简介:Inthiswork,thewettability,agingandshearpropertiesofanewtypeoflead-freesolderpasteSn-07Ag-05Cu+BiNi(SACBN07)wasinvestigatedbyconductingaseriesofcomparisonexperimentswithSAC305andSAC0307solderpaste.TheresultsshowthatwettabilityofSACBN07isalmostequaltoSAC305,andbetterthanthatofSAC0307solderpaste.Thethicknessofintermetalliccompound(IMC)layerinSACBN07/Cuislowerthanthatofothertwotypesofsolderjointafteraging.AndCu_3SnlayerofSACBN07/CuisthinnerthanthatofSAC305andSAC0307.Inaddition,theSACBN07solderjointsperformthebestshearstrengthamongthesethreetypesofsolderpastes.
简介:摘要小学科学课堂中实验内容较多,教师在实验过程中还要维持实验秩序,所以有必要在课堂中选择小助手来辅助教学,培养小助手变为小老师,从学生的角度去看待问题、讲解知识。本文从小助手的选拔、小助手的作用及小助手的成长三个方面来阐述了自己在科学课堂上的尝试。