The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Li Cheng - One of the best experts on this subject based on the ideXlab platform.
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Vapor Pressure assisted crack growth at interfaces under mixed mode loading
Computational Materials Science, 2004Co-Authors: C. W. Chong, Tianfu Guo, Li ChengAbstract:Abstract Moisture diffuses into the numerous pores and cavities formed in polymeric molding compounds, at the filler particle–polymer matrix interfaces and at polymer–silicon interfaces of IC packages. During reflow soldering, the rapidly expanding moisture generates High internal Pressures within the voids which are comparable to yield strengths of the molding compounds at glass transition temperatures. The combined action of thermal stresses and High Vapor Pressure accelerates void growth, and ultimately leads to interface delamination and package cracking. In this study, the molding compound is taken to be an elastic–plastic material while the silicon substrate is treated as an elastic material. The extended Gurson model which incorporates Vapor Pressure as an internal variable is used to characterize the void growth and coalescence process at the interface. When the mode II loading is dominant, High Vapor Pressure can cause several-fold reduction in the interface fracture toughness.
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Vapor Pressure Assisted Void Growth and Cracking of Polymeric Films and Interfaces
Interface Science, 2003Co-Authors: Li Cheng, Tianfu GuoAbstract:Pores and cavities form at filler particle-polymer matrix interfaces, at polymer film-silicon substrate interfaces as well as in molding compounds of IC packages. Moisture diffuses to these voids. During reflow soldering, surface mount plastic encapsulated devices are exposed to temperatures between 210 to 260°C. At these temperatures, the condensed moisture Vaporizes. The rapidly expanding water Vapor can create internal Pressures within the voids that reach 3–6 MPa. These levels are comparable to the yield strengths of epoxy molding compounds and epoxy adhesives, whose glass transition temperatures T g range between 150 to 300°C. Under the combined action of thermal stress and High Vapor Pressure (relative to the yield strength at T g), both pre-existing and newly nucleated voids grow rapidly and coalesce. In extreme situations, Vapor Pressure alone could drive voids to grow and coalesce unstably causing film rupture, film-substrate interface delamination and cracking of the plastic package. Vapor Pressure effects on void growth have been incorporated into Gurson's porous material model and a cohesive law. Crack growth resistance-curve calculations using these models show that High Vapor Pressure combined with High porosity bring about severe reduction in the fracture toughness. In some cases, High Vapor Pressure accelerates void growth and coalescence resulting in brittle-like interface delamination. Vapor Pressure also contributes a strong tensile mode component to an otherwise shear dominated interface loading. An example of Vapor Pressure related IC package failure, known as “popcorn” cracking, is discussed.
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Modeling Vapor Pressure effects on void rupture and crack growth resistance
Acta Materialia, 2002Co-Authors: Tianfu Guo, Li ChengAbstract:The phenomenon of Vapor Pressure assisted void growth and rupture is studied. Plastic electronic packages absorb moisture which condenses within numerous micropores in the substrate, solder mask and die attach materials as well as near their interfaces. During reflow soldering, the condensed moisture Vaporizes with the result that these micropores as well as interfaces are subjected to High Vapor Pressure. Under extreme conditions, our study suggests that Vapor Pressures can attain High enough levels to drive the voids to grow to rupture, thereby causing package failure. Under other conditions, residual/thermal stresses assisted by Vapor Pressure can cause crack growth within the polymeric materials as well as along interfaces. Vapor Pressure effects on void growth have been incorporated into the Gurson model for porous ductile material. Using this model, a finite element study shows that the combination of High Vapor Pressure and High porosity is very detrimental to fracture toughness.
Tianfu Guo - One of the best experts on this subject based on the ideXlab platform.
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Vapor Pressure assisted crack growth at interfaces under mixed mode loading
Computational Materials Science, 2004Co-Authors: C. W. Chong, Tianfu Guo, Li ChengAbstract:Abstract Moisture diffuses into the numerous pores and cavities formed in polymeric molding compounds, at the filler particle–polymer matrix interfaces and at polymer–silicon interfaces of IC packages. During reflow soldering, the rapidly expanding moisture generates High internal Pressures within the voids which are comparable to yield strengths of the molding compounds at glass transition temperatures. The combined action of thermal stresses and High Vapor Pressure accelerates void growth, and ultimately leads to interface delamination and package cracking. In this study, the molding compound is taken to be an elastic–plastic material while the silicon substrate is treated as an elastic material. The extended Gurson model which incorporates Vapor Pressure as an internal variable is used to characterize the void growth and coalescence process at the interface. When the mode II loading is dominant, High Vapor Pressure can cause several-fold reduction in the interface fracture toughness.
