You won't find a spec that says non-functional lands *shall not* be removed.

The IPC's postion is that if you think it is okay for the fabricator to
remove
them, they are not going to argue with you about it, but it has always been
their position that they *should* be retained.

but...

If you decide that they can be removed with no detrimental effects, you
still
need to have them in the coupon so measurements can be made.

If you want to retain them for hole reliability, you have to say it in a
note
(I think... Does anyone disagree with this?)

There's plenty more discussion about why they should be removed or retained,
but you didn't ask that, so I assume you know the issues and were just
asking
about the IPC specification
onward thru the fog,
Jack


.

On 4/25/08, James, Ron CAR <[log in to unmask]> wrote:
>
>  Senile designer needs help.  ;-)
>
> It has been a while since I have dealt with the question of removing or not
> removing non-functional pads from inner layers.  I can't seem to find any
> record of what I told our board fabricators in the past.  So I tried looking
> it up in the IPC specs.
>
> IPC-2222, 9.1.4 says that non-functional lands "should" be included on
> internal layers for all plated-through holes.  It says "should" where many
> other paragraphs say "*shall*" in bold type; I assume that was done
> deliberately?  Is this just a recommendation, and not a requirement?
>
> IPC-2221 only seems to mention non-functional lands in paragraph 12.4.1
> describing test coupons, where it says that the coupon* shall* represent
> the design except that non-functional lands* shall* be included on all
> layers.  The wording of this section suggests that non-functional lands
> would normally be missing, but they want them present on the test coupons.
>
> I can't find anything else, but I don't have a searchable PDF copy of the
> IPC specs, so there may be information that I am missing while flipping
> through my paper copy.
>
> A web search using the mighty Google shows multiple board suppliers who
> list removal of non-functional inner layer pads as a standard step in their
> CAM processing of customer Gerber files.
>
> I guess my question is:  what IPC spec can I refer to to tell the fab house
> that they* shall not* remove unused inner layer pads?  Or is it really OK?
>
>
> Ron
>
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