De-soldering When Things Go Wrong - The 2 techniques
Friday, 8 July 2016 | Richard
Playing with electronics can be a very rewarding experience, you get to feel “a part” of the ever growing maker community all over the world, and you get to impress people when you know all about how that latest gadget works. But with great power comes great responsibility. Its tricky stuff and things will inevitably go wrong.
Maybe you are approaching this hobby from a software background - you want to code with the Raspberry Pi and the actual physical electronic connection to an accessory board is all new to you?
When you are staring at that accessory board, that was working 5 minutes ago and is now lying there on the bench with smoke whisping up at your face, it can be very tempting just to bin that board and start again.
But don’t do that! You can fix it.
De-soldering components from PCBs is a skill that you need just as much as you need to know how to solder those components to the board in the first place.
Here at Proto-PIC we receive many calls from customers who have blown a component and what would have been a simple “remove-blown-resistor-replace-with-new-resistor” type thing quickly degenerates to PCB tracks being ripped off etc. and before you know it the only thing to do is to buy a new board.
We are going to show you how to de-solder properly, so you can remove the offending component quickly and get it replaced, without damaging the rest of the board in the process.
There are two main techniques that we favour here.
We are going to remove a component from a board completely intact.
We might want to do this because we have say, put a chip on a board round the wrong way or in the wrong position and we want to de-solder it, move it and re-solder it in the correct place.
This is quite tricky.
Okay, so we have killed that component on the board. It’s never going to get any better – it needs replaced.
We don’t care about the component, its going in the bin, so let’s make our job as easy as possible so we minimise any chance of damaging any other part of the board.
So lets see how each method is done;
We have a simple board here, with an IC socket that we are going to de-solder.
Start off with a hot clean soldering iron tip. We have our Hakko FX-888D set to 355degreesC for de-soldering.
There are two tools you can use to help you de-solder.
Desoldering tool – Creates a vacuum at its tip using a spring loaded plunger. I prefer this tool as it gives instant results.
Heat the solder just long enough for it to liquefy. Bring the de-solder tool over the join and press the plunger
The solder will be removed from the join
De-soldering braid – A high quality flux impregnated copper braid, that solder loves to wick into. Place the braid on the join and heat up braid and solder, the braid will wick up any excess solder. This leaves a lovely neat finish but does require heat to be on the join for longer, which is sometimes not ideal.
Heat the join and the braid up with the soldering iron. Don’t be afraid to add MORE solder to the join to get a better heat transfer.
The solder will start to leave the join and travel up the braid, remove the braid BEFORE you remove the heat, otherwise all you have done is to solder the braid to the join!
Give each join a final clean up with the braid to ensure there is no solder left that connects the pin to the inside of the hole.
Removing the device.
Turn the board over and using a flat blade jewellers screwdriver, or similar, gently lever the device up slightly at one end.
Repeat at the other side, take care not to dig the screwdriver into the board under the device, you are just trying to gently lever the device up and out.
Keep repeating until the device is completely removed.
We have a device on this board that is known to be faulty. We just want to get it out of the board safely so we can replace it. In this situation, we care more about protecting the board than we care about the device, so we can essentially destroy the device to make the removal process easier.
Using a pair of fine snips, cut away each pin from the body of the device. Cut as close to the device as you can so a long leg is left sticking out the board – you will need this leg later!
Continue until each leg of the device has been snipped.
Lift out the device and discard, leaving the exposed pins in the board.
Heat the solder with a soldering iron. Using long nosed pliers, hold onto the pin and gently remove it from the hole as the solder liquefies. Make sure you have a nice clean iron here, you will need good heat transfer as the pliers act like a large heatsink and will cool the joint a little.
Continue until you have removed all the pins.
There may be some excess solder left in the holes, so clean them up with a de-soldering tool before you fit the replacement device.
And that’s it.
With a little practise, you will be able to de-solder like a Pro.
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