SOT23 launched into space!

Thread Starter

AlbertHall

Joined Jun 4, 2014
12,328
I was trying to replace a SOT23 device on a small PCB. I used a hot air gun and tweezers to remove the faulty part - all good so far.
I fetched the replacement part from my stock and used the tweezers to place the part on the board but there was a small sharp 'ting' noise and the replacement part disappeared. I fetched another one from my stock - my very last one - and, you guessed it, that one joined the first in orbit.

Please tell me a better way of holding such parts ready for soldering.
 

Ian0

Joined Aug 7, 2020
9,494
Have you got the air speed turned up too high?
Melt the solder on the pads first, place the transistor on the most en solder, keep holding it with the tweezers until the solder has flowed on to the pins, then move the hot air gun away.
 

Thread Starter

AlbertHall

Joined Jun 4, 2014
12,328
Have you got the air speed turned up too high?
Melt the solder on the pads first, place the transistor on the most en solder, keep holding it with the tweezers until the solder has flowed on to the pins, then move the hot air gun away.
I hadn't got the air gun anywhere near it yet. I was just trying to position the part on the pads with the tweezers. Presumably the grip slipped and the springiness of the tweezers launched the part somewhere unknown. If you simply drop a part then you have a general location to search but withe tweezers you don't see which way the part went. It could be anywhere.
 

seanstevens

Joined Sep 22, 2009
236
Its a part of SMD hand soldering, watch out for the tiny caps and resistors, they will fly the same way. They can also fly in to one's face and eye so be careful!
 

Dodgydave

Joined Jun 22, 2012
11,236
It’s not while soldering it that he has the problem, it is while placing it with tweezers. I have the same problem.
i know, but it's easier with something sticky like wax to grab it from the bit box or reel and place it rather than use tweezers, I've been there several times and resorted to wax.
 

SamR

Joined Mar 19, 2019
5,019
Reverse action tweezers where you have to squeeze to release. Only problem is sometimes they don't put enough tension on the part while holding and allow the part to rotate between the blades.
 

WBahn

Joined Mar 31, 2012
29,854
I have had very few issues with this. But I suspect I take more care and go slower and am more deliberate in my moves than a lot of people are. I tend to make sure that both tips of my tweezers are down on the surface on either side of the part before I close them in on it. That might be a major reason why I get so few fliers. I also don't squeeze the tweezers hardly at all. In fact, the far more common problem I have is simply dropping the part straight down.

I don't use a hot air gun, I was able to get a real nice Metcal station dirt cheap a long time ago. So I tend to put a bit of solder on one of the pads and then use the tweezers and the iron to position the part and solder it onto that pad at the same time. Then it's not going anywhere until I get around to the other pad. For efficiency, I usually prespot solder on pads for a couple dozen parts (usually ones that are all oriented the same way), then position them all, then solder the other end on all of them.
 
I believe this is a corollary of Murphy’s law:
Whichever component you need the most and/or have the lowest availability, is the one that becomes lost.
 
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