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Recapping pc motherboards.

Discussion in 'Troubleshooting and Repair' started by 486dx33, Nov 14, 2018.

  1. 486dx33

    486dx33

    3
    0
    Nov 14, 2018
    I bought myself a desoldering gun so I would be able to recap old pc motherboards. Today I started practicing removing capacitors on some scrap pc motherboards. I managed to remove about dozen of them, but the holes in the motherboard are not very clean and it might be difficult to put new capacitors there.

    Anyone has any advice on what is the best way to remove components from those multilayer pc motherboards. What kind of temperature I should use with the soldering gun and how long I should be holding the tip of the desoldering gun on the legs of the capacitors before I try to suck the solder out of the hole?

    I will keep on practicing before I desolder anything on pc motherboards that I want to keep, but I would appreciate any help that would make the desoldering results cleaner.
     
  2. kellys_eye

    kellys_eye

    4,284
    1,145
    Jun 25, 2010
    Quite often it is easier and less damaging to simply 'crush' and snip/remove the remains of the old capacitor and solder a new one to the leads that remain.
    Not pretty but it works.
    Depends on how proficient you get with the desoldering tool.

    Personally I would remove the capacitor using the tool and then use additional flux and de-soldering braid to clean up the area. The balance between getting it tidy and lifting copper track/pads is a delicate one.
     
  3. Bluejets

    Bluejets

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    698
    Oct 5, 2014
    Helps to add new tin/lead solder (60/40) to each joint before even thinking about removing the old one.
    Kellyseye approach the quickest easy way.
    I have done the "remove and replace" in the past way back when but even then, hardly worth the effort.
     
    davenn likes this.
  4. 486dx33

    486dx33

    3
    0
    Nov 14, 2018
    It is worth to me if I spend hours changing capacitors and end up with a working motherboard. That is why I got the desoldering gun. I am just trying to find out information what temperatures, what kind of tip to use with the soldering gun and generally what is the best way to use it when desoldering pc motherboards.
     
  5. Kabelsalat

    Kabelsalat

    105
    20
    Jul 5, 2011
    Had success replacing caps to an old MB last year.

    Before I did any solder - I slightly warmed up the area of the motherboar where the legs on the cap with an air gun.

    I then warmed up first leg with soldering gun, and after the led melted I used a vacuum pump to remove most of the soldering around the leg. Then I repeated on the other leg.
    In most cases, some soldering will still be left, but not much - and I used a plier to jerk the capacitor leg forth and back until the remaining soldering break loose.
    The opposite cases is when there is a larger portion of leftover soldering. When that happen, just repeat adding heat to the capacitor leg and use the vacuum pump once again. Then jerk the leg using a plier.

    Now days I don't solder very often, so I removed 3 capacitors in order to figure out how much time neccesary for the capacitors legs to warm up the solder so that the vacuum pump get most of the solder.
     
  6. Bluejets

    Bluejets

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    698
    Oct 5, 2014
    It's not THAT difficult to look up the melting points of both 60/40 and lead free solder.
    I did ......and 60/40 comes in at typically 180 degrees C and lead free at around 240 - 250 degrees C.
    So....cook away and best of luck.
     
  7. dave9

    dave9

    743
    166
    Mar 5, 2017
    I have recapped many many different things in including motherboards. My technique and equipment may differt slightly than what others have available but the following works best for me.

    Don't worry too much about temperature. Unless your iron exceeds 60W, you will need every degree temperature you have at the max output of the iron to get the most failure prone capacitors off the power and ground planes present on motherboards.

    I do not try to suck solder off first. Leave all the original solder there, and sometimes you may even need to add some. I use almost exclusively 63/37 so that is what I add when needed, whether it's a old lead-based solder mobo or a newer lead-free soldered board.

    I want a good amount of solder there, and a very clean, high quality broad chisel shaped soldering iron tip (the shape is somewhat of a personal preference, other shapes may work too but they should be broad not fine tip), and I heat one leg of the capacitor at a time and rock the capacitor to the opposite side (other hand on the front of the board to push on it) once the solder is molten.

    It usually takes a couple passes, rocking it one direction to get one leg of the capacitor out 1mm, then the other side 1 to 2mm, then the first side and second side again. This all happens within 10 seconds, not a long drawn out process.

    Once the capacitor is out, if I have a solder sucker I may try that to clean the hole but the last step is heat that pad and insert a stainless steel pick, similar to a dental tool. What I use is actually a few pieces from a dental pic set, but before I had such a set I came up with other makeshift tools to use, for example a fairly thick sewing needle put into the end of a mechanical pencil.

    Whichever it is, you will find that solder clings to it less if you keep it polished and it is better to push it through the hole from the front side of the board while heating the back, so you need a bench setup that holds the board in place vertically whether it be a bench vice or clamps or stacks of books or whatever.

    Much of the above is just one way to do it. You could use a heat gun for example, and just pull the whole capacitor out in one shot, then just clip the leads on the new capacitor to the same length so you can hold them both straight in the holes, then come back again with the heat gun to the back of the board and push the capacitor in when the solder gets molten. Next use an iron and solder to solder it down while holding it in with your other hand.
     
  8. 486dx33

    486dx33

    3
    0
    Nov 14, 2018
    My desoldering gun is Hakko fr-301 and it is 110W and has temperature settings between 350C and 500C. I used 450C setting and 1mm tip when I was practicing with my scrap board. I also bought some extra tips for it since I am not sure which size is correct for those pc motherboards, so I have 1mm tip that it came with and I also got 0.8mm and 0.6mm tips.
     
  9. H2814D

    H2814D

    65
    8
    Nov 4, 2017
    I've done a few re-caps as well. I mostly use dave9's method for removal, but instead of using a needle or anything made of steel after cleaning with the solder braid, I use a wooden toothpick. The toothpick will open the hole without sticking to the solder. You heat the remaining solder and shove the toothpick into it. All I need is the hole to be open when re-inserting the cap legs and this works well.
     
  10. bushtech

    bushtech

    886
    139
    Sep 13, 2016
    And use flux often
     
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