Hello Jim,

I agree with Chuck.

AFAIK there is no definition of the solder mask undercutting.

The acceptance criteria is the adhesion (flaking or peeling).
See IPC-A-600 2.9.5 and IPC-6012 3.7.2.

In my opinion the undercutting is to severe.
The soldermask overhang can easily break away and the flakes will cause
problems.

Check the drying process before exposure and developing process.

Regards,
Simon


Chuck Brummer wrote:
> Jim.
> 
> Aside from the spec, pictures 1 & 3 don't bother me much as
> there is still
> a dam.  Picture 2 on the other hand looks like it could
> easily be broken
> off removing any barrier at all.
> 
> Assuming this to be photo imaginable?  I suspect we spent a
> little bit to
> much time in the developer.  Possible underexposed but
> probably to much
> develop.
> 
> Chuck Brummer
> 3M Manufacturing Engineer
> 8357 Canoga Ave.
> Canoga Park, CA 91304-2605
> (818) 734-4930
> 
> 
> 
> 
> From:
> J W <[log in to unmask]>
> To:
> [log in to unmask]
> Date:
> 09/03/2009 12:55 PM
> Subject:
> [TN] Acceptability of Printed Boards (Solder Mask)
> Sent by:
> TechNet <[log in to unmask]>
> 
> 
> 
> Hello All,
> 
> Can someone point me to the section (s) in either IPC-6012 or
> IPC-A-600 or other standards that explains the acceptance criteria
> for Solder Mask UNDER-CUTTING?  Please go to Steve's web-site
> following the 
> links below to
> see a few pictures of a Solder Mask defect that was discovered by our
> customer (they only stated "reject due to severe
> undercutting").  With
> this
> situation, we are trying to help our China source fix this
> issue, and we
> need to help them understand what section (s) of the standard (s) they
> should be looking at so they can establish a corrective action.
> http://stevezeva.homestead.com/files/Solder_Mask_Undercutting.jpg
> 
> http://stevezeva.homestead.com/files/Solder_Mask_Undercutting_2.jpg
> 
> http://stevezeva.homestead.com/files/Solder_Mask_Undercutting_3.jpg
> 
> 
> Thanks,
> Jim
> 

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