Problems with PCB

[Sunsun22]

I have a 3 layers PCB that has a very large ground plate in the middle layer. When I desolder a cap from the PCB, the solder remains in the negative (ground) hole and I have tried the following methods but in vain:

1. Add solder, increase the solder temp to 340 degree F and pump from the other side.

2. Add solder paste and solder, increase the solder temp to 340 degree F and pump from the other side.

3. Increase solder to 390 degree F (for a very short time)

4. Change the solder tip to a sharp one - the solder did not even melt inside the hole!

Can anygone give me more alternatives? Thank you

[Jan Dupont]

Try placing the PCB either vertically or horisontal and heat up the area with the pad using a hotair gun or a hair dryer. Then try again with as to your earlier attempts.

If the above does not work, heat up the pad again and try inserting a component leg into the whole in the pad. It should be quite easy to remove the rest of the solder, if you success to make just a little hole through the solder

[Sunsun22]

I have a hot air gun and I have tried in the past by blowing hot air at 300 degree C. After a minute or so, the PCB get burnt. What temp should I use and how long can I keep on blowing the PCB (polyester PCB)?

[Jan Dupont]

Keep the temperature well below the soldering melting point. The point is that when you use the soldering iron, the solder easyly melts and is long time to cool down and get hard again.
Try with different temperatures - starting with the lowest.

Same technique is quite usefull when soldering components on PCBs with large copper areas and thick copper layers

[gmphadte]

Use compressed air to blow it out. Beware of flying solder.

[Sunsun22]

I use a hot air gun at 200 degree C to warm up the PCB for about 2 minutes then apply solder gun at 330 degree C but with no luck. The solder is just too hard to melt.

I also use a pin trying to pin through the hole but in vain.

Preparing to purchase a drill bit at 0.6mm to drill through the hole. Any comment?

[Jan Dupont]

Have you tried to add some fresh solder to the pad?
That normally help to melt the old solder.....

[Andrew.Thompson]

I've found that in the past if you add some new solder to the hole until it has built up a bump you can then use some solder wick/briad and a hot solderinging irion to clear out the solder from the hole.

This often takes a few tries but since my desoldering iron broke I've become quite handy with the braid and hand pump and have managed some quite nasty jobs using the methods already suggested as well.

[Sunsun22]

Yes, adding new solder is always my first trial but I can't get the old solder out of the hole.

Tonight I tried another method. I use a wooden tooth-pick to pin through the hole with hot air gun and solder iron. The tooth-pick does not dispense the heat in the hole while component legs do. It works! I manage to get the old solder out of the PCB holes.