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Old 03-25-2017, 05:26 PM   #1
Spork Schivago
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Default How do you remove smd electrolytic caps?

Hello,

I have a Lenovo touch screen that's making a clicking sound through the speakers. I made sure the power source was good. I suspect a bad capacitor, but they're surface mount. I found one that doesn't look right and want to remove to test it. What's the best way to do this?

Google shows people just using pliers and twisting them or rocking them back and forth until they come off. A soldering iron hasn't seemed to help at all.

Is there a trick to this? Do I really just rock them back and forth until they break free? I want to to remove it in such away where after testing, if it's good, I can put it back on.

Thanks!
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Old 03-25-2017, 05:55 PM   #2
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Default Re: How do you remove smd electrolytic caps?

I would use a scope to check if the cap is doing what it is suposed to do in the circuit, another option would be to tack another radial cap across it to see if it fixes the problem, sometimes only half the value of the one on the board should make a difference. Then if it is bad add new solder then use solder wik or cut the can off with side cutters then remove each leg.
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Old 03-25-2017, 06:02 PM   #3
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Default Re: How do you remove smd electrolytic caps?

I would take that cap out. You can always put a radial cap over there. Is a bit more difficult but nothing crazy.
Or try with your iron and add some solder to take it out without breaking it apart
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Old 03-25-2017, 06:12 PM   #4
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Default Re: How do you remove smd electrolytic caps?

Quote:
Originally Posted by R_J View Post
I would use a scope to check if the cap is doing what it is suposed to do in the circuit, another option would be to tack another radial cap across it to see if it fixes the problem, sometimes only half the value of the one on the board should make a difference. Then if it is bad add new solder then use solder wik or cut the can off with side cutters then remove each leg.
Okay, I might be able to add another cap over place, but getting a scope in there would be really hard. It's just in a really bad place and there isn't much room.

So, even if the cap is good, adding another cap over top it won't hurt anything? Thanks!
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Old 03-25-2017, 06:15 PM   #5
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Default Re: How do you remove smd electrolytic caps?

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I would take that cap out. You can always put a radial cap over there. Is a bit more difficult but nothing crazy.
Or try with your iron and add some solder to take it out without breaking it apart
I tried that, but being a surface mount cap, it isn't budging. I thought adding solder would do the trick. I've seen videos and so far, the only way I seen someone do how I'd consider it right was by using hot air. We just ordered a 7mm nozzle, which we've needed for a while but just never had the cash for. Once that comes, I shouldn't have any problems removing them.

Here's a video that shows what I think is the proper way (same type of capacitor, btw): https://www.youtube.com/watch?v=5Ts6lPkYDsU

Here's a video that I think is the wrong way, I found a lot of these videos using the same way this guy uses: https://www.youtube.com/watch?v=Y1l7qSezFDQ

The cap I'm trying to remove is the same type as the ones in both videos.
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Old 03-25-2017, 06:18 PM   #6
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Default Re: How do you remove smd electrolytic caps?

post a picture of it .
generally you can simply add more solder or flux then simply get it flowing and remove it .
look up "chip quick" . that would certainly do it and give you plenty of time .
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Old 03-25-2017, 06:55 PM   #7
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Default Re: How do you remove smd electrolytic caps?

Yes hot air works, I replaced thousands of them in Sony camcorders using solder wik and solder station and sometimes hot air, if the caps leaked they would sometimes loosen the foil so one had to be very carefull.
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Old 03-25-2017, 10:17 PM   #8
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Default Re: How do you remove smd electrolytic caps?

Going against the cardinal sin, I use pliers to twist the cap off the PCB.

I don't know WHY it works so well and why it doesn't rip pads every time but I've found it more effective that dealing with hot air.
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Old 03-26-2017, 02:00 AM   #9
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Default Re: How do you remove smd electrolytic caps?

Grab capacitor with pliers, keep a gentle pressure downwards (the rubber bottom will basically make sure the pads on pcb won't lift this way) and slowly twist the capacitor a few degrees left and right until it breaks off.

The bend of the wires from capacitor to the part where the metal flattens under the rubber bottom is the thinnest part of the leads and is easily weakened so simply twisting it left and right a bit will break those leads while the slight downwards pressure will make the plastic bottom press on the pads and prevent the pads from lifting off the pcb
After, you put the solder iron tip with a bit of solder on the pads and since there's no capacitor sucking out the heat, the remaining leads and rubber bottom will lift off easily

See norcal's video here from around 10:30 : https://youtu.be/p1zhfYHUIIY?t=10m32s
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Old 03-26-2017, 03:53 AM   #10
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Default Re: How do you remove smd electrolytic caps?

Quote:
Originally Posted by mariushm View Post
Grab capacitor with pliers, keep a gentle pressure downwards (the rubber bottom will basically make sure the pads on pcb won't lift this way) and slowly twist the capacitor a few degrees left and right until it breaks off.