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Vapor Pressure Assisted Void Growth and Cracking of Polymeric Films and Interfaces
Interface Science, 2003Co-Authors: Li Cheng, Tianfu GuoAbstract:Pores and cavities form at filler particle-polymer matrix interfaces, at polymer film-silicon substrate interfaces as well as in molding compounds of IC packages. Moisture diffuses to these voids. During reflow soldering, surface mount plastic encapsulated devices are exposed to temperatures between 210 to 260°C. At these temperatures, the condensed moisture Vaporizes. The rapidly expanding water Vapor can create internal Pressures within the voids that reach 3–6 MPa. These levels are comparable to the yield strengths of epoxy molding compounds and epoxy adhesives, whose glass transition temperatures T g range between 150 to 300°C. Under the combined action of thermal stress and High Vapor Pressure (relative to the yield strength at T g), both pre-existing and newly nucleated voids grow rapidly and coalesce. In extreme situations, Vapor Pressure alone could drive voids to grow and coalesce unstably causing film rupture, film-substrate interface delamination and cracking of the plastic package. Vapor Pressure effects on void growth have been incorporated into Gurson's porous material model and a cohesive law. Crack growth resistance-curve calculations using these models show that High Vapor Pressure combined with High porosity bring about severe reduction in the fracture toughness. In some cases, High Vapor Pressure accelerates void growth and coalescence resulting in brittle-like interface delamination. Vapor Pressure also contributes a strong tensile mode component to an otherwise shear dominated interface loading. An example of Vapor Pressure related IC package failure, known as “popcorn” cracking, is discussed.
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Modeling Vapor Pressure effects on void rupture and crack growth resistance
Acta Materialia, 2002Co-Authors: Tianfu Guo, Li ChengAbstract:The phenomenon of Vapor Pressure assisted void growth and rupture is studied. Plastic electronic packages absorb moisture which condenses within numerous micropores in the substrate, solder mask and die attach materials as well as near their interfaces. During reflow soldering, the condensed moisture Vaporizes with the result that these micropores as well as interfaces are subjected to High Vapor Pressure. Under extreme conditions, our study suggests that Vapor Pressures can attain High enough levels to drive the voids to grow to rupture, thereby causing package failure. Under other conditions, residual/thermal stresses assisted by Vapor Pressure can cause crack growth within the polymeric materials as well as along interfaces. Vapor Pressure effects on void growth have been incorporated into the Gurson model for porous ductile material. Using this model, a finite element study shows that the combination of High Vapor Pressure and High porosity is very detrimental to fracture toughness.
Juping Ding - One of the best experts on this subject based on the ideXlab platform.
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The Response of Water Dynamics to Long-Term High Vapor Pressure Deficit Is Mediated by Anatomical Adaptations in Plants.
Frontiers in plant science, 2020Co-Authors: Xiaocong Jiao, Xiaoming Song, Jiayu Zhang, Ping Bai, Juping DingAbstract:Vapor Pressure deficit (VPD) is the driver of water movement in plants. However, little is known about how anatomical adaptations determine the acclimation of plant water dynamics to elevated VPD, especially at the whole plant level. Here, we examined the responses of transpiration, stomatal conductance (gs), hydraulic partitioning, and anatomical traits in two tomato cultivars (Jinpeng and Zhongza) to long-term High (2.2-2.6 kPa) and low (1.1-1.5 kPa) VPD. Compared to plants growing under low VPD, no variation in gs was found for Jinpeng under High VPD conditions; however, High VPD induced an increase in whole plant hydraulic conductance (Kplant), which was responsible for the maintenance of High transpiration. In contrast, transpiration was not influenced by High VPD in Zhongza, which was primarily attributed to a coordinated decline in gs and Kplant. The changes in gs were closely related to stomatal density and size. Furthermore, High VPD altered hydraulic partitioning among the leaf, stem, and root for both cultivars via adjustments in anatomy. The increase in lumen area of vessels in veins and large roots in Jinpeng under High VPD conditions improved water transport efficiency in the leaf and root, thus resulting in a High Kplant. However, the decreased Kplant for Zhongza under High VPD was the result of a decline of water transport efficiency in the leaf that was caused by a reduction in vein density. Overall, we concluded that the tradeoff in anatomical acclimations among plant tissues results in different water relations in plants under High VPD conditions.
Xiaocong Jiao - One of the best experts on this subject based on the ideXlab platform.
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The Response of Water Dynamics to Long-Term High Vapor Pressure Deficit Is Mediated by Anatomical Adaptations in Plants.
Frontiers in plant science, 2020Co-Authors: Xiaocong Jiao, Xiaoming Song, Jiayu Zhang, Ping Bai, Juping DingAbstract:Vapor Pressure deficit (VPD) is the driver of water movement in plants. However, little is known about how anatomical adaptations determine the acclimation of plant water dynamics to elevated VPD, especially at the whole plant level. Here, we examined the responses of transpiration, stomatal conductance (gs), hydraulic partitioning, and anatomical traits in two tomato cultivars (Jinpeng and Zhongza) to long-term High (2.2-2.6 kPa) and low (1.1-1.5 kPa) VPD. Compared to plants growing under low VPD, no variation in gs was found for Jinpeng under High VPD conditions; however, High VPD induced an increase in whole plant hydraulic conductance (Kplant), which was responsible for the maintenance of High transpiration. In contrast, transpiration was not influenced by High VPD in Zhongza, which was primarily attributed to a coordinated decline in gs and Kplant. The changes in gs were closely related to stomatal density and size. Furthermore, High VPD altered hydraulic partitioning among the leaf, stem, and root for both cultivars via adjustments in anatomy. The increase in lumen area of vessels in veins and large roots in Jinpeng under High VPD conditions improved water transport efficiency in the leaf and root, thus resulting in a High Kplant. However, the decreased Kplant for Zhongza under High VPD was the result of a decline of water transport efficiency in the leaf that was caused by a reduction in vein density. Overall, we concluded that the tradeoff in anatomical acclimations among plant tissues results in different water relations in plants under High VPD conditions.
