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SOD-523二极管引脚可焊性提升研究
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作者 陶金 黄坤 周钢 《新技术新工艺》 2023年第3期13-19,共7页
目前SMT所用的元器件正朝着微小化发展,PCB板上的元件密度也日渐增大。超微型SOD-523二极管因电性能优良且封装尺寸小等优点,广泛应用于模块电源等产品中。针对SOD-523二极管回流焊后常见的引脚爬锡不良问题,开展该元件引脚可焊性提升... 目前SMT所用的元器件正朝着微小化发展,PCB板上的元件密度也日渐增大。超微型SOD-523二极管因电性能优良且封装尺寸小等优点,广泛应用于模块电源等产品中。针对SOD-523二极管回流焊后常见的引脚爬锡不良问题,开展该元件引脚可焊性提升工艺研究。首先采用外观检测分析、EDS分析、金相切片分析及引脚润湿性分析的手段确认引脚镀层不完整、塑封壳设计存在缺陷;其次通过扩大钢网开孔内距与阶梯钢网的工艺手段进行可焊性提升,虽然解决了该元件引脚爬锡不良问题,但阶梯钢网的使用影响了该元件周围焊盘的印刷锡量,并不适用于生产实际;最后通过元件制程改善创新,将镀层不完整区域由引脚端面上部转移到引脚端面下部,同时强调对塑封壳底部多余塑封材料的去除,从根源上解决了SOD-523二极管引脚可焊性差的问题。 展开更多
关键词 SOD-523 回流焊 可焊性 阶梯钢网 元件制程
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Finite element analysis of rolling process for variable cross-section blade 被引量:2
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作者 孔祥伟 李佳 礼宾 《Journal of Central South University》 SCIE EI CAS 2013年第12期3431-3436,共6页
Due to the variation of the blade cross-section, the deformation stress and strain of the workpiece keep changing during the rolling process and the conventional rolling theory is no longer valid. The complexity and d... Due to the variation of the blade cross-section, the deformation stress and strain of the workpiece keep changing during the rolling process and the conventional rolling theory is no longer valid. The complexity and diversity of the blade cross-section determine it impossible to establish an universal theoretical model for the rolling process. Finite element analysis(FEA) provides a perspective solution to the prediction. The FEA software DEFORM was applied to discovering the deformation, stress, strain and velocity field of the variable cross-section workpiece, and the effects of friction coefficient and rolling speed during the rolling process. which indicates that the average rolling force at friction coefficient of 0.4 is 6.5% higher than that at 0.12, and the rolling velocity has less effect on the equivalent stress and strain distribution, which would confer instructive significance on the theoretical study as well as the engineering practice. 展开更多
关键词 variable section rolling finite element analysis forming law BLADE
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Test of a low-mass contact binary model by comparing the relations obtained from theory with those from observations 被引量:1
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作者 SONG Fen HUANG RunQian 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2012年第4期706-716,共11页
The W UMa-type contact binaries have been observed for several decades.To construct the evolutionary model for W UMa-type contact binaries,many difficulties were encountered due to the existence of complicated physica... The W UMa-type contact binaries have been observed for several decades.To construct the evolutionary model for W UMa-type contact binaries,many difficulties were encountered due to the existence of complicated physical processes in such systems.The model introduced by Huang,Song and Bi includes some special and unique understandings of the physical processes of contact binaries.It is necessary to test whether this model can be used for W UMa-type contact binaries.The best way to test a theoretical model is to know whether this model can explain the observational phenomena of such systems.For this aim,a comparison is performed for the relations of mass-luminosity,mass-radius,and the distribution in the HR diagram obtained from the model introduced by Huang et al.and those from the astronomical observations.The result of the comparison indicates that this model can be applied to W UMa-type contact binaries and can explain the observational phenomena of such binaries. 展开更多
关键词 binaries: close stars: evolution stars: fundamental parameters stars: rotation
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