Desoldering issues

Thread Starter

woozycactus

Joined Jan 4, 2021
52
So I have been trying to harvest parts off of my old 520watt pc power supply and it is almost impossible to desolder. It has solder tracks going to every component and I just cant get the solder to belt and let go of the component with out messing with it for a very long time. Is their a trick to this or how should I be doing it?
 

SamR

Joined Mar 19, 2019
2,909
Flux and a bit of fresh solder blobbed on the tip help. Flux helps with the oxidation and a blob of solder helps with the heat transfer. Not a magic bullet but it helps.
 

dendad

Joined Feb 20, 2016
3,657
You may need a bigger soldering iron, one with more thermal mass as large tracks wick away the heat from a small iron so the solder cannot melt.
This does not mean an iron that is a lot hotter. But, even saying that, increasing the iron temp can help.
I also use a hot air tool to heat the board up. And sometimes, 2 soldering irons.
 

SamR

Joined Mar 19, 2019
2,909
Yup, forgot, use your biggest iron tip to help with the heat transfer and maybe turn the iron temp up if it is adjustable.

Also, I love my vacuum desoldering station...
 

Thread Starter

woozycactus

Joined Jan 4, 2021
52
so i always use flux and tin the tip which i noticed helps a bit but the hot air seems like 20 mins of .5 inches away does not do anything. I was using my rework station iron set to 800F with a big wedge tip and then tried my 100watt gun and its still a fight. using a wick and pump as well. broke 3 out of 6 caps so far.
 

KMoffett

Joined Dec 19, 2007
2,918
One issue may be getting all the pins on a component hot at the same time so you can pull it. I've dealt this with over the years by making a custom de-soldering tool. I use a Weller soldering gun. Removed the standard tip, and replaced it with a shaped 14Ga or 12Ga copper wire. I bend the wire into a shape that will make contact with all pins of the component. Tin the wire where it will contact the pins. Flux the component's pins before applying the new wire tip to it. This works great on things like relays and radial capacitors that have wide pin spacing. Also DIP ICs and connectors that have a lot of pins.
 

dendad

Joined Feb 20, 2016
3,657
In stead of trying to remove the solder around the pins, another way is to melt the solder in the joint whiles applying pressure to lift the part out, a bit at a time.
There is such a thing as a solder pot. A pool of solder that will allow you to melt an area.
 

jpanhalt

Joined Jan 18, 2008
10,953
You can also use a propane torch. Great for things that have lots of solder, like RF shields, but also for parts. I usually heat the back side. rather than the part. Parts either fall off or you can use a quick flick in a bucket/trash can to get them.

I used that method before getting my hot air tool. If I were to harvest parts nw, I would give that a try.
 

andrewmm

Joined Feb 25, 2011
907
As its a PSU, there are a few possibilities, depending upon its provenance.

The board is designed to dissipate heat, so you have to heat a large area up to compensate.
The board could be conformably coated, making de soldering a pain
The board could be using a higher temperature solder, used in some Industrial and Mill PSU's.

Its not unusual to soak a board on a hot plate for 30 minutes to heat it all up to say 180 degrees C.
 

MrSalts

Joined Apr 2, 2020
110
Grab the component gently with a pair of needle nose or channel locks and hit the solder with a hot air gun. The board falls to the bench and drop the part in your storage bin.
Better yet, go to Digikey.com and just buy the new pieces you need for your project and throw the power supply in the bin.
 

Ian0

Joined Aug 7, 2020
1,158
I use a baking tray turned upside down. It spreads the heat, but keeps it insulated from the bench. Then I place the board on the baking tray and heat it up with a hot-air gun (the type used for stripping paint), set to 330 Celsius by measuring it with a thermocouple . IF it is too hot it oxidises the solder and makes the job harder.
The same technique also works beautifully for soldering with solder paste. The steel tray acts as the preheat, and the hot air takes the solder paste to its melting temperature.
 

Thread Starter

woozycactus

Joined Jan 4, 2021
52
so all these are good ideas but I do have a rework station. Last time i tried to desolder with it, it melted the board, which is fine in this case but it never melted the solder. I never used a rework untill the other day. What tip, and air flow should i be setting. I see the one about 330c
 

SamR

Joined Mar 19, 2019
2,909
For removing through-hole components, I would not use hot air. Put the biggest tip you have on the iron, flux the component legs, and crank up the heat. Blob on some solder or even melt some on top of the joint to help with heat transfer. I also use some "soldering tools" or small tweaker screwdrivers like prybars to help lift the component one leg at a time. Although I've never tried the torch method, it sounds like a good idea. I might want to try a jet butane lighter to get a more concentrated and smaller area heated. I have harvested components but rarely ever use them. Transformers are always useful. I don't bother with chips unless they were socketed. Electrolytic caps from old equipment are questionable. Resistors, diodes, ceramic, mylar, hi voltage, and tantalum caps I have harvested but almost never use. But it's good experience in removing components to learn how for when you need to do a repair to replace a bad component. Without a Vacuum Station, you're stuck with using solder wicks and suckers which are bad enough doing one component but would get old real fast doing an entire board.
 

MrSalts

Joined Apr 2, 2020
110
When you desolder through hole components with hot air gun and channel lock pliers...
First, add a bunch of tin/lead solder to each pin to dilute the high melting all-tin solder.
second - clip a steel binder clip to the plastic case, to act as a heat shield and deflect some hot air from the case
Third - grab the component by the short end with channel lock pliers
Forth - apply hot air and lift the part off the bench and wiggle a bit until the board falls to the bench.
 

Mrchow

Joined Jan 12, 2021
5
All the suggestions give above is gold mine. I usually put some fresh solder on top of the factory solder. Because you never know what type of solder the factory uses or it's melting point. Putting fresh solder on the component leads give you a better chance of getting the solder to melt. Also douse the component with flux.

Hope this helps.
 
Top