pcbpcb-assemblysoldering
I swapped the base and emitter of my NPN transistor land pattern. If I flip over the part, the pins are in the correct orientation, although there is a 1mm between the pins and the pads. When I tried to solder one I just made a mess. I soldered wire wrap wire in the vias and then tried to solder the wire to the pins. Is there a better technique?
Here is a photo of the part before I would desolder:
Here is the mess I made of a different one:
A SMD pad is not a good way to attach a wire. That should be done with a thru-hole pad. You might even want two thru-hole pads to loop the wire thru for better strength.
If the wire is vibrating a lot, then maybe a few zig-zags in the wire near the PCB will cushion or decouple the wire motion from the PCB a bit.
A crimp is usually used inside heaters for connecting nichrome wire to other metal parts or wires. Since it can get hot, you'd need a bare metal (not plastic coated) butt crimp.
Its a very reliable method if you use the right tool and a very poor method if you make-do with pliers and brute force. With the right tool, the two metals in a crimped bond are actually cold-welded together, forming a gas-tight bond. Other connection methods (including soldering without sufficient flux) may leave oxide layers or admit oxygen which can affect conduction and mechanical strength.
The "right tool" is the ratchet crimp tool recommended by the manufacturer for the particular crimp and wire. Ratchet tools ensure that the correct pressure is applied before they release (unless you use the emergency release lever which is only meant in case of trapped fingers). As opposed to a pair of pliers, which may under or overcrimp the part, not shape the crimp correctly, slip off etc. Ratchet crimp tools can and should be calibrated.
Best Answer
One way is to leave the SOT-23 soldered to the board, simply cut those two traces on the PCB, and solder jumper wires to the base and emitter on the part, swapping the wires over to the correct vias. Cleaner, less risk of mess-up.