I recently did a design having 4 BGA's. Two were
.8mm and two were .75mm. This is what I used after I talked
with our manufacturing people and several fab shops.
(My units are in inches)
BGA PAD = .013"
Solder mask opening = .019"
Paste screen opening = .015"
VIA = .017"
FINISHED HOLE = .006"
Traces on outer layer connecting BGA PAD to VIA = .006"
Inner layer traces = .004"
SPACE (Trace to via) = .0048"
90 degree breakout and or tangency was allowed. As in the spec.
Filleting was required.
Vias were tented.
Via holes can be filled but only 100%. Checked by x-ray.
My board thickness was .060".
This was a blind via card but all BGA vias were through hole.
Aspect ratio was 6:1.
We have built about 120 of these with no problems in the BGA's.
Regards,
Jerry Schwartz, CID
IPC Certified Interconnect Designer
"May the Schwartz be with you"
Jerry Schwartz, CID Designer 3
Harris Corporation GCSD Voice (321)-727-5474
P.O. Box 37, MS 1/9843 Fax (321)-729-5990
Melbourne, FL 32902-0037 Pager (321)-690-9797
mailto:[log in to unmask]
http://harris.com
-----Original Message-----
From: Cliff Lamson [mailto:[log in to unmask]]
Sent: Wednesday, January 10, 2001 8:48 AM
To: [log in to unmask]
Subject: Re: [DC] Routing suggestions on 0.8mm uBGA
At .8 mm pitch, you are entering the world of HDI and microvias. If the
device pin count is small enough, and it's not a perimeter matrix, try to
fan out the vias as usual. If it is high pin count, and/or full matrix and
you need to do a 'dog bone' fanout or via in pad, then microvia's is the way
you need to go. Get a copy of IPC-2315 and IPC-2226 (working draft) through
the IPC. There are numerous web sites available with info on microvia
design, such as Motorola, Merix, Hadco, and DDI, to name a few. Remember to
work with your board supplier in advance. Also see the informative article
in the Feb 2000 issue of Printed Circuit Design magazine.
Good luck!
Cliff Lamson, C.I.D.
Manager, PCB Design
Plexus Technology Group
940 Main Campus Drive, Suite 200
Raleigh, N.C. 27606
919-807-8047
The Product Realization Company
www.plexus.com <http://www.plexus.com>
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