8 results on '"Dejanovic, Slavko"'
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2. A 183-GHz Schottky Diode Receiver with 4 dB Noise Figure
- Author
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Anderberg, Martin, primary, Sobis, Peter, additional, Drakinskiy, Vladimir, additional, Schleeh, Joel, additional, Dejanovic, Slavko, additional, Emrich, Anders, additional, and Stake, Jan, additional
- Published
- 2019
- Full Text
- View/download PDF
3. Blood coagulation on electron beam melted implant surfaces, implications for bone growth
- Author
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Ek, Rebecca, Hong, Jaan, and Dejanovic, Slavko
- Subjects
electron beam melting ,Additive manufacturing ,Medical Materials ,Medicinska material och protesteknik ,rapid prototyping - Abstract
INTRODUCTION Implants for arthroplasty, plates and screws for orthopedics, maxillofacial and dentistry are more frequently being customised. Ti and CoCr alloys are common materials for bone implants. Surface roughness, porosity and choice of material may have an impact on the bone ingrowth. EBM (Electron Beam Melting) is a 3D-printing technique melting metallic powder layer by layer according to the corresponding CAD (Computer Aided Design) model of implants1.With EBM technology customised implants can be manufactured with a lower cost compared to conventional technologies2. Implants for bone replacement made from CT images with EBM technology will fit accurate and lead to simpler and better planed surgeries also3. The EBM technique, as such, is always resulting with rough surface on the implants (typically 20-45µm). That roughness can be controlled, in some extent, by changing the process parameters. Some authors claim that roughened surfaces are promoting bone ingrowth4. This work was aiming on the question: are EBM made surfaces good for bone ingrowth and is it possible to change the bone ingrowth by varying the machine settings? In order to answer this question a number of coin like specimens of CoCr were manufactured with the different surface roughness. The blood chamber model has shown how the first steps of bone healing were proceeding on specimen surfaces, indicating how the coagulation and complement systems can behave in vivo5. EXPERIMENTAL METHODS The manufacture of the test specimens was carried out with Arcam A2 EBM® equipment. Process parameters were changed in the software EBM controle6 and three groups of eight specimens with different parameter setting were made. The specimens were then tested with whole blood from two individuals in a modified version of the blood chamber model named above7. Surface roughness was characterised with a stylus profiler Dektak® 6M. RESULTS AND DISCUSSION Table 1 percents Ra (average roughness) and plt (platelets) activated for each group. Table 1 group Ra mean std plt mean std 1 35.0µm 3.24µm 92.9% 5.25% 2 28.5µm 2.14µm 85.3% 7.61% 3 28.2µm 1.75µm 84.4% 10.3% The results indicate that rougher surfaces are more thrombogenic which could imply that they are more suitable for bone ingrowth then smooth surfaces. Increase of total surface area (due to larger roughness) might be a reason for the improved trombogenic response. Figure 1 shows how many platelets were stuck on the specimen surfaces. Horizontal lines represent mean values and standard deviation. CONCLUSION The surface properties of EBM produced implants are affected by the made parameters. The results in Figure 1 corresponds well with previous results that rougher surfaces promotes bone ingrowth4. The increased thrombogenicity and platelet binding with rougher surfaces indicates that EBM made surfaces can affect the final bone response and will possibly suit as implant material. REFERENCES 1. Raennar, L.E., et al., Efficientcooling with tool inserts manufactured by electronbeam melting. Rapid Prototyping Journal. 13:128-35, 2007 2. Cronskaer, M. Applications of Electron Beam Melting to Titanium Hip Stem Implants 3. Mazzoli, A., et al., Direct fabrication through electron beam melting technology of custom cranial implants designed in a PHANToM-based haptic environment. Materials and Design. 30:318-3192, 2009 4. Frosch, K.H., et al., Metallic Biomaterials in Skeletal Rapair. Eur J Trauma. 32:149-59, 2006 5. Thor A., et al.. The role of whole blood in thrombin generation in contact with various titanium surfaces. Biomaterials. 28:966-97, 2007 6. Arcam AB (www.arcam.com) 7. Hong, J., et al., A new in vitro model to study interaction between whole blood and biomaterials. Studies of platelet and coagulation activation acid the effect of aspirin. Biomaterials. 20:603-611, 1999
- Published
- 2011
4. Manufacture and characterization of elastic interconnection microstructures in silicone elastomer
- Author
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Dejanovic, Slavko
- Subjects
assembly ,RIE of silicone elastomer ,Other Electrical Engineering, Electronic Engineering, Information Engineering ,packaging ,elastic interconnection ,Annan elektroteknik och elektronik ,silicone elastomer ,chip socket ,metallization - Abstract
