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April 2000

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Subject:
From:
Timothy Reeves <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 5 Apr 2000 12:16:37 -0700
Content-Type:
text/plain
Parts/Attachments:
text/plain (67 lines)
Steve, I think, looking at the pictures and based on my own understanding of
the spec. that exposed copper IS allowed ONLY on the vertical edges of
traces and pads, nowhere else (they fail to clearly state that the vertical
surface clause is an exception to the no exposed copper clause)
 So your boards meet the spec. It is a confusing spec, isn't it!

> ----------
> From:         Stephen R. Gregory
> Sent:         Wednesday, April 5, 2000 8:55
> Subject:      Exposed copper around the periphery of anular pads..
>
> Hi ya'll!
>
> I got called back to incoming this morning to look at a PTH board that
> shows
> exposed copper, but it's only at the side edges around the periphery of
> the
> anular pads...it's like this over the whole board. The top surfaces have
> tin/lead plating, but not the side edges.
>
>                             Top surface of pad is plated
>                                                |
>                                 ________V_________
> __________________|__________________|__<-----Exposed copper on sides
>
>                                             PCB
>
> Is this a defect? Looked in the IPC-A-600F on page 85, (3.3.10 Solder
> coating
> thickness) and there's a conflicting statement I think. It says;
> Acceptable -
> Class 1,2,3, "Solder coating thickness is uniform. Vertical (conductor and
> land) areas may not be covered. No exposed copper is evident."
>
> On one hand it says that the vertical surface may not be covered, but on
> the
> other hand it says you can't have exposed copper. If the vertical surface
> doesn't have to be covered, then you're gonna have exposed copper. So
> which
> is it?
>
> Also there's a statement at the bottom of the page that visual
> observations
> are made on cross sections only. I can see this with my own two
> eyeballs...don't need a cross section to see it.
>
> This board is for a hi-rel product by the way....
>
> Thanks!
>
> -Steve Gregory-
>

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