Good flux for soldering 16MSOP

[cupoftea]

Hi,
Just spent the day trying unsucessfully to solder a ltc7803 (16MSOP)
At 15:45 of this video

..he uses some clear flux, which is quite pasty, do you know where to get it....he says he buys stuff from BLT circuits, but i dont see it there.
He also says use small conical tip..but i already did that and failed dismally.
Also, howcome he doesnt burn up the solder resist like i do? That burned up, gunged up solder resist really impedes soldering....i find no flux deals with it.

Also, he has the blue solder resist between each pin...thats usually impossible with a 0.5mm pitch chip...how does he manage to get that solder resist inbetween the pins like he does? No PCB manufacturer can do that?

 

[wwfeldman]

i've use this to solder 0.5 mm spacing:

Tang Hong Solder Paste Model OL-3016

Amazon.com

i suggest using a heat gun instead of a soldering iron

 

[KlausST]

Also, howcome he doesnt burn up the solder resist like i do?

It seems you use too high temperature.
This makes soldering difficult, because it burns the flux (it does not work anymore) and it makes the solder to seperate it´s metals. Which makes it grey, does not smoothly flow, causes spikes when pulling the tip away.

***
For MSP16 soldering I use
* about 370°C
* fresh solder (remove old solder from PCB and IC and clean them with alcohol)
* fresh PCB (older PCBs are hard to solder, especially with ENIG finish. HAL finish has a higher shelf life)
* a rather big, clean, not corroded tip. If corroded replace it, it introduces unwanted metal to the solder and makes it impossible to work
..
I put a very small piece of solder on one pad at the edge and fix the IC with it.
Then (clean the tip) I solder the rest of the pins with new solder. With the big tip it should take about 2 seconds for one row.
After this I remove the solder from the tip, then the excess solder (short circuiting) from the pins. (usually the last ones soldered in the row)

All in all it should take less than a minute (cleaning and fixing included) ... the time for the tip touching the IC pins maybe less than 10 seconds in total.
The longer it takes the more difficult the solder will become.

If you have some Pb solder leftover, then it may be used for repair. It´s way easier to work with, especially when you are not that experienced in soldering.


Klaus