Author Topic: First attempt at desoldering..some advice please?  (Read 8566 times)

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Offline Rob LoTopic starter

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First attempt at desoldering..some advice please?
« on: August 01, 2016, 03:33:36 pm »
Hi, I am relatively new to DIY and soldering as well. Long story short I purchased a set of pcb's from a synth based DIY site. The board which is the control surface for the synth was already populated.

I soon realized my error in buying the board because the LED's were soldered too low and sit too recessed when the face panel is attached.

So I have to desolder roughly 80 LED's and some diodes.

I've done two rows so far with a desoldering braid and some liquid flux pen as I don't have a desoldering gun and/or a solder sucker, and I didn't want to buy a hot air gun for this purpose only (even though eventually I will). I am a bit worried about doing it this way and I'm not sure if I am damaging the pads or not. I've attached some close up of the rows done so far. Am I killing the board? Also, the parts do not need to be reused. I will be installing all new LED's

Any help is appreciated
« Last Edit: August 01, 2016, 03:35:39 pm by Rob Lo »
 

Offline Rob LoTopic starter

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Re: First attempt at desoldering..some advice please?
« Reply #1 on: August 01, 2016, 03:35:13 pm »
Also, not sure how bad this is...but i thought it was just flux but apparently I delaminated the board..and killed a trace? This is the botyom.
« Last Edit: August 01, 2016, 03:59:28 pm by Rob Lo »
 

Offline Simon

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Re: First attempt at desoldering..some advice please?
« Reply #2 on: August 01, 2016, 03:41:44 pm »
lots of heat for a short time on braid, use a large tip as if you can't get the heat in fast enough you will be sitting there waiting for it to heat and just burn it up mean time.
 
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Offline StillTrying

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Re: First attempt at desoldering..some advice please?
« Reply #3 on: August 01, 2016, 03:53:19 pm »
If you're not going to re-use the LEDs, I would cut them off, desoldering the lead ends when they're separated from each other should be much easier.
.  That took much longer than I thought it would.
 
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Offline Rob LoTopic starter

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Re: First attempt at desoldering..some advice please?
« Reply #4 on: August 01, 2016, 03:58:23 pm »
Yea that's what I did, cut the leads from the top them use the braid on the bottom. Then heat the leads on bottom til they wiggle and pull them with tweezers or just push with the iron til they fall out the bottom.

In the second post is it possible to see if I burned the trace?
 

Offline Simon

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Re: First attempt at desoldering..some advice please?
« Reply #5 on: August 01, 2016, 04:00:41 pm »
The pads do look a bit mashed up.
 
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Offline rstofer

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Re: First attempt at desoldering..some advice please?
« Reply #6 on: August 01, 2016, 04:01:34 pm »
In my experience, desoldering with solder-wick will almost inevitably ruin the board.  Pads will lift, vias (through-hole plating) will be damaged, etc.

A few years back I bought a Hakko 808 desoldering tool and it is magnificent for working on through-hole components.  Unfortunately, it has been discontinued and replaced by something else.  Like:

http://www.testequipmentdepot.com/hakko/desoldering-irons/desoldering-iron-kit-fr300-05p.htm

I know, it's terribly expensive and I don't believe I paid anything like that for my 808 but if saving the board is important, using the right tool makes a lot of sense.

You're in and off the pad in a couple of seconds and wiggling the tip side to side guarantees the component won't still be soldered to the edges of the via.
 
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Offline StillTrying

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Re: First attempt at desoldering..some advice please?
« Reply #7 on: August 01, 2016, 04:13:18 pm »
Yea that's what I did, cut the leads from the top
In that case I'd be just heating the lead from top or bottom and then tapping the board on the edge of the desk so that the lead and most of it's solder drops through. You have to do it so that the straight part of the lead is to drop through the hole and not the bent end. Of course this is a very messy but quick way.
.  That took much longer than I thought it would.
 
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Offline CatalinaWOW

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Re: First attempt at desoldering..some advice please?
« Reply #8 on: August 01, 2016, 04:26:03 pm »
I have done a lot of desoldering with solder wick.  It is certainly possible to damage boards with solder wick, but I don't find it inevitable.

I don't see any real problems with your board.  This won't be suitable for high reliability (space, medical, aerospace) applications, but I don't doubt that it will function and last for years for you.  There is a solder splash that should be cleaned up in your follow up photo.  A touch of the iron, or just mechanical removal with an exacto knife or equivelant will do it quickly.  It is possible that the trace underneath is damaged, but from the photo it doesn't seem likely.

