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how to use PTH reference calculator

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=1788
Printed Date: 18 Nov 2024 at 8:27pm


Topic: how to use PTH reference calculator
Posted By: fishoutofwater
Subject: how to use PTH reference calculator
Date Posted: 04 Nov 2015 at 1:35pm
Hello again, 


I have a few more basic question, regarding the PTH reference calculator:

1. Hole over Lead - this refers to how much larger the hole diameter should be, WRT lead diameter?

2. Minimum Annular Ring - this refers to the minimum pad-hole width, irrespective of the Pad-to-Hole ratio?

3. Thermal ID over Hole - this refers to the min distance between a hole and a plane it passes through, but does not want to connect to?

4. What is the difference between the pad on layer3 (thermal pad) and the antipad on layer4, other than that the antipad is bigger?

5. Thermal OD to Hole ratio - why do we need to specify this? Isn't both the Thermal OD and Hole diameter already specified previously?

6. Spoke width - why is it specified as 75?


Thank you very much.


Replies:
Posted By: Jeff.M
Date Posted: 05 Nov 2015 at 9:40am
1. Yes, WRT lead diameter or diagonal if not round.
2. Yes, Minimum Annular Ring will never be less than this value.
3. Thermal ID over Hole defines the inner clearance, Thermal OD is the outer clearance.  The clearance is bridged by the spokes.
4. Thermal OD and Anti-pad are equal.
5. Thermal OD to Hole ratio allows the OD to increase in proportion to the hole.
6. Spoke width is calculated as a (percent of the thermal OD) / 4. 75% is the default.


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Posted By: fishoutofwater
Date Posted: 05 Nov 2015 at 9:54am
Thank you!


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