The bend of the wires from capacitor to the part where the metal flattens under the rubber bottom is the thinnest part of the leads and is easily weakened so simply twisting it left and right a bit will break those leads while the slight downwards pressure will make the plastic bottom press on the pads and prevent the pads from lifting off the pcb
After, you put the solder iron tip with a bit of solder on the pads and since there's no capacitor sucking out the heat, the remaining leads and rubber bottom will lift off easily

See norcal's video here from around 10:30 : https://youtu.be/p1zhfYHUIIY?t=10m32s
Okay, this explains things a bit. The caps are acting as a bit of a heatsink. That's why I can't seem to lift them with a soldering iron. But if I remove them this way, can I reuse the cap, if it's good, or do I have to replace it? Does it ruin the capacitor, essentially? That's the biggest reason I haven't tried it yet. I don't want to ruin them if they're good. I don't want to have to replace all the caps just because to test them, you know?
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Old 03-26-2017, 03:55 AM   #11
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Default Re: How do you remove smd electrolytic caps?

Quote:
Originally Posted by petehall347 View Post
post a picture of it .
generally you can simply add more solder or flux then simply get it flowing and remove it .
look up "chip quick" . that would certainly do it and give you plenty of time .
I can actually heat up both leads at the same time, but I don't think it'll help. I'll post a picture once it gets light out, if you really want to see it, but these little buggers are hard to remove. I can melt the solder on one side, but the cap doesn't lift on that side. I think there's solder underneath that doesn't get melted or something. For shits and giggles, I'll add an iron to one side while my wife adds an iron to the other side, and we'll see if we can lift it that way, after she wakes up.

From reading the other posts after this, I now believe the capacitor itself acts as a heatsink. I originally thought maybe my iron was accidently touching the capacitor, because of the close quarters on the one side, but now I don't think that's the case.

When I save up some money, I want to buy one of these: http://www.tequipment.net/Weller/T0051317899/?v=0

It's tweezers for SMD type work. I bet that would come in handy.

Last edited by Spork Schivago; 03-26-2017 at 04:29 AM..
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Old 03-26-2017, 04:08 AM   #12
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Default Re: How do you remove smd electrolytic caps?

Quote:
Originally Posted by R_J View Post
I would use a scope to check if the cap is doing what it is suposed to do in the circuit, another option would be to tack another radial cap across it to see if it fixes the problem, sometimes only half the value of the one on the board should make a difference. Then if it is bad add new solder then use solder wik or cut the can off with side cutters then remove each leg.
R_J, out of curiosity, how would I use the scope to check the cap live, in-circuit? Wouldn't I need a schematic that gives me waveforms to know what it's supposed to look like? What exactly would I be testing for? ESR is what normally rises when a cap starts to go bad, unless it shorts open or closed, right? Thanks for the info!
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Old 03-26-2017, 05:08 AM   #13
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Default Re: How do you remove smd electrolytic caps?

All the people I have seen just broke the legs and then they pull the legs with the iron, and sometimes they replaced them with tantalums...
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Old 03-26-2017, 06:10 AM   #14
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Default Re: How do you remove smd electrolytic caps?

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All the people I have seen just broke the legs and then they pull the legs with the iron, and sometimes they replaced them with tantalums...
Oh, so they break the legs and just replace the capacitors, whether they're good or bad? The one I'm looking at, I decided to check out the datasheet. I believe it's an FK series Panasonic, 100uF, rated at 25V (6.3mm in diameter). I'd hate to replace all these caps if none of them are broken.

Maybe I'll tear the whole board out and put some hot air to it. Thanks!
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Old 03-26-2017, 10:25 AM   #15
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Default Re: How do you remove smd electrolytic caps?

Before I actually start removing components here, I want to test the transformer, just to make sure. I tested the voltage, and that's good, but with a recent desktop I was working on, I learned the hard way that just because a power supply is producing the required voltage doesn't mean it's good.

Any suggestions on how to test this transformer? It looks like a laptop transformer. 19.5VDC output, but 120 watt (6.15A). We were thinking of purchasing a universal from bestbuy, but all the universals I can find locally are 90 watt. Do you guys think that really matters? Would a 90 watt be powerful enough to turn this on? I think the reason it requires so much juice is because of the huge screen....60$ for a 90 watt universal transformer.
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Old 03-26-2017, 11:45 AM   #16
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Default Re: How do you remove smd electrolytic caps?

I removed the capacitor. I tried with hot air, but it didn't go so well. Eventually, the legs stayed on and the cap came off, but all the liquid that was in the cap leaked out onto the board. I'm going to order a replacement.

Any suggestions on a good replacement? This was a 100uF 25V FK series (Panasonic) SMT capacitor.
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Old 03-26-2017, 12:01 PM   #17
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Default Re: How do you remove smd electrolytic caps?

