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May 2009

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Subject:
From:
"McGlaughlin, Jeffrey A" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, McGlaughlin, Jeffrey A
Date:
Tue, 12 May 2009 06:51:24 -0400
Content-Type:
text/plain
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text/plain (60 lines)
Dave -

IPC-4761 covers via structure. There is a great chart listing out all of the possible via configurations and application based trade-offs. As to your application the answer is, as usual, it depends... How big of a via hole? Are they drilled or lazar ablated? Are they through hole or blind vias? What is the pitch and ball diameter of the BGA?   

Hope this helps,

Jeffrey A McGlaughlin, CID
Engineering Designer
Battelle
505 King Ave
Columbus Ohio 43201-2693
Phone (614)424-7582


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Schaefer
Sent: Monday, May 11, 2009 4:52 PM
To: [log in to unmask]
Subject: [TN] Via Tenting Under BGAs .. Again (apologies!)

I've read through the archives of this and other forums, also questioned
CM's and Fabricators about preferred Via soldermask features. I thought I
had resolved the issue once and for all that the best (and only reliable)
options were:

1. Conductively filled vias covered by LPI mask.
2. Partially LPI mask tented vias with via barrel exposed both sides
("encroached").

Seems there are still proponents of full LPI Via tenting without any type of
plugging.

Are there any studies with proof that a particular method of via masking
causes problems, or a method that should be the preferred practice?

Is there any IPC standard or activity to develop a standard on via masking?

Thanks,
Dave

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