MMaximus wrote:
I have no previous experience in soldering but I just managed to remove two DS1287 chips from two different motherboards with it today. Granted, I had to pull the chips quite hard with some pliers and they got a few bent pins, but I don't care so much as I'll put new chips and I don't intend to rework the old ones. The motherboard doesn't appear to have sustained any damage in the process and that's what I was most worried about.
Yes you can desolder through hole components with hot air stations and with some experience they work very well. But using pliers to pull out the chips with force - Really really don't do this! If the chip does not come out of the board with just an a minimum amount of force (in fact it should practically fall out) then you have not got all the solder molten on every pin. Have a look at the chips you desoldered. Do any seem to have small flanges or metal collars on or in the solder that is still on them? If so those are the vias that run through the PCB from the external pcb tracks . They connect to internal tracks as thePCB will have several layers. If you pulled any out then the PCB is pretty much scrap now. If you were lucky not to cause any damage this time, you probably won't be next time!
I assume you are removing the DS1287 chips because they are faulty? Then why do you need them in one piece? The way to do this sort of work is to use component snips like these https://www.amazon.co.uk/Component-Cutters-of … r/dp/B001YHJHEI to cut all the legs off the chip as near to the body as you can. Then remove the pins from the PCB one at a time. Simples.
Also apply 60/40 solder to all the pins before you desolder with hot air or an iron. It forms an alloy with the existing lead free solder and lowers the melting
point. This also means you can melt the resulting amalgamated 60/40+lead free solder alloy without accidentally desoldering nearby components
Now I need to figure out the best way to remove the old solder - I tried with a cheap solder pump but it's tedious and doesn't work so well. I've also tried with braid but it doesn't work at all.
To remove the reamaining solder, again add some 60/40 solder to each pad then use soldering iron and braid and dip the braid in flux first, I guarantee that will clean solder from holes 90% of the time. I use this type https://www.tme.eu/en/details/pasta-l-35/flux … a-do-lutowania/ you can get it on ebay. It is solid so you melt a channel in the flux with your soldering iron tip then dip the flux in the channel of molten flux.
If you still have problems cleaning out the holes, use the hot ait gun to pre-heat the area you are reworking to about 150C and then use the soldering iron braid and flux. Add more 60/40 and try again if you can't get the hole clear all the way through
Worse case scenario - use your hot air gun to heat the pcb hole from the rear side while pushing a stainless steel needle through also from the rear. No force required, just wait till the pcb is hot enough. If you add a it of 60/40 to th pad, then use the hot air you will see the shape of the solder go from convex to concave when the solder melts. Then push the needle in. https://uk.banggood.com/10-Kinds-Stainless-St … ur_warehouse=CN
Re hot air stations, the cheap 858D are perfectly good enough for this sort of work, I use one myself sometimes. If you want something much more capable than the 858D+ get the Quick 861DW. Thats is defacto the best you can get even compared to very expensive professional stations
Rich