Spork , the technique I mentioned is distructive, it's to be used when you don't care about the old capacitors.
Generally, smt electrolytic capacitors are crappier than through hole ones, so if you have doubts about them (if you exhausted all the other debugging and start to suspect them) you'd probably be better off replacing them anyway.

If you want to desolder and test... well..
the capacitors could leak electrolyte that would cover the pads and make it hard for the soldering iron tip to heat up the pads and put additional solder on the pads, so it would make it difficult to desolder the capacitors.
My advice would be to source some good liquid flux (RA or no-clean/rosin
with decent amount of activators) and be generous with liquid flux around the pads. Then use a hot air gun or paint stripping gun or some source of heat on the back side to raise the temperature of the flux to the point where it starts to do its magic , stripping the layer of oxides and crap that may be on the pads.
And then you can bring in some leaded solder, some 63/37 or 60/40 and put a bunch of solder on both tabs and try to slide a spudger (tool to open monitors etc) or tiny flat screwdriver under the rubber bottom of the capacitor.
As you go left and right heating each side of the capacitor, the spudger/screwdriver acts as a level and with its weight it should lift the capacitor off the tabs.. with minimal risk of lifting the pads off the pcb as well.
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Old 03-26-2017, 12:41 PM   #18
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Default Re: How do you remove smd electrolytic caps?

Quote:
Originally Posted by mariushm View Post
Spork , the technique I mentioned is distructive, it's to be used when you don't care about the old capacitors.
Generally, smt electrolytic capacitors are crappier than through hole ones, so if you have doubts about them (if you exhausted all the other debugging and start to suspect them) you'd probably be better off replacing them anyway.

If you want to desolder and test... well..
the capacitors could leak electrolyte that would cover the pads and make it hard for the soldering iron tip to heat up the pads and put additional solder on the pads, so it would make it difficult to desolder the capacitors.
My advice would be to source some good liquid flux (RA or no-clean/rosin
with decent amount of activators) and be generous with liquid flux around the pads. Then use a hot air gun or paint stripping gun or some source of heat on the back side to raise the temperature of the flux to the point where it starts to do its magic , stripping the layer of oxides and crap that may be on the pads.
And then you can bring in some leaded solder, some 63/37 or 60/40 and put a bunch of solder on both tabs and try to slide a spudger (tool to open monitors etc) or tiny flat screwdriver under the rubber bottom of the capacitor.
As you go left and right heating each side of the capacitor, the spudger/screwdriver acts as a level and with its weight it should lift the capacitor off the tabs.. with minimal risk of lifting the pads off the pcb as well.
I thought I remembered reading something a while back about SMT electrolytics being crap. That was for the Sega Game Gears I believe though, when the technology was still fairly new (I think). I figured with this being a newer board, maybe the technology improved.

So, if those SMT electrolytics aren't that good, maybe I should recap the entire board. There's a spot for a GPU but there's no GPU on this board (other boards include one though). The boards are a bit pricey. If I were to recap the entire board, what would be a good choice?

I mean, it's almost like a laptop motherboard. Can I use surface mount tantalum (the ones that look like little rectangles) or maybe surface mount aluminum polymers, to get better reliability? Would I have to change the farad rating at all if I went either of those routes? I see there's tantalum polymers as well...
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Old 03-26-2017, 12:43 PM   #19
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Default Re: How do you remove smd electrolytic caps?

Remember, you can change them with some radial caps, just solder the legs to the pads, they are cheaper and easier to find, and don't forget to look for similar esr and capacitance
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Old 03-26-2017, 01:55 PM   #20
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Default Re: How do you remove smd electrolytic caps?

Quote:
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R_J, out of curiosity, how would I use the scope to check the cap live, in-circuit? Wouldn't I need a schematic that gives me waveforms to know what it's supposed to look like? What exactly would I be testing for? ESR is what normally rises when a cap starts to go bad, unless it shorts open or closed, right? Thanks for the info!
I would just look at how its used in the circuit, In a switching supply secondary for example when one side of the cap is ground the ther side should have very little ripple, if you check it and you see a couple volts of ripple on it, its a good chance its going bad, If it was in an audio or video amp for example and used to couple the signal from one section to another, you should have close to the same waveform on both sides, if the input side had 1 volt p/p and output side had 1/2 volt again its a good chance its not doing its job.
I've seen the output of regulator ic's with so much noise they start to radiate into other parts of the circuit but ther dc voltage was still acceptable and when checked with a meter they looked fine.
I find the scope a real time saver, If you use it all the time you get familiar with what you should see, it sure beats removing parts to check them, if what I see does'nt look right,then I would pull the cap and check it, or if its just a small one I would just replace it with a new one if I had one.
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