The heat and tap method is good.  If you have access to compressed air, heating and blowing out the solder also works well.  Don't wear shorts when using either of these techniques, and evaluate your own position on lead safety.  Some would find this hazardous to you and the environment.  Is not a concern to me.

When desoldering it is easy to overlook keeping the iron tip clean and tinned.  It really helps on heat transfer, which then reduces the time heat is applied and reduces the chances of board damage.
 
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Offline Simon

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Re: First attempt at desoldering..some advice please?
« Reply #9 on: August 01, 2016, 04:38:19 pm »
but heat it enough, it could be that the braid is soldering to the pads and the pads are being pulled with the braid, lots of heat, fast, in and out!
 
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Offline richnormand

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Re: First attempt at desoldering..some advice please?
« Reply #10 on: August 01, 2016, 04:44:29 pm »
I have a much better result using the solder wick using a higher temperature and a larger tip.
Shorter time applying heat helps a lot.
Also run the wick in rosin solder flux beforehand.
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Offline Rob LoTopic starter

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Re: First attempt at desoldering..some advice please?
« Reply #11 on: August 01, 2016, 05:01:18 pm »
I've been using a 3.2 chisel tip. The temp I've been careful to not go over 600f (about) because I have no reliable way to test my iron temp and I'm using a hakko clone (936b).

Thanks so much for the input everybody.
 

Offline drdanke

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Re: First attempt at desoldering..some advice please?
« Reply #12 on: August 01, 2016, 05:24:44 pm »
I find that desoldering wick (braid) is almost useless without applying a little flux to the wick braid first.  I put a little flux paste on my fingers and rub it up the wick.  Once the wick is fluxed, get in and out, and with a hot enough iron, you will see a large amount of solder get sucked all the way up the wick, sometimes up to 1" up the wick...  Properly fluxed and with a hot iron, solder wick can definitely be used without damaging the board. 

It's impossible to judge if you are destroying the board with the flux not cleaned off. With the flux still on the board, it looks pretty bad.. but with the flux cleaned off, it might still be in perfect condition.  It's just hard to tell.
« Last Edit: August 01, 2016, 05:29:36 pm by drdanke »
 
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Offline StillTrying

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Re: First attempt at desoldering..some advice please?
« Reply #13 on: August 01, 2016, 05:32:20 pm »
I don't go by the temperature, I go by how quick the solder joint melts. In your top picture where the lead ends are still showing I would expect that to be fully molten in 1 to 1.5 secs, especially if the length of remaining lead on the other side is very short, another 1 sec to allow the heat to travel through the hole to the other side, and tap it quick.
Don't forget, you only need to have the holes clean enough to be able to get the new LED's leads through the holes, a bit of solder still left around the hole won't matter when you come re-solder them.
Yes, you've got to keep the tip clean and tinned so it makes a good quick thermal contact with the joint.
What you've done so far looks fine to me, I could do worse than that and I've been desoldering since about 8.
.  That took much longer than I thought it would.
 
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Offline Rob LoTopic starter

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Re: First attempt at desoldering..some advice please?
« Reply #14 on: September 03, 2016, 08:27:35 pm »
I've been taking breaks doing this because it's been a nightmare.

I've gotten about 85% of it done. Basically I've used wick and tacky flux to suck the solder then pull the lead out of the top side with tweezers.

The issue i have now is there are a handful holes that have become blocked with solder and im unable to push leads for the new component through. It's near impossible to get the wick on it.

Anybody have anytips?
 

Offline julian1

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Re: First attempt at desoldering..some advice please?
« Reply #15 on: September 03, 2016, 08:53:05 pm »
Quote
The issue i have now is there are a handful holes that have become blocked with solder

a mechanical spring loaded solder sucker is cheap and quite effective for clearing holes,

https://www.google.com.au/search?q=solder+sucker&newwindow=1&source=lnms&tbm=isch&sa=X&biw=1118&bih=749
 

Offline tautech

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Re: First attempt at desoldering..some advice please?
« Reply #16 on: September 03, 2016, 09:10:11 pm »
Quote
The issue i have now is there are a handful holes that have become blocked with solder

a mechanical spring loaded solder sucker is cheap and quite effective for clearing holes,

https://www.google.com.au/search?q=solder+sucker&newwindow=1&source=lnms&tbm=isch&sa=X&biw=1118&bih=749
+1
I've got one the same as the 2nd one top row, a MUST HAVE item for soldering/desoldering.

You can stick your braid, I rarely if ever need to use it.

OP, get yourself some old PCB's, anything at all, practice salvaging components and replacing them, all invaluable skills.

