Author Topic: How to Remove Solder that Won't Melt?  (Read 3825 times)

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Offline superscott319

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How to Remove Solder that Won't Melt?
« on: August 17, 2013, 01:20:40 PM »
Even as a beginner, this is pretty bad.  :palm: So I'm working on my first real electronics project which involves desoldering a number of components from a PCB and soldering on new ones. I've since realized what some of my mistakes were such as using cheap solder which was also too thick. I'm not sure what went wrong with the desoldering process but getting the solder to become molten so my solder sucker and wick could remove it was very difficult. Eventually I was able to remove all the old solder but not without making a mess of the board. Adding more solder only made it worse.

Right now I'm trying to clean the existing solder off the board but can't get it to melt even when setting my iron to a high temperature. Applying solder wick doesn't absorb it. Maybe all the flux burned off and that's causing it not to melt? What would be the best way to clean up a PCB that's been badly soldered like this?



Thanks for any advice.  :)
« Last Edit: August 17, 2013, 01:23:26 PM by superscott319 »

Offline c4757p

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Re: How to Remove Solder that Won't Melt?
« Reply #1 on: August 17, 2013, 01:40:35 PM »
Jesus tap-dancing Christ, that poor, poor PCB! :wtf:

My suspicions: 1) "High temperature" ain't as high as you think. 2) Corroded tip - not making good contact with the solder to transfer heat. 3) Lead-free solder was brought to this world by Satan himself. Try cleaning the tip with a gentle brass brush or a wet sponge and lots of flux and fresh solder, then clean the board with isopropyl alcohol, then flood the board and the solder wick with liquid flux. Try again.

Looks like you may have ripped up a couple pads. If so, sand/scrape away the solder mask around them to expose the copper, then repair with wire.

If your soldering iron is a $10 RadioShack special, then my diagnosis is "fucked".
« Last Edit: August 17, 2013, 01:43:37 PM by c4757p »

Offline superscott319

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Re: How to Remove Solder that Won't Melt?
« Reply #2 on: August 17, 2013, 02:08:12 PM »
Jesus tap-dancing Christ, that poor, poor PCB! :wtf:

My suspicions: 1) "High temperature" ain't as high as you think. 2) Corroded tip - not making good contact with the solder to transfer heat. 3) Lead-free solder was brought to this world by Satan himself. Try cleaning the tip with a gentle brass brush or a wet sponge and lots of flux and fresh solder, then clean the board with isopropyl alcohol, then flood the board and the solder wick with liquid flux. Try again.

Looks like you may have ripped up a couple pads. If so, sand/scrape away the solder mask around them to expose the copper, then repair with wire.

If your soldering iron is a $10 RadioShack special, then my diagnosis is "fucked".

I'm using a decent quality soldering station (X-Tronic 4010) that cost about $80 and even when raising the temperature to it's max setting, 480c, the blobbed solder shown in the picture still won't melt. There is what appears to be some corrosion on my tips so that could be the cause. As for the solder, I'm using some cheap unnamed stuff that came along with a PC repair kit so it could possibly be lead-free.

I will try your suggestion of cleaning the tip and board although I'll need to order those items. What kind of flux would you recommend for cleaning a soldering tip and the board? Would flux pen or the brush on kind work better?

Thanks once again for the help.

Offline c4757p

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Re: How to Remove Solder that Won't Melt?
« Reply #3 on: August 17, 2013, 02:19:40 PM »
OK, 480C should be plenty. Though, a warning - not all soldering stations that can be set to 480C can actually maintain that temperature when applied to a large thermal mass.

I have had cheapo soldering tips that disintegrated in lead-free, you might want to try something different. (That ugly blob looks exactly like my first foray into the sadistic hell that is lead-free solder, so I think that's what you've got. Either way, the stuff already on the board is definitely lead free.) I use Kester 44 (eutectic) - don't gasp too much at the price, remember, that's a full pound of it. It's a bit thicker than what Dave and company recommend, but I like it.

Either type of flux will work, and I find both equally convenient, so just get whatever you think you'll prefer. I think you'll find that a lot of things magically start working better with a liberal application of flux :-+
 

Offline Sigmoid

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Re: How to Remove Solder that Won't Melt?
« Reply #4 on: August 17, 2013, 03:01:39 PM »
I'm using a decent quality soldering station (X-Tronic 4010) that cost about $80 and even when raising the temperature to it's max setting, 480c, the blobbed solder shown in the picture still won't melt. There is what appears to be some corrosion on my tips so that could be the cause. As for the solder, I'm using some cheap unnamed stuff that came along with a PC repair kit so it could possibly be lead-free.

I'm quite certain that the heat isn't getting from the tip to the solder.
My little experience with corroded lead-free is that adding a generous amount of solder to the tip, so you have a gob hanging off, and applied to the problematic joint will eventually get the heat conductance in order and the joint melted.

