| 1. |
- Chen, Si, 1981, et al.
(författare)
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Sn-3.0Ag-0.5Cu Nanocomposite Solder Reinforced With Bi2Te3 Nanoparticles
- 2015
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Ingår i: IEEE Transactions on Components, Packaging and Manufacturing Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 2156-3985 .- 2156-3950. ; 5:8, s. 1186-1196
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposite solders are regarded as one of the most promising interconnect materials for the high-density electronic packaging due to their high mechanical strength and fine microstructure. However, the developments of nanocomposite solders have been limited by the inadequate compatibility between nanoparticles and solder matrix with respect to density, hardness, coefficient of thermal expansion, and surface activity. The compatibility issue will lead to a huge loss of nanoparticles from the solder matrix after the reflow soldering process. The thermal fatigue resistance of solder joint will also become degraded. Therefore, aiming to solve this problem, a novel nanocomposite solder consisting of Bi2Te3 semiconductor nanoparticles and Sn-3.0Ag-0.5Cu (SAC305) solder is presented. The effect of nanoparticles on the viscosity of solder paste and the void content of solder bump was first studied. Then, a series of analysis on the composition and microstructure of the solder bump were completed using transmission electron microscopy, X-ray diffraction, inductively coupled plasma-mass spectrometry, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The survival rate of nanoparticles in the solder bump after reflow soldering process reaches as high as 80%. The refined microstructure was observed from the cross section of the nanocomposite solders. The shear test showed that the average mechanical strength of SAC305 solder after the addition of Bi2Te3 nanoparticles was higher. Meanwhile, no thermal fatigue resistance degradation was detected in the nanocomposite solder after 1000 thermal cycles in the range of -40 degrees C to 115 degrees C.
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| 2. |
- Liu, Johan, 1960, et al.
(författare)
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A new solder matrix nano polymer composite for thermal management and die attach applications
- 2014
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Ingår i: Composites Science and Technology. - 0266-3538. ; 94, s. 54-61
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Tidskriftsartikel (refereegranskat)abstract
- The increasing integration of microelectronics, raising the need for effective heat dissipation, requires new and improved composite materials technologies. For both thermal interface and die attach materials, a major challenge is to combine low thermal resistance joints with sufficient thermomechanical decoupling and reliability. In this paper, we present the fabrication and characterisation of a new type of solder matrix nano polymer composite (SMNPC) aiming to address these challenges. The SMNPC is fabricated into preforms by liquid-phase infiltration of a Sn–Ag–Cu matrix into a silver nanoparticle coated electrospun polyimide fibre mesh. The composite is demonstrated to possess high heat transfer capability, close to that of a direct soldered interface, lower elastic modulus compared to pure Sn–Ag–Cu alloy, and reliable thermomechanical performance during thermal cycling. Taken together, the results indicate that the developed SMNPC can be a useful composite alternative compared to conventional solders and polymer matrix materials for thermal management applications.
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| 3. |
- Luo, Xin, 1983, et al.
(författare)
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Boron nitride nanofiber and indium composite based thermal interface materials for electronics heat dissipation applications
- 2014
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Ingår i: Journal of Materials Science: Materials in Electronics. - 1573-482X .- 0957-4522. ; 25:5, s. 2333-2338
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Tidskriftsartikel (refereegranskat)abstract
- With increased power density and continued miniaturization, effective thermal dissipation is of significant importance for operational lifetime and reliability of electronic system. Advanced thermal interface materials (TIMs) with excellent thermal performance need to be designed and developed. Here we report novel TIMs consisted of boron nitride (BN) nanofibers and pure indium (In) solder for heat dissipation applications. The BN nanofibers are fabricated by electrospinning process and nitridation treatment. After surface metallization by sputtering, the porous BN film is infiltrated with liquid indium by squeeze casting to form the final solid composites. The new composites show the in-plane and through-plane thermal conductivity respectively of 60 and 20 W/m K. The direction dependence thermal properties of the TIM are due to the anisotropic thermal performance of BN nanofibers in the composite. A low thermal contact resistance of 0.2 K mm2/W is also achieved at the interface between this new composite and copper substrate. These competent thermal properties demonstrate the great potential of the BN–In TIMs in thermal management for electronic system.
