Thanks Dr. Higgens.

I'd be interested in the data.  The boards that I did the filled microvias
was a data acquisition board used in flight and it passed vibration tests.

That doesn't mean we didn't get lucky.

If I could make any design better able to take mechanical shock and drop
testing, I'd be happy to do it.

Regards,

Bob Wilson, CID
Electro-Mechanical Designer
SpectraSensors, Inc.
972 N. Amelia Ave.
San Dimas, CA 91773
800-619-2861 x239
www.spectrasensors.com




-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leo Higgins
Sent: Monday, April 24, 2006 1:52 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

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