Hy all. I just got my solder station and i notice something that bothers me. I put some old PCB and wanted to try out heat gun to remove some of components from PCB. And i put air flow on 4 (8 Max) .. and try to steady increase the heat on the gun . .start from 180C and i could not get solder to melt until i get around the 450C! And in that time i notice that pcb circuit was lift off from pcb, i try couple off other pcb's and the result was more less same. When i try to melt the solder wire, it melt in a second. So question one is. Why is there so much difference in melt point in those two solders. And question number two. How can i use the solder gun if i need to put 450C to melt solder for component and in 455C i destroy the PCB.

 

There many types of solder , the most common is 60/40 tin / lead .. reducing the amount of tin saves money but increases melting point to around 200C ... lead free melts around 220C

I don't know how you are measuring temperature , but no way could the solder be 450 and not melt , the air from the heat gun maybe.

 

Can't say I see to many devices with actual lead solder here in the states anymore. Maybe this is a different case around the world. I believe TS is setting his hot air to 450c and not measuring the actual temp of the solder. You will never remove any component setting your hot air to 220c.
I set my irons to 320-350 and my hot air to 350-450 but you have to be very careful and know the boards your working on when you use this high of temp or the epoxy used to hold the pads will give way. Sounds like you are spending too much time heating the same area with the hot air and maybe holding the nozzle to close.

I suggest you use a middle sized nozzle with temp at 320c and airspeed around 6.
Keep a good 3 inch space between your nozzle and the pcb so you can more slowly bring the area up to temperature, after 5-10sec or so you can move a little close. Maybe 1 inch from pcb. Keep your hot air gun moving at all times in a swaying or circling motion.

 

Always keep in mind heat is one thing; temperature is another.
To solder or desolder, three parts need to reach the eutectic temperature : the component, the solder, and the pads.
Greater heat is important for massive parts, temperature of the heat should be observed. A house on fire may be at the same temperature of a match, but their amount of heat differ considerably.
A 100W heat soldering tool may not have enough temperature for a large task; a 25W heat soldering tool may yield too much temperature for a tiny task. And multi-pin components should reach same conditions simultaneously to desolder.

 

Thanks for all answers, yes when i say temperature that's what i put in value for my heat gun. Once when i put medium nozzle and put air flow on 6 (max 8) i got beater results. But still there is thin line between the melt point and burn off pcb ..

 

You can apply the iron until the solder melts, then turn on the suction. This will lessen the cooling effect of the air flow.

 

...when i say temperature that's what i put in value for my heat gun.

Yes, that is tricky. The temperature has to be read at the working distance from the nozzle.

But still there is thin line between the melt point and burn off pcb ..

That is when skills and the experience as you are obtaining now come to play. Practice with discarded boards.