To say it first, there are many more or less successful methods to desolder your desired parts and i wont offer a new method, but a clever combination for desolder parts with many legs.
Maybe not so good for heat sensitive parts like IC's but for hard stuff like terminals, relays or transformers. It's meant for parts plugged with legs and no SMD devices.
Also always keep in mind if the part is worth to desolder. Many parts like capacitors will wear out in their life cycle and quit their job after you ran the device a coupe of weeks.
For a new project i needed terminal-screw clamps to soldering on my new pcb. Ordering new ones i found a bit expensive related to the amount i'll get for my euros and had laying around many of them in my shop.
Unfortuneatley the guys where soldered yet in those annoying multi-layered epoxy pcb's. If you ever tried to salvage parts out of them, without set them on fire, you know what i' am talking about.
So i figured out a method to harvest them without get frustrated and saving the parts from get melted before i can pull them out.
At the last step you can read a detailed description..
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Step 1: What You Must Have Before We Can Start..
- Fine meshed copper cord like high-flexible wires or speaker cables.
I made mine from a 4-square/mm speaker cable by uninsulate it and disentangle it up in the single wires. I mean supply cables for your speakers set, not the cables inside the speakers.
(sure desoldering strand will work too, but you can save the money for other nice things)
- soldering flux. Those which looks and feels like grease.
- of course a vise
- patience and no fear on hot stuff
- and the star of the show: a hot air gun
-depending to your age and optical skills a LED Magnifier on you desk. Since i entered almost 50, i need one too.
Step 2: Let's Do It
Make sure to fix your sacrifice PCB in the vise facing the solder side to you.
Pick the wire and clamp it at a point near to the legs you want to start
Now wrap it S-shaped tight between the legs until the end of the desired part. Fix it there again to prevent it from falling off.
Now smear a bit of the soldering-flux along the wire.
Heat the soldering points by panning the gun a bit until the solder melts. Now watch the solder soaking into the wire. If there is no more solder to soak it's time to pull out the part before the PCB starts to burn.
Done! Get lucky with new parts an a new soldered copper snake as pet.
Sure, it needs a bit testing and experience to get good results and less burned PCB's.
If you have a 2 Step Hot air gun like me, you may vary the heat by setting the distance between the gun and the pcb.
Always take care for good ventilation to prevent you from breathing hazardous fumes. Due the fact that the most of you are no more little children, i don't explain you that you will burn your fingers by touching the hot stuff ;)
Step 3: En Detail..
Finally the main question why i use this method to desolder?
Desoldering multi layered PCB's is a strange task because the parts legs are soldered in a via, (a small tunnel) from the bottom to the top of the PCB, which connects in some cases the tracks of each layer. Unlike a "primitive" bottom layered PCB you have to melt the solder from the bottom to the top. In most cases the top of the legs are covered by the part itself and can get heated only from the bottom.
To break the contact between the leg and the PCB you had to get rid of all solder in the via or keep the solder in melt state while pulling the part.
It's almost impossible to keep all points of the part melted on multi legged or rowed parts unless you ow a multi tip soldering iron.
So you can at least apply a huge amount of heat with a heating gun, to keep the solder melt in the vias from bottom to the top. But now you will see that the PCB rather burns or the plastic of the part melts until you can pull the part.
Thats why i figured out this method. Once i soak out the solder at every point a the same time and can pull out the part earlier because there is no more (or not much) solder i the via (which is also melted)
Less time means less burning of the PCB and less heat treatment of the part.
Hope you enjoyed it and it will help you by the next part desoldering party :)