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I have little boards that allows soldering one SMD chip, but these must be soldered to pins and then the pins plugged into a breadboard or soldered to a perfboard.

Instead, it occurred to me to design a generic PCB in which there are a number of SOIC chip placements, with the leads fanning out until they are separate enough to solder wires to I don't know if this is a terrible idea, but good or bad, I can't even figure out how to do this easily. Eagle does not allow building out traces without the wires being connected to the other side.

So first, as a practical matter, is there any way in Eagle to lay out traces directly, not connecting two wires. I want to design in bus lines for power, for example, and then connect.

Second, if this is a terrible idea please explain why?

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    \$\begingroup\$ Look for smd landing pads \$\endgroup\$ – Passerby May 25 '16 at 3:30
  • \$\begingroup\$ do you mean using "wire" command instead of "route"? \$\endgroup\$ – Wesley Lee May 25 '16 at 3:38
  • \$\begingroup\$ No, just trying to create routes spreading out the pins so I can solder to them. \$\endgroup\$ – Dov May 25 '16 at 3:41
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If you want to bring traces out to solder to, you basically need a footprint which you solder on to - you then route the pads out to the solder point. Typically these are called test-pads - Eagle has a testpad library that has lots of different shapes and sizes, both through-hole and SMD.

As to your second question, it is and it isn't. Helpful I know.

  1. The good - You can solder more than one footprint, and if you get the boards made by your pick of PCB pooling services, you can get a large number of such boards for much much less than the breakouts that you can buy - those adapter boards usually cost $10 or more which is ridiculous if your IC costs only $1.

  2. The bad - Except for a few things like the 7400 series logic and some amplifiers, there is no one footprint fits all. There are many different shapes, sizes, pitches, widths, pin arrangements, etc. You couldn't do something like a simple power supply bus because they all have pins in different places.

  3. The ugly - Soldering wires to surface mount pads or traces is asking for trouble. 1oz copper is only 35um thick, which is really quite thin. The adhesion between the copper and FR4 is also not that great. It is very easy to rip SMD pads of boards by soldering wires to them - very very easy. Once the pad or trace is gone, you can't easily put it back. If you have 10, 14, 18, even 32 wires dangling off the board, you can pretty much guarantee you will lose pads every time. Now if you use through-hole test pads for soldering, or place a couple of vias in the pad you can reduce this problem a bit as the copper going through the board can act as an anchor for the pad.

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  • \$\begingroup\$ What about connecting to a through hole which can then have a wire soldered in? \$\endgroup\$ – Dov May 25 '16 at 3:42
  • \$\begingroup\$ @Dov that works (see the end of point 3). What you end up with is basically the same thing as those breadboard adapters that you can get - though a lot cheaper if you panelise a few into something like a 5cm x 5cm area and send it to one of the many Chinese PCB houses. \$\endgroup\$ – Tom Carpenter May 25 '16 at 3:43

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