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  • 1.
    Dejanovic, Slavko
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Elastic interconnection micro contact stuctures-manufacture and characterisation2004Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    ...The task that was put to the author of this thesis was to find solutions for manufacturing of single elastic micro bump contacts as well as complete elastic sockets and interconnections down to the carrier substrate. Use of more or less standard equipment and methods in electronic industry was a demand too. The casting mold was made in Si by anisotropic wet etching of Si wafers in KOH, and in order to manage and keep preferred distance between casting mold and the currier substrate small columns of SU 8 photo resist were made on the mold as well. For prevention of silicone elastomer sticking to the mold, Parylene was deposited on to the mold. Additionally, making of via holes is treated in this work. Two techniques were tried practically. Laser drilling has shown some potential but RIE of silicone elastomer was found to be more useful so far. Deposition of required metal layers was realized by sputtering and patterning was conducted by applying electro plated photo resist and exposing in a low divergence light mask aligner. Some limited characterization of manufactured elastic micro bump contacts by measuring their contact resistance is also reported. Some advantages of elastic micro bump contact based structures relative to already existing similar interconnection techniques is discussed. Some discussions concerning remaining technological problems and thin film contact resistance estimation issues are presented as well as the promising results, up to 45 000 contact points per cm2, achieved by scaling down the structures.

  • 2.
    Dejanovic, Slavko
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hesselbom, Hjalmar
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Norberg, Gunnar
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Manufacturing of Via Holes in Silicone ElastomerManuscript (Other (popular science, discussion, etc.))
    Abstract [en]

    In this work a possibility of making via holes in silicone elastomer was investigated. The methods that were taken into consideration were punching, mechanical drilling, laser drilling and RIE. Laser drilling and RIE were found to be viable and both were tried. Laser drilling of silicone elastomer has shown a big problem with burnt residues and has to be investigated much further to be usable. RIE of silicone elastomer is reported in this work. Several phenomena were observed. The etch-residues can be removed by washing them away in an ultra sonic water bath and subsequently totally removed by using a lift-off process based on wet Cu etch. A good anisotropy was achieved by applying CF4 plasma. Gradually broadening of the openings in the etch mask has contributed to a favorable etch profile and thus easier metallization of side-walls of via holes.

  • 3.
    Dejanovic, Slavko
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Kuttainen, S
    Persson, Ulf
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Westerfur, L
    Measurement of electrical parameters using Mixed-Signal Test Bus, IEEE Std. 1149.42001Report (Other academic)
  • 4.
    Dejanovic, Slavko
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Persson, Ulf
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Kuttainen, Stefan
    Westerfur, Lars
    Measurement of Electrical Parameters Using Mixed-Signal Test Bus, IEEE Std. 1149.42005In: Measurement, ISSN 0263-2241, Vol. 37, no 3, p. 260-277Article in journal (Refereed)
    Abstract [en]

    Test Access Port and Boundary-Scan Architecture, IEEE Std. 1149.1, was developed to ease the test of printed circuit board assemblies (PCBAs). The development of packaging technology and the increasing functionality of a circuit have made traditional testing methods, such as in-circuit tests and functional testing through edge connectors much more difficult or even impossible. Mixed-Signal Test Bus, IEEE Std. 1149.4, which is a further development of IEEE Std. 1149.1 has been developed to enable the testing of analog components and analog interconnects on PCBAs. IEEE Std. 1149.4 compliant circuits contain an analog bus and analog switches. Techniques applicable to the measurement of impedances via IEEE Std. 1149.4 compliant circuits are presented. A filter has been tested and the results are promising. It has been shown by both measurement and simulation that switching impedances can be managed in such a manner that the influence of deviations from their nominal value can be estimated.

  • 5.
    Ek, Rebecca
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Hong, Jaan
    Uppsala University, Immunology, Genetics and Pathology.
    Dejanovic, Slavko
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Blood coagulation on electron beam melted implant surfaces, implications for bone growth2011In: Proccedings of EBS 2011, Dublin, 2011Conference paper (Other academic)
    Abstract [en]

    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

  • 6.
    Haglund, Daniel
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hesselbom, Hjalmar
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Dejanovic, Slavko
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Metal Covered Elastic Micro-Bump Contacts as an Alternative to Commercial Elastic Interconnection TechniquesManuscript (preprint) (Other (popular science, discussion, etc.))
    Abstract [en]

    In this work, a novel chip-to-board interconnection structure have been manufactured, and some of its characteristics have been investigated. This chip connection technique can for instance serve as a FCOB (Flip Chip on Board) technique, for connecting test equipments during testing bare chip on wafer, and with some more development, in three dimensional multi chip modules. A setup of elastic micro-bumps was cast, metal covered, patterned, and electro-mechanically characterized. The metal-covered silicon elastomer contact-structures were manufactured on FR-4 carrier-plates. Visual inspection of the micro-bumps was conducted in a SEM (Scanning Electron Microscope). The electro-mechanical properties were measured by simultaneous use of a DMA (Dynamic Mechanical Analyzer) and a Kelvin Bridge structure for resistance measurement. The measurements gave the micro-bump to chip resistance behavior as a function of the micro-bump deflection distance and applied mechanical force when direct current was applied. The results obtained from the measurements have revealed that such a technique requires less than one tenth of the mechanical contact force for achieving the contact resistance of the same magnitude as for commercial elastic interconnection techniques. This would be of significant advantage because the amount of electrical contacts per unit of area has tendency of continued growth.

