这个柱子影响信号的通路,在通讯信号会引起信号完整性问题。所以将这个多余的柱子(业内叫STUB)从反面钻掉(二次钻)。所以叫背钻,但是一般也不会钻那么干净,因为后续工序会电解掉一点铜,且钻尖本身也是尖的。所以PCB厂家会留下一小点,这个留下的STUB的长度叫B值,一般在50-150UM范围为好。
1、 执行菜单命令,选择Edit->Properties,激活属性命令,如图2所示。
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▲图1 背钻孔示意图
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▲图2 背钻孔示意图
2、在激活“property edit”的命令状态下,find面板中只勾选nets对象。
3. 然后选择要背钻的网络,随即会自动弹出“Edit Properties”对话框,左边的选项栏中选择“Backdrill_max_pth_stub”选项增加背钻属性,背钻Stub值可以填8,但是工厂加工能力可能达不到,此Stub值意义不大,随后点击”Apply”
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4.选择Manufacture->NC->Bacdrill Setup and Analysis…进入背钻层设置
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5.设置需要背钻的层,如需要背钻的信号分布在Layer5、Layer8,背钻从Botom->Top方向背钻,将要钻掉的层设置分别设置为Bottom->Layer6、Bottom->Layer9,设置如下。
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6、选择Manufacture->NC->Drill Legend输出背钻符号
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7.选择Manufacture->NC Drill输出钻孔文件
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