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    extreme measures

    Here's another stupid question... I have had what seems to be pretty good success removing and putting in caps on my practice board. Now, on my 5th try I haven't been so lucky. Like usual, I remove the cap, then add solder to the back, heat it up and use a bulb sucker to clean it. After the second drag there still isn't a large enough hole for the cap so I went to the needle proceedure. I added solder heated it up agin and put the needle in and it won't go through very far. I didn't force it but tried the needle process again. No go. Now I'm a little worried. Tried it again and now things are looking a bit spooky. The hole is a bit discolored on the inside and the solder isn't penetrating. I have feeling by now the traces or whatever are screwed, burnt, have copious amounts of residue or whatever. I don't know. My soldering iron is good. I'm using silver bearing solder with a resin core... uhh..

    I have 2 questions, does anyone know what might have happened... and, are there some extreme measures that a person might try to open the via up when it probably doesn't matter anymore and maybe I could just get lucky trying?

    Thanks
    Better to have it and not need it...
    than to need it and not have it!...

    #2
    Re: extreme measures

    i usually heat from the rear and get the needle in while still heating. if i have probs i flip the board over, add a bit of solder to the front (then push the solder in with the iron) and heat from the front while pushing the needle from the back. needs some care while working from the front though otherwise burn some plastic etc...

    others like to heat from the same side as the needle. its all personal preference really, whatever works use it.

    the most important thing is not to have long heating. so like the above, we alter the technique as the situation changes. if it is not working then no length of heating is going to succeed.

    you say that your soldering iron is good but that doesnt say much. actually it could be good but the tip is not the best choice and is not transferring the heat well. or just it is a difficult hole perhaps with crappy solder inside and/or big ground traces around drawing the heat away. some boards even one hole is easy and the hole for the other lead is not easy and perhaps smaller and this continues for the whole job.

    i dont know about silver solder but good old 60/40 is fine for me.
    capacitor lab yachtmati techmati

    Comment


      #3
      Re: extreme measures

      If I can't get a clean hole after using a solder sucker or trying a needle (one try each), I simply heat the pads while 'walking' (for want of a better word) the new capacitor in, one lead at a time - in pretty much the same way as you heat and remove them one lead at a time. Given a bit of practice I find it works and so far I've had no problems with tracks or vias lifting. Or, if you can get only one hole clear you can simply heat the other pad while sliding the lead of the new capacitor in.

      As willawake says, adding a bit more fresh solder can often work wonders too - if there isn't enough the heat won't conduct, and also you'll never get a clean 'suck' if you don't have enough solder for the vacuum to pull on.

      Its just a matter of practice.

      Comment


        #4
        Re: extreme measures

        Yeah have to agree having a bit on the tip to help with heat transfers is good also sometime the quickest way is to basically resolder (flow) the hole and go again.

        If you haven't got it with 2 pumps go for the needle is the recommendation

        each time you heat reheat it and the longer time you spend trying does increase the chances of damage.
        (also oxide type crap, flux whatever building up)

        I'm using silver bearing solder with a resin core.
        Not exactly sure what that is but there are 2 types (you probably know this but I'll state it anyway) of solder being used these days and its not a good idea to mix them from what I understand

        the orginal 60/40 tin/lead stuff and the newer requirement of RoHS (brief on it)

        RoHS requires hotter iron temps and different solder (lead free, mostly tin)
        (probably different type plate on tips if you want them to last)

        I haven't as yet had to deal with Rohs so not really tooled up for it but most everything now will be so yeah a pain for techs having to keep separate stuff for soldering pcb's

        So now I guess its important to identify what solder was used.....

        the joints on older stuff should be somewhat shiny compared to Rohs stuff (which will probably have a sticker saying it RoHS)
        Although with flux washes they seem some what duller....then hand soldering 60/40

        My suspicion is maybe that was RoHS PCB so thats why you had trouble...

        There was at one time some crap I think $ony were putting on the pcb to make it hard for modders to solder to, so they couldn't mod consoles easily
        Dont know what it was or even for that matter how much truth was in the story (maybe they just did a Rohs thing )

        BTW not a stupid question ...it happens often enough

        Oh extreme measure!!!
        That will get you "put up against a wall" by some members of this forum
        is using a drill bit
        (some do though, very gently by hand and slightly smaller diameter...using it more like a file...... HIGHLY NOT Recommended method!!!!)

