PCB Libraries Forum : IPC-7352 Mathematical Model https://www.PCBLibraries.com/forum/ Mon, 24 Aug 2026 15:04:28 +0000 Sat, 15 Aug 2026 11:00:54 +0000 http://blogs.law.harvard.edu/tech/rss Web Wiz Forums 12.07 360 https://www.PCBLibraries.com/forum/RSS_post_feed.asp?TID=3675 <![CDATA[PCB Libraries Forum]]> https://www.PCBLibraries.com/forum/forum_images/PCBLForumLogo.gif https://www.PCBLibraries.com/forum/ <![CDATA[IPC-7352 Mathematical Model : The IPC-7352 standard defines...]]> https://www.PCBLibraries.com/forum/ipc7352-mathematical-model_topic3675_post14614.html#14614 Author: Nick B
Subject: 3675
Posted: 15 Aug 2026 at 11:00am

The IPC-7352 standard defines the mathematical model for creating reliable surface mount (SMD) PCB footprints by providing formulas to calculate pad width (X), pad spacing (G), and pad span (Z), based on component dimensions, solder fillet goals, and manufacturing tolerances.

The following images illustrate potential pad and terminal relationships under various Material Conditions – Minimum, Nominal, and Maximum.

  1. The Nominal Material condition of the component package & Nominal Terminal.
  2. The Minimum Material condition of the component package & Nominal Terminal.
  3. The Maximum Material condition of the component package & Nominal Terminal.
  4. The Minimum Material condition of the component package & Minimum Terminal.
  5. The Maximum Material condition of the component package & Maximum Terminal.


    The resulting pad stack must have terminal leads on the pad stack regardless of every possible Material Condition possible to pass assembly inspection and meet the requirements set forth in the IPC J-STD-001 Standard and the IPC-7352 Guideline.

    i.e.: regardless of the Component Package and Terminal Lead Material Condition, the Terminal Lead must never be exposed outside the calculated pad stack.

    Note: most component packages are created in the Nominal Material Conditions. The package tolerances play a key role in the resulting pad stack.

  6. Nominal Package Dimensions & no Package Tolerances.
The Footprint Expert uses the IPC-7352 Mathematical Model.
For details, see IPC-7352.


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