通过实验研究了印刷电路板(print circuit board,PCB)设计对小尺寸薄型封装(thin small outline package,TSOP)焊点可靠性的影响.实验制作了包含引脚焊盘的长度、焊盘的表面处理方式及背靠背的双面贴装偏移量3种设计参数的可靠性测试板...通过实验研究了印刷电路板(print circuit board,PCB)设计对小尺寸薄型封装(thin small outline package,TSOP)焊点可靠性的影响.实验制作了包含引脚焊盘的长度、焊盘的表面处理方式及背靠背的双面贴装偏移量3种设计参数的可靠性测试板,并采用表面贴装工艺(surface mount technology,SMT)将TSOP器件焊接到测试板上;经-40～85℃的高低温循环试验后,收集了TSOP引脚焊点裂纹的生长数据;讨论了焊点失效的机理,相应考虑了2种可靠性判断准则,并对各参数条件下的裂纹数据进行比较.结果表明,长尺寸焊盘、有机保焊膜(organic solderability preservatives,OSP)及不对称的两面布置方式有助于提高TSOP引脚的焊点可靠性.展开更多
The valence band offsets of the strained and longitudinally relaxed diamond/cubic boron-nitride （c-BN） （110） superlattice are investigated by the plane wave density functional theory approach and using the on-site...The valence band offsets of the strained and longitudinally relaxed diamond/cubic boron-nitride （c-BN） （110） superlattice are investigated by the plane wave density functional theory approach and using the on-site core electron as a reference energy level. For the strained diamond/c-BN superlattice, the valence band offset of around 1.50 eV is in good agreement with those using all the electrons methods. As for the longitudinally relaxed superlattice, the valence band offset of around 1.28 eV is smaller than that of the strained superlattice. The reason for this is mainly due to the split of the valence band maximum caused by the anisotropic strain.展开更多
Isotope separation by laser deflecting an atomic beam is analyzed theoretically. Interacting with a tilted one- dimensional optical molasses, an ytterbium atomic beam is split into multi-beams with different isotopes ...Isotope separation by laser deflecting an atomic beam is analyzed theoretically. Interacting with a tilted one- dimensional optical molasses, an ytterbium atomic beam is split into multi-beams with different isotopes like 172yb, Jv3yb, and J74yb. By using the numerical calculation, the dependences of the splitting angle on the molasses laser intensity and detuning are studied, and the optimal parameters for the isotope separation are also investigated. Furthermore, the isotope separation efficiency and purity are estimated. Finally a new scheme for the efficient isotope separation is proposed. These findings will give a guideline for simply obtaining pure isotopes of various elements.展开更多
The intrinsic defect of cadmium vacancy （Vcd） in cadmium telluride （CdTe） has been studied by first-principles cal- culations using potentials with both the screened hybrid functional of Heyd, Scuseria, and Ernzer...The intrinsic defect of cadmium vacancy （Vcd） in cadmium telluride （CdTe） has been studied by first-principles cal- culations using potentials with both the screened hybrid functional of Heyd, Scuseria, and Ernzerhof （HSE） approximation and the generalized gradient approximation of the Perdew-Burke-Ernzerhof form （PBE-GGA）. Both results show that the Ta structure of the Vctl defect for different charges is the most stable structure as compared with the distorted C3v structure with one hole localized at one of the four nearest Te atoms. This indicates that the John-Teller distortion （C3v） structure may be unstable in bulk CdTe crystal. The reason likely lies in the delocalized resonance nature of the t2 state of the Vcd defect. Moreover, the formation energy obtained by the HSE method is about 0.6-0.8 eV larger than that obtained by the PBE method. The transition levels calculated by the PBE method and the HSE method are similar and well consistent with the experimental results.展开更多
The Si overlayers are grown by molecular beam epitaxy on atomically smllth Er_(2)O_(3)(111)films prepared on Si(111)substrates.Single crystalline Si overlayers are achieved and are evident due to the spot-like reflect...The Si overlayers are grown by molecular beam epitaxy on atomically smllth Er_(2)O_(3)(111)films prepared on Si(111)substrates.Single crystalline Si overlayers are achieved and are evident due to the spot-like reflective high energy electron diffraction(RHEED)patterns and x-ray diffraction patterns.The epitaxial relationship of the Si overlayer along the surface with respect to the orientation of Er_(2)O_(3)and the Si substrate is as follows:overgrown Si(111)//Er_(2)O_(3)(111)//Si(111).The rough surface of Si overlayers,as identified by both RHEED patterns and atomic force microscopy images,indicates a three-dimensional growth mode.The reason for this is based on the interfacial energy argument.Further growth of Er_(2)O_(3)films on this rough Si overlayer leads to the polycrystalline nature of the topmost Er2O3 layer.展开更多
文摘通过实验研究了印刷电路板(print circuit board,PCB)设计对小尺寸薄型封装(thin small outline package,TSOP)焊点可靠性的影响.实验制作了包含引脚焊盘的长度、焊盘的表面处理方式及背靠背的双面贴装偏移量3种设计参数的可靠性测试板,并采用表面贴装工艺(surface mount technology,SMT)将TSOP器件焊接到测试板上;经-40～85℃的高低温循环试验后,收集了TSOP引脚焊点裂纹的生长数据;讨论了焊点失效的机理,相应考虑了2种可靠性判断准则,并对各参数条件下的裂纹数据进行比较.结果表明,长尺寸焊盘、有机保焊膜(organic solderability preservatives,OSP)及不对称的两面布置方式有助于提高TSOP引脚的焊点可靠性.