        Needle trick much safer method


        The problem is you dont want to destroy the via (hole) as substrate traces are, maybe connected to it. PCB's are Multilayer these days and there are tracks inside the pcb (like a sandwich)

        HTH

        Cheers
        You step into the Road, and if you don't keep your feet, there is no knowing where you may be swept off to." Bilbo Baggins ...

        Comment


          #5
          Re: extreme measures

          Thanks guys... I got a lot of good info here.

          I changed to good old 60/40 and ran the needle method again and voila! it went right through. I thought I was being cool by using 60/38/2 where 2 is silver which is supposd to be stronger, and a better conductor. The problem I suppose is that it is harder to heat and is also harder when cool. Maybe it's good for attaching but not removing??? Don't know...

          question... is there a way to make a basic check on the new caps connection to the board before setting up to the power supply? Playing around (hopefully I wasn't being foolish) I used my trusty multimeter to try a couple of points and got some readings connecting to one or two reletivly distant points on the back of the board to one or the other pole on each cap one at a time. have no idea what the reading meant but the number was obscure and the same on each cap. Using that as a reference I got the idea that the poles of each cap were respected separately from several points on the board but not when turning the poles the opposit direction. I'm sure that doesn't tell me that the thing works but it does seem to mean that there are connections being made somewhere. ?????? Yes? No?
          Better to have it and not need it...
          than to need it and not have it!...

          Comment


            #6
            Re: extreme measures

            humm using an MM for continuity checking is one way

            Most if not all large values will be across power rails
            In the case of the VRM they will be in parallel on the I/P and O/P
            ( side point: The VRM stands for "Voltage Regulator Module" and in days gone by was separate Board, now they are mostly integrated on the motherboard so the term is not quite correct but the function is the same)

            The trouble is with the older analog they tend to turn on semiconductors
            One thing to check on the mm is the dc voltage polarity on resistance range.
            The older analogs had the negative probe as positive to battery

            I just checked 3 DMM's from el-cheapo to somewhat expensive diode and 200 ohm showed about 3V DC probes + is + red - is - Black 2K and up 300mV
            (0.3 volt or less)

            You can see the charging action of large value capacitors with a MM on the resistance range. (it becomes a RC time constant type circuit)

            starts at zero and climbs up to infinite or near infinite ohms (better with analogs really)
            in a non linear fashion (it moves quickly then slows down)

            specific test equipment
            A lot of capacitance meters will measure in circuit without turning on semiconductors.
            The ESR meter is a very handy device to have as well

            Of course you have to apply a bit of Grey matter here, as for example if a resistor is in parallel with a capacitor...your going to measure it not the cap.
            (example only here)

            I guess the biggest worry is dropping a short across the PSU rails on the motherboard and resistive tests should show that. (zero ohms between + rail and ground)

            This is why a good visual of your work is important to do....its easy to bridge something sometimes were it shouldn't be, so pay attention to the pcb before and after each connection
            (taking photos (a few close ups as well) of the PCB is not a bad idea before.
            you start)

            Anyway guess some that do it on a day to day basis should have good advice on what to do so I'll leave it to them.

            HTH Cheers
            You step into the Road, and if you don't keep your feet, there is no knowing where you may be swept off to." Bilbo Baggins ...

            Comment


              #7
              Re: extreme measures

              I don't know if it was stated, but I noticed on a motherboard I was working on that predominantly, using the solder sucker works better on one side of the board for the negative pad and the other side for the positive pad. It's really weird, but it worked like this almost everytime unless I just had a hole that was stubborn.
              Presonus Audiobox USB, Schiit Magni 3, Sony MDR-V700

              Comment


                #8
                Re: extreme measures

                Hmm - must be a multi-layer board with a Vcc plane and GND plane. The pad which is being heated will reach a higher temperature if the plane to which it is connected is further away from the point of contact of the soldering iron (the copper in the plane acts as a heat sink). The higher the pad temperature, the easier it is to suck out the solder.

