Removing solder from SMD pads, MY way! Please can anyone test this out?

Discussion in 'General Electronics Chat' started by dodgyangle, Jul 28, 2014.

  1. dodgyangle

    Thread Starter New Member

    Jul 28, 2014
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    So, I'm no expert, I just like assembling things, I can't really put my head to work on designing circuits. I fell into working on electronic by accident after I quit IT. I'm slightly Aspergers so I have some learning difficulties or cognitive complications. I also means I tend to write a lot, so I hope you're in book-worm mode and not in the hurry for a quick answer.


    I was at work the other day removing SMD fuses from a batch of PCBs and replacing them with 0R0 links, 1206 size I think they were. Hot tweezers were used to remove the fuse (my first time using those!), then instead of using braid to remove solder from the pads, I used my quicker method. No, not with the sucker. Tissue! :eek:
    I found myself doing this in a previous job where I first started soldering SMD, down to 1206 size, and hadn't yet mastered the way to use braid, I had a go but it was just too time consuming and braid kept getting stuck to the pad and I couldn't clear enough solder off.

    So how DID I do it? Well I just took a small piece of paper tissue, rolled it up super thin (as wide as the pad) and chopped the end off square, held it in some tweezers and used the squared end of the tissue roll to push the solder off the pad as I remove the iron. So, it happens all really quick, the iron goes on, and as soon as the solder on the pad has melted I move the solder side-ways with the tissue (so it slides across the pad) taking the iron away as soon as tissue makes contact with solder (upwards more than sideways, lets say roughly 45°). Most of the solder comes away on the iron, hardly any sticks to the tissue, some blobs might end up on the non-stick surface of the PCB but it's not too hard to get them off. The pad is left looking clean, flat and it's still solder-coated. I can put a new a component on and new solder adheres to everything without a problem. This works better with lead-free/rosin-free solder. I think I tried it a bit with leaded/rosin solder too and tissue traces were left stuck on the board with the leftover flux so I had to clean the board some more.

    So anyway, just the other day my supervisor came in and asked me why I was using tissue and requested I resort to using just the braid because it was the industry standard and tissue wasn't. There's plenty of people out there who love to pick at anything and find every reason why not to. He said someone said there could be a risk of residues left on the board.

    Could anyone with the equipment go and test this out? Measure and compare the difference in resistance through a solder joint which *MIGHT* have a layer of foreign atoms in the way.
    Also what other problems could there be with this?

    Or...if you know of a place where it says it been tested (tissues method for solder removal from pads) point me to it.

    Hey, this method was just an idea of my own - and nobody told me there was a set way to do things, I learn as I go, different ways from different people. The tools we already have are there to be used, but that doesn't mean new ways can't be invented and used, right? We just get the rule-followers spouting the usual top-down dictatorship, industry standards, regulations, law, etc, so they don't accept creative ideas or the slightest chance of risk anymore, not even 'if it works, use it' - no, everything has to have an official stamp of approval, traceability, and accountability.

    In the meantime...it's looking like this solder-braid method could be just a nifty little earner for the copper industry, and may be a reason why there's not a lot of competition. hehe Save some bucks, use TISSUE!
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Quick tip. Considering your apparent entry-level job, your supervisor is right, even when you think s/he is wrong. What if the solder joints you make fail in part do to your new procedure? Are you prepared economically to cover for that error, or will you want your employer to cover for you?

    Your analysis of the issue,
    only confirms your lack of understanding of the potential issues.

    Are you trying to build a case for job discrimination or trying to solve a problem?

    John
     
  3. to3metalcan

    Member

    Jul 20, 2014
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    I don't know how much I can help you as far as testing, but I'm ALWAYS looking for new ways to remove SMD components, and I'll certainly give your method a try!
     
    Sakthirenga.A likes this.
  4. dodgyangle

    Thread Starter New Member

    Jul 28, 2014
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    I lack a lot of knowledge, I'd love to get trained properly, get some IPC certifications and whatever else there is, and generally keep up with the changes in technology.

    In the olden days companies would train you up and keep you for decades, these days they want you to be a pro from day 1 and expect you to know how to do everything, and then they only want keep you for a few months for their busy period. They'll show you how to operate particular things, and yeah I get shown over and over again how to do things I already know, but everyone has something different to say, and somethings they miss out.

    I'm not interested in any legal matters. That discussion can go right out of the window. Law-heads need to learn about forgiveness. I just want to know if there is a problem with using tissue to shift solder off a pad, such as increased resistance or a structural weakness which might cause the joint to crack?
     
  5. dodgyangle

    Thread Starter New Member

    Jul 28, 2014
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    I only used the tissue AFTER the component was removed. I rolled it up as thin as a cocktail stick (like those lollipop sticks made of rolled up paper), or larger for bigger areas. It's great for getting rid of any solder messes/splashes on unused pads and the best way I can think of to get the pad back down to totally flat.

    Someone would need to have a very sensitive/high-precision meter gadget to check for a difference between groups of identical pads. More than one pad per group is best. I was thinking at least 10) ....a group done with tissue, another group done by braid, another group of new joints un reworked. It's probably better if there's track running off the pads so you can attach wires for the meter. Perhaps some old PCI cards would be good as you could just use the interface pads on the edge of the card. Need to tin pads then remove with tissue/braid and then solder again attaching something, a wire or SMD link to measure from...or just probe the top of the solder on the pad when you measure.

    It would take a lot of time to see what the lifetime of the joint would be, what with any oxidation going on.
     
