What is this? I can't even get the solder to melt.

Thread Starter

fr0ntsight

Joined Jun 30, 2020
8
I'm simply trying to learn and practice soldering and desoldering.
I have an old board i am working on and can't for the life of me get ANY of the components off. I can't even get the solder to melt.
Do they use something other than solder during manufacturing? Here is a picture.

I have already tried adding flux, adding solder, and using the wick...I literally can't make a dent in this solder.

Any help would be appreciated.
 

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narkeleptk

Joined Mar 11, 2019
461
Its just solder. Sounds like you need more heat. What type of tip do you have and what temp are you using? Personally I usually hang around 350c-380c with a large knife tip or med chisel.
 

SamR

Joined Mar 19, 2019
2,125
Keep the tip wetted with fresh solder. Old solder oxidizes and creates some crusty muck. Some flux does help and sometimes even a small blob of fresh solder. For desoldering, a big tip with lots of mass helps with the heat transfer to get the old stuff to melt. And hi heat, you want to melt it fast.
 

Thread Starter

fr0ntsight

Joined Jun 30, 2020
8
I'm using a hakko fx-888d with a smallish chisel. I've tried temperatures from 500-750. I'm not worried about ruining this board I just want to learn.
When i put a little solder on the tip of the chisel and touch the old solder the new solder will move around like mercury but it doesn't actually stick. If I put the wick on with a little flux and then put the iron tip on top of that, nothing happens at all....if I put a little solder on the tip it will just flow onto the wick leaving the old solder in perfect condition.
Should I try a different tip than the one that came with my hakko? It is a good tip but perhaps SamR is right and its a matter of more mass? Thanks for the help guys.
 

SamR

Joined Mar 19, 2019
2,125
If it's really oxidized and crusty the solder-wick won't work very well. Time for a solder-vac. Sounds like you are getting it to melt. Then quickly remove the tip and hit it with a solder pump. Kind tricky using both hands and timing is everything. Usually takes a couple of tries with the pump to really get it all off. If you are scrapping the board then don't worry about the heat and crank it up but if repairing then be careful about overheating and lifting a trace or pad. You will definitely have better results desoldering with a big heavy tip.
 

Thread Starter

fr0ntsight

Joined Jun 30, 2020
8
Here is a better picture and a pic of the iron tip.
Should I go bigger on the iron tip? I have a small set of some sharp flat ones and conical etc...

I just tried again on 800 F temperature and still couldn't get it to melt. The new solder melts fine but the old stuff isnt moving at all. I can keep the iron on it for 30 seconds at 800 and it doesn't leave a dent.
 

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Thread Starter

fr0ntsight

Joined Jun 30, 2020
8
So I used a bigger different style tip and bumped the heat to 800 and it actually melted :) Thank you for the tip on the tip
Would a de solder pump help me remove other through hole components? It seems like the hole always fills right back up so I can't run wire through it. Thanks for your help...it feels good making some progress!
 

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SamR

Joined Mar 19, 2019
2,125
I solder ~350C and my vacuum desoldering station is set at 380C which is high. The chisel point you have should be good. I got tired of fighting desoldering with iron/solder-sucker/wick etc. and stepped up to a vacuum station, especially when stripping scrap PCBs. What flux are you using? I typically use Kester 951 liquid but MG Chemicals #8341 paste seems to work well on the stubborn stuff.
 

Thread Starter

fr0ntsight

Joined Jun 30, 2020
8
Probably so. I usually use hot air + iron if something gives me the trouble your experiencing.

Side note:
Place some heat shrink on your alligator clips there. The bare teeth like to scratch up pcb's and can even damage traces.
Thank you! Yeah it looks like the extra mass definitely helped to melt it. I have a heat gun coming in the mail tomorrow.
I had no idea how much of an art their is to soldering. I ordered some pre cut heat shrink from amazon. Should I put it over the teeth?
 

SamR

Joined Mar 19, 2019
2,125
Not always but sometimes. Sometimes I have to drill them out... At least until I started using the vacuum pump station which cleans them out very nicely.
 

Thread Starter

fr0ntsight

Joined Jun 30, 2020
8
I solder ~350C and my vacuum desoldering station is set at 380C which is high. The chisel point you have should be good. I got tired of fighting desoldering with iron/solder-sucker/wick etc. and stepped up to a vacuum station, especially when stripping scrap PCBs. What flux are you using? I typically use Kester 951 liquid but MG Chemicals #8341 paste seems to work well on the stubborn stuff.
I wonder if that larger tip i used would work on a lower temp...i'm going to try that with the next joint.

My goal is to be able to scrap and reuse components from trashed electronics.
 

SamR

Joined Mar 19, 2019
2,125
Covering the alligator teeth is a must do trick. Reapply as needed. I used to wrap them with rubber bands but they don't like heat and were always breaking.
 