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Stomatal responses to long-term High Vapor Pressure deficits mediated most limitation of photosynthesis in tomatoes
Acta Physiologiae Plantarum, 2018Co-Authors: Guoming Xing, Xiaocong Jiao, Xiaoming SongAbstract:Plants grown at High Vapor Pressure deficit (VPD) usually present decreased photosynthesis, but stomatal and mesophyll limitation to photosynthesis remain poorly quantified. To better understand the regulation of High VPD on photosynthesis and plant growth in tomatoes, we investigated the limitation of stomatal conductance and mesophyll conductance to photosynthesis and relative importance of stomatal morphology and function in stomatal conductance. Both the net photosynthesis rate and total biomass were significantly limited by High VPD. Meanwhile, stomatal conductance and mesophyll conductance were decreased under High VPD. The stomatal conductance limitation was responsible for 60% of the total photosynthetic limitation. Moreover, a reduction in stomatal density and stomatal size occurred under High VPD, which was significantly correlated with the down-regulation of stomatal conductance. The stomatal morphology contributed to more than half the change in stomatal conductance. Nevertheless, stomatal movement was also an important factor in regulating stomatal conductance. The decrease of hydraulic conductance and transpiration rate with no significant difference in relative water content, leaf water potential, and/or osmotic potential suggested passive hydraulic regulation in the feedforward responses of stomata to High VPD.
Xiaoming Song - One of the best experts on this subject based on the ideXlab platform.
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The Response of Water Dynamics to Long-Term High Vapor Pressure Deficit Is Mediated by Anatomical Adaptations in Plants.
Frontiers in plant science, 2020Co-Authors: Xiaocong Jiao, Xiaoming Song, Jiayu Zhang, Ping Bai, Juping DingAbstract:Vapor Pressure deficit (VPD) is the driver of water movement in plants. However, little is known about how anatomical adaptations determine the acclimation of plant water dynamics to elevated VPD, especially at the whole plant level. Here, we examined the responses of transpiration, stomatal conductance (gs), hydraulic partitioning, and anatomical traits in two tomato cultivars (Jinpeng and Zhongza) to long-term High (2.2-2.6 kPa) and low (1.1-1.5 kPa) VPD. Compared to plants growing under low VPD, no variation in gs was found for Jinpeng under High VPD conditions; however, High VPD induced an increase in whole plant hydraulic conductance (Kplant), which was responsible for the maintenance of High transpiration. In contrast, transpiration was not influenced by High VPD in Zhongza, which was primarily attributed to a coordinated decline in gs and Kplant. The changes in gs were closely related to stomatal density and size. Furthermore, High VPD altered hydraulic partitioning among the leaf, stem, and root for both cultivars via adjustments in anatomy. The increase in lumen area of vessels in veins and large roots in Jinpeng under High VPD conditions improved water transport efficiency in the leaf and root, thus resulting in a High Kplant. However, the decreased Kplant for Zhongza under High VPD was the result of a decline of water transport efficiency in the leaf that was caused by a reduction in vein density. Overall, we concluded that the tradeoff in anatomical acclimations among plant tissues results in different water relations in plants under High VPD conditions.
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Stomatal responses to long-term High Vapor Pressure deficits mediated most limitation of photosynthesis in tomatoes
Acta Physiologiae Plantarum, 2018Co-Authors: Guoming Xing, Xiaocong Jiao, Xiaoming SongAbstract:Plants grown at High Vapor Pressure deficit (VPD) usually present decreased photosynthesis, but stomatal and mesophyll limitation to photosynthesis remain poorly quantified. To better understand the regulation of High VPD on photosynthesis and plant growth in tomatoes, we investigated the limitation of stomatal conductance and mesophyll conductance to photosynthesis and relative importance of stomatal morphology and function in stomatal conductance. Both the net photosynthesis rate and total biomass were significantly limited by High VPD. Meanwhile, stomatal conductance and mesophyll conductance were decreased under High VPD. The stomatal conductance limitation was responsible for 60% of the total photosynthetic limitation. Moreover, a reduction in stomatal density and stomatal size occurred under High VPD, which was significantly correlated with the down-regulation of stomatal conductance. The stomatal morphology contributed to more than half the change in stomatal conductance. Nevertheless, stomatal movement was also an important factor in regulating stomatal conductance. The decrease of hydraulic conductance and transpiration rate with no significant difference in relative water content, leaf water potential, and/or osmotic potential suggested passive hydraulic regulation in the feedforward responses of stomata to High VPD.