[SI-LIST] Re: Capacitors UNDER a BGA??
- From: "Fred U. Rosenberger" <fred@xxxxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Tue, 4 Feb 2003 09:14:57 -0600
The original post asks for info on a capacitor that would fit under a BGA
package. It does not say that only one capacitor will be used. If it's 20
or so capacitors with one BGA package, or perhaps 5 BGA packages with 20
caps each, or 100 packages with 2 caps each, then it's no longer true that
the capacitors can be placed anywhere on the board. The paper by Hubing et.
al. (IEEE Transactions on Electromagnetic Compatibility) shows that with a
single capacitor the placement is not important. That is far from showing
that the placement of 100 or more caps is not important. Any place on the
PC board is not fine in this case.
Regards,
Fred
----- Original Message -----
From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>; "Michael Khusid" <mkhusid@xxxxxxxxxx>
Sent: Thursday, January 30, 2003 10:48 AM
Subject: [SI-LIST] Re: Capacitors UNDER a BGA??
>
> Mike,
>
> It is not necessary to place decoupling capacitors under ICs. Any place
on
> the surface of the PCB is fine. See Todd Hubing's paper "Power Bus
> Decoupling on Multilayer PCBs" published on May 1995 in the IEE
Proceedings
> on Electromagnetic Compatibility for more information on this. You can
> download this paper from the IEEE web site.
>
> Lee
>
> Lee Ritchey
> leeritchey@xxxxxxxxxxxxx
> Why Wait? Move to EarthLink.
>
>
> > [Original Message]
> > From: Michael Khusid <mkhusid@xxxxxxxxxx>
> > To: <si-list@xxxxxxxxxxxxx>
> > Date: 1/29/2003 7:01:34 PM
> > Subject: [SI-LIST] Re: Capacitors UNDER a BGA??
> >
> >
> > There are sockets made for BGAs. If you have a socket for your BGA, you
> > may get enough height to put caps under it.
> >
> > Also, I am not certain whether you can reliably solder caps under BGA
> > without shorting the BGA balls to each other and to the cap.
> >
> > Best regards,
> > Mike
> >
> > -----------------------------------------------------------------
> > Michael Khusid
> > Ansoft Corporation
> > SI/HF Application Engineer
> >
> > 25 Burlington Mall Road, 6th floor
> > Burlington, MA 01803-4100
> >
> > Tel 781-229-8900 Ext. 34
> > Fax 781-229-8624
> > --------------------- http://www.ansoft.com ---------------------
> >
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> > On Behalf Of Grasso, Charles
> > Sent: Wednesday, January 29, 2003 7:55 PM
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Capacitors UNDER a BGA??
> >
> > Hi Si'ers
> >
> > I am looking for a very thin decoupling cap
> > that will fit under a BGA. Is there anyone
> > out there that knows of such a device??
> >
> > Best Regards
> > Charles Grasso
> > Senior Compliance Engineer
> > Echostar Communications Corp.
> > Tel: 303-706-5467
> > Fax: 303-799-6222
> > Cell: 303-204-2974
> > Email: charles.grasso@xxxxxxxxxxxx; <mailto:charles.grasso@xxxxxxxxxxxx;
> > >
> >
> > Email Alternate: chasgrasso@xxxxxxxx <mailto:chasgrasso@xxxxxxxx>
> >
> >
> >
> >
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