Hi Ed
Table 3-5 would only be used if they are buried.
You have blind vias (table 3-3) or blind microvias (table 3-4).

After much painful debate, by rule categorization as "micro" has nothing to do with formation technique or lamination sequences.
Currently 6012C:
Any plated hole less than 0.006 inch diameter = microvia
Blind and < 1:1 aspect ratio = microvia

The ballot build of 6012D:
Blind and < 1:1 and <0.25 mm [0.00984 in] = microvia

So, your lased vias are probably microvias, and if 6012D definition carries, you might be able to build your option 2 as microvias also.

Chris Mahanna
Robisan Lab



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Edward Szpruch
Sent: Thursday, November 20, 2014 6:15 AM
To: [log in to unmask]
Subject: [TN] IPC-6012C Cu thickness in 1-2 vias

Hi IPC Specs gurus,
I have question regarding rigid multilayer , say 16 layers , to be manufactured according to Class 3 with 1-2 vias. The question is on copper thickness in 1-2 vias.
We can manufacture such PCB in two ways :
1) Final PCB, laser drilled blind microvia to layer 2 , plated as blind structure. 
2) Double side core, drilled , plated as 2 layers via core , and then laminated as final PCB 

Looking into tables 3-3 , 3-4 and 3-5 it seems, that in case 1 fall into definition of microvia covered by table 3-4 ( average copper thickness 12 microns) while the second case, it should follow requirements of table 3-5 ( average 15 microns) rather than of table 3-3 ( average 25 microns).

What are other opinions?


Edward Szpruch|Manager of Process Engineering | Eltek Ltd. | | +972 (3) 939 5098 |+972 (54) 807 4298 |  +972 (3) 939 9581 |   [log in to unmask] | www.eltekglobal.com


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