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Step 4: Soldering components onto a circuit board

Up until pretty recently I spent most of my life soldering speaker wire and crossover components for speakers. This meant mostly wires twisted around wires or big resistor leads twisted around inductors and capacitors. At that level soldering doesn't really get any more complicated than what I did in the previous step. Lots of the projects on Instructables, however, use smaller electrical components and circuit boards, so I figured I would give that a try too.

Soldering on a circuit board takes a little more care and attention, but it's still very doable. I pushed a few of the leads from some spare LEDs and resistors that I had from my LEDs for beginners post through some open holes in a circuit board that was lying around. I soldered the leads onto the bottom of the circuit board where the electrodes push through. This is called through hole component soldering.

To solder the LEDs and the small resistors to the circuit board I switched to the adjustable temperature soldering iron. The tip was smaller so it would be easier to get the solder right where I wanted it, and using the soldering gun on a circuit board is probably way more heat than necessary and it could end up damaging the components. I set the temperature of the iron to 675 degrees Fahrenheit and waited for the tip to heat up. I then loaded the circuit board into the alligator clips and got myself ready to solder - iron in one hand, coil of solder in the other.

When soldering leads into circuit boards you want to heat the metal contact on the board and the lead itself. Applying too much heat can damage the circuit board or even your components. The surfaces being joined in this application were much smaller than the twisted wire, so things heated up a lot faster.

I touched the tip of the iron to the crack between the lead and the metal pad on the circuit board. After waiting a couple of seconds, I dipped the tip of the solder into the joint and placed a very small amount of solder at the connection - no more than the head of a pin or so.

Once the solder pooled a bit and soaked into the joint I removed the solder wire and then the iron. I remove the solder a second or two before I remove the iron so that the tip of the solder doesn't get stuck to the joint. The solder begins to harden as soon as you remove the iron.

Using the proper amount of solder is more important while soldering small components on a circuit board than when soldering wires. If you apply too much solder and it pools up outside of the metal pad, it can cause a short. Too little solder and your component won't make a good connection with the circuit board and might not work the way you want it to. When you've got the right amount of solder it looks like a small ant hill that forms right at the base of the lead and the circuit board.

Here is a video of the process.


