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SMT Terminal size/shape vs pad size/shape
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    Posted: 17 May 2017 at 6:17pm

For the built-in component types, we enter the dimensions and tolerances of the component terminals, and Library Expert automatically calculates the pad shape and size based on various preferences. For example, I usually select the rounded-rectangle shape, and the pad size is usually somewhat larger than the terminal size.

However, it appears that with custom components (FP Designer), there is no way to specify the terminal size/shape. Instead, we must directly specify the pad stack geometry – even though the terminal size/shape is the thing that is truly constant for a part, while the pad stack geometry could conceivably change with different preferences.

Given the goals of the FPX library architecture, it seems like there ought to be a way to define custom parts in the same way built-in parts are defined: Instead of directly entering pad-stack details, enter the truly constant physical aspects of the part – Lead type, size, and shape, location, and tolerances – and let the software calculate the pad-stack geometry from that information combined with the preferences.

  • Is there a way to do that that I am overlooking?
  • Short of that, how do I calculate the dimensions of, say, a rounded-rectangle pad stack, given the dimensions and tolerances of a component terminal, using the same rules Library Expert uses for built-in components?
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Tom H View Drop Down
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Points: 5717 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2017 at 6:39pm
FP Designer is strictly for mfr. recommended patterns for connectors and non-standard parts.

Or you can push any Calculator part to FP Designer to edit the pad stack names and do customized editing.

However, we're not working on V2017 anymore. Everyone is working on V2018 which is a complete 100% re-write in C# with WPF (Windows Presentation Foundation) and it will make it's first appearance in July for Symbol Expert beta for 5 months. V2018 Library Expert will have Symbols, Footprints, 3D STEP and you can see the entire set at once and cross-probe between them.

FP Designer does use the Through-hole and Drafting Preferences but SMT pad stacks are user defined using the mfr. recommended pad sizes.

V2018 FP Designer have much more flexibility with irregular shape pads and some new features, but SMT pad size calculation should be done in the Calculator and then moved to FP Designer.

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Points: 41 		Post Options Post Options   Thanks (0) Thanks(0)   Quote SWB01 Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2017 at 7:10pm
Quote V2018 FP Designer have much more flexibility with irregular shape pads and some new features
That sounds good.
Quote SMT pad size calculation should be done in the Calculator and then moved to FP Designer
Do you mean that I should be able to use the Calculator to calculate a rounded-rectangle pad geometry for a given terminal type/shape/size? If so, I don't see where to do this. The through-hole calculator is very useful, as it will give you hole and pad size for a given lead size/shape and fabrication level, but the surface-mount calculator doesn't really seem to do much "calculating" – it appears to be more of a "definer" or "designer" than a "calculator."

I suppose, though, that I could pick a standard component that has a similar terminal type (for the component I'm working on now, that could be a DFN, PQFN, or PSON), enter my terminal dimensions there, see what pad-stack geometry is calculated, and copy that pad stack to my custom component.
Quote a complete 100% re-write in C# with WPF (Windows Presentation Foundation)
Hope that's going well for you! WPF has a few nice abilities, especially for simple stuff, but every time I try to do something with it of any complexity, it ends up being a lot more difficult that it would have been to have stuck with WinForms. (Maybe I'm just not a sophisticated enough coder! Tongue)
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Points: 5717 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2017 at 7:14pm

It explains the feature for pad calculation and move to FP Designer.

Check out the other 70 videos while you're there.

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