The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Wu Z. - One of the best experts on this subject based on the ideXlab platform.
-
Finite Element Analysis of Bondline Effects on Multilayer Ultrasonic Transducers
2005Co-Authors: Wu Z., Mcrobbie G., Cochra S., Kno E., Gallaghe S.Abstract:The use of multiple active layers within an ultrasonic transducer permits the designer an additional degree of freedom compared with single active layer configurations. Amongst other advantages, this can be exploited to reduce the electrical impedance of the transducer or to increase the mechanical output for a given input voltage. However, unless a co-fired piezoceramic configuration is used, multiple active layers must be bonded together with adhesives and the Bondlines will detract from the performance of the device. Hence, detailed studies of bondline behaviour and effects are of importance within this area of research. This paper reports one such study. The practical configuration under investigation comprised two layers of lead metaniobate piezoelectric ceramic bonded together with a hard-setting epoxy potting compound. This configuration was chosen rather than the more modern use of multilayer piezocomposite material because it is relatively easy to obtain high-quality Bondlines between continuous ceramic and lead metaniobate suffers relatively little from interfering width-vibrational modes. Two basic finite element analysis model configurations were set up. The first included a uniform thickness bondline, with the actual thickness dimension set to 10.36 m in accordance with a fitting procedure described elsewhere. The second configuration included a bondline designed to match a measured surface profile. The measurement provided data with a 9.06 m peak-to-peak excursion sampled at 800 points/mm. For the purposes of modelling, these data were processed to provide a peak-to-peak excursion of 8 m sampled at 100 points/mm. Both models were run for three different bondline thicknesses, with the surface profile scaled to match the total thickness, generating electrical impedance data and surface displacements. Excellent agreement was found between both sets of modelled data and experimental measurements when the fitted thickness dimension was used. This provides an initial indication that surface roughness of levels similar to the total bondline thickness does not need to be taken into account in FEA modelling. However, when the bondline thicknesses and surface roughnesses were increased, it was found that significantly smaller surface displacements were obtained with the uniform bondline thickness model. The reasons for this require further investigation, but in the interim, the results indicate that care must be taken to ensure thin Bondlines in multilayer piezoelectric configurations
-
Nondestructive and Destructive Investigation of Bondlines for High-power Multilayer Ultrasonic Transducers for Underwater Sonar
2005Co-Authors: Wu Z., Mcrobbie G., Cochra S., Kirk K.j.Abstract:Ultrasonic transducers with prestressed mass-spring structures are often used for high power underwater projection in the 20 - 50 kHz frequency range but with the limitation of narrow bandwidth. Multilayer piezoceramic or piezocomposite transducers without prestressing may help solve this problem but will require Bondlines able to withstand strong tensile forces. This paper, therefore, reports a systematic investigation of bondline failure encompassing experimental measurements and theoretical analysis. Three different adhesives were investigated, a potting compound, a structural adhesive, and an electricallyconductive adhesive. In this investigation, a series of two-layer length-extensional mode PZT-5H piezoceramic structures were manufactured with the original silver electrodes fired onto the material during ceramic manufacture as the bonding surfaces. The specimens were subjected to static tensile testing at ambient temperature and elevated temperatures up to 100°C, with the failure forces and the bonding surface conditions after failure recorded. Finite element analysis was also used to calculate the tensile stress amplitudes under high levels of static and dynamic electric field excitation. These simulations were then used to analyze possible critical values under various conditions when combined with the experimental results
-
Piezocomposite Transducers for Operation in 15-25 kHz Range
2004Co-Authors: Abra A., Cochra S., Choi D., Kirk K., Marin-franch P., Skea A., Walsh M.p., Wu Z.Abstract:The demands on underwater sonar transducer performance have increased in recent years, as the capabilities of modern electronics have increased. Broad bandwidths and high source level are now in demand at low frequencies, in turn calling for transducers in which materials, composition and geometry are exploited innovatively. In this paper, we report initial finite element analysis (FEA) studies for a piezocomposite transducer exhibiting promising results in the 15-25 kHz frequency range. Measurements taken in air and underwater at various excitation signal levels compare well with the theoretical predictions. Key results are presented to demonstrate the TVR, RVS and beam width of the prototype device. Previous work on optimisation of multilayer designs suggested that the new design may be further improved by varying its properties layer-to-layer. We discuss this and indicate potential performance improvements. Bondlines are another important issue in multilayer devices and their effects are carefully considered
B. Michel - One of the best experts on this subject based on the ideXlab platform.
-
HIGH PERFORMANCE THERMAL INTERFACE TECHNOLOGY OVERVIEW
2007Co-Authors: R. Linderman, T. Brunschwiler, B. Smith, B. MichelAbstract:An overview on recent developments in thermal interfaces is given with a focus on a novel thermal interface technology that allows the formation of 2-3 times thinner Bondlines with strongly improved thermal properties at lower assembly pressures. This is achieved using nested hierarchical surface channels to control the particle stacking with highly particle-filled materials. Reliability testing with thermal cycling has also demonstrated a decrease in thermal resistance after extended times with longer overall lifetime compared to a flat interface.
. Michel - One of the best experts on this subject based on the ideXlab platform.
-
High Performance Thermal Interface Technology Overview
2008Co-Authors: Linderma R., Unschwile T., . Smith, . MichelAbstract:An overview on recent developments in thermal interfaces is given with a focus on a novel thermal interface technology that allows the formation of 2-3 times thinner Bondlines with strongly improved thermal properties at lower assembly pressures. This is achieved using nested hierarchical surface channels to control the particle stacking with highly particle-filled materials. Reliability testing with thermal cycling has also demonstrated a decrease in thermal resistance after extended times with longer overall lifetime compared to a flat interface.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions
Mingyu Li - One of the best experts on this subject based on the ideXlab platform.
