Dave
IPC 2221 and 2222 provide guidelines for this. IPC 2221 has a Table (6-1) that lists the minimum electrical conductor spacing for various voltages. IPC 2222 section 10.1.1 Edge Spacing says the minimum spacing between conductors and the board edge shall not be less than the minimum value from Table 6-1 plus 0.4 mm (.0157"). Table 6-1 has different values for internal and external conductors and whether the external conductors are coated/uncoated and at what elevation the boards will be used at. Picking even the lowest values, you're looking at at least .020" spacing.
That being said, I see lots of board designs that have features closer than this. In some cases the holes are on the edge of the board (castellation). So depending on the application you're looking at, you can go a lot closer than the IPC Standard.
You also get into issues such as how the board will be de-panelized. Boards that are scored and broken or that have breakaway tabs require more spacing because the laminate does get damaged when the panel is broken out.
Let me know if I can answer any other questions.
Mike McMaster
RF Product Engineer
Merix Corporation
503-992-4263
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From: David Harman[SMTP:[log in to unmask]]
Reply To: TechNet E-Mail Forum.;David Harman
Sent: Tuesday, July 22, 2003 5:38 PM
To: [log in to unmask]
Subject: [TN] Design Question
Hello technet.
I have a question on PCB design. We are redesigning our board and a
question came up that I am unable to verify. We are looking at having a
plated through-hole near the end of the board. This plated through hole
will be used to place a post through and soldered into place for
electrical contact.
The question that I have is as follows,
? Is there a requirement indicating that an annular ring is to be a
certain diameter larger than the actual through hole? And how far from
the edge of board should an annular ring be placed?
Thanks for your help.
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