It is interesting how a few words can get many interpolations....Here is
mine...

1. I have not seen a conflict.

2. 3.8.1 is written for the solder mask area..."manufacturing variations
resulting in skips, voids,.....   any resulting exposed copper needs
touchup".


3. 3.5.4.6.  Is written for finished boards. It allows exposed copper only
on non-solderable surfaces, For example circuit lines, ground planes,
plating thieving.  The resulting exposed copper could be for any number of
reasons, solder mask missing, small scratch, design error, etc. I don't know
of anyone having a functional issue with this amount of exposed area.

 As written this applies to any finish including OSP. The percent thing is a
little flaky.  I have always thought the intent is a "very small" about of
exposed copper is allowed on the bd's nonsolderable features. A max
dimension and a max number per bd would be a better way to define it than a
percentage.  Today if I had to determine  a percent, I would default to the
percent definition for measles we used in IPC-600.  The area of all measles
divided by the total board area.  Obviously this is very hard or impossible
to calculate.

Bottomline:  If we can change the percent to a max size and max number, that
maybe the only change necessary.

Mike


-----Original Message-----
From: IPC-600-6012 Mail Forum [mailto:[log in to unmask]]On Behalf Of
John Perry
Sent: Wednesday, May 08, 2002 5:46 PM
To: [log in to unmask]
Subject: [IPC-600-6012] EXPOSED COPPER/FINAL FINISH


Do we have a conflict here within the IPC-6012a?


In IPC-6012a, Section 3.5.4.6, it states that exposed copper on areas not to
be soldered is permitted on 1% of the conductor surfaces for Class 3 and 5%
of the surfaces for Class 1 and Class 2.

But, Section 3.8.1 Solder Resist Coverage sub-paragraph a.  states "Metal
conductors shall not be exposed or bridged by blisters in areas where solder
resist is required."

The percent allowance issue has been discussed before at Expo 2001 but we
did not walk away from that meeting with a clear cut definition of what
constitutes X percentage on a board, let alone potential conflict with
section 3.8.1.

Best Regards,



John Perry
Technical Project Manager
IPC
2215 Sanders Road
Northbrook, Il 60062
1-847-790-5318 (P)
1-847-509-9798 (F)
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