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April 2006

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Subject:
From:
Leo Higgins <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Leo Higgins <[log in to unmask]>
Date:
Mon, 24 Apr 2006 21:29:55 -0700
Content-Type:
text/plain
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text/plain (161 lines)
Std stencil design was used for same pad design with and without via in pad.
Nothing special, no math.

Best regards,
Leo

Leo M. Higgins III, Ph.D.
Vice President, Technical Operations
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas     78704



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Guy Ramsey
Sent: Monday, April 24, 2006 7:59 PM
To: [log in to unmask]
Subject: Re: [TN] Solder joint reliability of BGAs and 0402 chip on
blind vias


True, but it these tests results came from a study where the solder stencil
had been optimized for knowing the attributes of the board. In the CM world
these things have a way of dropping in on us. The arithmetic is not complex,
but it is also not a no-brainer.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Leo Higgins
Sent: Monday, April 24, 2006 4:52 PM
To: [log in to unmask]
Subject: Re: [TN] Solder joint reliability of BGAs and 0402 chip on
blind vias


Some work has been published actually showing better mechanical shock / drop
test results for unfilled via-in-pad solder pad structures, even with the
common presence of a void in the solder located right in the recessed via.
This helps avoid the issue of lifted copper that is often seen over the top
of filled microvias.

Best regards,
Leo

Leo M. Higgins III, Ph.D.
Vice President, Technical Operations
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas     78704



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Bob Wilson
Sent: Friday, April 21, 2006 1:11 PM
To: [log in to unmask]
Subject: Re: [TN] Solder joint reliability of BGAs and 0402 chip on
blind vias


Yup.

Laser drill at 4 mil diameter and fill with good conductive epoxy.

When I hooked the board up I eased the fabrication a bit by doing the blinds
only from layer 1 to layer 2 and layer 15 to layer 16.  (Layers 2 and 15
were flooded GND planes).

Boards were fabbed at Hallmark Circuits in San Diego.  I talked to them
before I routed a signal and the boards worked fine.

Bob Wilson
CID

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ted Kong
Sent: Friday, April 21, 2006 10:57 AM
To: [log in to unmask]
Subject: [TN] Solder joint reliability of BGAs and 0402 chip on blind vias


Hi all,

Has anyone used blind vias on BGAs or 0402 chip
packages? Will they form reliable solder joints?

Thanks all in advance.

Ted

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