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Thread: Soldering is not Pasteing

  1. #1
    Junior Member
    Join Date
    Oct 2012
    Posts
    2

    Soldering is not Pasteing

    You can have a lot of satisfaction from doing something correct. In order of importance is to remove oxide from the two parts to be soldered, wires are best to discuss first. Copper should solder instantly if its clean, the iron is hot and there is flux melting on the surface. You can pull a resistor out of stock and while it looks ready there is a vast difference in trying to solder a resistor's leads. Use an eraser, even a white ink eraser that is abrasive will work fine. Try for three wraps around each of the two leads you are putting together. In other words the mechanical connection is there to take the stress off the soldered connection. Big clue: if the solder balls up on the tip of the iron or the wires, stop and clean the solder tip with sandpaper or steel wool. Clean the bench, you don't want steel fibers getting into you project.

    After a clean tip and cleaned parts the next impediment to soldering is enough heat. We are talking electronic parts soldering and for the record only rosin core solder and rosin flux is used to tin the leads, never acid core, thats for sheet metal workers. Lets see, a 5 or 10 watt iron will handle 24 to 40 gage wire, two ends to be soldered together. For larger wires like 18 towards 24 the iron works best at 15 to 30 watts, more toward 30 if you have more than two 18 gage wires to solder.

    Next point, you have twisted the clean wires together, now to solder put a small amount of flux on the parts or if using flux core solder touch the solder to the wires to be joined about one second after you put the iron on it. Watch and in one to two seconds the solder should have flowed. Take the solder away and in the next second remove the iron. Look at the joint, it should be smooth, not rough or looking irregular.

    You must experience a few soldering and unsoldering episodes, all the while watching what you are doing. Remember, if you can't make a good solder connection in the total of 5 seconds figure out if you need clean parts or more heat. In soldering transistors and pins on integrated circuits, each pin should take about two seconds. After doing a few pins, let it cool off for 30 seconeds.

    Soldering is definitely a skill learined by doing. Reading the above paragraphs is the basics that must be applied. Can you imagine the skill of NASA assembly people, all there work is closely inspected, exrayed and some of them have done many, many thousands of connectons without error. Yes I know wave soldering nd other techniques have replace a lot of hand solderig but we don't have that machine at home, good luck.

    Ron

  2. #2
    Thanks for all your advice Ron. Learning by doing and practice, practice, practice seems to be the heart of many of the tips Greg got so far. Be sure to check the April newsletter for the results of his soldering adventures...which we absolutely have a video of

  3. #3
    Junior Member
    Join Date
    Mar 2014
    Posts
    2
    On big soldering jobs i.e., coax connectors, a little extra flux can help the process.

  4. #4
    @Ronald: While your theory is sound about mechanical connections, it's dated. In the old days of point-to-point wiring, the rule was to make a good mechanical connection around the terminal before you soldered. (I still have an assortment of tools made for hooking, looping, bending, etc. the leads, but they don't see much use now.) The mechanical connection was for strength, and the soldering made a good electrical connection. Most electronics now is on printed circuit boards (PCBs), and in most cases there's no mechanical connection at all from the component lead to the solder pad. It's only the solder fillet from the lead to the board. In fact, with surface-mounted parts there aren't even leads, just a metal bump on the package. Some parts such as switches or connectors may have mechanical mounting to the PCB, but the electrical connection is still just soldered. This leads to many problems being caused by failed connections. In my days making a living in electronic servicing, a huge number of repairs involved nothing more than resoldering bad connections. This was especially true in connections to power components where there might be considerable heat in the area. It's not unusual for connections to surface-mounted parts to break if a product is dropped or handled roughly. And in many cases connections were never soldered to begin with; either the solder never made it from the lead to the board, or was never even soldered at all.

    I know it's been said many times, but it's true. Practice does make perfect. Unfortunately it's hard to learn from a video, so the best thing is to get a cheap kit of some kind and build it to get the practice. (Personally, I developed my chops on a lot of Heathkit stuff...remember them?) Or just get a junked piece of gear and practice both unsoldering (also a very handy skill) and soldering the parts back.

    @K4MHM: On big jobs, heat is also important. People get so used to soldering on small parts now that they may use too low a wattage when making a big connection. Sometimes too little heat can be worse than too much. When soldering a large item like a connector or a lead soldered to a large ground area on a PCB, a good hot iron will heat the connection quickly enough for successful soldering. Too little heat can lead to collateral damage (lifted tracks, melted insulation, etc.) as you try to get the desired area hot enough. The size of the solder should also match the connection being soldered; use the real skinny stuff on the small connections, but heavy connectors need larger diameter solder. Since electronic roll solder already has a flux core, extra flux usually isn't required if the connection is hot enough to begin with. Also, I've seen boards where people used extra flux...but grabbed acid (plumbing type) paste by mistake. Not a pretty sight!
    Last edited by SolKA3O; 03-12-2014 at 08:38 AM.

  5. #5
    om the two parts to be soldered, wires are best to discuss first. Copper should solder instantly if its clean, the iron is hot and there is flux melting on the surface. You can pull a resistor out of stock and while it looks ready there is a vast difference in trying to solder a resistor's leads. Use an eraser, even a white ink eraser that is abrasive will work fine. Try for three wraps around each of the two leads you are putting together. I
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