基金supported by the National Natural Science Foundation of China (Grant No.60877017)the Innovation Program of Shanghai Municipal Education Commission (Grant No.08YZ04)the Shanghai Leading Academic Discipline Project (Grant No.S30107)
文摘The valence band offsets of the strained and longitudinally relaxed diamond/cubic boron-nitride （c-BN） （110） superlattice are investigated by the plane wave density functional theory approach and using the on-site core electron as a reference energy level. For the strained diamond/c-BN superlattice, the valence band offset of around 1.50 eV is in good agreement with those using all the electrons methods. As for the longitudinally relaxed superlattice, the valence band offset of around 1.28 eV is smaller than that of the strained superlattice. The reason for this is mainly due to the split of the valence band maximum caused by the anisotropic strain.
基金Project supported by the National Basic Research Program of China （Grant No. 2012CB821302）, the National Natural Science Foundation of China （Grant Nos. 11134003 and 10774044）, and the Shanghai Excellent Academic Leaders Program, China （Grant No. 12XD1402400）.
文摘Isotope separation by laser deflecting an atomic beam is analyzed theoretically. Interacting with a tilted one- dimensional optical molasses, an ytterbium atomic beam is split into multi-beams with different isotopes like 172yb, Jv3yb, and J74yb. By using the numerical calculation, the dependences of the splitting angle on the molasses laser intensity and detuning are studied, and the optimal parameters for the isotope separation are also investigated. Furthermore, the isotope separation efficiency and purity are estimated. Finally a new scheme for the efficient isotope separation is proposed. These findings will give a guideline for simply obtaining pure isotopes of various elements.
基金supported by the National Natural Science Foundation of China(Grant No.A050506)the Innovation Program of Shanghai Municipal Education Commission,China(Grant No.12ZZ096)+1 种基金the Shanghai Leading Academic Disciplines,China(Grant No.S30107)the Science and Technology Commissionof Shanghai,China(Grant No.11530500200)
文摘The intrinsic defect of cadmium vacancy （Vcd） in cadmium telluride （CdTe） has been studied by first-principles cal- culations using potentials with both the screened hybrid functional of Heyd, Scuseria, and Ernzerhof （HSE） approximation and the generalized gradient approximation of the Perdew-Burke-Ernzerhof form （PBE-GGA）. Both results show that the Ta structure of the Vctl defect for different charges is the most stable structure as compared with the distorted C3v structure with one hole localized at one of the four nearest Te atoms. This indicates that the John-Teller distortion （C3v） structure may be unstable in bulk CdTe crystal. The reason likely lies in the delocalized resonance nature of the t2 state of the Vcd defect. Moreover, the formation energy obtained by the HSE method is about 0.6-0.8 eV larger than that obtained by the PBE method. The transition levels calculated by the PBE method and the HSE method are similar and well consistent with the experimental results.
基金Supported by the Key Basic Research of Science and Technology Commission of Shanghai Municipality(10JC1405900)and Shanghai Leading Academic Disciplines(S30107)。
文摘The Si overlayers are grown by molecular beam epitaxy on atomically smllth Er_(2)O_(3)(111)films prepared on Si(111)substrates.Single crystalline Si overlayers are achieved and are evident due to the spot-like reflective high energy electron diffraction(RHEED)patterns and x-ray diffraction patterns.The epitaxial relationship of the Si overlayer along the surface with respect to the orientation of Er_(2)O_(3)and the Si substrate is as follows:overgrown Si(111)//Er_(2)O_(3)(111)//Si(111).The rough surface of Si overlayers,as identified by both RHEED patterns and atomic force microscopy images,indicates a three-dimensional growth mode.The reason for this is based on the interfacial energy argument.Further growth of Er_(2)O_(3)films on this rough Si overlayer leads to the polycrystalline nature of the topmost Er2O3 layer.
