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Thermal Pad and Paste Mask Apertures

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=3622
Printed Date: 06 Mar 2026 at 2:19pm


Topic: Thermal Pad and Paste Mask Apertures
Posted By: pcbfreedomcad
Subject: Thermal Pad and Paste Mask Apertures
Date Posted: 05 Mar 2026 at 3:19am
If a bottom pad of a QFN for example, has multiple paste mask openings generated from PCB Libraries, do these openings need to have rounded corners, or do the fabricators handle the issue with 90 degree corners on stencil openings automatically?

I know the bottom pad itself can have rounded corners.


Replies:
Posted By: Tom H
Date Posted: 05 Mar 2026 at 7:39am
All out Texas Instruments footprints on https://www.pcblibraries.com/POD" rel="nofollow - www.pcblibraries.com/POD that have thermal pads, have the exact checkerboard pattern dimensions and spacing as their datasheets provide. Including 0.05 mm corner radius. 

These parts include QFN, SON, QFP, SOP, PSON, PQFN, DPAK with thermal pads. There are approximately 40,000 TI footprints with thermal pads on the Parts on Demand cloud database. 

The only way to accomplish this is to build the footprint using the calculator and setup all the TI package and footprint dimensions and save to FPX for the 3D STEP model. 

Then move the footprint to FP Designer for customizing the paste mask apertures in the thermal pad stack. Then save to FPX as the real footprint. 

Rename the Calculator footprint and Physical Description to match the FP Designer data. 

Output to CAD the FP Designer footprint footprint first. Then open the Calculator footprint and create the 3D STEP only and overwrite the FP Designer 3D STEP model. 

Then import into your CAD tool and you'll get the perfect mfr. recommended pattern with a high-quality 3D STEP model. 



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