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  • 1.
    Akbari, Saaed
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Lövberg, Andreas
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Brinkfeldt, Klas
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Andersson, Dag
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Effect of PCB cracks on thermal cycling reliability of passive microelectronic components with single-grained solder joints2019In: Microelectronics and reliability, ISSN 0026-2714, E-ISSN 1872-941X, Vol. 93, p. 61-71Article in journal (Refereed)
    Abstract [en]

    Lead-free tin-based solder joints often have a single-grained structure with random orientation and highly anisotropic properties. These alloys are typically stiffer than lead-based solders, hence transfer more stress to printed circuit boards (PCBs) during thermal cycling. This may lead to cracking of the PCB laminate close to the solder joints, which could increase the PCB flexibility, alleviate strain on the solder joints, and thereby enhance the solder fatigue life. If this happens during accelerated thermal cycling it may result in overestimating the lifetime of solder joints in field conditions. In this study, the grain structure of SAC305 solder joints connecting ceramic resistors to PCBs was studied using polarized light microscopy and was found to be mostly single-grained. After thermal cycling, cracks were observed in the PCB under the solder joints. These cracks were likely formed at the early stages of thermal cycling prior to damage initiation in the solder. A finite element model incorporating temperature-dependant anisotropic thermal and mechanical properties of single-grained solder joints is developed to study these observations in detail. The model is able to predict the location of damage initiation in the PCB and the solder joints of ceramic resistors with reasonable accuracy. It also shows that the PCB cracks of even very small lengths may significantly reduce accumulated creep strain and creep work in the solder joints. The proposed model is also able to evaluate the influence of solder anisotropy on damage evolution in the neighbouring (opposite) solder joints of a ceramic resistor.

  • 2.
    Andersson, Dag
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Wetter, Göran
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    The impact of conformal coatings on the environmental protection of PCBassemblies and the reliability of solder joints2018Conference paper (Other academic)
  • 3.
    Brinkfeldt, Klas
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Amen, Rafael
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Adolfsson, Erik
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Johander, Per
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Andersson, Dag
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Thermo-mechanical simulations and measurements on high temperature interconnections2011In: 12th Int. Conf. on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2011, 2011, article id 5765772Conference paper (Refereed)
    Abstract [en]

    In order to place sensors or electronics in very high temperature environments, new materials and methods for interconnection are required. A comparative study between different electrical interconnection methods for very high operation temperatures (500 °C - 800 °C) is presented. Thermo-mechanical simulations and characterization of samples of the interconnection types during high temperature exposure are presented. The results of the thermo-mechanical simulations showed that stresses are low in a connection system based on liquid interconnection. This system, however, proved to be difficult to realize due to problems with oxides and sealing of the metallic liquid. Modeling of an interconnection based purely on mechanical pressure without any solder or metallic bond showed high stress. This was also confirmed during high temperature exposure where the connection failed. High stress was also predicted for an interconnection based on nano-Ag paste. The high temperature tests, however, showed promising results at 800 °C for over 100 hours. © 2011 IEEE.

  • 4.
    Brinkfeldt, Klas
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Wetter, Göran
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Lövberg, Andreas
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Andersson, Dag
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Goncalves, Johnny
    NOTE Norrtelje AB, Sweden.
    Söderlund, Jonas
    NOTE Norrtelje AB, Sweden.
    Strandberg, Jan
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Kwarnmark, Mikael
    Cogra Pro AB, Sweden.
    Feasibility of PCB-integrated vibration sensors for condition monitoring of electronic systems2018In: ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems, InterPACK 2018, 2018Conference paper (Refereed)
    Abstract [en]

