SMD封装设计准则GuidelinesforFootprintDesign

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1、SMD封装设计准则GuidelinesforFootprintDesignThefirststepincircuitboarddesignistoconsiderhowthesurfacemountedboardwillbemanufactured.Thisisbecausethemanufacturingprocessdeterminesthenecessarydimensionsofthesolderlands,theminimumspacingbetweencomponents,theareaunderneaththeSMD

2、wheretracksmaybelaiddown,andtherequiredcomponentorientationduringwavesoldering.ThereforeafootprintrelatedtothemanufacturingprocesswithallthisinformationisanessentialtoolforSMDcircuitboarddesign.AtypicalSMDfootprint,asshowninfollowingfigureiscomposedof:在电路板设计的第一步是要考虑如何

3、将生产表面贴装板。这是因为制造过程中确定必要的焊盘尺寸，组件之间的最小间距，区下方的轨道可放下贴片，波峰焊接过程中所需的组件方向。因此，所有这些信息的制造过程有关的封装是SMD电路板设计的一个必不可少的工具。由一个典型的SMD封装图所示：Thesefootprintdetailsdependonthefollowingparameters:Componentdimensionsandtolerancesasgiveninthecomponentdata;Boarddimensionalaccuracy;Placementaccur

4、acyofthecomponentwithrespecttothesolderlandsontheboard;Solderpastepositiontoleranceswithrespecttothesolderlands(forreflowsolderingonly);Thesolderingprocessparameters;Solderresistpositiontoleranceswithrespecttothesolderlands;Solderjointparametersforreliablejoints.这些的封装

5、细节取决于以下参数：?组件尺寸和公差组件中的数据给予;?板尺寸精度;?方面板上的焊盘与元件的位置精度;?锡膏焊盘位置公差，（仅回流焊有）;?焊接工艺参数;?焊锡抵制与焊盘位置公差;?可焊性参数。FootprintdesignfordiscreteCHIP-RReflowSoldering回流焊WaveSoldering波峰焊FootprintdesignfordiscreteMLCCReflowSolderingWaveSolderingStencilthickness模板厚度Thefollowingrelationbetween

6、thesolderlanddimensions(CxD)andthesolderpasteaperturesdimensionsmustbetakenintoaccountofsolderforeachsolderjoint:焊盘尺寸之间的下列关系（CXD）和焊膏孔径尺寸，必须考虑到为每个焊点焊接：