DBC substrates are the standard circuit boardsfor power modules. Using the DBC technologythick copper foils (0.125mm - 0.Tmm) arecladded to Alumina or Aluminum Nitride,The strong adhesion of the copper to ceramicbond ...DBC substrates are the standard circuit boardsfor power modules. Using the DBC technologythick copper foils (0.125mm - 0.Tmm) arecladded to Alumina or Aluminum Nitride,The strong adhesion of the copper to ceramicbond reduces the thermal expansion coefficientin horizontal direction only slightly above theTEC of the ceramic itself. This allows directsilicon attach of large dies without using TECcontrolling layers.As DBC technology is using copper foils,integralleads overhanging the ceramic can be realized...展开更多
The accuracy of brackets placement is a key factor in successful orthodontic therapy. An in vitro study was conducted in ten models from a natural maxillary teeth model in order to compare the accuracy of brac- kets p...The accuracy of brackets placement is a key factor in successful orthodontic therapy. An in vitro study was conducted in ten models from a natural maxillary teeth model in order to compare the accuracy of brac- kets placement between two direct bonding instru- ments: the Pole-like Bracket Positioning Gauge and the Star-like Bracket Positioning Gauge. Our results have shown that: The Star-like Bracket Positioning Gauge is more precise in placing brackets vertically, whereas the Pole-like Bracket Positioning Gauge al-lows a better angulation of the bracket. Considering each tooth separately, there is no statistically signifi-cant difference between the two positioning gauges, except that the Star-like gauge gives better results in bracket’s height for the second premolar and the ca-nine, whereas the Pole-like gauge allows for a better positioning and a better vertical angulation of the brackets for the lateral incisor. No statistically signi- ficant difference was found between the two gauges on the mesiodistal position. Overall, the Star-like gau- ge showed a better accuracy in positioning brackets.展开更多
Manufacturing and integration of micro-electro-mechanical systems （MEMS） devices and integrated circuits （ICs） by wafer bonding often generate problems caused by thermal properties of materials. This paper present...Manufacturing and integration of micro-electro-mechanical systems （MEMS） devices and integrated circuits （ICs） by wafer bonding often generate problems caused by thermal properties of materials. This paper presents a low temperature wafer direct bonding process assisted by 02 plasma. Silicon wafers were treated with wet chemical cleaning and subsequently activated by 02 plasma in the etch element of a sputtering system. Then, two wafers were brought into contact in the bonder followed by annealing in N2 atmosphere for several hours. An infrared imaging system was used to detect bonding defects and a razor blade test was carried out to determine surface energy. The bonding yield reaches 90%--95% and the achieved surface energy is 1.76 J/m2 when the bonded wafers are annealed at 350 ~C in N2 atmosphere for 2 h. Void formation was systematically observed and eli-mination methods were proposed. The size and density of voids greatly depend on the annealing temperature. Short O2 plasma treatment for 60 s can alleviate void formation and enhance surface energy. A pulling test reveals that the bonding strength is more than 11.0 MPa. This low temperature wafer direct bonding process provides an efficient and reliable method for 3D integration, system on chip, and MEMS packaging.展开更多
Studies of direction of photoisomerization of retinal,retinonitrile,a- retinonitrile and a trienenitrile analog in different solvents with varying wave- lengths of excitation and reaction temperature led to the conclu...Studies of direction of photoisomerization of retinal,retinonitrile,a- retinonitrile and a trienenitrile analog in different solvents with varying wave- lengths of excitation and reaction temperature led to the conclusion that the well known solvent dependent photochemistry of retinoids is due to selective excitation of the hydrogen bonded species.展开更多
文摘DBC substrates are the standard circuit boardsfor power modules. Using the DBC technologythick copper foils (0.125mm - 0.Tmm) arecladded to Alumina or Aluminum Nitride,The strong adhesion of the copper to ceramicbond reduces the thermal expansion coefficientin horizontal direction only slightly above theTEC of the ceramic itself. This allows directsilicon attach of large dies without using TECcontrolling layers.As DBC technology is using copper foils,integralleads overhanging the ceramic can be realized...
文摘The accuracy of brackets placement is a key factor in successful orthodontic therapy. An in vitro study was conducted in ten models from a natural maxillary teeth model in order to compare the accuracy of brac- kets placement between two direct bonding instru- ments: the Pole-like Bracket Positioning Gauge and the Star-like Bracket Positioning Gauge. Our results have shown that: The Star-like Bracket Positioning Gauge is more precise in placing brackets vertically, whereas the Pole-like Bracket Positioning Gauge al-lows a better angulation of the bracket. Considering each tooth separately, there is no statistically signifi-cant difference between the two positioning gauges, except that the Star-like gauge gives better results in bracket’s height for the second premolar and the ca-nine, whereas the Pole-like gauge allows for a better positioning and a better vertical angulation of the brackets for the lateral incisor. No statistically signi- ficant difference was found between the two gauges on the mesiodistal position. Overall, the Star-like gau- ge showed a better accuracy in positioning brackets.
基金Project supported by the Foreign Cultural and Educational Experts Employing Plan,Ministry of Education,China (No. TS2010CQDX 056)the Fundamental Research Funds for the Central Universi-ties,China (No. CDJZR12135502)
文摘Manufacturing and integration of micro-electro-mechanical systems （MEMS） devices and integrated circuits （ICs） by wafer bonding often generate problems caused by thermal properties of materials. This paper presents a low temperature wafer direct bonding process assisted by 02 plasma. Silicon wafers were treated with wet chemical cleaning and subsequently activated by 02 plasma in the etch element of a sputtering system. Then, two wafers were brought into contact in the bonder followed by annealing in N2 atmosphere for several hours. An infrared imaging system was used to detect bonding defects and a razor blade test was carried out to determine surface energy. The bonding yield reaches 90%--95% and the achieved surface energy is 1.76 J/m2 when the bonded wafers are annealed at 350 ~C in N2 atmosphere for 2 h. Void formation was systematically observed and eli-mination methods were proposed. The size and density of voids greatly depend on the annealing temperature. Short O2 plasma treatment for 60 s can alleviate void formation and enhance surface energy. A pulling test reveals that the bonding strength is more than 11.0 MPa. This low temperature wafer direct bonding process provides an efficient and reliable method for 3D integration, system on chip, and MEMS packaging.
文摘Studies of direction of photoisomerization of retinal,retinonitrile,a- retinonitrile and a trienenitrile analog in different solvents with varying wave- lengths of excitation and reaction temperature led to the conclusion that the well known solvent dependent photochemistry of retinoids is due to selective excitation of the hydrogen bonded species.