    The increasing complexity of electronics in systems used in safety critical applications, such as for example self-driving vehicles requires new methods to assure the hardware reliability of the electronic assemblies. Prognostics and Health Management (PHM) that uses a combination of data-driven and Physics-of-Failure models is a promising approach to avoid unexpected failures in the field. However, to enable PHM based partly on Physics-of-Failure models, sensor data that measures the relevant environment loads to which the electronics is subjected during its mission life are required. In this work, the feasibility to manufacture and use integrated sensors in the inner layers of a printed circuit board (PCB) as mission load indicators measuring impacts and vibrations has been investigated. A four-layered PCB was designed in which piezoelectric sensors based on polyvinylidenefluoride-co-trifluoroethylene (PVDF-TrFE) were printed on one of the laminate layers before the lamination process. Manufacturing of the PCB was followed by the assembly of components consisting of BGAs and QFN packages in a standard production reflow soldering process. Tests to ensure that the functionality of the sensor material was unaffected by the soldering process were performed. Results showed a yield of approximately 30 % of the sensors after the reflow soldering process. The yield was also dependent on sensor placement and possibly shape. Optimization of the sensor design and placement is expected to bring the yield to 50 % or better. The sensors responded as expected to impact tests. Delamination areas were present in the test PCBs, which requires further investigation. The delamination does not seem to be due to the presence of embedded sensors alone but rather the result of a combination of several factors. The conclusion of this work is that it is feasible to embed piezoelectric sensors in the layers of a PCB.

  • 5.
    Brinkfeldt, Klas
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Wetter, Göran
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Lövberg, Andreas
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Andersson, Dag
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Strandberg, Jan
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Goncalves, Johnny
    NOTE Norrtelje AB, Sweden.
    Söderlund, Jonas
    NOTE Norrtelje AB, Sweden.
    Kwarnmark, Mikael
    Cogra Pro AB, Sweden.
    Feasibility of Printed Circuit Board-Integrated Vibration Sensors for Condition Monitoring of Electronic Systems2019In: Journal of Electronic Packaging, ISSN 1043-7398, E-ISSN 1528-9044, Vol. 141, no 3, article id 031010Article in journal (Refereed)
    Abstract [en]

    The increasing complexity of electronics in systems used in safety critical applications, such as self-driving vehicles, requires new methods to assure the hardware reliability of the electronic assemblies. Prognostics and health management (PHM) that uses a combination of data-driven and physics-of-failure models is a promising approach to avoid unexpected failures in the field. However, to enable PHM based partly on physics-of-failure models, sensor data that measure the relevant environment loads to which the electronics are subjected during its mission life are required. In this work, the feasibility to manufacture and use integrated sensors in the inner layers of a printed circuit board (PCB) as mission load indicators measuring impacts and vibrations has been investigated. A four-layered PCB was designed in which piezoelectric sensors based on polyvinylidenefluoride-co-trifluoroethylene (PVDF-TrFE) were printed on one of the laminate layers before the lamination process. Manufacturing of the PCB was followed by the assembly of components consisting of ball grid arrays (BGAs) and quad flat no-leads (QFN) packages in a standard production reflow soldering process. Tests to ensure that the functionality of the sensor material was unaffected by the soldering process were performed. Results showed a yield of approximately 30% of the sensors after the reflow soldering process. The yield was also dependent on sensor placement and possibly shape. Optimization of the sensor design and placement is expected to bring the yield to 50% or better. The sensors responded as expected to impact tests. Delamination areas were present in the test PCBs, which requires further investigation. The delamination does not seem to be due to the presence of embedded sensors alone but rather the result of a combination of several factors. The conclusion of this work is that it is feasible to embed piezoelectric sensors in the layers of a PCB.

  • 6. Chaillot, A.
    et al.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Venet, N
    Hokka, J
    ENEPIG Finish: An Alternative Solution for Space Printed Circuit Boards2014Conference paper (Other academic)
  • 7.
    Grönqvist, Hans
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Lidström, Oscar
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Wünscher, Heike
    CiS Forschungsinstitut für Mikrosensorik GmbH, Germany.
    Steinke, Arndt
    CiS Forschungsinstitut für Mikrosensorik GmbH, Germany.
    Richert, Hans
    SETEK Elektronik AB, Sweden.
    Lagerkvist, Peter
    Niranova AB, Sweden.
    Unit for Investigation of the Working Environment for electronic units in harsh environment2017In: Advanced Microsystems for Automotive Applications 2017: Smart Systems Transforming the Automobile / [ed] Zachäus, C., Müller, B., Meyer, G., Springer, 2017, p. 13-22Conference paper (Refereed)
    Abstract [en]