  • 7.
    Hesselbom, Hjalmar
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Norberg, Gunnar
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Dejanovic, Slavko
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Haglund, Daniel
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Solder and adhesive free chip assembly using elastic chip sockets: Concept, Manufacture and Preliminary Investigations2004In: Proceedings of 2004 International IEEE Conference on the Asian Green Electronics (AGEC), Piscataway, NJ, USA: IEEE , 2004, p. 12-17Conference paper (Other academic)
    Abstract [en]

    Flip Chip connections enormously reduces the amount of solder as compared to mounting packaged devices, apart from also offering superior high frequency properties and placement density. However, when assembling chips to substrates having different thermal expansion coefficient, the solder balls are exposed to strain, the more so the denser the connections (and consequently smaller balls), and the higher the power densities, resulting in wider temperature cycles. This will usually result in loss of contact reliability. Using other materials than solder or using underfills may partially improve the situation, but causes other problems. In order to test another concept maintaining or exceeding the excellent HF and density properties of conventional Flip Chip, while practically eliminating the thermal mismatch problems and providing effortless chip replacement, the Elastic Chip Socket was developed. Silicone elastomer was molded in a precision mold made using anisotropic etching of Si. These structures were subsequently metallized and the metal patterned using electro plated resist. So far functional chip sockets with pin densities of 45 000 pins per cm2 (22 500 simultaneously functional connections to a 7 x 7 mm die) and more have been achieved which endure multiple repeated matings and quick temperature cycling between -40 °C and +90 °C. The following is a summary of the group's achievement this far, Oct. 2003

  • 8.
    Norberg, Gunnar
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Dejanovic, Slavko
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. KTH.
    Hesselblom, Hjalmar
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Very High Density Interconnect Elastomer Chip2006In: IEEE Transactions on Advanced Packaging, ISSN 1521-3323, E-ISSN 1557-9980, Vol. 29, no 2, p. 202-210Article in journal (Refereed)
    Abstract [en]

    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.

  • 9.
    Norberg, Gunnar
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Dejanovic, Slavko
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hesselbom, Hjalmar
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Contact Resistance of Thin Metal Film Contacts2006In: IEEE transactions on components and packaging technologies (Print), ISSN 1521-3331, E-ISSN 1557-9972, Vol. 29, no 2, p. 371-378Article in journal (Refereed)
    Abstract [en]

    To be able to reduce the size of products having electronic devices, it becomes more and more important to miniaturize the electro-mechanical parts of the system. The use of micro mechanical 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.

  • 10.
    Norberg, Gunnar
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Dejanovic, Slavko
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hesselbom, Hjalmar
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Elastomer Chip Sockets for Reduced Thermal Mismatch Problems and Effortless Chip Replacement, Preliminary Investigations2003In: IEEE Transactions on Advanced Packaging, ISSN 1521-3323, Vol. 26, no 1, p. 33-40Article in journal (Refereed)
    Abstract [en]

    To avoid the problem with thermo-mechanical stress induced fatigue using conventional flip-chip mounting of bare chips, an elastic chip socket has been developed. The socket is made by casting silicone elastomer into micro structured silicon molds to form micro bump arrays. After the elastomer is cured and released from the mold, a metal layer is deposited and patterned. A chip is placed in the socket utilizing guiding structures for chip self alignment. The chip is then held in place by a spring loaded back-plate which can also serve as a heat sink for highly effective chip cooling. Since no adhesives, underfills or solders are used, the rework process becomes very simple and it can also be repeated many times for the same socket. Initial contact resistance and thermo-mechanical robustness measurements indicates that this type of sockets could work as a superior replacement for conventional flip-chip technologies in many applications. The particular design of the contact bumps results in metal structures that resemble (although up side down) and are scalable as those in the Chip-First technology. Preliminary thermal shock experiments from room temperature to liquid nitrogen and back show good survival. Thus, this new chip interconnect method indicates the possibility of getting the advantages of the Chip-First technology while eliminating the demand of placing the chip first. The concept will work for chips with rim positioned pads as well as for high density area arrays.

  • 11. Petrovic, V
    et al.
    Jordá, O
    Martin, A
    Rännar, Lars-Erik Rännar
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Dejanovic, Slavko
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Knowledge assisted Rapid Manufacturing, KARMA Project2011Conference paper (Refereed)
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