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I have a really small transistor with very little space between its pins. I want to solder resistor to base and wires to collector&emitter. So I am worried about transistor pins come in contact by accident. The wire is about three times as thick as transistor pin, which doesn't help either.

Edit:

Here is small schematic of the things that I need to solder. Wires that connect to relay will be soldered to connector instead of wiring directly to relay. enter image description here

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    \$\begingroup\$ Uhh, carefully. More detailed answer for a more detailed question :) Part number? Photos? \$\endgroup\$
    – Samuel
    Oct 4, 2013 at 5:27
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    \$\begingroup\$ Why not get a larger transistor? Or a PCB to secure it to? \$\endgroup\$ Oct 4, 2013 at 5:32
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    \$\begingroup\$ Please specify package, is it a TO-92? \$\endgroup\$
    – jippie
    Oct 4, 2013 at 5:40
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    \$\begingroup\$ Your transistor is a 2N3904, which is a leaded part. Just spread the leads, and there will be plenty of space between them. Those leads are just wires. You can bend them like other wires. Of course bending them too much will break them eventually, but that's not going to happen from just spreading them for easier soldering. Of course this is all obvious, so I really don't see what problem you are asking about exactly. \$\endgroup\$ Oct 4, 2013 at 11:47
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    \$\begingroup\$ "The wire is about three times as thick as transistor pin" - so use some more appropriate wire! \$\endgroup\$
    – pjc50
    Oct 4, 2013 at 11:59

4 Answers 4

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Soldering wires to TO92 packages may be a bit fiddly but it is well within the capabilities of an amateur hobbyist.

enter image description here enter image description here

When I have trouble, I use a magnifier and some "helping hands"

enter image description here

If I wanted to hand soldering SOT23 to wires, that would be much more of a challenge!

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    \$\begingroup\$ In the model railway world, it's not unheard of to solder wires to 0402 LEDs youtube.com/watch?v=7gNPy9AsrVg \$\endgroup\$ Oct 4, 2013 at 13:40
  • \$\begingroup\$ @PeteKirkham "Here's one. I'll do another one quickly." That is insane, at least it is to me. \$\endgroup\$
    – jM2.me
    Oct 4, 2013 at 14:54
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I solder a lot of 2n3904's (working to drive relays the same as your circuit). I'll ignore the obvious suggestion of soldering it to a circuit board as you sound like you want to solder wires directly to the device.

One method is to bend the legs out a bit in different directions, that gives you a lot more space to solder.

If you need to package it up small once soldered, put some heat-shrink sleeving over the wires/legs so they can't make contact.

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If space is an issue, you can always cut a pcb to 3 ports/pins, and insert the transistor and solder it. Soldering wires should not be a problem, if you have had soldering experience before. You can also use a vice to make it easy for you.

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I would use a wire about as thick as the transistor pins.

Put a little solder on the wire and the pin (just a little coating, not big blobs), then solder them together.

Use heat shrink tube for insulation. You can also use electrical tape, but that is messier and less convenient.

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