altiumfootprintpcbpcb-design
I'm a student trying to create a library part in Altium for an Analog Devices AD8232. Most IC datasheets give a recommended footprint to use, but the AD8232 datasheet only shows the IC itself:
I have been searching, but have been unable to find a recommended layout for this footprint.
If you were designing the footprint for this device, how would you determine the pad sizes to use?
In my PCB CAD package I am free to select the origin anyplace I want. When I am in the midst of creating a footprint I will place some pads and then move the origin around as suits the task at hand and according to the drawing. When the thing is completed I then place the final origin at a place that makes the most sense for the part centroid.
That is a recommendation of layout, not the size of the pin itself. In this case, the hole should still be 1.3mm.
If you look at the mechanical drawing of the part, it shows that the pin is 1.18mm wide, so 1.30mm clearly accounts for some margin.
If you are really unsure, you can ask you assembly house if such tolerance is enough for the placing machine. If you are placing by hand, you should be fine.
A different question is how your fab house interprets those hole dimensions (some interpret as finished dimensions, other as drill size), but this is a problem for plated holes mostly - not the case here.
Best Answer
Method #1:
Tools->IPC Footprint Wizard->QFN and go from there.
This wizard is based on IPC-7351 standard, the main standard for footprint creation. The standard is not straightforward if you want to calculate the footprint dimension by your own so it´s highly recommended to use the wizard.
Method #2:
Refer to AN-772. A Design and Manufacturing Guide for the Lead Frame Chip Scale Package (LFCSP)