Soldering 101

Discussion in 'Electronics & Electrics' started by BluBoy, Jan 17, 2017.

  1. BluBoy

    BluBoy Member

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    I've watched a few raspberry pi hobby projects videos, and thought it would be easy enough to do. Acquired a nice variable temperature soldering station, purchased some 0.3mm and 0.8mm 63/37(?) solder and got stuck into it... This is when I discovered I can't solder.

    My problem, is that the solder is forming little balls on the end of the solder wire. I then get frustrated and make the ball fall off and onto the pin hole I want to solder. From there, the solder doesn't want to bond with the wire (or the pin hole itself) no matter how much I heat it.

    This is what frustrates me the most. The videos I have watched have made it seem like if you heat the solder, it will lodge itself perfectly in the hole, bonding with the board and the wire instantly.

    Yes, I have tried tinning the wire and heating that first. I've also tried heating the pinhole itself too, but admit it's very brief, as I'm scared of just toasting the raspberry pi doing this.

    What am I doing wrong? And are there any videos showing a very basic intro to solderin (especially with the pi?)
     
  2. Mjollnir

    Mjollnir Member

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    Sounds like not enough heat and lack of flux/rosin. You need to 'wet' the area you're soldering. (i.e. adding solder & flux to the area and heating it)

    If you have a temperature controlled station, set the temp to 350C.

    Unless you're soldering directly onto the pin of an IC, circuit boards are not that fragile.
     
  3. Life_Essence

    Life_Essence Member

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    Set the iron to ~350C and let it heat up
    Melt a small blob near the tip of the iron
    Touch the melted blob itself onto the pad
    Push a little bit more solder into a bit of solder closest to the pad/pin you want to solder
    At this point the solder should pretty much do all the work for you and wash over the whole pad and pin, if it's just washing over the pad touch a bit more solder into the melted solder close to the pin and it should attach itself to it.

    If not there might be some crap on the pin or pad (left over glue?)

    You're basically trying to get the solder to do all the work, the iron just heats up the solder, the solder is then what heats up the pad/pin/whatever.

    Or as above not enough flux or more likely the flux is burning off, if you wait too long between melting the soldering and actually soldering the flux evaporates and it won't solder, you'll notice it cause the solder will go sort of matte instead of shiny. In that case wipe it off and start again.
     
  4. RobRoySyd

    RobRoySyd Member

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    Apart from all the good advice above what you're doing wrong is trying to learn to solder with something you're worried about damaging.
    Get yourself some matrix / vero board and some cheap components and practice on that.

    Your specific problem of the solder refusing to melt is a common one, I've been soldering for 50 years and it still happens. The problem is it's the molten solder that transfers heat but when the tip is really clean there's none available to melt the solder, Catch 22. As already said melting a little onto the tip is the go but even if your iron is hot enough the bloody solder can still refuse to melt onto the tip. Solution is to rub / swipe the solder and the tip of the iron. I don't know for sure what causes this and it can be frustrating but a rub / swipe fixes it.

    Also use the right tip, the conical ones that come as standard with most irons are pretty bad as there's no flat area on the tip. The small chisel shaped bits are much better.

    Another tip: Soldering really needs two hands so secure the PCB and component. You do need generally to apply some small force with the iron to whatever you're soldering. That's hard to do if the board is just sitting on the bench.
     
  5. Matthew kane

    Matthew kane Member

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    60/40 is easier to work with and flows better at its melting point. Working with higher temps means faster solder melting point and easier flow but you must be quick with the component you are soldering as certain PCB's and parts can be damaged if you hold your iron temp at it for too long. Good soldering is all dependant on the technique rather than the iron itself (provided it ain't a soldering gun).
     
    Last edited: Jan 18, 2017
  6. @rt

    @rt Member

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    Practice is what D-Link routers are for.

    When I solder, the iron tip will be freshly tinned but with as little solder as possible on it.
    Then the solder is fed into the point where the iron tip meets the part being soldered and worked away from there.

    I think if I wanted, I could get two free D-Link routers tomorrow.
     