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| 4. |
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| 5. |
- Luo, Xin, 1983, et al.
(författare)
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Investigation of accelerated surface oxidation of Sn-3,5Ag-0,5Cu solder particles by TEM and STEM
- 2011
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Ingår i: Proceedings of the IEEE 2011 International Symposium on Advanced Packaging Materials (APM), Xiamen, China, October 25-28, 2011. - 1550-5723. - 9781467301473 ; , s. 73 - 79
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Konferensbidrag (refereegranskat)abstract
- The composition and thickness of surface oxide of solder particles has a direct effect on adhesion and electrical resistance of soldering joint and resultant the quality of interconnect and the reliability of packaged system. Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) were used to examine the oxide layer on solder powders in the present paper. However, for the surface oxide layer of a lead-free solder particle, the TEM sample for the oxide layer has never been done for studying its thickness or appearance before. And it is the first time in this work to use Focus Ion Beam (FIB) technology to prepare TEM specimen for solder particles and show TEM pictures of their surface oxide layer. High angle annular dark field (HAADF) pattern was applied to distinguish between the oxide layer and the solder matrix by the contrast of average atomic number. The solder powders were exposed in air (70% relative humidity) at 150°C for 0, 120 and 240 h to simulate the accelerated growth of oxide. The surface oxide thickness was 6 nm and 50 nm measured by TEM for 0 h and 120 h samples respectively. Confirming by AES measurement, the thickness of 5 nm and 50 nm were gotten using intersection analysis method for AES depth profiles. It is found that the increase of surface oxide thickness of solder particles is proportional to the rooting of time. The elemental distribution along the oxide was quantified by line scanning using STEM and the atomic ratio of Sn to O in the oxide layer nearer to the outer, the middle, and the inner (adjacent to the solder matrix) were found to be 1:2, 2:3 and 1:1, respectively. The result was validated using XPS which gave Sn to O ratio of 1:2 at 5 nm depth of surface oxide. © 2011 IEEE.
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| 6. |
- Luo, Xin, 1983, et al.
(författare)
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Novel thermal interface materials: boron nitride nanofiber and indium composites for electronics heat dissipation applications
- 2014
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Ingår i: Journal of Materials Science: Materials in Electronics. - : Springer Science and Business Media LLC. - 1573-482X .- 0957-4522. ; 25:5, s. 2333-2338
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Tidskriftsartikel (refereegranskat)abstract
- With increased power density and continued miniaturization, effective thermal dissipation is of significant importance for operational lifetime and reliability of electronic system. Advanced thermal interface materials (TIMs) with excellent thermal performance need to be designed and developed. Here we report novel TIMs consisted of boron nitride (BN) nanofibers and pure indium (In) solder for heat dissipation applications. The BN nanofibers are fabricated by electrospinning process and nitridation treatment. After surface metallization by sputtering, the porous BN film is infiltrated with liquid indium by squeeze casting to form the final solid composites. The new composites show the in-plane and through-plane thermal conductivity respectively of 60 and 20 W/m K. The direction dependence thermal properties of the TIM are due to the anisotropic thermal performance of BN nanofibers in the composite. A low thermal contact resistance of 0.2 K mm(2)/W is also achieved at the interface between this new composite and copper substrate. These competent thermal properties demonstrate the great potential of the BN-In TIMs in thermal management for electronic system.
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| 7. |
- Luo, Xin, 1983, et al.
