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SOT-223 tab pad

Printed From: PCB Libraries Forum
Category: PCB Footprint Expert
Forum Name: Questions & Answers
Forum Description: issues and technical support
URL: https://www.PCBLibraries.com/forum/forum_posts.asp?TID=2671
Printed Date: 25 Nov 2024 at 3:39pm


Topic: SOT-223 tab pad
Posted By: jhansonxi
Subject: SOT-223 tab pad
Date Posted: 06 Sep 2020 at 4:02pm
I'm normalizing my SOT-223/TO-261 FPs across multiple manufacturers.  The dimensions I'm using are identical across 4, 5, and 6 pin except for the pitch and pin widths.  I've noticed that with LEP 2019.07 the tab pad size changes along with its corner radii when the smaller pins on the other side change.  For example, the Y size on a 4-pin is 1.8mm but on a 5 or 6-pin it is 1.65mm.  Is this intentional?  What is the rationale?


Replies:
Posted By: Tom H
Date Posted: 06 Sep 2020 at 4:42pm
You are in 100% control of the Preference Options. 

If you are using Library Expert Pro, you can select the "Rules" tab and change the "Corner Radius Size" values to anything you want. There is: 
  • Corner Radius Size (% of Pad Width)
  • Corner Radius Size Limit
  • Corner Radius Round-off
Change the "Corner Radius Size Limit" to 0.10 and you'll tighten up your corner radius values. 

If you get the Free Library Expert Enterprise on a Cloud License you just pay for the yearly maintenance to get all the updates and technical support. 

Then you can have access to the Global Preferences so that you set the values once and it applies to every footprint. The Enterprise edition allows you access to over 1,000 preference settings to globally apply to every footprint. 



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Posted By: jhansonxi
Date Posted: 07 Sep 2020 at 9:06pm
I know I can change it in the preferences. 

I can also change it in Altium.  

But that doesn't answer my question: Why does the small pin dimensions affect the Tab Pad?


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