  7. mtma

    mtma Member

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    Well unless the iron is shot. If the tip plating has been ruined it won't wet properly and it will grief you the entire way.

    In any case being able to wet the tip with the solder is relatively fundamental, if that isn't happening it should be fixed first (whilst you could probably still solder with it, any further practice will be frustrating)

    By the way if you are stuck with a sponge to wipe your iron with, make sure you dampen it for results. However the wire ball thing is the recommended method of wiping which only requires poking and no set up in particular is necessary unless you are using it a lot.
     
    Last edited: Jan 18, 2017
  8. Mathuisella

    Mathuisella Member

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    tip :

    use tin/lead solder... much easier to work with, especially for beginners
     
  9. OP
    OP
    BluBoy

    BluBoy Member

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    Thanks all.

    I was trying with the 0.3mm solder (tin/lead). I've read the thicker (0.8mm) stuff may have more flux, so will practice with that.

    I was also using the coned shaped tip, will switch to a flat one, which I'll tin first.

    I've got some spare pcb/breadboards, so might go very simple with a few LED lights.

    As for the actual motion, does this sound right... I've got pegs and alligator clips I use to hold the parts as needed. I'll tin the soldering iron a bit, as well as tinning the wire too. Hold the wire in the hole and briefly heat up the wire with the soldering iron. Heat should transfer to the metallic parts of the pin hole at the same time, leaving me with a hot wire, and warm pin hole.
    At this point, I slowly add the solder focusing on 'melting' it onto the hot wire, so it 'drips' down into the hole and 'fuses' with the warm pin hole.

    (That is a very rough summary of a bunch of things I watched/read over night.. Just double checking it sounds reasonable to you guys).
     
  10. elvis

    elvis Old school old fool

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    1) 60/40 tin/lead solder. Don't use anything but unless you're a robot.

    2) Flux. Not enough is bad, too much is bad. Play around with it, learn how to use it. That includes learning how to clean up afterwards.

    3) Watch the two videos below (Number 1 is about the tools, which you're already on top of. Number 2 is the technique).

    4) Practice, practice, practice.



     
    Last edited: Jan 18, 2017
  11. cvidler

    cvidler Member

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    My technique, is

    - ensure tip is wet - but no big globs of old solder on it - use bronze wool to clean off regularly. Sponges suck, dry they're useless and wet they cool off the tip too much.

    - align component lead and hole

    - use tip to heat both the tip and the pad (hole)

    - then add solder, ensure it 'wicks' (wets) the lead and pad.

    - done.

    whole process takes but a second when you're up to speed.

    use flux cored solder - both 0.8 and 0.3mm solder should have it.

    lead-free solder is much harder to DIY, as covered 60/40 is easier to use, but 63/37 shouldn't be too bad (I've never used it however, only lead-free and 60/40).
     
  12. aXis

    aXis Member

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    #1 tip that most beginners don't realise is that you don't add solder to the iron. A tiny bit on the tip of the iron to wet it is ok (otherwise it's hard to transfer heat) but you want to add the majority of the solder to the hot component.

    I.e. Put the iron on one side of the comonent, and poke the solder at the other side of it. When the component is hot enough it will melt the solder. The flux will be released on the component which is where it's needed, instead of corroding your tip.


    edit: Cvidler's technique above is spot on, that's how I do it. Lead free solder sucks and you need to use a hotter iron with risk of damaging components if you take too long. Do yourself a favour and practice with leaded stuff.
     
  13. maldotcom2

    maldotcom2 Member

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    Sounds like you're trying to add molten solder to a joint that isn't hot enough. Or possibly, if the solder has formed a glob either on the end of the iron or end of the wire, the flux would have burnt away. If you're forming globs anywhere you're doing it wrong. The way I do it is hold the clean and tinned iron tip against the joint for a second, then just touch the solder wire to the joint/hole. That's it, the whole process should only take a couple of seconds.

    Also as has been said multiple times, avoid lead free solder. I can solder a circuit board like a machine with traditional lead solder, but the day I bought lead free without realising was the day I thought I was losing my mind. :lol:
     
  14. shredder

    shredder Member

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    It seems your fundamental error is not knowing that the items to be bonded must be sufficiently heated by the iron, else the solder won't bond to the items.

