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Thermal Pad Issue

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=3541
Printed Date: 15 Sep 2025 at 12:08pm


Topic: Thermal Pad Issue
Posted By: m.elsayed
Subject: Thermal Pad Issue
Date Posted: 14 Sep 2025 at 5:56pm
I can adjust Thermal Pad by this parameter, but when open in Altium gives wrong value.

Can have more explain how to adjust this?

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uploads/11979/exposed_pad_paste_mask=-3.2_same_as_size.jpg" rel="nofollow - uploads/11979/exposed_pad_paste_mask=-3.2_same_as_size.jpg

uploads/11979/ep.fpx" rel="nofollow - uploads/11979/ep.fpx



Replies:
Posted By: Tom H
Date Posted: 14 Sep 2025 at 6:15pm
80% Paste Mask Reduction will not give you a Checker Board Pattern. 

80% Paste Mask Reduction will provide a single paste mask aperture. 

70% is the highest Paste Mask Reduction to generate a Checker Board Pattern. 



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Posted By: m.elsayed
Date Posted: 14 Sep 2025 at 9:48pm
 i have attached fpx, can please we have explain on it , 
if 80% not applicable why tool not block user , rather than get wrong values, please add more details for this point, when apply 70 % what values should appears in Altium

Posted By: Tom H
Date Posted: 15 Sep 2025 at 7:29am
You must consider all the rules. 

You have a Minimum Paste Mask web set to 0.20 mm. 

You need to keep the Thermal Pad Paste Mask 0.10 mm indented from the pad edge. 

80% is doable however, you're not going to get a Checker Board Pattern. 

Many users set Thermal Pad Paste Mask to 100% and allow the Assembly Shop Stencil Mfr. design the paste mask reduction. 

All we're saying is that we found out that 70% is the highest you can go a still get a Checker Board Pattern. 

We're not going to limit the software program and not allow 80%. If you're not educated on the mathematics of paste mask reduction, and the consequences of your Option settings, that's not our responsibility. It's trial and error. 



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