Confused about pad size

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   LS,
I am creating a footprint for an 0201 resistor and I am a bit confused about the pads for the generated component.

The size of the 0201 is defined as 0.60mmx0.30mm, with a 0.03 tolerance. The terminal width = 0.15x0.30mm.

The visible grid is 0.01mm. The settings in the Footprint Expert fort the pad size are;

The placement tolerance is set to the default 0.025mm

The generated part however has a toe value of 0.148mm. I do not understand how this value is calculated. 
The same applies for the side and heel value. I would expect it to fall inside the terminal.

What am I missing ?

Regards, Charles

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magnus.lictor Members Profile Send Private Message Find Members Posts Add to Buddy List Advanced User Joined: 27 Aug 2012 Location: Amsterdam, NL Status: Offline Points: 60	Post Options Post Reply Quote magnus.lictor Report Post Thanks(0) Quote Reply Topic: Confused about pad size Posted: 20 Mar 2023 at 6:57am
	LS, I am creating a footprint for an 0201 resistor and I am a bit confused about the pads for the generated component. The size of the 0201 is defined as 0.60mmx0.30mm, with a 0.03 tolerance. The terminal width = 0.15x0.30mm. The visible grid is 0.01mm. The settings in the Footprint Expert fort the pad size are; The placement tolerance is set to the default 0.025mm The generated part however has a toe value of 0.148mm. I do not understand how this value is calculated. The same applies for the side and heel value. I would expect it to fall inside the terminal. What am I missing ? Regards, Charles



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: 5716	Post Options Post Reply Quote Tom H Report Post Thanks(1) Quote Reply Posted: 20 Mar 2023 at 8:35am
	You are missing the package tolerances. The package tolerances are included in the mathematical model to determine the pad size. Make all the package tolerances 0.00 and see what happens. The Fabrication and Assembly tolerances are also used in the mathematical model to determine the pad size. Turn them to 0.00 to see the results. You can also turn the negative values in the solder joint goals to 0.00 and see what happens.
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