-
Low Temperature Bonding by Infiltrating Sn3.5Ag Solder into Porous Ag Sheet for High Temperature Die Attachment in Power Device Packaging
Scientific Reports, 2018Co-Authors: Chunjin Hang, Junjian He, Zhihao Zhang, Hongtao Chen, Mingyu LiAbstract:We have proposed a high temperature die attach method with porous Ag sheet as an interlayer for power device packaging. Sn-3.5Ag solder paste can infiltrate into the porous Ag sheet through capillary forces and Sn can react with the porous Ag sheet and Ag metallizations at the interfaces to form Ag3Sn after reflow at 260 °C for 10 min. The large specific surface area and the high diffusion rates between Ag and Sn accelerate the Sn consumption in the porous Ag structure, thus significantly reducing the processing time. The difference of the melting points of the die attach material before and after reflow could be expanded as large as 259 °C. The Bondlines show good electrical and thermal conductivities. Furthermore, the average shear strength of the Bondlines at 300 °C is higher than 20 MPa. The porous Ag skeleton remained in the bondline would contribute greatly to the heat dissipation and the electrical signal transmission in power devices.
Cochra S. - One of the best experts on this subject based on the ideXlab platform.
-
Finite Element Analysis of Bondline Effects on Multilayer Ultrasonic Transducers
2005Co-Authors: Wu Z., Mcrobbie G., Cochra S., Kno E., Gallaghe S.Abstract:The use of multiple active layers within an ultrasonic transducer permits the designer an additional degree of freedom compared with single active layer configurations. Amongst other advantages, this can be exploited to reduce the electrical impedance of the transducer or to increase the mechanical output for a given input voltage. However, unless a co-fired piezoceramic configuration is used, multiple active layers must be bonded together with adhesives and the Bondlines will detract from the performance of the device. Hence, detailed studies of bondline behaviour and effects are of importance within this area of research. This paper reports one such study. The practical configuration under investigation comprised two layers of lead metaniobate piezoelectric ceramic bonded together with a hard-setting epoxy potting compound. This configuration was chosen rather than the more modern use of multilayer piezocomposite material because it is relatively easy to obtain high-quality Bondlines between continuous ceramic and lead metaniobate suffers relatively little from interfering width-vibrational modes. Two basic finite element analysis model configurations were set up. The first included a uniform thickness bondline, with the actual thickness dimension set to 10.36 m in accordance with a fitting procedure described elsewhere. The second configuration included a bondline designed to match a measured surface profile. The measurement provided data with a 9.06 m peak-to-peak excursion sampled at 800 points/mm. For the purposes of modelling, these data were processed to provide a peak-to-peak excursion of 8 m sampled at 100 points/mm. Both models were run for three different bondline thicknesses, with the surface profile scaled to match the total thickness, generating electrical impedance data and surface displacements. Excellent agreement was found between both sets of modelled data and experimental measurements when the fitted thickness dimension was used. This provides an initial indication that surface roughness of levels similar to the total bondline thickness does not need to be taken into account in FEA modelling. However, when the bondline thicknesses and surface roughnesses were increased, it was found that significantly smaller surface displacements were obtained with the uniform bondline thickness model. The reasons for this require further investigation, but in the interim, the results indicate that care must be taken to ensure thin Bondlines in multilayer piezoelectric configurations
-
Nondestructive and Destructive Investigation of Bondlines for High-power Multilayer Ultrasonic Transducers for Underwater Sonar
2005Co-Authors: Wu Z., Mcrobbie G., Cochra S., Kirk K.j.Abstract:Ultrasonic transducers with prestressed mass-spring structures are often used for high power underwater projection in the 20 - 50 kHz frequency range but with the limitation of narrow bandwidth. Multilayer piezoceramic or piezocomposite transducers without prestressing may help solve this problem but will require Bondlines able to withstand strong tensile forces. This paper, therefore, reports a systematic investigation of bondline failure encompassing experimental measurements and theoretical analysis. Three different adhesives were investigated, a potting compound, a structural adhesive, and an electricallyconductive adhesive. In this investigation, a series of two-layer length-extensional mode PZT-5H piezoceramic structures were manufactured with the original silver electrodes fired onto the material during ceramic manufacture as the bonding surfaces. The specimens were subjected to static tensile testing at ambient temperature and elevated temperatures up to 100°C, with the failure forces and the bonding surface conditions after failure recorded. Finite element analysis was also used to calculate the tensile stress amplitudes under high levels of static and dynamic electric field excitation. These simulations were then used to analyze possible critical values under various conditions when combined with the experimental results
-
Piezocomposite Transducers for Operation in 15-25 kHz Range
2004Co-Authors: Abra A., Cochra S., Choi D., Kirk K., Marin-franch P., Skea A., Walsh M.p., Wu Z.Abstract:The demands on underwater sonar transducer performance have increased in recent years, as the capabilities of modern electronics have increased. Broad bandwidths and high source level are now in demand at low frequencies, in turn calling for transducers in which materials, composition and geometry are exploited innovatively. In this paper, we report initial finite element analysis (FEA) studies for a piezocomposite transducer exhibiting promising results in the 15-25 kHz frequency range. Measurements taken in air and underwater at various excitation signal levels compare well with the theoretical predictions. Key results are presented to demonstrate the TVR, RVS and beam width of the prototype device. Previous work on optimisation of multilayer designs suggested that the new design may be further improved by varying its properties layer-to-layer. We discuss this and indicate potential performance improvements. Bondlines are another important issue in multilayer devices and their effects are carefully considered