Soldering questions

[Hornnumb2]

I am by no means a beginner but at time have such a hard time desoldering something. I was working on a TIPM last night to replace a relay. My process was add a little leaded solder to the unleaded, wick it up with my hakko iron, then use hot air to get the through hole solder melted. my hot air is just one of those cheap ones but I had it set on 500 and max air but still seems like it took forever to release. The board is pretty thick and looks like the via's had quite a bit of solder in them. Is it time to give up the cheap hot air or any other tricks to remove these relays. Put pressure on the relay to remove it scares me that a trace will tear. Thanks Michael

[Hornnumb2]

Yeah I tried the low melt on the first relay, while I had the iron set lower at 350. When I pulled that one out it still had quite a bit of solder left on the legs through the holes. When i bumped up the heat on both iron and hot air it work better but still took some work to get it out of hole, wicked as much as I could and the hot air. I do have my hakko air solder sucker but it is stopped up right now and needed to unclog it.

[bdunham7]

Chip-quick (spelling?) is one company / brand of the rework alloy.
Others exist, SRA solder in the US, has another brand, et. al.
They're indium based just for rework / removal.

Chip-quik.  The alloys vary (there's ROHS and leaded) and contain indium and bismuth, as well as silver, tin, lead and copper in varying amounts.  You can get ever more expensive alloys that melt below 100C, but that's not necessary.

Just be careful with alternatives--there is an Indium brand of solder that is just regular solder. 

[DavidAlfa]

Desoldering multiple pin parts from these boards is always complicated.
To fully empty and clean the pins, usually the pads take a lot of heat and it's easy to cause damage.
Specially in ROHS boards (A complete nightmare in thick boards)

My aproach is to carefully break the device when possible, so in the end I have single pins, much easier to handle.
If not an option, then preheating the board helps a lot. Applying a heat gun, until the whole board is at 60-70ºC, way hot but not enough to damage anything.
And then these holes will be much easier to work with. Oh, I said something weird again!

[wickated]

just use copper tips for your soldering iron. in power supply pcb is not multilayered

[Shock]

Hot air is perfectly acceptable as long as no damage is done. I prefer to leave joints soldered as the molten solder is a good indicator when it's at temp and helps distribute heat, flux helps as well.

If it's a high mass board you need to pay special attention to preheating low and slow first, your goal is to reduce the heat dissipation during the actual reflow and removal. 

Obviously tools like tweezers and desoldering guns help as well to reflow all pins at once or get superior suction. If the pins are stuck hard in tight holes destructive removal can work as long as you are careful. In the case of most components you can dremel from the top and carefully expose pins. Then pull them out individually from the top while you heat with a regular iron.