The vias can be drilled with a 0.2mm tool and with the trace
intersection improved to maintain a reliable connection - 2:1 in pads
less than .020" is where we see the minimum pad to hole to keep the
trace integrity.

With a PTH via of .018" the same drill can be used - the increasing
aspect ratio will require some attention to plating but is not that
exotic.  You can purchase 0.25mm drills which are also an option.  Via
types in this case will have 90 degree breakout, not affecting minimum
trace width at pad intersection.

Cavity features will need to be assessed for depth, size, finish, etc.
A milled non-plated cavity is fairly standard, but plated and build-up
cavities can increase to PCB cost of mfg.   

Jeffrey Bush
Director, Quality Assurance and Technical Support

VERMONT CIRCUITS INCORPORATED
  76 Technology Drive - POB 1890
    Brattleboro, Vermont 05302
      Voice: 802.257.4571.21 Fax: 802.257.0011
           http://www.vtcircuits.com
 

-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]] 
Sent: Tuesday, May 03, 2005 1:56 PM
To: [log in to unmask]
Subject: [TN] Annular ring:- What should we sign up for ????

We have a tough brd to manu. and want to know what kind of annular ring
requirement should we sign up for.

This is for SPACE so it requires IPC-6012 class 3, w/ exceptions to
annular
ring.

12 layers

1)  Burried vias 7-11
2)  Burried vias 6-11
3)  Blind vias  6-12

4)  Burried and blind vias have 16 mill pads for vias  (thickness  ~ 60
mils)

5)  Thru holes (~90 mils)  18 mil pads.

6) Cavity brds w/ broad side coupled diff. impedance control

Thanks for your help in advance

Rush
[log in to unmask] (mailto:[log in to unmask])
818-768-3919

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Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
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