Offline pickle9000

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Re: How to Remove Solder that Won't Melt?
« Reply #5 on: August 17, 2013, 03:11:41 PM »
Kester 44 is excellent solder, I've used it for many many years. There are several things that can be wrong but start with the solder (and I don't mean the solder on the pcb). Can you melt solder you have on hand with your iron? Does the solder smoke? Is the tip silver with solder and is the solder clinging to the surface of the iron? If the solder does not smoke it's not flux cored, if the soldering iron tip is not holding solder and a nice silver colour it's dirty.

Use your solder as a tool, apply a fresh bit to an already soldered joint to get the melting action started. Be quick no "flux smoke" means that you need to speed up. Adding extra flux is good but most professionals I know just use solder unless working on surface mount stuff and then they tend to use other tools (like hot air) to get the job done.

Get in the habit clean tip, fresh solder on tip, if the soldering iron ends up back in its stand then clean tip and retin the tip.

 

Offline andyturk

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Re: How to Remove Solder that Won't Melt?
« Reply #6 on: August 17, 2013, 03:12:34 PM »
If your soldering iron is a $10 RadioShack special, then my diagnosis is "fucked".
:-DD

Online G7PSK

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Re: How to Remove Solder that Won't Melt?
« Reply #7 on: August 17, 2013, 07:20:16 PM »
I think that the black around the solder gives it away (looks like soot), your iron is too hot and you are applying heat to the area for far too long. This usually comes down to not enough or no flux, placing the iron to one side in order to see the solder ( a mistake made by many beginners) you should place the tip firmly on top of the joint and not keeping the soldering iron tip clean and not cleaning the joint before hand (there could easily be a coating put over the board after soldering in the factory). Also check that your solder is flux cored I have seen people try to solder with plumbers solder that does not contain flux cores.

Offline sub

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Re: How to Remove Solder that Won't Melt?
« Reply #8 on: August 17, 2013, 08:12:39 PM »
My little experience with corroded lead-free is that adding a generous amount of solder to the tip, so you have a gob hanging off, and applied to the problematic joint will eventually get the heat conductance in order and the joint melted.

Do this.  And not just for lead-free, but any time where you want to get heat from one place to another in short order.  Still add some fresh solder so that the joint gets flux, but a blob of solder will touch the joint with far greater surface area than any tip will.

Offline tld

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Re: How to Remove Solder that Won't Melt?
« Reply #9 on: August 17, 2013, 10:22:45 PM »
Do this.  And not just for lead-free, but any time where you want to get heat from one place to another in short order.  Still add some fresh solder so that the joint gets flux, but a blob of solder will touch the joint with far greater surface area than any tip will.

Do this, he's right. Also, there's a difference between adding more of the crappy possibly lead-free solder, and adding something like kester 44. Even if you got burned (pardon the pun) adding crappy solder, I'd still add more when you have some decent leaded, first for thermal-transfer from iron to the stuff you want to remove - don't worry abou getting everything in one go - and then for mixing with the old stuff, to get all of it off.

Oh, and leadfree solder isn't the work of the devil. You need a political comitee to come up with something that bad. ;p

tld

Online bookaboo

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Re: How to Remove Solder that Won't Melt?
« Reply #10 on: August 17, 2013, 11:06:21 PM »
Practice practice practice is what you need, I'm willing to bet everyone in the forum hacked something as badly as that when they started off.
Grab some boards that are total scrap, watch a bunch of relevant youtube vids then remove and replace components until you are competent.

Online KJDS

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Re: How to Remove Solder that Won't Melt?
« Reply #11 on: August 17, 2013, 11:29:56 PM »
Is it just me that has no problems whatsoever using lead free solder?

Offline c4757p

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Re: How to Remove Solder that Won't Melt?
« Reply #12 on: August 17, 2013, 11:38:50 PM »
Yes.

Offline free_electron

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Re: How to Remove Solder that Won't Melt?
« Reply #13 on: August 18, 2013, 12:22:30 AM »
Nobody spotted that this looks like  a computer motherboard with multilayer thick copper ? And he's trying to replace the capacitors ? You can see what looks like the staggered pins of a pci connector top right of the picture.

So, This board is probably 2 ounce copper ground and power planes... So you will need a soldering iron with a high wattage to be able to heat the damn thing to melting point ! Cranking up temperature is not the correct way ! The poor soldering iron simply doesnt have the -oopf- to get that 'heatsink' up to temperature
« Last Edit: August 18, 2013, 12:24:48 AM by free_electron »
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Offline ablacon64

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Re: How to Remove Solder that Won't Melt?
« Reply #14 on: August 18, 2013, 12:24:37 AM »
Yes.

+1! Lead free sucks....

On topic, it's easier to remove solder by adding new solder to the joints. For large, heat dissipating areas, use low melt desolder wire.


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