Paste Mask Thermal Tab DPAK
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=3257
Printed Date: 12 Oct 2024 at 7:28pm
Topic: Paste Mask Thermal Tab DPAK
Posted By: phil.holden
Subject: Paste Mask Thermal Tab DPAK
Date Posted: 13 Apr 2023 at 2:38am
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Hi Tom, I have used the latest Enterprise Edition 23.06 to create a D2PAK footprint. I have noticed that the 50% Paste Mask checkboard is no longer being applied. Is there a reason for the change?
I noticed in the release notes of an earlier version it mentioned something about the tab being identified as 'mechanical' rather than 'thermal'. Would this mean that the thermal pad pattern would no longer be applied to DPAK thermal tabs? |
Replies:
Posted By: Tom H
Date Posted: 13 Apr 2023 at 8:59am
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We originally made a mistake and identified the large DPAK pad as a thermal pad with a checker board paste mask. It's actually a Flat Lug Lead. We're now following IPC J-STD-001 standard and it requires visible solder wetting on the end of the large tab. A Flat Lug Lead has a Toe solder joint and the pad is larger than the flat lug so the solder needs to run out to the end of the flat lug onto the extended pad to form a solder fillet. Wetting is evident (visible). A Thermal Pad is 100% under the package body and has no Toe, Heel or Side solder joint goals. There is no where for the solder to flow. i.e.: There is no evidence of visible wetting on a thermal tab. ------------- Stay connected - follow us! https://twitter.com/PCBLibraries" rel="nofollow - X - http://www.linkedin.com/company/pcb-libraries-inc-/" rel="nofollow - LinkedIn |
Posted By: Tom H
Date Posted: 13 Apr 2023 at 9:38am
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We are working on a new feature for the DPAK to allow a negative value for the L1 dimension. This removes to Toe Solder Joint and turns the Flat Lug Lead into a Thermal Pad. If the large tab on the DPAK is 100% under the package it will have a checker board pattern. ------------- Stay connected - follow us! https://twitter.com/PCBLibraries" rel="nofollow - X - http://www.linkedin.com/company/pcb-libraries-inc-/" rel="nofollow - LinkedIn |
Posted By: phil.holden
Date Posted: 14 Apr 2023 at 1:37am
| Makes total sense now you explain the initial mistake. Thanks for the explanation. |
Posted By: phil.holden
Date Posted: 14 Apr 2023 at 1:41am
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I also found the calculator for the DPAK a bit more logical.... It was perhaps that the datasheet dimensioning was a lot more in-line with the calculator as i'm not sure if you have made any changes to that part? Previously when creating DPAK footprints i have always had to make numerous calculations in order to add the numbers in the format that the calculator wants, if that makes sense? |
Posted By: Tom H
Date Posted: 14 Apr 2023 at 9:33am
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There is a new V23.07 Footprint Expert Enterprise pre-release today that adds more features to the DPAK component family. https://www.pcblibraries.com/downloads" rel="nofollow - www.pcblibraries.com/downloads Fixed for DPAKs Negative tab terminal value L1 (shown as tab protrusion
beyond the body) is now allowed. (meaning L1 becomes the pull back distance of the
thermal tab and the tab can be entirely under the body).  If the L1 dimension is less than zero (tab is entirely
under the body) and set back from the D dimension)
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