how do I solder a power switch to a mobile board

You need a fine tipped iron, some fine solder and some SMT skills, definitely NOT a soldering gun! If the switch is detached, are you sure it didn't take the solder pads with it? That would make a straightforward repair into a very tricky or even impractical one.

Dave

Can I have (pointers to) more instructions as to how to solder the switch? What are solder pads? The contact points are silver if this helps. I did manage to power on the mobile by connecting those points via a wire

Solder pads = contact points. The fact they are still silver indicates they are probably OK, so that's a good start.

That's Good. You'll need a fine tipped soldering iron, preferably a temperature controlled one but it's not essential. Use fine rosin cored solder. Put the switch in place, and if possible get someone to hold it down for you. When you are happy that the switch is located correctly, apply the tip of the iron gently to one of the switch legs and solder pad. Quickly put the solder onto the contact (not the iron!) and it should flow freely and join the leg and the contact point. Repeat on each connection. Each one should take a second of soldering time, any more and something is wrong- either your iron is not hot enough, your technique is incorrect or the parts to be soldered are tarnished/coated with something. If you keep the iron on too long, the solder pad and possibly the switch will be destroyed and the repair will be difficult to impossible.

While working on the phone, you must take antistatic precautions. Working on an earthed metal kitchen sink will suffice if you don't have antistatic wristbands etc.

Dave

A wooden clothes peg (possibly with the jaws whittled to a suitable shape) is great for this.

*Quickly* (1-2 seconds) tinning the switch legs & the PCB pads will make the above quicker & easier. Let both parts cool for a short time (30 seconds) before soldering them to each other.

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   W          
 . | ,. w ,   "Some people are alive only because
  \|/  \|/     it is illegal to kill them."    Perna condita delenda est
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I am not expert on using the soldering iron and I am afraid I may damage the circuit. Isn't there another way of doing this? How about liquid solder or something else?

[...]

That's a legitimate fear - it's very easy to damage a PCB if you're inexperienced. My advice is to practice. If you can spare the time/cash, go to a hobby electronics shop (Tandy/Radioshack, etc) & buy a tiny piece of strip board or other prototyping PCB & practice soldering small pieces of wire to the strips.

The only sensible alternative would be to take the device to someone with lots of soldering experience on small devices. If you take it to any kind of repair shop, a half-hour of their standard labour charge would be a fair price for a customer like yourself walking in off the street. If it's a one man shop & you ask very politely, they may charge you less. (If it were me, & you were someone I knew socially, I'd probably charge you $20-30, depending on how messed up the damaged area is, & turn it down if I didn't think it was fixable.)

Most of those sorts of things don't work make all that good an electrical connection in the first place, & for a power switch, you'll probably need a very good mechanical join as well, which you won't get with any of the no-solder methods.

Sorry to sound like such a wet blanket, but I'd hate to give you overly optimistic advice that'd most likely ruin your phone. Soldering small parts safely requires practice, & if you can't find any way of getting some practice, you should take it to an expert.

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   W          
 . | ,. w ,   "Some people are alive only because
  \|/  \|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

Lionel wrote in news: snipped-for-privacy@4ax.com:

Got any dead electronics? Practice on those. My advice is to try one of the tasks I found hard: desoldering with a solder sucker bulb (Radio shack, ~$5 US). If the joint isn't hot enough you won't get all the solder. Too hot and you'll melt the board.

One more tip: Keep the tip clean. You can use a damp sponge or folded paper towel to wipe off any collected gunk without unplugging the iron.

Puckdropper

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