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December 1999

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Subject:
From:
Bob Dube <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Sat, 11 Dec 1999 10:27:40 -0500
Content-Type:
text/plain
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text/plain (126 lines)
Hey All,

All good points Matt, but what really is at the root of it all is process
capability and the stacking of tolerances. Good point about the V-score, but
in addition to that 1 mil (for instance) you would also best check your
drawing for what manufacturing tolerance you are allowing for score
location. If the toleance given is ±0.005" then the spacing from the edge
just allowing for score alone would be 0.006" (0.001" slope plus the
manufacturing tolerance). Take a look at all the processes that could bring
the ground plane in contact with the edge of the board, start stacking
tolerances. That will give your best answer. ) 0.039" should be very doable.

Bob Dube
ES&D

-----Original Message-----
From: Matthew Lamkin <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Friday, December 10, 1999 11:59 AM
Subject: Re: [TN] Edge Clearance for power & ground planes


>Hi there Ken,
>
>Rather than just give a measurement I'll explain why I keep power &
>ground planes away from the edge of the board.
>
>If the board goes into a panel that is scored, you will need to bear in
>mind that the edge of the board will have
>a slope on it, caused by the V-scoring machine. This is typically 0.5mm
>between boards in a panel.
>Therefor you will lose 0.25mm (0.01") of the laminate around the edges.
>
>If the board is routed, you will not lose this, but it is always good
>practice to keep the same distance away no matter what
>method of panelisation.
>
>Once that is done, then you have to think about the solder resist edges.
>If you have copper and solder resist
>edges at the same distance from the edge you can get nasty things
>creeping under it and corroding the board.
>You need to leave a gap for an area of solder resist before the start of
>your copper areas.
>
>I dare say that this also applies to the bonding of multiple layers, in
>order to provide good adhesion of laminates
>between the layers.
>
>What this then boils down to is keeping copper about 1mm (0.039") away
>from the edge of the board.
>If the board is large & has plenty of room then obviously this can be
>increased, but should never be decreased.
>
>I dare say that its mentioned in one of the IPC specs somewhere. (I'd
>like to know which one?).
>
>There... That's my tuppence...
>
>Hope it helps & doesn't confuse.... TIA - Matt.
>
>
>>-----Original Message-----
>>From:  Ken Patel [SMTP:[log in to unmask]]
>>Sent:  Thursday, December 09, 1999 9:13 PM
>>To:    [log in to unmask]
>>Subject:       [TN] Edge Clearance for power & ground planes
>>
>>Guys,
>>How far my power & ground planes should be away from the egge of the
board?
>>
>>re,
>>ken patel
>>______________________________________________________
>>Ken Patel                       Phone:  (408) 490-6804
>>1708 McCarthy Blvd.             Fax:    (408) 490-6859
>>Milpitas, CA 95035              Beeper: (888) 769-1808
>>
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