Layout Footprint sot23

V

visand

Guest
Hi to everybody! I'm new to this list.
I'm trying to learn to use Layout from Cadence and I've to place a
component in a SOT23 package. I've searched it in the standard
libraries but I was not able to find it. Does anybody know where I
can find this footprint or how I can draw it by myself (any
tutorial...?).
Thanks a lot!
Andrea
 
Andrea, the library would be the SM.LLB Library, atleast
for v9.1 it was so it might be the same.

A word of caution though ! Make sure the pin numbering
scheme for the schematic symbol matches the correct pad
placement numbering for the footprint in layout. Also alot
of the sm parts in layout were not very well made i.e pad
size were incorrect for manufacture of a real pcb. Soldermask
on most of them was not oversized enough for the pad land.

At one time Orcad created a ipc standard library of SM footprints for
layout so the SOT23 part might be in such a library also. You can
check the download section of the Orcad/Cadence website.

Your safest bet on the footprint if in doubt is to look at the part
manufacturers data sheet for a land pattern and create one or modify
the existing one.

Good Luck...

Paul H









On Mon, 02 Jan 2006 18:05:17 -0600,
visand.eln@libero-dot-it.no-spam.invalid (visand) wrote:

Hi to everybody! I'm new to this list.
I'm trying to learn to use Layout from Cadence and I've to place a
component in a SOT23 package. I've searched it in the standard
libraries but I was not able to find it. Does anybody know where I
can find this footprint or how I can draw it by myself (any
tutorial...?).
Thanks a lot!
Andrea
Click to expand...
 
On Mon, 02 Jan 2006 21:46:11 -0500, Blastoff <none@nospam.net> wrote:
On Mon, 02 Jan 2006 18:05:17 -0600,
visand.eln@libero-dot-it.no-spam.invalid (visand) wrote:

Hi to everybody! I'm new to this list.
I'm trying to learn to use Layout from Cadence and I've to place a
component in a SOT23 package. I've searched it in the standard
libraries but I was not able to find it. Does anybody know where I
can find this footprint or how I can draw it by myself (any
tutorial...?).
Thanks a lot!
Andrea

Andrea, the library would be the SM.LLB Library, atleast
for v9.1 it was so it might be the same.

A word of caution though ! Make sure the pin numbering
scheme for the schematic symbol matches the correct pad
placement numbering for the footprint in layout. Also alot
of the sm parts in layout were not very well made i.e pad
size were incorrect for manufacture of a real pcb. Soldermask
on most of them was not oversized enough for the pad land.

At one time Orcad created a ipc standard library of SM footprints for
layout so the SOT23 part might be in such a library also. You can
check the download section of the Orcad/Cadence website.

Your safest bet on the footprint if in doubt is to look at the part
manufacturers data sheet for a land pattern and create one or modify
the existing one.
Paul H
Click to expand...
It still can be found in the SM.LLB library in 20 flavors. Another way
of finding parts is use GREP (or you can use M$ file search utility)
to search for text strings in the library files. In your case,
grep -i sot23 *.llb
The reason I use GREP is I can use a batch file to find all the
footprints for a project.

As Paul states, don't trust Orcad's footprints. You should check them
against trusted footprints and then store them in your own library.
About 100% of Orcad's footprints are unusable out of the box. Better
yet, learn to make this from scratch. Making your own footprints is a
necessary skill to learn for any PCB program.

---
Mark
 
Hello Paul,

A word of caution though ! Make sure the pin numbering
scheme for the schematic symbol matches the correct pad
placement numbering for the footprint in layout. ...
Click to expand...

Oh yeah! There really is no standard and even within the same
manufacturer I have seen two different numbering schemes. And I have
seen lots of people getting a black eye because of it. One of them is
yours truly :-(

Regards, Joerg

http://www.analogconsultants.com
 
On Wed, 04 Jan 2006 19:02:23 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello Paul,

A word of caution though ! Make sure the pin numbering
scheme for the schematic symbol matches the correct pad
placement numbering for the footprint in layout. ...


Oh yeah! There really is no standard and even within the same
manufacturer I have seen two different numbering schemes. And I have
seen lots of people getting a black eye because of it. One of them is
yours truly :-(

Regards, Joerg

http://www.analogconsultants.com
Click to expand...

Count me in. Lately I made it a rule to always double check all three pin
devices especially when it comes to function vs pin number and the
corresponding footprint match. Been there and burned.
Here is what prompted me.

SOT-223 package 5 volt regulator

http://www.zetex.com/3.0/pdf/zr78l.pdf

We later decided that a LDO from National would be a better choice.
Of course the board was already built.

http://www.national.com/ds/LM/LM2937.pdf

Like two gloves



Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

void _-void-_ in the obvious place
 
On Wed, 04 Jan 2006 19:02:23 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello Paul,

A word of caution though ! Make sure the pin numbering
scheme for the schematic symbol matches the correct pad
placement numbering for the footprint in layout. ...


Oh yeah! There really is no standard and even within the same
manufacturer I have seen two different numbering schemes. And I have
seen lots of people getting a black eye because of it. One of them is
yours truly :-(
Click to expand...

I have multiple copies of the same 3-pin footprint under different
names. The footprint name I use is the same as the device name.
This way, if I have not used the device before, the footprint is not
found, and I can then make sure the schematic and footprint pins
are matched when I make yet another copy of the specific footprint.
So far I have not been bitten a second time by this particular
problem.

Regards
Anton Erasmus
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top