| 1. |
- Bonnaud, Etienne L.
(författare)
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Issues on Viscoplastic Characterization of Lead-Free Solder for Drop Test Simulations
- 2011
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Ingår i: Journal of Electronic Packaging. - : ASME International. - 1043-7398 .- 1528-9044. ; 133:4, s. 041013-
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Tidskriftsartikel (refereegranskat)abstract
- Reliable drop test simulations of electronic packages require reliable material characterization of solder joints. Mechanical properties of lead-free solder were here experimentally investigated for both monotonic and cyclic loading at different strain rates. With regards to the observed complex material behavior, the nonlinear mixed hardening Armstrong and Frederick model combined with the Perzyna viscoplastic law was chosen to fit the experimental data. This model was subsequently implemented into a commercial finite element code and used to simulate drop tests. Actual drop test experiments were conducted in parallel and experimental results were compared to simulations. Prediction discrepancies were analyzed and explanations suggested.
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| 2. |
- Brinkfeldt, Klas, et al.
(författare)
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Feasibility of Printed Circuit Board-Integrated Vibration Sensors for Condition Monitoring of Electronic Systems
- 2019
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Ingår i: Journal of Electronic Packaging. - : American Society of Mechanical Engineers (ASME). - 1043-7398 .- 1528-9044. ; 141:3
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Chen, Liu, 1973, et al.
(författare)
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Reliability Investigation for Encapsulated Isotropic Conductive Adhesives Flip Chip Interconnection
- 2006
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Ingår i: Journal of Electronic Packaging, Transactions of the ASME. - : ASME International. - 1528-9044 .- 1043-7398. ; 128:3, s. 177-183
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Tidskriftsartikel (refereegranskat)abstract
- Isotropic conductive adhesives (ICA) are gaining more and more application interests in electronic manufacturing, however, their failure mechanism is not been fully understood. In this paper we present reliability investigations on an encapsulated ICA flip chip interconnection. Experimental work included product lifetime measurement, cross section observation, and whole module warpage scanning. Results revealed that the chip-size effect on the ICA lifetime was obvious. A theoretical analysis was conducted with Finite Element Method (FEM) simulation. Viscoelastic models for adhesives and underfill materials were employed, and the comparison with an elastic model was made. Calculated equivalent stresses S eqv and shear stress σ xy fitted well with the experimental lifetime measurement, thus a lifetime relationship similar to the Coffin-Manson formula was established to predict the thermal fatigue life of an encapsulated ICA flip chip. Furthermore, the influences of underfill properties on the ICA reliability were discussed. Copyright © 2006 by ASME.
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| 4. |
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| 5. |
- Martinez-Galvan, Eduardo, et al.
(författare)
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Film Thickness and Heat Transfer Measurements in a Spray Cooling System With R134a
- 2011
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Ingår i: Journal of Electronic Packaging. - : ASME International. - 1043-7398 .- 1528-9044. ; 133:1, s. 011002-
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Tidskriftsartikel (refereegranskat)abstract
- Experimental measurements in a spray cooling test rig have been carried out for several heat fluxes in the heater and different spray volumetric fluxes with the dielectric refrigerant R134a. Results of the heat transfer and the sprayed refrigerant film thickness measurements are presented. The film thickness measurements have been made with a high speed camera equipped with a long distance microscope. It has been found that there is a relation between the variation in the average Nusselt number and the film thickness along the spray cooling boiling curve. The heat transfer regimes along that curve are related not only with a variation in the average Nusselt number but also with changes in the film thickness. The qualitative analysis of those variations has served to understand better the heat transfer mechanisms occurring during the spray cooling.
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| 6. |
- Palm, Björn E., et al.
(författare)
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Choosing working fluid for two-phase thermosyphon systems for cooling of electronics
- 2003
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Ingår i: Journal of Electronic Packaging. - : ASME International. - 1043-7398 .- 1528-9044. ; 125:2, s. 276-281
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Tidskriftsartikel (refereegranskat)abstract
- The heat fluxes from electronic components are steadily increasing and have now, in some applications, reached levels where air-cooling is no longer sufficient. One alternative solution, which has received much attention during the last decade, is to use heat pipes or thermosyphons for transferring or spreading the dissipated heat. In this paper two-phase thermosyphon loops are discussed. Especially, the choice of fluid and its influence on the design and performance is treated. The discussion is supported by results from simulations concerning heat transfer and pressure drop. In general it is found that high-pressure fluids will give better performance and more compact designs as high-pressure results in higher boiling heat transfer coefficients and smaller necessary tube diameter.
