1206 or 0603

Chat about pick and place machines, reflow ovens, assembly techniques and other SMT tips & trix

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westfw
 
Posts: 2008
Joined: Fri Apr 27, 2007 1:01 pm

Re: 1206 or 0603

Post by westfw »

At least a few versions back (based on my existing designs probably over a year ago), the Eagle RCL library was significantly updated. The description claims all footprints are IPC now.
Was it? I have an RCL library from the latest version, and the gap between the SMTs of the R0805 package is still smaller than the gap between the R0603 package, for example!

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macegr
 
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Joined: Fri Apr 04, 2008 4:46 pm

Re: 1206 or 0603

Post by macegr »

Yes, but just barely, nowhere near what it was. It's still significantly better than the old libraries. I took some designs I hadn't touched since Eagle 4.16, and hit Update All, and the gaps really widened out, it looked like double the space. I also compared some of the footprints to what the IPC calculator suggested, and they're reasonably close now. Of course the calculator has a zillion parameters to tweak for various uses. That's why it's a calculator instead of a list of standard measurements.

alex_dubinsky
 
Posts: 188
Joined: Wed Jul 30, 2008 5:17 pm

Re: 1206 or 0603

Post by alex_dubinsky »

Big footprints with small spacing between them are good. They don't look like your aesthetic conception of the "ideal footprint," but what's wrong with them? A nice big area for the solder to spread out onto (as it needs when anchoring to the sides of components). A nice big target for the PnP machine. It makes sense for production soldering (using reflow and PnP), and maybe for hand-soldering.

There's a lot of parameters in the IPC calculator (and in Altium's footprint wizard, which uses the same technology), and these control a number of things. 1) How dense a design you are making (it won't generate small pads unless there is a reason). 2) The size of components (which is actually slightly different between "0805" resistors, capacitors, and leds) and 3) The shape of the components' leads (which, again, differ slightly). But unless you really constrain it, you'll have pretty big, non-pretty footprints.

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