Desoldering smd: braid or hot air station?

[CharlotteSwiss]

Following the EEV video above, using the same technique (in the video it uses a flat tip, I used the concave tip), I was able to solder an IC with pitch 0.80.
Now I could see how the ChipQuik flux does its job, helping in soldering; but especially where there is a need to touch up some badly soldered pins, prevent the tin from creating bridges between adjacent pins.
My concave tip measures 3.2 mm, I would say maybe too big (maybe I would have done better to take the 1.6mm one), more than anything else if there was another smd close to the pins it would be difficult to pass ...
It is then difficult to evaluate well if the pins are soldered with sufficient tin or not, if in doubt, in addition to plugging above the soldering points as in the video, I went over all the pins by dragging the tip from the body of the IC towards the terminal part of the pins; however, this has also drawn tin in the peripheral areas.
Anyway, I then tensioned all the pins with tweezers, and they turned out to be pretty firm (except one that was broken earlier).
One thing I have noticed with this flux is that the solders are bright / bright silver, very good.

[thinkfat]

 

[CharlotteSwiss]

thanks Thinkfat 
it is only a first test with pitch 0.80, I can and will certainly improve   

[nigelwright7557]

I have had trouble with some solders and SMD.
I bought some cheapo stuff and the iron would hardly melt it !
So bought in some better solder and that was much better.

Pads coming away is either cheap pcb's or solder with too high melting point or just being too rough.

[CharlotteSwiss]

in fact there are solders that melt first and others that are more stubborn; however, if the component is lifted only when the tin is well melted, while still heating, the pads do not rise

[thinkfat]

Yes, but if you need excessive heat to melt the solder, pads might come of anyway.

[CharlotteSwiss]

you are right, in fact in the tests by heating some IC pitch 0.80, the pad were unglued exclusively for the heat. It should also be said that they would have done their job anyway by soldering a new IC on it

[nigelwright7557]

Desolder braid can't get rid of the surface film of solder and therefore the component will still have a pretty strong connection to the pad, more than enough to rip it off.

I use this fact when soldering TQFP's.
I drag solder all the pins then if any shorts I use braid to remove it.
This tends to remove a lot of the solder but the solder behind and along the side of the pins is left intact.

[tooki]

Desolder braid can't get rid of the surface film of solder and therefore the component will still have a pretty strong connection to the pad, more than enough to rip it off.

I use this fact when soldering TQFP's.
I drag solder all the pins then if any shorts I use braid to remove it.
This tends to remove a lot of the solder but the solder behind and along the side of the pins is left intact.

Next time, try this: apply flux to the bridge. Thoroughly re-tin your iron, so that it’s free from “overcooked” solder, wipe off the excess, then quickly go back and remelt the bridge. That’ll usually take care of it.

[perieanuo]

I stole some old electronic boards to do some desoldering tests (smd component).
I have both the desoldering braid and a Chinese hot air station: the hot air station I took it on purpose to unsolder smd...
But today's tests disappointed me 
Two pin smd: according to my theory, a hot air temperature of 300 °, a low speed, use a small round nozzle and rotate over the smd .. would have been enough and it would have unsoldered easily. Actually I had to set 400 °, and many times pushing the smd the pads of the board were also detached ... 
With the braid, on the other hand, I can quite well unsolder the two-pin smd. Maybe today I learned that to unsolder a two pin smd you don't need a hot air station?
 
Maybe old electronic boards have solders that are difficult to unsolder?
Which procedure is best for unsoldering two pin smd?
I'm a disaster... 
Charlotte

hi,
i see you're a frequent contributor here hence my surprise you ask this
no doubt, hotair is the best one (just gotta work your hand), they do it in industrial manufacturing (but not like most of us, they heat from 2 sides, so for difficult jobs you'll need some heating plate)
is you need to rise over 400C you got a technique problem or tooo cheap soldering hotair station.
we start from what device manufacturer says about soldering time and temp and if we just respect this, it'll work 100%
standard reflow profiles like one from maxim shows temp peaks like 220C and total time ~270 secs, so that's the correct approach imho, otherwise overcooking the devices result in less device life
the braid is better to use it to clean after removing the part

[thinkfat]

hi,
i see you're a frequent contributor here hence my surprise you ask this

You see, some frequent contributors don't know yet how to handle SMD repairs, and some other frequent contributors ignore 5 pages of conversation, adding redundant information.

[CharlotteSwiss]

hi,
i see you're a frequent contributor here hence my surprise you ask this
no doubt, hotair is the best one (just gotta work your hand), they do it in industrial manufacturing (but not like most of us, they heat from 2 sides, so for difficult jobs you'll need some heating plate)
is you need to rise over 400C you got a technique problem or tooo cheap soldering hotair station.
we start from what device manufacturer says about soldering time and temp and if we just respect this, it'll work 100%
standard reflow profiles like one from maxim shows temp peaks like 220C and total time ~270 secs, so that's the correct approach imho, otherwise overcooking the devices result in less device life
the braid is better to use it to clean after removing the part

hi, are you telling me that I should heat at 220 ° for 270 seconds to desolder? I could try ... However, the message you quoted was at the beginning of my journey, then by choosing a nozzle with a more suitable diameter I was able to easily unsolder the smd. Thanks   

[nigelwright7557]

I always use hot air station.
Braid wont pick up solder from behind the pins.