    It's not just a case of "heating the solder". You have to heat the items to be joined. Once enough temperature is attained at the joint (with a lightly tinned iron), the solder can be applied and will simply melt and flow into the joint.

    You should be able to easily solder two simple wires together using the proper methodology, before moving on to anything else.
     
  15. RobRoySyd

    RobRoySyd Member

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    Not keen on the use of the word "drip" there. Molten solder should flow onto the pad and wire through surface tension. Molten solder has quite an affinity for most metal e.g. copper, tin, gold, silver and nickel. It doesn't "like" iron.

    Also if you're talking about soldering components on PCBs the idea of melting the solder with the hot wire is not going to work. The leads (wires) on components are too small to effectively melt the solder. Hold the tip so it's touching the pad and the wire/lead and melt the solder with the tip of the iron and it will flow onto the wire and pad. as it has a greater affinity for the metals they're made of. This also ensures much of the flux will also flow onto the lead and pad. The flux removes any oxide film paving the way for the solder to easily flow.
     
  16. OP
    OP
    BluBoy

    BluBoy Member

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    Just wanted to give a quick update for anyone else starting off.

    The advice here has been great. My joints are starting to get a bit better after some practice on a breadboard type piece.

    Two final questions:

    A lot of my leads are stranded and I struggle with these. Any secrets to dealing with cheap cables like this?

    And how long can I heat up the pad of a pi zero connector? This was my biggest fear when starting out (and I'd barely give any heat to it at all!).
    While I'm getting braver by applying more heat to the pad, at what point should I worry about damaging the board by overheating the GPIO pads?
     
  17. SLATYE

    SLATYE SLATYE, not SLAYTE

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    My approach is:

    (1) Strip the end of the cable.

    (2) Twist the exposed strands by hand.

    (3) Put the soldering iron tip on the bottom of the exposed strands.

    (4) Apply solder to the top. The solder should melt pretty readily, and wick itself into the strands. Stop applying solder before it forms a blob.

    (5) Remove the soldering iron.

    You should now have all the strands in the exposed wire end soldered together. This (a) makes manipulating it much easier because the strands don't keep separating, and (b) simplifies future soldering (eg. to a PCB) because there's already plenty of solder on the wire. If you keep the iron on too long then the wire insulation will melt away, and you'll have to re-strip the wire and start again.

    Hard to say, really. A couple of seconds? If you've had the iron on the pad for more than a few seconds and the solder's not melting, something is wrong (or you're trying to solder to a ground plane, which can be really painful in some situations).

    If you're connecting a wire to a through-hole on a board, feed the wire through the hole, put the iron tip in so it touches both wire and pad, and immediately feed-in some solder where the pad meets the board. You should be able to get a situation where there's essentially a single point of contact between pad, wire/pin, solder, and iron tip. If the solder is not melting now, something is wrong - because it really should melt immediately when it touches the iron.
     
  18. RobRoySyd

    RobRoySyd Member

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    First of "stranded" is more expensive than solid. It's used because it's more flexible. A single solid core of copper can "work harden" and snap.

    How I handle directly terminating them to a PCB is to strip a decent length, carefully and gently twist all the strands and then tin just the end. Then I can poke it though the hole in the PCB or connector, solder it and trim the excess.

    As a general rule though it's not good practice to solder wires directly to PCBs for several reasons.

    I can't really answer that question, there's too many variables. Instead I'd say if you cannot get the joint made in under two seconds Stop. Take the iron away, wait for 10 seconds while thinking about what you were doing and then try again. Maybe even suck all the solder off the joint and start fresh.
     
  19. cvidler

    cvidler Member

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    pertinent tip...

    [​IMG]
     
  20. aXis

    aXis Member

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    The secret is not to solder them, stranded connections should really be crimped. Getting a good crimp can be difficult in itself and requires some special tools, but it is by far the most reliable method if done properly.

    That said myself and lots of other people still solder them, however you have to give them good strain relief as the solder makes them brittle and more susceptible to fatigue. I use the same method as SLATYE.
     

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