Mismatch Footprint Expert & IPC7352

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   Hello,
Does anyone understand how the numbers in the terminal settings are determined?

For example, for the Flat No-Lead, according to Footprint Expert, the toe is 300 um long.

According to IPC-7352, the toe is calculated based on the height of the solderable leads.

That doesn’t seem to match up for me — how do you interpret this?

I have loaded the ipc-7352.opt file.
Thank You

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eCADLER_94 Members Profile Send Private Message Find Members Posts Add to Buddy List New User Joined: 15 hours 59 minutes ago Status: Offline Points: 2	Post Options Post Reply Quote eCADLER_94 Report Post Thanks(0) Quote Reply Topic: Mismatch Footprint Expert & IPC7352 Posted: 15 hours 49 minutes ago at 5:13am
	Hello, Does anyone understand how the numbers in the terminal settings are determined? For example, for the Flat No-Lead, according to Footprint Expert, the toe is 300 um long. According to IPC-7352, the toe is calculated based on the height of the solderable leads. That doesn’t seem to match up for me — how do you interpret this? I have loaded the ipc-7352.opt file. Thank You



Tom H Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 05 Jan 2012 Location: San Diego, CA Status: Offline Points: 6001	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply Posted: 10 hours 39 minutes ago at 10:23am
	There are several moving parts here. IPC-7351B had Flat No-Lead QFN/SON Toe value at 0.30. IPC-7351C changed the Flat No-Lead QFN/SON Toe value at 0.20 (or 100%) of the terminal height. However, IPC-7351C was never released but we included it in Footprint Expert as the 'PCB Libraries' solder joint goals. It is the program default setting. IPC-7352 was released in a hurry because IPC wanted to get the through-hole technology completed. Through-hole was started in 2011 and finally released in 2023. Footprint Expert has always worked with hard coded solder joint goal values. It never supported percentages of terminal heights. So when IPC-7352 was released, we just moved the IPC-7351B numbers across to fill in for any solder joint goals that percentages. The main reason for not using percentages in solder joint goal calculations is because it would increase the number of solder pattern footprints for the same package Case Code from different component manufacturers with various terminal heights. All Option files are 100% editable by the end user. Just select 'File > Save As > Your Name - IPC-7352' and all the cells will become editable. Change the values to meet your company rules.
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