| 1. |
- Andersson, Cristina, 1969, et al.
(author)
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Thermal cycling aging effect on the shear strength, microstructure, IMC and initiation and propagation of surface mounted Sn-3.8Ag-0.7Cu and wave soldered Sn-3.5Ag ceramic chip components
- 2008
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In: IEEE Transactions on Components and Packaging Technologies. - 1521-3331. ; 31:2, s. 331-344
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Journal article (peer-reviewed)abstract
- Temperature cycling of electronic components was carried out at two different temperature profiles, the first ranging between -55°C and 100°C (TC1) and the second between 0°C and 100°C (TC2). Totally, 7000 cycles were run at TC1 and 14500 cycles at TC2. The test board’s top-side components were surface mounted using Sn-3.8Ag-0.7Cu solder alloy, and bottom side SMD components were wave soldered with Sn-3.5Ag alloy. The solder joint degradation was investigated as a function of cycle number by means of shear strength measurements and cross-sectioning. The shear strength drop was correlated to both crack initiation time and propagation rate, and Microstructural changes. The effect of manufacturing process (reflow versus wave soldering) and component size (0805 versus 0603 components) on the shear strength were also investigated.For both reflow and wave soldered components, the harsher the test environment the faster and largest the decrease in shear strength. The shear force is higher for the 0805 components compared to the 0603. The effect of component size on the residual shear strength is higher for the testing condition TC1. TC1 also seems to have a higher effect on the residual shear strength compared to TC2. The main difference between wave soldered and reflow soldered components is that the shear strength is in average higher for the wave soldered components compared to the reflow soldered. For the reflow soldered components using SAC, the microstructure coarsens, especially the Ag3Sn intermetallic particles. Furthermore, this alloy shows an increase of the IMC layer (Cu-Ni-Sn) thickness, and the IMC layer growth is controlled by a diffusion mechanism. The IMC growth coefficient is for the SAC system tested at TC1 0.0231 μm/hr1/2 (0.00053μm/hr) and for TC2 0.0054 μm/hr1/2 (2.9*10-5μm/hr). The microstructural changes during thermal cycling are a result of both static and strain-enhanced aging. For the wave soldered components the microstructure also became coarser, however, the IMC layer (Ni3Sn4) thickness did not change.The IMC layer growth does not affect the shear strength for the test conditions applied in this work. The shear strength decrease observed in the present work as a result of thermal cycling is a result of both microstructural coarsening and crack propagation inside the solder joint.
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| 2. |
- Anton Remirez, Raul, et al.
(author)
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Compact CFD modeling of EMC screen for radio base stations : A porous media approach and a correlation for the directional loss coefficients
- 2007
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In: IEEE transactions on components and packaging technologies (Print). - : IEEE Press. - 1521-3331 .- 1557-9972. ; 30:4, s. 875-885
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Journal article (peer-reviewed)abstract
- A methodology to obtain the directional pressure loss coefficients in a porous media model of an electromagnetically compatible screen of a radio base station model is presented. The directional loss coefficients of this compact model are validated against a detailed computational fluid dynamics model not only by comparing the total pressure drop, but also by evaluating the flow pattern after the screen. The detailed model was validated in an earlier article by the authors. A parametric study is conducted for 174 cases. Seven parameters were investigated: velocity, inlet height, screen porosity, printed circuit board (PCB) thickness, inlet-screen gap, distance between two PCBs and screen thickness. Based on the compact model parametric study, two correlations for the directional loss coefficients are developed as a function of the Reynolds number and the above geometrical parameters. The average disagreement between the compact model that uses the directional loss coefficients from the correlations and the detailed model was of 3% for the prediction of the total pressure drop and less than 6.5% and 9.5% for two coefficients that accurately characterize the flow pattern. © 2007 IEEE.
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| 3. |
- Anton Remirez, Raul, et al.
