[SI-LIST] Re: BGA Breakout.
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "Surita Chandani" <surita.chandani@xxxxxxxxx>, si-list@xxxxxxxxxxxxx
- Date: Mon, 18 Jan 2010 09:30:13 -0800
Surita,
I believe this kind of routing is possible with very thin PCBs with very
small holes such as in laptop motherboards. However, with very large BGAs
such as yours, it is unlikely that it w ill route on a thin PCB. My
experience with BGAs of your size is that a 22-26 layer PCB will be needed
and that will likely be 100+ mils thick resulting in the need for 12 mil
drills.
Lee
> [Original Message]
> From: Surita Chandani <surita.chandani@xxxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Date: 1/15/2010 11:43:41 AM
> 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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