Backdrill相关设置及Backdrill文档输出方法
发布时间：2010-10-17 11:41
发布者：techshare
如果PCB的层数超过4层，PCB的走线从其中的某两层走线（除从表层到表层外），总会产生类似于下图这种情形的stub：产生多余的镀铜部分，当电路信号的频率增加到一定高度后，多余的镀铜就相当于天线一样，产生信号辐射对周围的其他信号造成干扰，严重时将影响到线路系统的正常工作，Backdrill的作用就是将多余的镀铜用钻孔的方式钻掉，从而消除此类EMI问题。其操作步骤和注意事项如下：  1.给net设定Backdrill_max_pth_stub属性 PropertyBACKDRILL_MAX_PTH_STUB PurposeIdentificationofnetstargetedforbackdrilling UsageRequired ValueMaxallowablestubinlength(databaseunits) ObjectsNets BackdrillanalysisflagS 2.给net设定Backdrill_min_pin_pth属性，Backdrill_min_pin_pth考虑可靠性,必须保证BACKDRILL去掉多余镀铜后,保证一定剩余一定长度.  PropertyBACKDRILL_MIN_PIN_PTH PurposeEnsuresminimumpinplatingdepthisnotcompromised UsageOptional ValueLength ObjectsSymbols,pins BackdrillanalysisflagP 3.压接的接插件backdrill：要保证良好的接触,必须保证下面的值：  PropertyBACKDRILL_PRESSFIT_CONNECTOR PurposeUse on pressfit connectors to permit backdrilling from both sides of the board. Backdrill depth will not protrude into contact range as defined by the property string. . UsageOptional Value＜value1:value2＞wherevalues=pincontactrange;thisvaluemustbeobtainedfromthemanufacturer ObjectsSymbols Backdrillanalysisflagn/a 4.有些场合不能用此功能的可以用下面的命令排除. Exclusions It may be necessary to exclude certain objects from backdrilling even though stub violations are present. The BACKDRILL_EXCLUDE property can be applied to symbols, pins or vias at both the library and design level using Edit - Property. Common examples might include solder tail connectors or a dense pin escape pattern in BGA areas. The PCB designer should consult with a manufacturing engineer before assuming all pin/via objects are suitable for backdrilling. PropertyBACKDRILL_EXCLUDE PurposeExcludesobjectsfrombackdrillingeventhoughstubmaybepresent UsageOptional ValueBoolean(true/false) ObjectsSymbols,pins,vias BackdrillanalysisflagX 5.定义层（可选） UserOverrides In most cases, the Backdrill layer ranges defined in the Backdrill Setup and Analysis user interface satisfy your requirements to manage stubs. The BACKDRILL_OVERRIDE property allows user-specified control of layer ranges for any pin or via and from ether side of the board or both. This is done regardless of violations that may result, such as testpoint conflicts or backdrilling through a connection. The override property was considered for the design of test coupons where the OEM wishes to evaluate the performance of the board fabricator with respect to the adherence of depth ranges. The designer may override the "to" layer to effectively drill out the layer where the trace connects the pin/via. The expected usage of this property is limited; please exercise caution to prevent accidental over-drilling. PropertyBACKDRILL_OVERRIDE PurposeUser-specifiedbackdrillrange UsageOptional:specialcircumstances ValueTOP:＜layer_name＞:BOTTOM:＜layer_name＞ ObjectsPins,Vias BackdrillanalysisflagOorW(warning) 定义方法：在Manufacture＞NC…Backdrillsetupandanalysis  6.NC＞DRILLLENGEND，输出钻孔表，注意要选择Includebackdrill   7.产生钻孔文件，输出钻孔文件，也要sIncludebackdrill  |
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