(author)
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Detailed CFD modelling of EMC screen for radio base stations : a parametric study
- 2009
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In: IEEE transactions on components and packaging technologies (Print). - 1521-3331 .- 1557-9972. ; 32:1, s. 145-155
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Journal article (peer-reviewed)abstract
- The objective of this paper is to make a parametric study of the hydraulic resistance and flow pattern of the flow after an electromagnetic compatibility screen and between two printed circuit boards (PCBs) in a model of a 90° subrack cooling architecture. The parametric study is carried out using a detailed 3-D model of a PCB slot. The detailed model was experimentally validated in a previous paper by the authors. Seven parameters were investigated: velocity, inlet height, screen porosity, PCB thickness, distance between two PCBs, inlet-screen gap and screen thickness. A correlation for the static anddynamic pressure drop, the percentage of dimensionless wetted area, Aw*, and the RMS* factor (a function of the flow uniformity along the PCB) after the screen is reported as a function of six geometrical dimensionless parameters and the Reynolds number. The correlations, that are based on 174 three dimensional simulations, yield good results for the total pressure drop, in which the values are predicted within the interval of ±15%. For the, Aw* all the predicted values are within the interval of ±22% of the observed values. Finally, for the RMS* factor, the majority of the values also have a disagreement of less than 20% of the observed values. These last two parameters are believed to provide a correct insight about the flow pattern after the screen.
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| 4. |
- Anton Remirez, Raul, et al.
(author)
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Detailed CFD modelling of EMC screen for radio base stations : a benchmark study
- 2007
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In: IEEE transactions on components and packaging technologies (Print). - 1521-3331 .- 1557-9972. ; 30:4, s. 754-763
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Journal article (peer-reviewed)abstract
- The objective of this paper is to investigate the performance of five well-known turbulence models, in order to find a model that predicts the details of the flow patterns through an electromagnetic compatibility (EMC) screen. The turbulence models investigated in the present study are five different eddy-viscosity models; the standard k-ε model, the renormalization group (RNG) k-ε model, the realizable k-ε model, the standard k-ω model, as well as the shear stress transport k-ω model. A steady-state 3-D detailed model, which serves as the most accurate representation of the model, was used in order to evaluate the details of the airflow paths and pressure field. The flow was assumed to be isothermal, turbulent and incompressible. A general model that covers a considerable range of velocities and geometries was validated experimentally by wind tunnel measurements. The result shows that for most of the k-ε models used with correct y+ and mesh strategy, the pressure drop and the velocity field deviation is small compared to experimental data. The k-ω models overpredict the overall pressure drop. When using the RNG k-ε model, the total static pressure drop predicted differs around 5%-10% and the average velocity deviation at several locations before and after the screen is around 5%.
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| 7. |
- Dejanovic, Slavko, et al.
(author)
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Metal Covered Elastic Micro-Bump Contacts as an Alternative to Commercial Elastic Interconnection Techniques
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In: IEEE transactions on components and packaging technologies (Print). - 1521-3331 .- 1557-9972.
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Journal article (other academic/artistic)abstract
- 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.
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| 8. |
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| 9. |
- Eriksson, P., et al.
(author)
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Design of accelerated corrosion tests for electronic components in automotive applications
- 2001
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In: IEEE transactions on components and packaging technologies (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1521-3331 .- 1557-9972. ; 24:1, s. 99-107
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Journal article (peer-reviewed)abstract
- Two new accelerated laboratory corrosion tests for electronic components in automotive applications have been developed, based on the use of metallic copper as a meter for corrosivity. The accelerated tests are designed so that they reproduce the same kind of corrosion effects as observed with exposure of copper in real vehicle environments. The test cycle that best simulates the corrosion characteristics of an engine compartment is composed of the following steps: a) exposure to neutral salt spray for 2 h; b) drying at 23 degreesC and 50% RH for 22 h; c) exposure to a test atmosphere of 1.5 ppm NO2 and 0.5 ppm SO2 at 25 degreesC and 95% RH for five days; d) drying at 23 degreesC and 50% RH for one day. The predominating corrosion products of copper, formed both during service exposure and in the accelerated test, are Cu2O and Cu2Cl(OH)(3), with a small amount of sulphur-containing corrosion products in the form of sulphates, In terms of corrosivity of copper, a test duration of six weeks corresponds to 7.5 years of exposure in the reference engine compartment selected for this study. The test cycle designed for the passenger compartment contains the steps: a) exposure for five days to a test atmosphere of 10 ppm NO2 and 95% RH at 35 degreesC, followed by b) drying at 23 degreesC and 50% RH for two days. In this case, Cu2O is the predominating corrosion product. Zn terms of corrosivity of copper, a test duration of four weeks corresponds to 7.5 years of exposure in the reference passenger compartment of this study.
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