Hi Dieter,
Many thanks for providing the wording from IPC-2222A. We do have ground planes that extend to within 0.254mm [0.010] as required by design. Component pad surfaces and non-ground plane trace geometries are pulled back further. As I mentioned in my response to Cherie Litson, the board dimensions are no longer than 60mm [2.362] and no thicker than 1.6mm [0.062] using standard 1oz IPC 4101/24 type FR-4 material. So that mitigates the better part of the risk, it would seem.
Thanks,
Gary
>________________________________
> From: Dieter Bergman <[log in to unmask]>
>To: 'Gary Koven' <[log in to unmask]>
>Cc: DesignerCouncil <[log in to unmask]>; John Perry <[log in to unmask]>
>Sent: Tuesday, February 26, 2013 10:49 AM
>Subject: RE: [DC] Edge spacing
>
>Hi Gary,
>
>The present IPC-2222A states the following:
>
>10.1.1 Edge Spacing Except for edge printed board contacts, the minimum distance between conductive surfaces and the edge
>of the finished printed board, or a NPTH, shall not be less than the minimum spacing specified in Table 6-1 of IPC-2221 plus
>0.4 mm [0.0157]. Printed boards that slide into guides shall have a minimum external conductor to guide distance of 1.25 mm
>[0.0492 in] or minimum electrical clearance (see Table 6-1 of IPC-2221), whichever is greater. Special design applications in
>areas such as high voltage, surface mount, and radio frequency (RF) technology may require variances to these requirements.
>Ground and heat sink planes may extend to the edge when required by design.
>The design should provide sufficient edge spacing to avoid unnecessary haloing and crazing rejections. Rejections can occur
>when the edge defect is greater than 50% of the clearance to edge spacing. Brittle material or heavier glass weights increase this
>risk.
>
>The fabricator can do this, but from a design point of view we worry about edge defects the can impact the assembly performance.
>
>Dieter
>
>-----Original Message-----
>From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Gary Koven
>Sent: Tuesday, February 26, 2013 9:10 AM
>To: DesignerCouncil
>Subject: [DC] Edge spacing
>
>We design small form factor PCBs with board edge to copper spacing typically 0.25mm (0.010").
>
>Thus far, no fabricator, whether our American prototype or our Asia Pacific production, has indicated this distance is a problem. Online prototype shops such as Advanced Circuits specify this distance as their minimum.
>
>
>Which IPC document addresses minimum edge spacing? My copy of IPC-2222 is 15 years old,and I was not able to find this information in any other IPC specs on hand.
>
>
>
>TIA and Best Regards,
>
>Gary M. Koven, C.I.D.
>InVue Security Products
>
>Charlotte, NC, USA
>Board Of Directors, RTP Chapter
>
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