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| 7. |
- Rundström, Daniel, et al.
(författare)
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Investigation of flow and heat transfer of an impinging jet in a cross-flow for cooling of a heated cube
- 2006
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Ingår i: Journal of Electronic Packaging. - : ASME International. - 1043-7398 .- 1528-9044. ; 128:2, s. 150-156
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Tidskriftsartikel (refereegranskat)abstract
- The current trends toward the greater functionality of electronic devices are resulting in a steady increase in the amount of heat dissipated from electronic components. Forced channel flow is frequently used to remove heat at the walls of the channel where a PCB with a few high heat dissipating components is located. The overall cooling strategy thus must not only match the overall power dissipation load, but also address the requirements of the "hot" components. In order to cool the thermal load with forced channel flow, excessive flow rates will be required. The objective of this study is to investigate if targeted cooling systems, i.e., an impinging jet in combination with a low velocity channel flow, can improve the thermal performance of the system. The steady-state three-dimensional (3-D) model is developed with the Reynolds-Stress-Model (RSM) as a turbulence model. The geometrical case is a channel with a heated cube in the middle of the base plate and two inlets, one horizontal channel flow, and one vertical impinging jet. The numerical model is validated against experimental data obtained from three well-known cases, two cases with an impinging jet on a flat heated plate, and one case with a heated cube in a single channel flow. The effects of the jet Re and jet to-cross-flow velocity ratio are investigated. The airflow pattern around the cube and the surface temperature of the cube as well as the mean values and local distributions of the heat transfer coefficient are presented.
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| 8. |
- Sundén, Bengt, et al.
(författare)
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Thermal Analysis of Air-Cooled Electronic Units With Integrated Offset Strip-Fin Heat Sink
- 2014
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Ingår i: Journal of Electronic Packaging. - : ASME International. - 1043-7398 .- 1528-9044. ; 136:2
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Tidskriftsartikel (refereegranskat)abstract
- This short communication addresses a numerical investigation of the thermal behavior of an electronic unit. The unit consists of several parallel planes and on the top and bottom planes heat is generated by a number of electronic chips. The heat is transported by conduction through plastic and copper-invar layers. Finally, the heat is rejected by a forced air stream in the center of the unit. The channel system for the cooling air is designed as an offset strip fin surface. A three-dimensional numerical method based on a thermal resistance or conductance network has been developed. The grid points on the cooling air side are staggered compared to the grid points in the solid materials. Details of the numerical method as well as some temperature distributions on the chip planes are provided.
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| 9. |
- Xie, Gongnan, et al.
(författare)
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Analysis of Flow and Thermal Performance of a Water-Cooled Transversal Wavy Microchannel Heat Sink for Chip Cooling
- 2012
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Ingår i: Journal of Electronic Packaging. - : ASME International. - 1043-7398 .- 1528-9044. ; 134:4
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Tidskriftsartikel (refereegranskat)abstract
- With the increasing output power of the integrated circuit chips, the heat flux involved is being accordingly increased. In such situation, the air has almost reached its limit of cooling capacity, and thus the liquid cooling technology incorporating microchannel heat sinks is desired to cool the electronic chips in order to remove more heat loads. However, these microchannel heat sinks are often designed to be straight with rectangular cross section. In this study, on the basis of a straight microchannel having rectangular cross section, a kind of transversal wavy microchannel is designed and then the laminar flow and heat transfer are investigated numerically. It is shown that for removing the identical load, the transversal wavy microchannel has great potential to reduce pressure drop compared to the straight microchannel, especially for higher wave amplitude at the same Reynolds number, indicating the overall thermal performance of the transversal wavy microchannel is superior to the traditional straight rectangular microchannel. It is suggested such wavy microchannel can be used to cool chips effectively with much smaller pressure drop penalty. [DOI: 10.1115/1.4023035]
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| 10. |
- Xie, Gongnan, et al.