The subject of this thesis is a new chip to substrate interconnection technique using self-aligning elastic chip sockets. This work was focused on the technology steps which are necessary to fulfill in order to realize the suggested technique. Elastic chip sockets offer a solution for several assembly and packaging challenges, such a thermo-mechanical mismatch, effortless rework, environmental compatibility, high interconnection density, high frequency signal integrity, etc. Two of the most challenging technology aspects, metallization and etching of the silicone elastomer were studied, but also, air bubble free casting of the silicone elastomer was taken into consideration. Elastic chip sockets and single elastic micro-bump contacts of different shapes and sizes were manufactured and characterized. The contact resistance measurements revealed that the elastic micro-bump contacts manufactured by using the developed methods require less than one tenth of the contact force to achieve the same low contact resistance as compared to commercial elastic interconnection structures. The analysis and measurements of the high frequency properties of the elastic micro-bump structures have shown that they can operate up to several tens of GHz without a serious degradation of the signal quality. The same methods were applied to manufacture very high density contact area array (approximately 80000 connections/cm2), which until now was achieved only using so called chip-first techniques. The low contact resistance, the absence of environmentally harmful materials, no need of soldering, easy rework as well as capability of very high interconnecting density and very high frequency compatibility, indicates a high potential of this technique for assembly and packaging. Moreover, the presented technology of the silicone elastomer micromachining (metallization and RIE in particular) can be used for manufacturing of other microstructures, like chemical or biological micro reactors. QC 20110114
- Published
- 2006
5. Elastic interconnection micro contact structures - manufacture and characterization
- Author
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Dejanovic, Slavko
- Published
- 2004
6. Contact Resistance of Thin Metal Film Contacts.
- Author
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Norberg, Gunmar, Dejanovic, Slavko, and Hesselbom, Hjalmar
- Subjects
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THIN films , *METALLIC films , *ELECTRIC resistance , *ELECTROMECHANICAL devices , *MINIATURE electronic equipment - Abstract
To be able to reduce the size of products having electronic devices, it becomes more and more important to miniaturize the electromechanical parts of the system. The use of micromechanical connectors and contact structures implies the need of methods for estimating the properties of such devices. This work will, by use of finite element modeling, treat the influence of a thin film constituting at least one of the contacting members of an electrical contact. The error introduced by using the traditional Maxwell/Holm contact constriction resistance theory will be investigated. Numerical methods are used to present a way to approximate the total resistance for the thin metal film contact. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
7. Very High Density Interconnect Elastomer Chip Sockets.
- Author
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Norberg, Gunnar, Dejanovic, Slavko, and Hesselbom, Hjalmar
- Subjects
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INTEGRATED circuit interconnections , *ELASTOMERS , *DENSITY , *IMPEDANCE matching , *MULTICHIP modules (Microelectronics) , *THERMAL stresses , *ELECTRONICS - Abstract
The integration of more and more functionality into smaller and smaller form factor electronic products, drives the need for denser chip to substrate interconnect systems. As the number of I/O pins increases, the use of area array chips or packages becomes inevitable. Metal patterned elastomer chip sockets have now been improved to work with contact densities as high as 80 000 contacts/cm² corresponding to a pitch of 36 μm. Sockets with 10 000 contacts and a 72-μm pitch have survived more than 400 cycles in air-to-air thermal cycling chambers as well as freezing shocks caused by dipping into liquid nitrogen. Although the daisy chain test circuits breaks for temperatures lower than -50 °C and higher than 90 °C, they always return to the initial resistance values when entering the normal temperature range. The combination of a gold-to-gold contact interface and the elastic features of the contact bumps makes this socket an ideal compliance layer between bare chips and different types of carrier substrates, reducing the problems caused by thermomechanical mismatch between the substrate and the chip. Bad dies can easily be replaced, since the chip is not soldered or glued to the socket. The size and the possibility to control the geometry of the contacts provides means to maintain a good high-frequency characteristic impedance matching all the way to the chip pad. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
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8. Elastomer Chip Sockets for Reduced Thermal Mismatch Problems and Effortless Chip Replacement, Preliminary Investigations.
- Author
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Norberg, Gunnar, Dejanovic, Slavko, and Hesselbom, Hjalmar
- Subjects
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INTEGRATED circuits , *ELECTRIC connectors , *MATERIAL fatigue - Abstract
Provides information on a study that developed an elastic chip socket to avoid the problem with thermo-mechanical stress induced fatigue using conventional flip-chip mounting of bare chips. Methodology of the study; Results and discussion on the study.
- Published
- 2003
- Full Text
- View/download PDF
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