    When electronic equipment is used in harsh environments with long expected lifetimethere is a need to understand that environment more in detail. This situationis today a reality for many application areas including the automotive sector,heavy industry, the defense sector and more.To fully understand the working environment a unit has been developed to monitorphysical data such as temperature, vibration, humidity, condensation etc. to beused in the product development phase for new products.The paper presents the underlying principles for the ESU (Environmental SupervisionUnit) and details on the design.

  • 8.
    Liu, Johan
    et al.
    Chalmers University of Technology, Sweden.
    Salmela, Olli
    Nokia Siemens Networks, Finland.
    Särkkä, Jussi
    Nokia Siemens Networks, Finland.
    Morris, James E
    Portland State University, USA.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Andersson, Christina
    Chalmers University of Technology, Sweden.
    Reliability of Microtechnology: Interconnects, Devices and Systems2011Book (Other academic)
  • 9.
    Lövberg, Andreas
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    The Stress State of BGA Solder Joints Influenced by the Grain Orientations of Neighboring Joints2018Conference paper (Refereed)
  • 10.
    Lövberg, Andreas
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Transgranular crack propagation in thermal cycling of SnAgCu solder joints2019In: 2019 20th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2019, Institute of Electrical and Electronics Engineers Inc. , 2019Conference paper (Refereed)
    Abstract [en]

    Lifetime predictions of lead-free solder joints remain a challenging task in assuring reliability of electronic packaging. Due to the complex interaction of a wide range of as-soldered microstructures, strong an isotropic properties and a failure mechanism that is not completely understood, life time predictions of SnAgCu solder joints remain a challenging task.In this work, we present experimental findings of transgranular crack propagation of SnAgCu solder joints in thermal cycling. These findings are in contrast with the established picture of a recrystallization-assisted intergranular crack propagation failure mechanism

  • 11.
    Lövberg, Andreas
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Akbari, Saeed
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Andersson, Dag
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    On the formation and propagation of laminate cracks and their influence on the fatigue lives of solder joints2018In: 2018 19th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2018, 2018, p. 1-13Conference paper (Refereed)
    Abstract [en]

    Lead-free solder joints have been shown to increase the risk for crack formation in the PCB laminate under the solder pads. As such cracks propagate during thermal cycling, they decrease the strain imposed on the solderjoint by acting as strain relief. In accelerated thermal cycling, these joints have been found to remain virtually undamaged even after a very high number of cycles. If these cracks do not form or propagate to the same extent under milder cycling conditions, typical of service conditions, it may lead to an overestimation of the fatigue life of the solder joints in accelerated testing. In this work, the extent of strain relief and the influence of grain orientations on the initiation and propagation of these cracks are investigated through FE-modelling and compared to what has been experimentally observed for cross-sections of solder joints moulded in epoxy resin with added fluorescent agent and inspected using UV-light and electron backscatter diffraction. Due to the strong anisotropy of lead-free solder joints, the stress transferred to the laminate will vary significantly depending on grain orientation. The presence of these laminate cracks adds another layer of uncertainty to the already complex SnAgCu system, where the strong effects of anisotropy, the continuously evolving secondary precipitate coarsening and its interaction with the recrystallisation process govern the damage evolution. If these effects are not properly accounted for, the interpretation of thermal cycling or modelling and simulation results may be strongly misleading.

  • 12.
    Lövberg, Andreas
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Wetter, Göran
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Brinkfeldt, Klas
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF, Elektronikhårdvara.
    Andersson, Dag
    Simulations of the impact of single-grained lead-free solder joints on the reliability of ball Grid Array components2017Conference paper (Other academic)
    Abstract [en]

    The microstructure of lead-free solder joints often consists of only one or a few randomly oriented tin grains as a result of a large degree of undercooling during solidification. Due to the severe anisotropy of single crystal Sn and the random nature of the microstructure, the stress state and microstructural evolution of each joint will be unique.

