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January 1998

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Subject:
From:
Larry Campbell <[log in to unmask]>
Reply To:
TechNet Mail Forum.
Date:
Mon, 19 Jan 1998 09:48:51 -0500
Content-Type:
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text/plain (109 lines)
At the risk of starting an uproar, I'd like to mention a couple of
things we've heard.

I've had board vendors remove the dead pads without telling me
about it, in which case the boards don't match my artwork any
more.  Deffinately a no-no.

Some board vendors say they don't want the pads to spin out
when they perform their drilling oberation while other board
vendors suggest the first vendor use sharp drills.

I've also heard that the internal pad may help the adhesion, and
possibly strengthen the plating in the hole.

I'd really like to have the IPC test this out and document the
resusts so this question can be put to rest.  Maybe they have
already done so, but I haven't been able to find any
documentation about it yet.

It basically boils down to a matter of preference and personal
choice at this point, I believe.  I'll expect to see a lot of response
to this but I'd really like to see some documented results.

Larry Campbell
Supervisor, PWB
BFGoodrich Avionics Systems
[log in to unmask]



>>> Per Viklund <[log in to unmask]> 01/19/98 02:48am >>>
Hi David,

I don't have any figures but this is common practice with all the
companies I work with.
But then, I MAY have a different definition of a dead pad.
I mean that the pad is dead on all inner layers that it does not
have
a connecting wire on.
On outer layers, I've never seen it but if a pad is unconnected in
an
inner layer, it's safe to remove it.

For plane layers, it's slightly different since it's either a matter of
connection or no connection where the 'no connection' is a form
of clearance rule.

However, you would not like to remove the pad completely -just
decrease the size. That will ease routing on that layer if your cad
tool
supports this dynamically.
You will need a small pad to prevent  plating chemicals to go
into the lamination between the layers. -How big of a risk it is
to get problems with plating chemicals if you do remove the pad
completely, I don't now.

Regards

Per Viklund
Dansk Data Elektronik AS
mailto:[log in to unmask]
http://www.dde.dk/eda/



David Backen wrote:
>
> We are looking for data, papers or personal experience with
regards to
> dead pad removal (both signal and plane layers) and the
impact on hole
> wall reliability.
>
> Board type: 4 - 14 layers,  20 - 100 mils thick, FR-4 material
and other
> material types if available.
>
> I appreciate any information you may have.
>
> Regards,
> Dave Backen
> [log in to unmask]

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