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Topic: [SOLVED] Unsoldering unsuccessful  (Read 1 time) previous topic - next topic

Marciokoko

Dec 10, 2015, 01:26 am Last Edit: Dec 11, 2015, 02:13 pm by Marciokoko Reason: image
What happened to this board?



I soldered some header pins but I didn't do a good job so I removed them by melting the plastic holding the pins and removing pin by pin.

Now I can't seem to be able to remove the solder from inside the holes even with a wick!

Is that not solder?

weedpharma

Fill the hole with solder then use the wick. This usually works.

Weedpharma

be80be

Looks like you got that way to hot you may of messed it up too. You may of lifted the copper pads.

MorganS

I have a Hakko 808 desolderer. It's the ultimate tool for hobbyist desoldering. It sucks the pins right out of the holes too. Usually I can re-use both the board and the component instead of having to sacrifice one to save the other.

But I still use solder wick. Old solder is much harder to melt than fresh solder. The solution (ho ho ho) is to flood some fresh solder in and dilute the old stuff. It also helps getting the heat to transfer down into the holes, using liquid solder as the heat transfer medium. The soak it up with the wick or suck it up with the vacuum tool.
"The problem is in the code you didn't post."

DrAzzy

I have never had any luck with solder wick. I suspect my technique is bad, since others say it works. I've always had access to a solder sucker though, and I've had great luck with those.

Those pads don't look to be in great shape at this point (pulling pin header doesn't do any favors for the pads in general, and messing around trying to get the solder out hasn't helped. Be gentle, and suck from the less beat up side.
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raschemmel

#5
Dec 10, 2015, 05:01 am Last Edit: Dec 12, 2015, 06:30 pm by raschemmel
I can tell you exactly how to get the solder out but you'll have to trust me.
First you need a hard smooth surface, like a solid wood table top. A solid block of smooth metal is even better. It must be hard and it must be smooth. the harder the surface, the better. My favorite is a solid block of aluminum 1 inch thick and 10 iinches long by 6 inches wide , machined to a smooth surface by a machinist friend of mine. Basically anything you can find that fits that description and can be put on your work bench will work. An example would be an automotive part that is hard and smooth. Once you have such an item on your bench , you can proceed.
Get a small pointed tip for your soldering iron (buy one somewhere). If you can't get this, then forget it, because this method won't work. Once you have this, you can proceed.
Place the tip of the iron on one of the holes just long enough to get the solder to flow, then quickly tap the board on the hard edge surface, from about 1 to 2 inches away. It must be a quick snap of the wrist.
[EDIT]
The point of contact must be the solder side of the board and should/must be on the edge of the hard , smooth striking surface. This is why a 1" thick 4" x 6" solid aluminum brick is ideal, because it has edges you can tap/rap/strike/ the pcb on A surface that is NOT cubular or rectangular lacks such corners and therefore is less desirable. Technically , you can slap the bottom of the PCB flat on the surface but for obvious reasons (this involves displacing the air underneath the pcb), it will not be as effective as rapping the pcb at a 45 degree angle on a raised square edge surface. This concentrates all the impact force to a single point , resulting in a higher deceleration of the molten solder causing it to leave the hole more rapidly .

I have had some success using the edge of a wooden work bench because the wood is so solid and it has a formica like surface. The disadvantage here is that it is not as easy to remove the solder splashes as it is from the machined aluminum brick, which just peels right off like burned cheese in a teflon pan.
If done correctly, the hot melted solder will fly out of the hole and splash all over the hard metal surface you just rapped it on. Needless to say, try not to hit any of the components on the hard surface. That would be bad. Hold it up to the light and see the light shine through the hole. Proceed to the next hole. When you are finished, you will have solder splashed all over the hard metal surface. This will peel off with a small flat blade screw driver or razor blade. This method has been used by professional electronics technicians since day one.
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Grumpy_Mike

All the above methods will work and I have used them all. However there is another one that also works.

Melt the solder and then put into the hole a pencil lead, ether from a propelling pencil or a sharpened normal pencil. Then remove the iron and the solder will set around the lead and it can be removed leaving a hole. Once you have a hole then when you melt it again with solder wick the surface tension of the solder will prevent the hole from filling up with solder again.

msssltd

What happened to this board?
Your iron wasn't hot enough. The excessive dwell time caused heat to build up in the substrate (an insulator)  and the glue bonding the pads melted, before the solder was fully molten. 

If you have a temperature controlled iron, turn it up ~50C for de-soldering.  If you don't have a temperature controlled iron, find someone who has.  A larger (thermal mass) bit is also useful.

Quote
Now I can't seem to be able to remove the solder from inside the holes even with a wick!
Because it was not fully molten, when the remaining solder cooled it formed an irregular crystal structure, not so efficient at conducting heat, which is a bugger to re-melt.  If there is a ground plane connected to any of those pins, re-melting the solder is going to be even more difficult.


PS.  You don't need to mess your iron up and fill the room with toxic fumes, melting plastic headers.  The pins will slide through with a little force.  I use a stiff pair of tweezers to lever the plastic former off the board.  Long headers can then be carefully snipped into manageable lengths with side cutters.


Marciokoko

Well I got 2 out of 6 holes open.  The first one I put fresh solder on it and I used a wick on it and it worked. The other one I just used a wick and it worked. I had to leave the house but I'll try the other 4 holes later.  I want to try the graphite lead one.

Thanks

STDummy

Solder suckers are the best option for removing solder from through holes I have found. Simply "cock" the sucker, melt the solder and quickly position the sucker nozzle over the hole and trigger the sucker release plunger.

There are several other methods described here as well.

HTH
Bernie
If you learn by your mistakes then I am the model pupil

raschemmel

The method in Reply#5 always works and in fact is so much more effective I don't even bother with the wick or sucker and I have both as well as a hotter iron for wicking. I could have done those 6 holes in 30 seconds to 60 seconds.
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pwillard

I agree.  Method from reply #5 often used by me even when solder vacuum and solder wick are in reach.

raschemmel

Quote
I agree.  Method from reply #5 often used by me even when solder vacuum and solder wick are in reach. 
My reason for always using that method first is that it has had a 99.999999% success rate and saves time screwing around with the solder sucker (which often jams due to blockage in the end) and the wick, which requires more heat.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

Marciokoko

OK I'm sold in method #5!!!

I'm only missing one hole. 

I put new solder on all 4 remaining holes.

Then I tried the wick on all and only got it to work on 1.  Turns out I was pressing the iron tip too softly over the wick so the solder wasn't melting so easily.  When I did manage to get it to melt, I might even burnt the pad.

So then I touched the tip of my iron on the remaining 3 holes and managed to get 2 nice little balls of solder out by tapping the shield over a towel that I have over the glass table.  I didn't get the last hole because it may not have had enough solder in it so that I reached with the tip of the iron so I'll try again later with more time.

How do I clean off the guck over the pcb?  I added some Flux yesterday and when I originally soldered the pins a while back and it's a mess.

raschemmel

Not a good idea to use a GLASS surface with method $5...
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

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