That said, most construction these days is with lead free solders that require higher temps and as a consequence PCB's can be easier to damage for the unwary. When the Pb free muck is encountered first dilute it with some leaded solder to reduce the melting temp, suck off excess, rinse and repeat and solder and components will be easy to remove.
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Offline StillTrying

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Re: First attempt at desoldering..some advice please?
« Reply #17 on: September 03, 2016, 11:21:05 pm »
The issue i have now is there are a handful holes that have become blocked with solder and im unable to push leads for the new component through. It's near impossible to get the wick on it.
You simply put the iron on the hole and then add a bit of new solder to the iron/joint, when your new solder flows into the hole tap it or suck it out.
.  That took much longer than I thought it would.
 

Online edavid

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Re: First attempt at desoldering..some advice please?
« Reply #18 on: September 03, 2016, 11:29:52 pm »
You don't need solder wick at all for this.  Just pull the leads out with pliers, and reopen the holes with a toothpick (in both cases while applying the soldering iron).

 

Online Mechatrommer

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Re: First attempt at desoldering..some advice please?
« Reply #19 on: September 03, 2016, 11:31:15 pm »
no need braid no need flux, just a normal tip iron at the right angle with the right hand at right temperature to melt both lead, left hand to pull the led hard from another side. LEDs can be reused for other purpose, no need cutting leads.

The issue i have now is there are a handful holes that have become blocked with solder and im unable to push leads for the new component through. It's near impossible to get the wick on it.
same method as above except pushing new LED to holes while both holes solder melted, you need to add solder on recessed dried solder so iron tip will reach it while doing acute angle solder. you are getting me? good!
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 

Offline mariush

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Re: First attempt at desoldering..some advice please?
« Reply #20 on: September 04, 2016, 06:28:12 am »
What's wrong with plain generic solder sucker? Set your iron to about 220-250c, lay the tip almost flat on the pcb, touch both leads of the led with the iron, when the solder melts put the solder sucker over the lead/iron tip and suck solder.

Or just heat both leads of leds and let them fall down from the board (tap the pcb gently if needed to make the led fall off), then you could use solder wick to clean but i personally don't like wasting wick for this.. solder sucker is good enough for this.
 

Offline JacquesBBB

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Re: First attempt at desoldering..some advice please?
« Reply #21 on: September 04, 2016, 09:08:42 am »
no need braid no need flux, just a normal tip iron at the right angle with the right hand at right temperature to melt both lead, left hand to pull the led hard from another side. LEDs can be reused for other purpose, no need cutting leads.

The issue i have now is there are a handful holes that have become blocked with solder and im unable to push leads for the new component through. It's near impossible to get the wick on it.
same method as above except pushing new LED to holes while both holes solder melted, you need to add solder on recessed dried solder so iron tip will reach it while doing acute angle solder. you are getting me? good!

+1 with this.

I would not use solder wick for these diodes. Just  a plain tip large enough to heat both leads at the same time.
Do not bother to remove the solder.
Put the board vertically, and heat the solder on one side, put the led on the other side starting with the long lead.
This will help you to position more precisely the second lead so it is in the hole.
Heat both holes at the same time.
Add a little bit of solder if needed, to help to melt the solder that is in the holes.
This should work without any problem.
 

Online Mechatrommer

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Re: First attempt at desoldering..some advice please?
« Reply #22 on: September 04, 2016, 11:02:26 am »
Or just heat both leads of leds and let them fall down from the board (tap the pcb gently if needed to make the led fall off).
those led wont fall off easily as the OP tried to mimick professionally made mass produced units by bending led's lead end at different angle before soldering them.. i had lot of fun salvaging passive components with that kind of bended leads termination, including using small tip plier or tweezer to pull them off forcefully...
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 

Offline GreyWoolfe

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Re: First attempt at desoldering..some advice please?
« Reply #23 on: September 04, 2016, 02:10:17 pm »
You don't need solder wick at all for this.  Just pull the leads out with pliers, and reopen the holes with a toothpick (in both cases while applying the soldering iron).

I do this with a cheap flea market dental pick that I heat directly instead of the pad.
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Offline JacquesBBB

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Re: First attempt at desoldering..some advice please?
« Reply #24 on: September 04, 2016, 02:56:05 pm »
When I need to open a hole,
I use small drill bits of the suitable  diameter

http://www.electrodragon.com/product/20pcs-straight-pcb-drill-bit-variable-0-50-70-81-0mm-diameter/

with a  small manual  drill
http://www.ebay.fr/itm/272336482733?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Which I heat directly with the soldering iron. Of course, it is not good for the steel, but these bits are very  cheap, and can be reserved for this kind of use. If  needed, one can finish by drilling  the hole a little, but need to be careful about removing the tin of the hole. For the present case, as there is a lead across, it does not matter.


 


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