SMD封装设计准则GuidelinesforFootprintDesign.doc

SMD封装设计准则Guidelines for Footprint DesignThe first step in circuit board design is to consider how the surface mounted board will be manufactured. This is because the manufacturing process determines the necessary dimensions of the solder lands, the minimum spacing between components, the area underneath the SMD where tracks may be laid down, and the required component orientation during wave soldering. Therefore a footprint related to the manufacturing process with all this information is an essential tool for SMD circuit board design. A typical SMD footprint, as shown in following figure is composed of :在电路板设计的第一步是要考虑如何将生产表面贴装板。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：These footprint details depend on the following parameters :Component dimensions and tolerances as given in the component data ;Board dimensional accuracy ; Placement accuracy of the component with respect to the solder lands on the board ;Solder paste position tolerances with respect to the solder lands (for reflow soldering only) ;The soldering process parameters ;Solder resist position tolerances with respect to the solder lands ;Solder joint parameters for reliable joints.这些的封装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。Footprint design for discrete CHIP-R Reflow Soldering 回流焊Wave Soldering波峰焊 Footprint design for discrete MLCC Reflow Soldering Wave Soldering Stencil thickness模板厚度The following relation between the solder land dimensions (C x D) and the solder paste apertures dimensions must be taken i