                Since the planes are at different distances to the pad from each side of the board, it will be easier to suck out the solder from the +ve terminals when heated from one side of the board, and -ve terminals when heated from the other side.

                Comment


                  #9
                  Re: extreme measures

                  Originally posted by cornflake
                  question... is there a way to make a basic check on the new caps connection to the board before setting up to the power supply?
                  the most important thing is to be careful about the polarity of the caps. if you have made a diagram then you can check this again. if its wrong then a cap will probably violently blow and reports here suggest the board probably wont be damaged but who knows

                  other than that i think its more likely to damage a via or lift some traces with excessive heating. not so hard to solder a cap in although some people have probs with that i dont know why?

                  so i dont think its really necessary to check the connections, just check the polarity and then do a close inspection in case you made any shorts with solder or there are bits of debris or solder blobs doing that.

                  and then just power up. its either gonna work or not and then you can check further.
                  capacitor lab yachtmati techmati

                  Comment


                    #10
                    Re: extreme measures

                    Thanks everbody... I've really picked up a lot. It's a good thing I did take the advice and diagram the polarity. The first board I worked on the other day was an Asus and if I hadn't made a note of it, I probably would have put them in backward.

                    I'll keep readin'
                    Better to have it and not need it...
                    than to need it and not have it!...

                    Comment


                      #11
                      Re: extreme measures

                      I've heard of people who have repaired broken solder pads by using tin foil or just a large blob of solder. After soldering in your replacement component, use a magnifying lens and find out where the trace is connected to. Do a continuity check with a multimeter - if it passes, the current is flowing through the trace to the component and it should work.

                      I once repaired a CD/Tape unit that had a small crack on the board by finding out where each of the broken traces went, then soldering wires from a component on one side of the crack to a component on the other side in accordance with the traces. The current flowed through the wires instead of being blocked by the crack, and the amplifier came to life! Luckily it was only 3 broken traces
                      You know there's something wrong when you open your PC and it has vented Rubycons...

                      Comment


                        #12
                        Re: extreme measures

                        just my thoughts on fixing pcb's by alternate routes

                        The trouble with that tom 41 and computers these days is the possibility of stray capacitances and inductances etc which can be introduced effecting signals on a computer board, but yeah I'd say still possible depending on what trace is lost, (how far you have to run and what you have to run near) for what type of circuit on the MB....

                        In older audio etc circuits you got more chance of not introducing problems then digital computer circuits boards.

                        RF circuits, again would be like computer circuits.
                        How the PCB is designed is part and parcel of the circuit as a total.
                        The higher you go frequency wise the worse it will get
                        (sky hooking things)

                        I guess what makes it really hard is you got no schematic for the MB, computer boards are so complex and PCB's are multi layer
                        A nightmare to know what connects to what and how it gets there.

                        I don't know for sure but guess faults like that are rare on MB's
                        more likely to find dry joints then a lost/ broken copper tracks for whatever reason.
                        Last edited by starfury1; 08-07-2007, 01:45 AM.
                        You step into the Road, and if you don't keep your feet, there is no knowing where you may be swept off to." Bilbo Baggins ...

                        Comment


                          #13
                          Re: extreme measures

                          I sometimes get those holes that won't clear out. I sometimes take the old clipped-off lead from a resistor (the thickest that will fit in the hole) and put it against the hole and heat it up and stick it through the hole. If the lead is long enough you can sometimes keep it moving while removing the iron so that it doesn't actually attach itself to the inside of the hole. At this point you can either pull it back out or pull it through the other side.
                          Presonus Audiobox USB, Schiit Magni 3, Sony MDR-V700

                          Comment


                            #14
                            Re: extreme measures

                            Greeting to all you who were so helpful in teaching me the basics as well as a few tricks here and there in recaping.

                            I just wanted to thank you guys for the help and all the advice which was excellent. Even though some of it was still over my head, I was able to learn by the stretch.

                            I just put up my first 2 boards and both posted and set up like they were new! Now I can start using my old RIMM 1066mhz modules again! I always liked those things.

                            Thanks again!

                            cornflake
                            Better to have it and not need it...
                            than to need it and not have it!...

                            Comment

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