I posted this a few months back....

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 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



> ----------
> From:         Robert Coburn[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;[log in to unmask]
> Sent:         Tuesday, September 09, 2003 7:20 AM
> To:   [log in to unmask]
> Subject:      [TN] Board edge to circuit spacing / IPC-2221 ?
>
>
> Hi TechNetters;
>
> The Design group I manufacture boards for has asked me if I know what the
> minimum spacing requirements are from board edge to circuit.
> I have looked through IPC-2221 and can't seem to identify anything.
>
> Can anyone steer me in the right direction?
>
> Thanks all; ---------------------------------------------------
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> -----------------------------------------------------
>
> Rob
>

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