Hi Wendi.
This is a known issue that got placed in the parking lot in the interest of publishing C before 2015.  I'm certain that the intent of 6012 was to propagate Bs by structure, and I'm fairly certain that the 2221 "plating cycle" verbiage wasn't fully vetted.
Obviuosly the two paths don't always lead to the same conclusion.  Personally, I believe 2221 holds authority for the decision, but every OEM we've asked intreprets it as structure.  So, it probably isn't worth the risk.  Yes, I know it is a major pain.  The new B coupon design might help.
Tents, via protection, backdrills, full/partial pad stacks...   oh my.
Chris

-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Wendi Boger
Sent: Thursday, June 17, 2010 6:30 PM
To: [log in to unmask]
Subject: [IPC-600-6012] Definition of "Via Structures"

 Need clarification on the definition of Via Structures as is relates to
Microsection Requirements.  

 

3.6.1.5 Microsection Requirements

 

            ..... Evaluation of all applicable PTHs and vias, including
blind and buried, for all such structures found on the finished printed
board shall be inspected in the vertical cross section in accordance
with Table 4-3. ...

 

 If a board has 1-2 lasers and 1-2-3 stacked lasers is it correct to
have 2 coupons one as 1-2 and one as 2-3.  Both drill cycles and plating
cycles are represented but the 1-2-3 total via structure is not.   Seems
like the 1-2 and 2-3 only is bending the intent.  

 

 

Wendi

 


 
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