Desoldering thru-hole PCB components

Discussion in 'The Workbench' started by Kutt, May 30, 2020.

  1. Micky

    Micky Well-Known Member VIP Member

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    The easiest way I have found to deal with 'lead-free' solder is to first remove all I can by conventional means, and then re-flow the joint with 60/40 multi-core. Then you can generally remove what is left, also at a lower temperature.
     
  2. Gene Ballzz

    Gene Ballzz Well-Known Member

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    Great tip there @Micky ! Right on the money!
    Just Sayin'
    Gene
     
  3. tmingle

    tmingle Well-Known Member

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    I'll try that the next time. Thanks
     
  4. Justin Whitstine

    Justin Whitstine Member

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    This. I am a hobbist solderer, not a professional. The first thing I would do is what Micky said, get off all the old solder you can (which you have already done), then apply a lot of regular solder (not lead-free).

    It is possible for you to get all those legs heated up at the same time if you add enough solder to it and move the iron around fast between all the pools of solder to try and get them all molten at the same time. That will be very difficult and require you to put a ton of heat into the board and possibly damage it.

    Since you are just starting out, I would do what another person above recommended and if possible clip the legs off the switch from the other side of the board. This will allow you to heat and remove one leg at a time. Apply solder, heat, and grab the leg with a pair of needle nose and gently pull on it. When the entire solder joint turns liquid it will slide out.

    Good luck and enjoy the learning process. :) Its never easy or done right when you are first starting out. If you are serious about soldering, a temperature controlled iron as is posted above was the single biggest improvement I ever made in my soldering journey.
     
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  5. Kutt

    Kutt Well-Known Member Gold Supporting Member

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    Thanks for all the input guys. I have some flux arriving around the end of the week. All I could find locally was flux intended for plumber's use, so I had to order online. I got most of the factory solder off, there is just a tiny bit left that's preventing those six legs from releasing. I will take all advice into account when I go for Round II.
     
  6. gullfo

    gullfo New Member

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    also consider - a proper suction tool - with some practice, you can gently move the pin or lead when the solder is hot and suck out the solder. and in most case, you'll get a clean opening. all the previous advice - wet it with new solder, practice, patience, etc are all excellent. watch some videos on proper PCB soldering techniques. digikey has the aven 17537 243-1184-ND 1992578
     
  7. southbound suarez

    southbound suarez Member

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    It is a definite acquired skill that requires practice.
    I love watching some of the videos on YouTube... Some of those guys make it look so simple!
    So far there has been some very good advice here.
    Especially important is the preparation. The points about keeping your iron tip well maintained.
    It is vital to keep the tip clean and tinned with shiny with fresh coat of molten solder. Note that the use of flux will be messy and will require even more diligence at keeping that tip clean. Flux is quick to burn and scorch. Once flux burns its a good indicator to remove heat, clean and start over again. More heat after it has darkened and you are at the point of wrecking the foil on the board. It may seem counterintuitive but Desoldering almost always will require a initial application of fresh solder to flood the joint and transfer the heat into one continuous molten puddle for extraction with a solder sucker or desoldering braid or mechanical tap as mentioned in a previous post. It often will take numerous gentle applications of flooding and removal to extract all the solder in plated thru hole devices. Often times with round tight fitting pins it will be impossible to extract all of the solder from one side of the board or even both sides no matter how much you flood the pad. In these instances you have to resort to the heat and pry method. This is the point where the most chance for damage occurs and will require much patience and a gentle hand. Often the pad get over heated and the foil will delaminate and while applying the force of yanking on the component lead will only hasten the damage to the foil. Sometimes damage such as this is unavoidable . In such case you must create new traces or vias, often with small jumpers of teflon insulated wire wrap hookup wire. Such repairs while necessary, really look terribly unprofessional and should be avoided as much as possible.
    It is not at all unusual for me to destroy or crush a faulty component such as a multi pin jack with a pair of dykes on the top side of the board, just for the luxury of having access to the pins where I can each individual pin for removal one at a time.
    If you plan to remove a component for replacement and you are just starting out with your skillset, I recommend cutting the component away from the topside of the board first and removing the indivdual pins one by one. Just be sure to try and leave enough pin protruding from the top of board as to be able to grip with a pair of needle nose or hemostats once you have heated it for extraction. Like prying, be very gentle and dont overheat as this is easy to botch with the foil pad delamination. Remember to apply solder first to flood the joint when extracting. I like the fact that hemostats can lock onto the lead and are hands free. The hemostats can add enough mass to the pin that the force of gravity can be just the right amount to pull the remaining pin out of the hole hands free while using both hands to apply solder and flood the joint.
    Once the pin falls out of the board you can suck off the remaining molten solder pool.
    A mechanical plunger type of solder sucker is a must to remove that pool of molten solder. With mechanical plunger types of solder suckers I refrain from using flux , it will gum up the tool and clog the tip too. I use the sucker to remove large molten pool of solder while sucking out the hole. I then add flux and use braid for fine cleanup and then wash the whole thing with a couple of shots from a spray cleaner bottle filled with anhydrous isopropyl alcohol. (if anhydrous is unavail. try to use no less than 70% being careful as to where the runoff might cause problem such as dripping into a transformer or a choke, meter movements ect.... basically stuff that you dont want moisture. Certain fiber boards such as vintage Fender eyelet boards will retain water vapour too, so thoroughly blow dry if your cleaning solvent has any water moisture content or is hydroscopic. Clean and oxide free surfaces are crucial to sucessful soldering!
    A note about flooding and extracting solder....
    Much criticism is made of ROHS lead free solders.
    It is a universal standard that lead solder and nonlead solder are incompatible and completely violates any and every professional and military standard. Any shop that must adhere to milspec or other standard do not allow for soldering tools to be used with both lead and unleaded solders. It is said a soldering station tinned with lead solder will contaminate the leadfree solder and cause for crystalization of the solder joints and will render the alloy to be brittle.... However my money I would bet that 95 to 99 % of all techs will continue to use leaded solder on ROHS circuits while instituting a repair. This is a do as I say nevermind what I do type of thing as I see it..... I am glad that I used up the one full spool of ROHS leadfree shir soldet and gave away the other half spool. I no longer have a virgin leadfree solder station anymore either! That stuff is evil! It takes more heat, and wont flow very well if overheated or heated too long. It oxydizes and kills soldering iron tips it short order. If the tip overheats or isnt kept constantly tinned, it quickly erodes. So with tounque in cheek "NEVER MIX LEAD AND LEADFREE SOLDER" WINK WINK!
    Seriously though, do your best to remove all the evil solder before resoldering with the lead.
    Also since I mention and emphasize flooding a joint with molten solder prior to sucking up or removal of the homogenous pool of molten material, take note that there are commercially avail. low melt alloy products such as Chipqwik that are designed just for such use. this is advantageous when trying to desolder multiple pins all at once . You introduce the alloy by flowing it into the joints and flooding the existing solder and it mixes in and remains fluid for a much lower temp for a much longer duration making it easy to melt several pins at once while prying or pulling the device out. Once again watch out ripping the foil off the board as the joints cure! Also you have to be sure to remove all that alloy or your soldered repair will mechanically fail in short order! Such desoldering alloys are very expensive but work very well. Especially on surface mount rework.
    While thats well past my own allocated two cents! Best of luck, but better yet practice practice practice.
    Hopefully maybe something I mentioned helps.
    Oh I almost forgot to mention the rattlesnake shake....
    Yes I do something very similar except it is more like a sharp flick of the wrist. The post was wise to mention having a trashcan to do this habit into...
    I will also mention that its good to have eye protection when doing this or at least be very wary if the flying molten solder. The carpet to left and beneath my bench is polluted with molten melted blobs of solder fused to melted carpet fiber!
    I suppose there will someday be a day of reckoning with the landlord of the shop! Old habits are hard to break!
     