  • 13.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Impact of Black Pad and Intermetallic Layers on the Risk for Fractures in Solder Joints to ElectrolessNickel/Immersion Gold2011In: The ELFNET Book on Failure Mechanisms, Testing Methods, and Quality Issues of Lead-Free Solder Interconnects / [ed] Grossmann, Günter, Zardini, Christian, London: Springer, 2011, p. 179-196Chapter in book (Refereed)
    Abstract [en]

    Solder joints to solder lands plated with electroless nickel and immersion gold are prone to fractures in the interface between the solder and the nickel surface. A common cause for these fractures has been a plating defect in the solder land coating called “black pad”. However, solder joints to solder lands plated with electroless nickel are inclined to fractures even if the black pad defect is not present. The causes of the black pad defect and the mechanisms for the increased inclination for fractures in solder joints to electroless nickel are discussed. Test methods for detecting black pad defects and assessing the risk for fractures in the solder joints are also described.

  • 14.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Impact of Humidity andContamination on Surface Insulation Resistance and Electrochemical Migration2011In: The ELFNET Book on Failure Mechanisms, Testing Methods, and Quality Issues ofLead-Free Solder Interconnects / [ed] Grossmann, Günter, Zardini, Christian, London: Springer, 2011, p. 227-254Chapter in book (Refereed)
    Abstract [en]

    Many electronics products are used in humid environments. High humidity in combination with various contaminants will affect the surface insulation resistance on printed board assemblies and may cause current leakage or in worse case short circuit due to electrochemical migration. This chapter discusses the failure mechanism for electrochemical migration and how it is affected by common contaminants on assemblies. Test methods for measuring surface insulation resistance and for assessing the risk for electrochemical migration are reviewed, and their relevance is discussed.

  • 15.
    Tegehall, Per-Erik
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Wetter, Göran
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Impact of laminate cracks under solder pads on the fatigue lives of ball grid array solder joints2015In: Microelectronics and reliability, ISSN 0026-2714, E-ISSN 1872-941X, Vol. 55, no 11, p. 2354-2370Article in journal (Refereed)
    Abstract [en]

    This paper reports how the solder joint fatigue lives of three types of lead free plastic BGA components were affected by cracks formed in the printed PCB laminate during a thermal cycling test. The investigation showed that cracks were formed in the laminate for all three tested components. For one of the components having a large chip with solder joints located under the chip, very large cracks were formed in the PCB laminate beneath some solder pads.For lead-free solder joints to BGA components consisting of near eutectic solders based on tin, silver and copper, a large fraction of the solder joints may consist of one single tin grain. Due to anisotropy of tin grains, each solder joint to a BGA component will experience a unique stress condition which will make laminate cracking more likely under certain solder joints.The laminate cracks increased the flexibility of the joints and thereby improved the fatigue lives of the solder joints. Therefore, an estimation of the fatigue lives of solder joints to BGA components based on the results from a thermal cycling test may lead to an overestimation of the fatigue lives if products will be exposed to smaller temperature changes in the field than in the test.If cracks are not formed in the PCB laminate, or if the extent of cracking is small, single-grained solder joints can be expected to result in a high spread in failure distribution with some quite early failures.

  • 16.
    Wünscher, Heike
    et al.
    CiS Forschungsinstitut für Mikrosensorik GmbH, Germany.
    Steinke, Arndt
    CiS Forschungsinstitut für Mikrosensorik GmbH, Germany.
    Ortlepp, Thomas
    CiS Forschungsinstitut für Mikrosensorik GmbH, Germany.
    Grönqvist, Hans
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Lidström, Oscar
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Richert, Hans
    SETEK Elektronik AB, Sweden.
    Lagerkvist, Peter
    Niranova AB, Sweden.
    Supervision unit for harsh environments2018Conference paper (Refereed)
1 - 16 of 16
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