[SI-LIST] Re: BGA Breakout.
- From: "James F. Herrmann" <jherrmann@xxxxxxxxxxxxxxxx>
- To: "'Surita Chandani'" <surita.chandani@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Fri, 15 Jan 2010 15:10:17 -0500
Hello Surita,
Check out the September, 2007 issue of Printed Circuit Design & Fab. There
is an article entitled "BGA/PCB Interconnect Design Guidelines" by Gil White
that will definitively answer your question and will give you a better
understanding of drill / pad / anti-pad combinations and includes references
to the relevant IPC Standards. The bottom line: dual-track routing is
readily achievable, certainly on all inner layers, with 1 mm BGA.
Regards,
Jim Herrmann
AppliedLogix, LLC.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Surita Chandani
Sent: Friday, January 15, 2010 2:44 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: BGA Breakout.
Thanks Lee for your comments.
The suggestions for two traces between Vias comes directly from Intel
document, also this document is from 2002. Their pitch is 1.067 mm. The
document itself is available at:
http://download.intel.com/support/processors/xeon/sb/25039702.pdf ;
; Page 43.
--- On Fri, 1/15/10, Lee Ritchey <leeritchey@xxxxxxxxxxxxx> wrote:
Surita,
You are right, you cannot successfully route two traces between pins on a 1
mm pitch BGA without significant risk of shorts.
If you drill a 12 mil hole, your antipad does not have to be larger than 32
mils. This leaves you with a 7.37 mil web, which works nicely for a single
trace, but not two traces.. Your surface or signal layer pads can be 24
mils for 1 mil annular ring and 26 mils for 2 mil annular ring.
There will only be pads on inner layers where traces connect.
By the way, what vendor told you to route 2 traces between pins?
Lee Ritchey
> [Original Message]
> From: Surita Chandani <surita.chandani@xxxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Date: 1/14/2010 9:19:08 AM
> Subject: [SI-LIST] BGA Breakout.
>
>
>
>
> Hello Gurus;
>
>
>
> I am doing some preliminary calculations on the breakout of
> a 1,400+ Ball , BGA. Roughly one half of them are signal
> connections which would need traces running up to them. The vendor claims
you
> can run two traces between Vias, my calculations are not adding up, I
have a
> few questions.
>
>
>
> 1. Generally, do the Vias have a pad even on the signal
> layer it is not connecting to?.
>
>
>
> 2. Do the Vias have a larger pad on the inner layers?
>
>
>
> 3. With a Ball pitch
> of 1 mm (39 mils.) and an Antipad of 35 mils, there is hardly any room
for one
> trace between Vias, what am I doing wrong?
>
>
>
> Thanks,
>
>
>
> Surita Chandani
>
>
>
>
>
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