(författare)
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Surface oxide analysis of lead-free solder particles
- 2013
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Ingår i: Soldering and Surface Mount Technology. - : Emerald. - 1758-6836 .- 0954-0911. ; 25:1, s. 39-44
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Tidskriftsartikel (refereegranskat)abstract
- Purpose - The composition and thickness of surface oxide of solder particles is extremely important to the quality of interconnect and reliability of packaged system. The purpose of this paper is to develop an observable measurement to research the issue. Design/methodology/approach - AES (Auger electron spectroscopy), XPS (X-ray photoelectron spectroscopy), TEM (transmission electron microscopy) and STEM (scanning transmission electron microscopy) were employed to examine the oxide layer on microscale solder powders. Conventional techniques and FIB (Focus Ion Beam) were employed for the TEM sample preparation. High angle annular dark field (HAADF) pattern was applied to distinguish the oxide layer and the solder matrix by the contrast of average atomic number. The results were confirmed by AES and XPS measurement. Findings - The solder powders were exposed to air (70% relative humidity) at 150 degrees C for 0, 120 and 240 h for the accelerated growth of oxide. The surface oxide thickness was 6 nm and 50 nm measured by TEM for Oh and 120 h samples, respectively. It was found that the increase in surface oxide thickness of solder particles is proportional to the rooting of time. The elemental distribution along the oxide was quantified by line scanning using STEM and the atomic ratio of Sn to O in the oxide layer nearer to the outer, the middle, and the inner (adjacent to the solder matrix) was found to be 1:2, 2:3 and 1:1, respectively. The result was validated using XPS which gave Sn to O ratio of 1:2 at 5 nm depth of surface oxide. Originality/value - This is the first time FIB technology has been used to prepare TEM specimens for solder particles and TEM pictures shown of their surface oxide layer. Though requiring more care in sample preparation, the measurements by TEM and STEM are believed to be more direct and precise.
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| 8. |
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| 9. |
- Luo, Xin, 1983, et al.
(författare)
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Unusual tensile behaviour of fibre-reinforced indium matrix composite and its in-situ TEM straining observation
- 2016
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Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454. ; 104, s. 109-118
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Tidskriftsartikel (refereegranskat)abstract
- Indium-based thermal interface materials are superior in thermal management applications of electronic packaging compared to their polymer-based counterparts. However, pure indium has rather low tensile strength resulting in poor reliability. To enhance the mechanical properties of such a material, a new composite consisting of electrospun randomly oriented continuous polyimide fibres and indium was fabricated. The composite has been characterised by tensile tests and in-situ transmission electron microscopy straining observations. It is shown that the composite's ultimate tensile strength at 20 degrees C is five times higher than that of pure indium, and the strength of the composite exceeds the summation of strengths of the individual components. Furthermore, contrary to most metallic matrix materials, the ultimate tensile strength of the composite decreases with the increased strain rate in a certain range. The chemical composition and tensile fracture of the novel composite have been analysed comprehensively by means of scanning transmission electron microscopy and scanning electron microscopy. A strengthening mechanism based on mutually reinforcing structures formed by the indium and surrounding fibres is also presented, underlining the effect of compressing at the fibre/indium interfaces by dislocation pileups and slip pinning.
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| 10. |
- Murugesan, Murali, 1979, et al.
(författare)
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Carbon fiber solder matrix composite for thermal management of high power electronics
- 2014
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501 .- 0959-9428 .- 2050-7534 .- 2050-7526. ; 2:35, s. 7184-7187
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Tidskriftsartikel (refereegranskat)abstract
- A carbon fiber based tin–silver–copper alloy matrix composite (CF-TIM) was developed via electrospinning of a mesophase pitch with polyimide and carbonization at 1000 °C, followed by sputter coating with titanium and gold, and alloy infiltration. The carbonized fibers, in film form, showed a thermal conductivity of [similar]4 W m−1 K−1 and the CF-TIM showed an anisotropic thermal conductivity of 41 ± 2 W m−1 K−1 in-plane and 20 ± 3 W m−1 K−1 through-plane. The thermal contact resistance of the CF-TIM was estimated to be below 1 K mm2 W−1. The CF-TIM showed no reduction in effective through-plane thermal conductivity after 1000 temperature cycles, which indicates the potential use of CF-TIM in thermal management applications.
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