[SI-LIST] Re: Importance of Package Height
- From: steve weir <weirsp@xxxxxxxxxx>
- To: bdewitt@xxxxxxxxxxxxx, <tom.biggs@xxxxxxxxxx>,<gsteinkogler@xxxxxxxxxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Sun, 03 Mar 2002 18:04:28 -0800
Brent,
The general consensus is that the larger package will have more inductance,
and therefore poorer performance. The smaller packages result from a lower
breakdown voltage, or higher dielectric coefficient, not usually a taller
package. On a related topic, there has been some discussion about
proximity effect leading to some advantage to mounting in one z-x rotation
or another.
The biggest gain that package can give you is if you go to either a reverse
geometry, or one of those fancy inductance cancelled packages( X2Y corp
). With these, and even normal geometry capacitors, the challenge still is
total mounted inductance. Your mileage may vary, but unless you can really
justify it through modelling, I would stick with normal geometry in a small
package and concentrate on low inductance interconnect to the plane. At
the end of the day the goal remains meeting the impedance profile across
frequency.
Regards,
Steve.
At 06:42 PM 3/3/2002 -0700, Brent DeWitt wrote:
>One of the things I've been curious about for a while is the advantage of
>using larger footprint devices (maybe 1206 vs. 0603) in the same capacitance
>value. Logic would _seem_ to suggest that the smaller package must be
>taller and therefore have a greater current vs. height function. Since they
>have the same 2D length to width, it would seem the larger part would be
>preferred. I don't have the equipment to measure this, so any thoughts
>would be appreciated.
>
>Brent DeWitt
>Datex-Ohmeda
>Louisville, CO
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx
>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Tom Biggs
>Sent: Friday, March 01, 2002 10:32 AM
>To: 'gsteinkogler@xxxxxxxxxxxxxxxxxxxx'; si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: Importance of Package Height
>
>
>
>Here is one from Dr. Johnson:
>http://www.sigcon.com/articles/edn/vertical.htm
>
> -tom
>
>-----Original Message-----
>From: Steinkogler, Gary [mailto:gsteinkogler@xxxxxxxxxxxxxxxxxxxx]
>Sent: Friday, March 01, 2002 7:38 AM
>To: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Importance of Package Height
>
>
>
>Not too long ago I ran across several articles - EDN?, Electronic Design,
>PCB Magazine -- on the importance of IC height above the circuit board, but
>have not been able to find them. Can anybody help me locate them?
>
>Gary Steinkogler
>Optical Gateway Development
>Optical Solutions
>16305 36th Ave. North
>Suite 300
>Minneapolis, MN 55446-2698
>Phone: (763) 268-3633
>Fax: (763) 268-3301
>Main: (763) 268-3300
>
>email:gsteinkogler@xxxxxxxxxxxxxxxxxxxx
>
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