How do I match a virtual component to its real life footprint?

[Sir Hackalot]

Hi there, I'm just learning how to do the end-to-end circuit/PCB design. I've done many schematics before so that isn't a problem. I am new to PCB design though and am having some functional dilemmas. So I followed the tutorial that came with CDS 10 and now I want to do my own design. I've created the schematic and simulated it without problems.

Now I'm faced with the PCB side of things: footprints. In the "Select a Footprint" dialog I see a long list to choose from. Let's say I have a capacitor with known dimensions. I've figure out how to use the filter to just see capacitor footprint. Unfortunately I don't know how to choose one. Yes, by clicking the "Select" button, but I mean choosing the correct one. Here's the question: given the real-life datasheet specs, how do I pick the footprint corresponding to it. Thanks for any input!

Just as an example, I have this capacitor: http://www.mouser.com/Search/ProductDetail.aspx?qs=YWUJW9zUqjbvkoAszL85Xg%3d%3d. What is the footprint to use with this?

[yyao]

Hi,

Page 2 of the datasheet gives you dimensions of the capacitor. My favourite method of finding a suitable footprint for a component is to use the footprint browser in Ultiboard. Do the following:

1. Open Ultiboard
2. Open an existing design or create a new one (don't worry, we won't be modifying the design)
3. Click Place>>From database
4. In the database tree, select Ultiboard Master>>Through Hole Technology>>Capacitors>>Axial
5. Now in the Available Parts list, you will see all the available footprintsin this family
6. Click Show Dimensions and change the display units to mm
7. Using the dimensions given in the datasheet and the dimensions shown in Multisim, you can now choose an appropriate footprint. Remember to choose a footprint that has lead spacings wider than the length of the capacitor. You can always print life size copies of your design to verify the suitability of footprints on life size components
8. Now copy the foot print name (CAPPAxxx or CAXx) to Multisim.

 Hope this helps get you started. You can do this to find any footprint that you may need for other components as well.

[Sir Hackalot]

Thanks for the answer! I tried this and it seems to work. Is there also a way to change the footprint for a part in Ultiboard and then bring that back into Multisim? Meaning that, let's say I pick a footprint for the capacitor in Multisim then transfer to Ultiboard only to find I picked the wrong one. I found an option called "Change Shape" but it removed the pin/net connections and it gave an error in Multisim saying "Component not found." I wonder if I'm doing it wrong...

[yyao]

The best way to change the footprint of a component in your design is to do so in Multisim. There are a few ways to do this:

• Double click the component, click Replace and select a different footprint form the list
• Double click the component, in the Value tab, click Edit Footprint, click Select From Database and select one from the list
• Double click the component, in the Value tab, click Edit Footprint, click Change and manually type in the footprint name

 Now, once you've done that, click Transfer>>Forward Annotate to Ultiboard 10. Multisim will ask you to save your updated netlist file, similar to when you initially transferred your design to Ultiboard. Once you've done that, Multisim will launch Ultiboard and tell it to update the PCB with any new component values and footprints that you've updated from your schematic.

[testin]

Is this really so clumsy that I have to browse available footprints in Ultiboard and memorize the footprint name and then go back to Multisim and type the name there - so basic task and so difficult!!

Message Edited by testin on 02-14-2010 01:52 PM

[RichardJennings]

I totally agree! Choosing the correct footprint shouldn't be as hard as it is now.

Richard