a thermal conductivity of 30 W/mK, measured by pulsed photothermal reflectance, and the total thermal interface resistance between aluminum blocks was measured to be 60 Kmm 2 /W using an ASTM D5470 compliant 1-D measurement setup. This method of directly synthesizing CNTs on graphene films is more energy efficient and capable of larger volume production compared to traditional CVD methods. It is also compatible with scaling up towards continuous roll-to-roll production for large scale commercial production, one of the major limitations preventing CVD-grown CNTs from commercial applications
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| 7. |
- Mu, Wei, 1985, et al.
(författare)
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Double-Densified VerticallyAligned Carbon Nanotube Bundles for Application in 3D Integration High Aspect Ratio TSV Interconnects
- 2016
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Ingår i: Proceedings - Electronic Components and Technology Conference. - 0569-5503. - 9781509012046 ; 2016-August, s. 211-216
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Konferensbidrag (refereegranskat)abstract
- The treatment of densification by vapor on pristineMWCNT bundles are necessary to improve the effective area of the CNT TSV. However, the CNT bundles might tilt partly because of the non-uniform densification at root of the bundle, especially when it comes to the high aspect ratio CNT bundles. In order to solve these problems, a double densification process has been proposed and developed here. First of all, the shape of partial densified CNT bundles were optimized as a function of time. After several steps such as transferring of partial densified CNT bundles into the via, second densification, epoxy filling and chemical mechanical polishing, the CNT filled TSV with aspect ratio of 10 was achieved. The current voltage response of the CNT TSV interconnection indicated good electrical connection was formed. The resistivity of CNT bundles in via was calculated to be around 2-3 milli-ohmcm.
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| 8. |
- Nylander, Andreas, 1988, et al.
(författare)
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Reliability investigation of a carbon nanotube array thermal interface material
- 2019
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Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 12:11
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Tidskriftsartikel (refereegranskat)abstract
- As feature density increases within microelectronics, so does the dissipated power density, which puts an increased demand on thermal management. Thermal interface materials (TIMs) are used at the interface between contacting surfaces to reduce the thermal resistance, and is a critical component within many electronics systems. Arrays of carbon nanotubes (CNTs) have gained significant interest for application as TIMs, due to the high thermal conductivity, no internal thermal contact resistances and an excellent conformability. While studies show excellent thermal performance, there has to date been no investigation into the reliability of CNT array TIMs. In this study, CNT array TIMs bonded with polymer to close a Si-Cu interface were subjected to thermal cycling. Thermal interface resistance measurements showed a large degradation of the thermal performance of the interface within the first 100 cycles. More detailed thermal investigation of the interface components showed that the connection between CNTs and catalyst substrate degrades during thermal cycling even in the absence of thermal expansion mismatch, and the nature of this degradation was further analyzed using X-ray photoelectron spectroscopy. This study indicates that the reliability will be an important consideration for further development and commercialization of CNT array TIMs.
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| 9. |
- Nylander, Andreas, 1988, et al.
(författare)
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RF properties of carbon nanotube / Copper composite through silicon via based CPW structure for 3D integrated circuits
- 2019
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Ingår i: 2019 IEEE 14th Nanotechnology Materials and Devices Conference, NMDC 2019.
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Konferensbidrag (refereegranskat)abstract
- The development of integrated circuits (ICs) has seen exponential growth in performance over the last couple of decades and has pushed the boundaries for how we use our electronics in our daily lives. The scaling of ICs, and therefore also the performance development, is now starting to slow down when the physical designs are reaching critical dimensions where quantum effects starts to become noticeable. One proposed route to circumvent these issues for a continued scaling is based on the implementation of 3D integration by chip stacking for an increased miniaturization potential. Miniaturisation will soon also result in interconnect dimensions that surpass the mean free path (MFP) in Cu, the commonly used material for interconnects today, with a sharp increase in resistivity as a result. By changing the through silicon via (TSV) interconnect material from Cu to a carbon nanotube (CNT)/Cu composite, continued scaling can be ensured both in terms of electrical conductivity, ampacity and signal delays. Furthermore, a reduced skin effect can be achieved ensuring lower signal losses at higher RF frequencies making the CNT/Cu composite an ideal candidate to replace tranditional Cu interconnects. In this paper, we are demonstrating a coplanar waveguide (CPW) test structure using CNT/Cu filled TSVs connected to Au transmission lines on SiO2-passivated high resistivity Si substrates. The parasitic losses of the CNT/Cu TSV based CPW test structure were measured using a Sparameters test setup. The results showed that the CNT/Cu TSVs with affiliated contacts increased the signal losses up to S21 = -5.5 dB compared to Au reference transmission lines. These results are in line with previous results using CNT based TSVs and will serve as a basis for future improvements of CNT based interconnect technology for 3D integration.
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| 10. |
- Satwara, Maulik, 1990, et al.
(författare)
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Finite element analysis of bond line thickness and fiber distribution in solder based thermal interface materials
- 2017
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Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging, NordPac 2017, Goteborg, Sweden, 18-20 June 2017. - 9781538630556 ; , s. 167-171
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Konferensbidrag (refereegranskat)abstract
- As microelectronic devices continue to decrease in size, failure of these devices is commonly attributed to ineffectual thermal management. Hence, increased thermal failures at elevated temperature has accounted for some of their reliability concerns and expected to be a major bottleneck for future development of microelectronics. For the thermal management, solder based materials give a better performance as thermal interface materials (TIM). However, these materials have a marginal reliability due to their higher Young's modulus. Therefore new type of solder based nano polymer composite (SMNPC) material is introduced. The SMNPC is composed of Sn-Ag-Cu (SAC) infiltrated through a silver coated PA6, 6 polymer fiber mesh to address electrical, thermal and mechanical challenges. In this work, finite element modeling was employed to investigate the thermal and mechanical properties of the composite material by varying polymer distribution, total volume of polymer and bond fine thickness (BLT). The composite is demonstrated to possess high heat transfer capability and lower elastic modulus as shown in Figure 1. All the results demonstrate that the developed SMNPC is proved a good alternative for conventional TIMs to improve thermal and mechanical properties.
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