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  8. Marvelicious

    Marvelicious New Member

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    Hakko also has a less expensive version.It REALLY works good for me. Down side: the negative angle pistol grip is probably superior from an ergonomic standpoint if you're doing a crapton of desoldering of something lying flat on a table, but it fights you when you're trying to get in somewhere (like inside an amp...). I'd really prefer a straight pencil style format, but aside from access issues, it really works slick. It still isn't cheap, but it's about a quarter the cost of the one you posted.

    [​IMG]
     
  9. ampmadscientist

    ampmadscientist Well-Known Member

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    I will show you a secret to UN-soldering.

    1. Clean the solder wick. Remove all the oxide. The copper must be shiny. (you can clean it with scotch brite pads)

    2. Coat the solderwick lightly with liquid electronic flux. (or use pre-fluxed solder wick which is more expensive)

    3. Apply fresh solder to the tip of the soldering iron first, before you start UN-soldering.

    When you do those 3 things: The solder will come off the board 10 times faster.
    The solder will come out of the holes 10 times faster.

    If you are having problems, follow those 3 things above. This is the difference between "working," and non-working.

    4. After UN-soldering, clean all the flux off the board with 90% isopropyl alcohol. (not rubbing alcohol)
    and let it dry.
    I use a hair dryer sometimes, with the cold setting, to blow dry the board.

    5. Pre Fluxed Solder Wick
    is the industry standard. But it costs a lot of money compared to "cheap radio shack" solder wick. The cheap solder wick has no flux in it.

    Cheap solder wick which has no flux in it:
    [​IMG]

    Expensive solder wick which is Pre-Fluxed
    [​IMG]


    Flux is extremely important in DE-soldering.
    The solder which is already on the board: does not contain enough flux to DE-solder.

    The solder which is on the tip of your soldering iron:
    does not contain enough flux to DE-solder.

    Now you know why
    your DE-soldering is too slow or non-working.
     
    Last edited: Jun 4, 2020
    Kutt likes this.
  10. dragonvalve

    dragonvalve Well-Known Member

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    Yes the tools need to fix the modern complicated electronics are not cheap. The technology is a whole other banana.

    I have this Millennia STT preamp. It was made 20 years ago.

    If I needed to swap out the lighted red and yellow buttons, i would need an expensive desoldering pump just to repair the switches.

    [​IMG]

    These days with circuits made by robots, you would need a robot to repair them!:eek:

    [​IMG]
    :drunk:
     
  11. Kutt

    Kutt Well-Known Member Gold Supporting Member

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    Whelp, I got back around to taking a second crack at this today after getting flux a couple weeks ago. I got the pedal buttoned back up and much to my surprise... it all worked. I laughed out loud. I'm not 100% happy with my re-soldering job but again this was my first pass at PCB work and the pedal is fully functional again. I learned a lot and no price can be put on that.

    Thanks for everyone's input and assistance.
     
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