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Sounds interesting, I'll have to try it.

    Part of the problem with braid is that it gets used up, and you have to keep snipping off the used bits and pulling new braid out the holder etc.

    Your way could have some nice advantages, thanks for sharing. :)
     
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    This place sounds like a mess. They tell you to use solder wick but they have no standard procedure to desolder?

    Also, your method sounds like technique is very important (timing, finesse, sliding components with the tip). If you are the only one talented enough to do this, then the method may not easily be worked into a standard operating procedure for everyone (if they had one).
     
  8. dodgyangle

    Thread Starter New Member

    Jul 28, 2014
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    oh yeah, and the trick is to push the solder off fast enough before it hardens again.

    But will this leave a fine layer of carbonized paper dust and cause a lack of conductivity or structural integrity problem?

    The end of the tissue soaks up a bit of flux and turns brown/black and goes hard and I just trim that off as it needs to be a soft edge. Perhaps pre-soaking the tissue with flux will prevent it burning up? I'm not sure. I haven't started a fire yet, but I don't even burn the tissue that far.
     
  9. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Using tissue paper is an interesting method indeed. I've always used solder wick, once it gets hot I can drag it over any pads and clean them all until that spot on the roll is full, so move to a clean spot and repeat. I always use wick with flux which akes it a bit easier to use, and I actually "tin" the spot where I start my iron.

    The tissue has the potential to leave some unknown residue behind, but that would be appparent when you try to solder down the replacement part. If those joints look clean you've done your own evaluation, confirmed by at least twice as many experients as parts you've replaced.

    I wonder if just a piece of PCB might work too as it sounds as the tissue is just pushing the solder aside.

    However, the boss is always right. I know, I *am* the boss in my shop. However, I do tell my men that rules I do not see broken are not broken, meaning off liits things like coffee cups I do not see are not on the shop floor. (If they are mostly out of sight I may push them further out of sight without comment.)

    So you could continue with your method as long as your boss never sees it. Then one day when you earn some productivity award you might announce your secret method.

    Good luck with your career !!!
     
  10. dodgyangle

    Thread Starter New Member

    Jul 28, 2014
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    Every company has it strengths and weaknesses, just like nobody is perfect. There's places that take ESD precautions to varying degrees, some places just have a strap on the desk, others want you wear ESD shoes or shoe-strap or have ESD flooring, ESD bags, daily strap testing, and whatever else I don't yet know about. Some places don't allow drinks in the work area or they'll allow a sealed bottle or they don't care at all. Most places have problems with communication and coordination. I just go with the flow, adapt to each company as they all behave differently.

    I wish I could video it for you, but I don't have soldering equipment at home nor the best camera if tried it at work which I wouldn't as I'm not paid for that. :p It's really not too hard, it's quicker and easier than braid, and if the circuit still works and passes the testing then there shouldn't be a problem doing it that way.

    There's no 'sliding components with the tip', the component is already taken off, we're just pushing the solder off with a bit of tightly packed tissue, not pushing the tissue hard against the iron but against the pad and and across while moving the iron out of the way at the same time, and once the tissue has reached the other side of the pad I lift the iron away and the solder mostly sticks to iron or drops might stay on pcb. Maybe some more flux could be thrown in here, but maybe places wouldn't want to use extra flux, like this place where I worked where I first started doing this tissue thing - they already had a problem caused by flux being left behind under some large capacitors, we had to make sure they were 'clean' before and after soldering, had to solder at a particular rate and motion to ensure flux didn't link pads underneath the component. I think one end of each cap was going straight onto ground plane which made using the braid even harder.
     
  11. tindel

    Active Member

    Sep 16, 2012
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    I would think that you would want to use kimwipes... kleenex will leave aloe and flaky paper residues. kimwipes are pretty clean as far as oils are concerned and don't leave paper residues. I'm guessing this is what you're doing. Interesting technique - I might try it.

    PS flux CAN cause issues with testing.
     
  12. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    In Post #1 you said,,,
    In your last post you said...
    Sounds like you are not too deep in the Aspergers issues if you go with the flow. Good to hear.
     
  13. dodgyangle

    Thread Starter New Member

    Jul 28, 2014
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    I don't like to hold onto Aspergers as a precise diagnosis but it's the closest match to my condition, but I don't suffer from the extreme classic symptoms, but for instance I have poor memory, can't manage time or organise things very much in my private life, a bit light on eye contact, can't hear speech over background noises, but can hear the smallest of sounds and see in the dark better than most people, chemical fumes affect me more and even perfume makes me feel sick. Constant background noises at work can deteriorate my health. Claustrophobic amongst crowds of people but not of small spaces. Bit of a 'daydreamer'....I literally go into trance-like states on purpose in order to relax and help me think 'deeper' about things, but it happens automatically most of the time my eyes go in out of focus as I think and so it's a little extra effort to maintain focus but not a problem when I have to use my eyes for driving and operating anything then I go into 'stay sharp' mode, which reduces my ability to listen and talk.

    I look and move fairly normally, and look 10 years younger than I should. It has it's advantages. Big disadvantage is I don't get on with people so well - no arguments but communication is so hard to judge what's appropriate to say. Besides that I often get my tongue-twisted, and don't have much vocal strength or enough control of my tone ,pitch, or loudness (often too quiet to be heard) had a tiny stammer that went away by the time I got to school. Strangers are the hardest. People don't bother to say hi to me and keep their distance if I don't appear to be behaving in a way they'd prefer.

    There's plenty more I could add....!
     
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