Gary,
Does this spec refer to unconnected pads and should it include thermal
reliefs? It does seem over the top to ask for minimum 0.010" clearance
on a thermal when it is already connected to the surrounding copper
plane. I don't see any problem manufacturing 0.005" clearance on thermal
reliefs and would rather have a larger pad to aim for given the choice.
However, there must be no unconnected pads with 0.005" clearance and I
would agree that 0.010" minimum would be sensible if these are required
for some special reason.(Preferably they should be removed but I know
some might want to retain them).
Question is, can the CAD system distinguish during layout between
connected and unconnected pads for different clearances?
Regards
Paul Gould
Teknacron Circuits Ltd

In message <[log in to unmask]>,
[log in to unmask] writes
>Nick
>
>IPC-D-275 states that the clear area should be no less than 0.010 inch. This
>number takes into account the difficulties in etching and the subsequent
>inspection of a large copper plane. 
>
>This requirement meets general board manufacturing capabilities . However,
>you may be able to find some specialized fabricators that can do better.
>
>Regards,
>
>Gary Ferrari
>IPC Staff
>

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