I just received an order of Arduino Pro-Minis, and I needed to solder header connectors on them. Since I use the I2C function in virtually all my projects, I couldn't ignore the fact that the A4 and A5 connectors are offset. The pins on this particular board are off-grid, they don't line up with the pins for the rest of the GPIO. So I found a sequence of soldering to get around it.
Step 1: Step 1: My Rig.
As you can see in the photos, I have clamped a piece of perfboard into my vice. I will eventually build a box to mount it on, since this is a great soldering jig. I clamped the perfboard in such a way that the vice jaw is above the surface equal to the thickness of the header connectors' plastic retainer.
I cut off a two-pin piece of header and placed it in the perfboard a distance from the jaw so that the Arduino board can rest on the jaw and be parallel to the perfboard when the pins are in the proper holes. Then I soldered the pins.
Step 2: Step 2: Adding FTDI and Remaining Askew Analog Connections.
Because my FTDI has a male connector already soldered on, I opted to use a female header on the Arduino. I ordered a bunch of 50 pin female connectors, and I just cut with snips the amount of pins I want. Then I file the rough edges with a metal file. The remaining analog pins take a three-pin male connector. so I inserted the three-pin connector into a scrap piece of female header, and put a scrap male into my six-pin female FTDI connector. Then I placed them in the perfboard at the proper locations and placed the arduino face-down over the top. There is a slight offset, but it's not hard to get the connectors in place.
Step 3: Step 3: Finally Adding the GPIO/Power Connectors.
These a simple, just drop the connectors into the perfboard. The kits I ordered came with these connectors and the right-angle FTDI connectors I opted not to use. When soldering these, I recommend soldering just one pin and then checking that the connectors stayed perpendicular. I suppose this tip is good for all steps, but these little boogers seem more inclined to roll. With one pin soldered, you adjust until you're satisfied. Then it's simple to solder the rest.
Step 4: Conclusion:
Now you can connect the FTDI and load your test sketch, verify your work, and your Arduino is ready to go into your next project.