Miniaturization of electronic package leads to high heat density and heat accumulation in electronics device, resulting in short life time and premature failure of the device. Junction temperature and thermal resistan...Miniaturization of electronic package leads to high heat density and heat accumulation in electronics device, resulting in short life time and premature failure of the device. Junction temperature and thermal resistance are the critical parameters that determine the thermal management and reliability in electronics cooling. Metal oxide field effect transistor（MOSFET）is an important semiconductor device for light emitting diode-integrated circuit（LED IC） driver application, and thermal management in MOSFET is a major challenge. In this study, investigations on thermal performance of MOSFET are performed for evaluating the junction temperature and thermal resistance. Suitable modifications in FR4 substrates are proposed by introducing thermal vias and copper layer coating to improve the thermal performance of MOSFET. Experiments are conducted using thermal transient tester（T3ster） at 2.0 A input current and ambient temperature varying from25℃ to 75℃. The thermal parameters are measured for three proposed designs： FR4 with circular thermal vias, FR4 with single strip of copper layer and embedded vias, and FR4 with I-shaped copper layer, and compared with that of plain FR4 substrate. From the experimental results, FR4I-shaped shows promising results by 33.71% reduction in junction temperature and 54.19% reduction in thermal resistance. For elevated temperature, the relative increases in junction temperature and thermal resistance are lower for FR4I-shaped than those for other substrates considered. The introduction of thermal vias and copper layer plays a significant role in thermal performance.展开更多
Controlling the tissue temperature rise during retinal laser therapy is essential for predictable outcomes,especially at non-damaging settings.We demonstrate a method for determining the temperature rise in the retina...Controlling the tissue temperature rise during retinal laser therapy is essential for predictable outcomes,especially at non-damaging settings.We demonstrate a method for determining the temperature rise in the retina using phasesensitive optical coherence tomography(pOCT)in vivo.Measurements based on the thermally induced optical path length changes(ΔOPL)in the retina during a 10-ms laser pulse allow detection of the temperature rise with a precision less than 1℃,which is sufficient for calibration of the laser power for patient-specific non-damaging therapy.We observed a significant difference in confinement of the retinal deformations between the normal and the degenerate retina:in wild-type rats,thermal deformations are localized between the retinal pigment epithelium(RPE)and the photoreceptors’inner segments(IS),as opposed to a deep penetration of the deformations into the inner retinal layers in the degenerate retina.This implies the presence of a structural component within healthy photoreceptors that dampens the tissue expansion induced by the laser heating of the RPE and pigmented choroid.We hypothesize that the thin and soft cilium connecting the inner and outer segments(IS,OS)of photoreceptors may absorb the deformations of the OS and thereby preclude the tissue expansion further inward.Striking difference in the confinement of the retinal deformations induced by a laser pulse in healthy and degenerate retina may be used as a biomechanical diagnostic tool for the characterization of photoreceptors degeneration.展开更多
基金Project supported by the Collaborative Research in Engineering,Science&Technology(Grant No.P28C2-13)
文摘Miniaturization of electronic package leads to high heat density and heat accumulation in electronics device, resulting in short life time and premature failure of the device. Junction temperature and thermal resistance are the critical parameters that determine the thermal management and reliability in electronics cooling. Metal oxide field effect transistor（MOSFET）is an important semiconductor device for light emitting diode-integrated circuit（LED IC） driver application, and thermal management in MOSFET is a major challenge. In this study, investigations on thermal performance of MOSFET are performed for evaluating the junction temperature and thermal resistance. Suitable modifications in FR4 substrates are proposed by introducing thermal vias and copper layer coating to improve the thermal performance of MOSFET. Experiments are conducted using thermal transient tester（T3ster） at 2.0 A input current and ambient temperature varying from25℃ to 75℃. The thermal parameters are measured for three proposed designs： FR4 with circular thermal vias, FR4 with single strip of copper layer and embedded vias, and FR4 with I-shaped copper layer, and compared with that of plain FR4 substrate. From the experimental results, FR4I-shaped shows promising results by 33.71% reduction in junction temperature and 54.19% reduction in thermal resistance. For elevated temperature, the relative increases in junction temperature and thermal resistance are lower for FR4I-shaped than those for other substrates considered. The introduction of thermal vias and copper layer plays a significant role in thermal performance.
基金funded by the National Institutes of Health(U01 EY032055)Air Force Office of Scientific Research(FA9550-20-1-0186)Research to Prevent Blindness.
文摘Controlling the tissue temperature rise during retinal laser therapy is essential for predictable outcomes,especially at non-damaging settings.We demonstrate a method for determining the temperature rise in the retina using phasesensitive optical coherence tomography(pOCT)in vivo.Measurements based on the thermally induced optical path length changes(ΔOPL)in the retina during a 10-ms laser pulse allow detection of the temperature rise with a precision less than 1℃,which is sufficient for calibration of the laser power for patient-specific non-damaging therapy.We observed a significant difference in confinement of the retinal deformations between the normal and the degenerate retina:in wild-type rats,thermal deformations are localized between the retinal pigment epithelium(RPE)and the photoreceptors’inner segments(IS),as opposed to a deep penetration of the deformations into the inner retinal layers in the degenerate retina.This implies the presence of a structural component within healthy photoreceptors that dampens the tissue expansion induced by the laser heating of the RPE and pigmented choroid.We hypothesize that the thin and soft cilium connecting the inner and outer segments(IS,OS)of photoreceptors may absorb the deformations of the OS and thereby preclude the tissue expansion further inward.Striking difference in the confinement of the retinal deformations induced by a laser pulse in healthy and degenerate retina may be used as a biomechanical diagnostic tool for the characterization of photoreceptors degeneration.
