Hi Mike,

I think it would be hard to get etchant between layer one and two copper
plating and if it did happen I would expect a round concave void.

I a pretty sure the crack was from thermal stressing and the microetch
from processing the cross section penetrated the crack. Over time the
micro-etchant out gasses and causes discoloration. 

This type discoloration is very common in thermal cycle testing. We see
it occurring during warm, humid Canadian summers; less often during
cold, dry Canadian winters. 

The horizontal crack that then propagates between layers is a result of
poor adhesion between the first and second electroplated copper. This is
a classic lead free failure mode. Significant pad rotation induced the
crack and separation at the knee of the PTH.

Sincerely, 
Paul Reid 

Program Coordinator 
PWB Interconnect Solutions Inc. 
235 Stafford Rd., West, Unit 103 
Nepean, Ontario 
Canada, K2H 9C1 
613 596 4244 ext. 229 
Skype paul_reid_pwb 
[log in to unmask] <mailto:[log in to unmask]> 


-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Michael G
Luke
Sent: August 16, 2010 10:22 PM
To: [log in to unmask]
Subject: Re: [IPC-600-6012] opinion poll

Are you sure this isn't chemical corrosion from leaked in etchant that
had
a path through the copper cracks either during fab or microsection?
I have never seen plating burn show up in this manner.

Mike Luke




 

 

             Chris Mahanna

             <cmahanna@ROBISAN

             .COM>
To 
             Sent by:                  [log in to unmask]

             IPC-600-6012
cc 
             <IPC-600-6012@IPC

             .ORG>
Subject 
                                       Re: [IPC-600-6012] opinion poll

 

             08/16/2010 12:43

             PM

 

 

             Please respond to

             "(Combined Forum

               of D-33a and

                   7-31a

              Subcommittees)"

             <IPC-600-6012@IPC

                   .ORG>

 

 

 





Hi Lance,
No solder
Let me add another picture to the story.

-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Lance A
Auer
Sent: Monday, August 16, 2010 1:35 PM
To: [log in to unmask]
Subject: Re: [IPC-600-6012] opinion poll

Chris,

        I think your picture shows an "E" crack and the initial plating
has separated from the copper that was subsequently plated.   Is that
solder in the area where the platings are separated?

Thanks,
Lance





From:
Chris Mahanna <[log in to unmask]>
To:
[log in to unmask]
Date:
08/16/2010 10:21 AM
Subject:
[IPC-600-6012] opinion poll
Sent by:
IPC-600-6012 <[log in to unmask]>



Hi Everyone,

Attached is a picture of a thru-hole corner after thermal stress.  The
plating is pulse.  I believe the corner was 'burnt' because of the
geometry of the (conformant) negative etchback.  All the corners show
burn; some show blisters; only this one cracked.

In your opinion, what are the non-conformance(s) if any?


Thanks

Chris

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