Thread Starter

fr0ntsight

Joined Jun 30, 2020
8
Not always but sometimes. Sometimes I have to drill them out... At least until I started using the vacuum pump station which cleans them out very nicely.
I'm using Oatey No.5 lead free solder paste flux. Its all they had at Home Depot.
Can you recommend a vacuum pump station? Hopefully they aren't overly expensive. I also have a heat gun coming tomorrow, I heard that can help to pre heat the board a bit.
 

SamR

Joined Mar 19, 2019
2,125
K then most things stand up well to the heat except chips. Do a few legs, maybe 3 at a time and the do something else and come back a do some more.
 
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narkeleptk

Joined Mar 11, 2019
461

Tonyr1084

Joined Sep 24, 2015
4,535
For desoldering, a big tip with lots of mass helps with the heat transfer
Thermal mass is the ticket. When soldering or desoldering, you have to make good thermal mass contact between the iron and the item being desoldered. As Sam said, lots of mass helps. Other things that also help is dwell time. Sam (in post #15) mentioned doing only a few leads at a time giving the chip time to rest (cool down).

When desoldering through hole components whether you use wick, solder pump or a solder sucker you will always leave a residual bond in the hole to the lead. My method is to take a flat needle nosed plier and gently bend the lead back and forth, pulling the lead away from the wall of the through hole it's stuck to. The solder will fatigue and give way, and the lead will become free. With surface mount devices, sometimes two solder irons is the cheap way to go. Depending on the component you can sometimes use a hot air pencil to melt the solder and liberate a component. But you have to be careful. Plastic component bodies don't like the heat. Even if you're working on another component, heat from the pencil will flow out over a large area of the board. You'll either have to shield the delicate plastics or use a different method. For surface mount, solder wick works the best. Remove as much solder as possible from one lead, then do the same from the other. The component is still going to be stuck to the board but with a gentle pressure from a pick or an exacto knife and a little more heat you can liberate one lead. But don't pry it up too high. Just high enough to get it away from the pad. Remove the heat and let the solder freeze. Then when you heat the other lead the component should come away easily.

With multi-leaded components - sometimes it's just best to expect to lose the device. 40 pin components typically require hot air to liberate them. If you don't have a large enough source of hot air (some can be found on this website - depends on who you're listening to) then you may want to liberate one lead at a time and bend it up out of the solder. Eventually you'll have all the leads out of the solder and the component can be removed. Damage is possible. Leads don't like a whole lot of bending.

Yes, there's an art to soldering. Even more so to removal of components. Sometimes I just use a paint stripping gun to apply massive amounts of heat to a scrap board. Get all the solder flowing then rap the board over a bucket to collect the components. I used to use water to quench the parts - but someone pointed out thermal shock as a potential killer of those components. Especially ceramic capacitors. Crack them and they're useless. Even knocking them around can be harmful. But it's a quick way to liberate a lot of components. The bad part of that method is that if the component is not marked then you have no idea what value it is. Many SMT resistors are so small they have no markings on them at all. Quality control is critical when installing them because the tech has to be SURE he's putting the right parts on the board. The only way to prove out the board is if it functions properly. But this is usually in large scale PCB's like computer mother boards and such.

For now - think thermal contact. A hot iron with no solder on it will have a very tiny contact area and very little heat transfer. A slight tinning of the iron before making thermal contact can aid in thermal transfer. And as more solder begins to flow the contact area increases.

I most often use a solder sucker. Mine has a slight notch in the tip so that I can apply heat with an iron and get a close vacuum when I press the trigger. It's an old trick I've used since the 80's. That way the iron keeps the joint hot while the vacuum action happens.

One last thing: Dwell time: You can over heat a solder joint if you leave the heat on too long. This can result in delamination of the copper pads and traces. It can also fracture the fiberglass in the PCB. A fracture in a through hole can cause outgassing during soldering and make it real hard to get a good solder joint. Plus, the fracture will tend to grow to the point of failure. So learn to solder with quick heat transfer, and reheat a solder joint as few times as possible. If the joint is 75% filled it's good enough for military grade electronics (class 3). 50% is good for commercial applications (class 2). Children's toys and other junk electronics - a simple connection is all that's required. As long as it works (class 1).
 

jpanhalt

Joined Jan 18, 2008
9,419
Covering the alligator teeth is a must do trick. Reapply as needed. I used to wrap them with rubber bands but they don't like heat and were always breaking.
I usually slip some convenient flexible tubing over them, like silicone tubing use for fuel lines in models, neoprene, or thinner walled Teflon.
 

BobaMosfet

Joined Jul 1, 2009
1,108
I'm simply trying to learn and practice soldering and desoldering.
I have an old board i am working on and can't for the life of me get ANY of the components off. I can't even get the solder to melt.
Do they use something other than solder during manufacturing? Here is a picture.

I have already tried adding flux, adding solder, and using the wick...I literally can't make a dent in this solder.

Any help would be appreciated.
Look at the layers and the traces- how much other copper is there, that is acting like a heatsink. Solder temperature is a key (they may have used a higher-temp solder). You have to use flux, and a heated solder-sucker at the right temperature, and use it properly to get the solder off without frying the component(s) you're trying to liberate.
 
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