John et.al. - I may be repeating what has already been stated.

We have always allowed cracks/voids in zone A (3.6.2.3/4) - eyebrows. As
can been seen from the response this is a common occurrence.

If in zone B they have been treated as cracks/voids per 3.6.2.3/4





Jim

-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of John Perry
Sent: Monday, November 09, 2009 10:52 AM
To: [log in to unmask]
Subject: [IPC-600-6012] Double-Blind Via Construction and IPC-6012C

Hello Everyone,

Recently, we updated the attached IPC-6012C Figure 3-9 to better
illustrate requirements for laminate anomalies in Zone A and Zone B.

A question has come up regarding laminate anomalies in double-blind via
constructions.  Please refer to the attached PowerPoint file.  The
questions are:


*         Are laminate defects in Zone A allowed after thermal stress?

*         Are any defects allowed in the non-thermal stressed condition
in Zone A?

*         What would be the size of defects allowed?  Would they be the
same as for standard PTHs?

*         If defects allowed in non-stressed condition is there a
minimum spacing requirement of resin/glass between layers?

Let's discuss this through this IPC-600-6012 e-mail forum and see if
there is a need to further update IPC-6012C Figure 3-9 (or duplicate it
and modify as needed for double-blind constructions).

Regards,

John Perry
Technical Project Manager
IPC - Association Connecting Electronics Industries(r)
3000 Lakeside Drive # 309S
Bannockburn, IL 60015-1249 USA
+1 847-597-2818 (tel)
+1 847-615-7105 (fax)
+1 847-615-7100 (Main)
[log in to unmask]
www.ipc.org



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