(författare)
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Comparative Study of Thermal Performance of Longitudinal and Transversal-Wavy Microchannel Heat Sinks for Electronic Cooling
- 2013
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Ingår i: Journal of Electronic Packaging. - : ASME International. - 1043-7398 .- 1528-9044. ; 135:2
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Tidskriftsartikel (refereegranskat)abstract
- Liquid cooling incorporating microchannels are used to cool electronic chips in order to remove more heat load. However, such microchannels are often designed to be straight with rectangular cross section. In this paper, on the basis of straight microchannels having rectangular cross section (SRC), longitudinal-wavy microchannel (LWC), and transversal microchannel (TWC) were designed, respectively, and then the corresponding laminar flow and heat transfer were investigated numerically. Among them, the channel wall of LWC undulates along the flow direction according to a sinusoidal function while the TWC undulates along the transversal direction. The numerical results show that for removing an identical heat load, the overall thermal resistance of the LWC is decreased with increasing inlet Reynolds number while the pressure drop is increased greatly, so that the overall thermal performance of LWC is inferior to that of SRC under the considered geometries. On the contrary, TWC has a great potential to reduce the pressure drop compared to SRC, especially for higher wave amplitudes at the same Reynolds number. Thus the overall thermal performance of TWC is superior to that of SRC. It is suggested that the TWC can be used to cool chips effectively with much smaller pressure drop penalty. In addition to the overall thermal resistance, other criteria of evaluation of the overall thermal performance, e. g., (Nu/Nu(0))/(f/f(0)) and (Nu/Nu(0))/(f/f(0))(1/3), are applied and some controversial results are obtained.
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| 11. |
- Xie, Gongnan, et al.
(författare)
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Constructal Theory Based Geometric Optimization of Wavy Channels in the Low Reynolds Number Regime
- 2014
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Ingår i: Journal of Electronic Packaging. - : ASME International. - 1043-7398 .- 1528-9044. ; 136:3
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Tidskriftsartikel (refereegranskat)abstract
- To obtain better fluid mixing and higher heat transfer in the low Reynolds number regime, various wavy fins are employed in heat sinks (heat exchangers) for electronic cooling applications. However, it was reported in previous works that in the low Reynolds number regime there are no remarkable differences in the thermal performance of a straight-plate and a wavy-wall channel. In this study, the constructal theory is applied to optimize the geometry of wavy-wall channels of an electronic heat sink, where the objective is to minimize the global thermal resistance. The domain has three degrees of freedom: The interplate-spacing (S), the wavelength ratio (lambda(1)/lambda(2)), and the amplitude ratio (a(1)/a(2)). The two times minimized global thermal resistance indicates that the thermal-hydraulic performance of the wavy channels is unaffected by the amplitude ratio, while the wavelength ratio and interplate separation have strong impacts on the overall performance. In addition, the thermal performances at four Reynolds numbers are evaluated, and it is found that the constructal-wavy channels can exhibit much better thermal performance in the low Reynolds number regime.
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| 12. |
- Zhang, Yan, 1976, et al.
(författare)
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Experimental and Modeling of the Stress-Strain Behavior of a BGA Interconnect Due to Thermal Load
- 2008
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Ingår i: Journal of Electronic Packaging, Transactions of the ASME. - : ASME International. - 1528-9044 .- 1043-7398. ; 130:2, s. 0210101-0210107
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Tidskriftsartikel (refereegranskat)abstract
- A plastic ball grid array component interconnect has been experimentally investigated and modeled on the basis of micropolar theory. The experimental results were analyzed, and the data also provided the verification for the micropolar interface model. Two different interconnect cross sections, namely, one near the component boundary and the other in the center region beneath the chip, have been measured. The effects of thermal cycling on the interconnect deformation have been considered. The deformation fields, due to the mismatch of the material properties of the constituents in the assembly system, have been observed by means of a multifunction macro-micro-moiré interferometer, whereby the displacement distributions have been obtained and analyzed for the different specimens. The interconnect layer is usually of smaller size as compared to the neighboring component, and there are even finer internal structures included in the interconnect. The scale difference makes conventional methods time consuming and of low efficiency. An interface model based on the micropolar theory has been developed, cf. Zhang, Y., and Larsson, R., 2007, "Interface Modelling of ACA Flip-Chip Interconnects Using Micropolar Theory and Discontinuous Approximation," Comput. Struct., 85, pp. 1500-1513, Larsson, R., and Zhang, Y., 2007, "Homogenization of Microsystem Interconnects Based on Micropolar Theory and Discontinuous Kinematics, " J. Mech. Phys. Solids, 55, pp. 819-841, aiming at predicting the interconnect behavior under thermal load, especially when there exist internal structures in the interface and the component/ structure sizes vary in a wide range. Numerical simulations, using the micropolar interface model, show a fairly good agreement between the experimental data and the numerical simulations.
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