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Reply To: | TechNet E-Mail Forum. |
Date: | Thu, 23 Jul 1998 16:18:50 -0400 |
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The only specified "rule" is in IPC-D-275 Section 5.3.1.2 Conductor Routing.
It states that for conductors that change direction with less than a 90
degree included angle should have their internal and external corners
rounded.
I've been designing boards for 18 years and have never run into a "T"
problem from either a design or manufacturability standpoint.
> ----------
> From: R. Christopher Lott
> Sent: Thursday, July 23, 1998 3:50 PM
> To: [log in to unmask]
> Subject: [TN] Conductor Routing Question
>
> First of all, I'm an engineer and don't do board layout every day.
> Please forgive what may be a dumb question...
>
> I have a nagging recollection in my mind that PWBs designed to
> MIL-STD-275 (now IPC-D-275) had a special requirement on the
> conductor routing. Namely, that all conductor traces have to
> begin and end on a land. That is, no conductor "tees" are
> permitted.
>
> Now that I may be making such a board, I reviewed both MIL-STD-275
> and IPC-D-275, and don't find this to be the case. The only remotely
> similar remark is in section 5.3.1.2 Conductor Routing (from the IPC,
> but the MIL-STD has very similar wording):
>
> "The length of a conductor between any two lands
> should be held to a minimum."
>
> You would be really stretching things to get my "no tees" rule from
> that section.
>
> Question: Am I really losing it (entirely possible), or is/was there
> such a rule, and if so, where is it and under what circumstances is/was
> it invoked?
>
> Thanks,
>
> -Chris Lott
>
> --
>
> ************************************************************************
> R. Christopher Lott, P.E. [log in to unmask]
> Huntsville, Alabama
> ************************************************************************
>
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