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<p>You will not transfer much heat to the wire joint to be soldered by just touching the bare tip to it. Instead, melt a blob of solder onto the hot tip, then touch the joint, and the molten solder will greatly help the heat transfer to heat the joint to soldering temperature. Then touch the joint with the solder wire and it will quickly melt right into the joint and flow well. You will be surprised at how much easier this makes the soldering process!</p>
<p>When exactly does one tin a new iron? Should the solder used to tin the iron be wiped off before its first use?</p>
<p>Can anyone give me some advice on which is the best soldering iron to use?</p><p><a href="http://amzn.to/1WDULoJ" rel="nofollow">This is what I am looking at right now&hellip;</a></p>
<p>I have that iron.. its not bad..but maybe its me.. the numbers on the dial are so tiny I cant figure out what temp it is at. I ended up buying a solder/heat gun station (building drones so needed heat gun as well): https://www.amazon.com/gp/product/B01AO7SH80/ref=oh_aui_detailpage_o02_s00?ie=UTF8&amp;psc=1 It works very well, allows more precise (and easier to read) control of heat, and has the heat gun too. :)</p>
<p>Should add that the one I bought heats up almost instantly.. which is nice to not have to wait a minute or two.</p>
<p>Requirement list plzzz</p>
Nice helpful tutorial. :)<br><a href="http://www.helpinghomesservices.in/" rel="nofollow">Home services in Ahmedabad</a>
<p>nice beginner tutorial. Bookmarked!</p>
<p>Hi, I've added your project to the <em style="">&quot;</em><em style="">Beginners Guide to Soldering</em><em style="">&quot;</em> Collection</p><p>This is the link If you are interested:</p><p><a href="http://www.instructables.com/id/Beginners-Guide-to-Soldering/">http://www.instructables.com/id/Beginners-Guide-to...</a></p>
<p>what do i do when i accidentally soldered my toddler to my chair should i call the police? </p>
<p>take a picture</p>
Make sure your iron is clean, make sure your solder is clean and make sure your work piece is clean and you will have the best opportunity of creating a good solder joint.
I bought a 30W soldering iron from Radio Shack. I'm having a lot of trouble because it takes as long as 90-120 seconds for the solder to heat up. And if I don't touch the solder directly to the iron, it never gets hot enough at all. Plus, the solder doesn't flow well and it turns into balls & blobs. I'm puzzled. What's wrong?
<p>sorry for the late reply</p>
I know this is an old post, but someone may benefit. <br>There's a few possible problems, the obvious one is you're iron isn't hot enough. I prefer a 40W iron over a 30W any day. It seems 30W are the most common, but they just don't cut it for me. <br>Try a cheapo model form ebay etc for $5 or so and see how it works for you. <br>Another fix is to heat the iron up a bit with a torch. I rarely need to do this to boost heat, but I will use a torch as the heat source for the iron if I'm too far from an outlet.. <br> <br>The other problem could be thinking the flux inside the solder is enough. It is not.... At least it has never been for me. You need to flux the surfaces and be sure the surface can be soldered in the first place. <br>The surface could be coated or plated with something that either the solder or the flux doesn't like. It might also be corrosion, a lubricant, protectant, or who knows what. In those cases I clean it with a chemical such as electric contact cleaner aka brake cleaner, or even carb cleaner, but most people use alcohol. If that doesn't work then it's probably some kind of coating you'll need to remove with force, like sandpaper or a Dremel tool to break thru to the good metal. Once you've ground the bad part off, clean it, coat it with flux and try again. <br>If it's still being difficult you can try using sandpaper on it while it's coated in flux. I like 320-400 wet/dry paper, maybe 180-220 if it's really bad. Cut a small piece for sacrifice because you don't want to use it again now that it has flux on it. After you have either roughed it up nicely, or ground thru the problem coating whatever it was, clean it, flux it, and try again. <br>I prefer to coat the problem item in solder first, that way I know it'll work when it's time to attach something. Assuming the iron is hot, clean, and will hold solder (plain old rosin core 60/40 works best for me), put a little on the tip, then apply it to the surface and hold until it flows and coats your surface. If it's a large item and you can't get it hot enough you will need to preheat the item with a torch or whatever, I've used anything from little butane torches to my oven, as long as everything can handle the heat that is. (fyi; preheating also works for welding when the machine can't generate enough heat). Once it's hot enough the solder will flow nicely into the area worked on, and your problem is solved. <br> <br>If you never could get the solder to stick then you might be working with the wrong metal, like aluminum, so use the appropriate method for that metal, or simply try using a screw or bolt as a contact. If you can figure out what the base metal is, then search the net for a bolt material that will not react with it. Example; drill a hole and use an appropriate bolt/nut and torque it down good, then apply solder to the bolt's head which should be a snap. Common steel bolts are usually coated with something which probably needs to be ground off. Grind off just enough area for what you need, and preferably solder it in a way you can still use the tool to remove it if needed. Now flux your spot and apply a little drop of solder like described above. Being a bolt it's probably heavier and may need a little boost with a torch. <br>I flux/solder each piece first so I know they're both good to go, then I put them together and add a drop of solder with the iron until it flows. <br> <br>I hope this helps some people with their soldering problems... <br>
<p>Chevota</p><p>I would probably avoid using brake cleaner then applying heat, because depending on the formulation you can emit phosgene gas:</p><p><a href="http://www.advrider.com/forums/showthread.php?t=488740" rel="nofollow">http://www.advrider.com/forums/showthread.php?t=48...</a></p>
<p>Thanks, something to think about. I don't think you can buy that kind of brake cleaner anymore, plus it evaporates almost instantly when cleaning stuff like that. I do remember spraying the older stuff on something red hot and the smell was horrible. Not sure if it was that particular gas, but omg it was bad! </p><p>Speaking of solder, I lost my old solder and flux in a move so I bought this new solder and flux, some &quot;safer&quot; crap or some bs but it was all I could find. I haven't been able to solder anything but clean copper wire and that barely sticks together and often fails. It's horrible stuff. Maybe that was the original posters problem? I guess I'll have to buy some from china on ebay or something. </p>
<p>Lead free solder melts at 218 deg C where leaded melts at 183 deg C. You may need to get a higher wattage iron to work with it. That thanks to the EU which started this lead free mess.</p>
<p>I've always preferred a higher heat than what most people use, for example I won't use a 30w, only 40w at min. I don't know the exact temp but to get the same effect from the adjustable solder station at work I need 800F/426C. Others at work used 700-750F and they struggled. This was back when we used real lead and flux btw. So I don't think 218C would work at all, but whatever the case I'm well above it. I've even tried boosting the temp by heating my iron with a propane torch, but it doesn't help. My latest project needed tabs soldered to rechargeable AA batteries to renew a cordless tool batt pack. I've done this in the past with lead 60/40 and acid flux no problem, but the new stuff refuses to stick to the batts. It's like trying to solder to glass... Very frustrating. My flux might be part of the problem so I will look for a different type. I may have to spot weld the tabs like the factory does, but it doesn't help me with other stuff. </p>
<p>sand the battery contacts, and make sure the battery is getting hot enough. it's a very difficult thing to do, getting something like that hot enough without getting it too hot. also, reheating it over and over, trying to get it right, will probably negatively affect the battery life and capacity. practice on one set to know exactly what you need to do, before moving on and doing it right on all the rest.</p>
<p>Yes, I have done this many times for decades on all kinds of projects with no problems. Then I lose my old 60/40 lead and &quot;good&quot; acid flux and have not been able to solder a single battery since. I plan on trying spot welding next, unless I get lucky and find my old solder &amp; flux. This new solder makes everything much harder btw, but it made the battery thing impossible. </p>
<p>A soldering iron is nowhere near hot enough to convert a chlorinated solvent to phosgene. Think arc welding or oxyacetylene temperatures.</p>
<p>Someone brought that part up because I said I used brake cleaner to clean parts that have grease/oil on them, then if the part is too big for the iron to heat you can preheat it with a propane torch. Not so much about the part getting too hot, but putting a torch on a the surface still wet with cleaner. Not a common circumstance, nor do I believe most cleaners sold today are an issue, but something to consider. Plus if you do manage to create the gas, which I think I might have once or twice, it's too nasty to breathe anyway. </p>
<p>great instructable. thanks!</p>
<p>boo</p>
<p>can i make friends on here? im a black belt at soldering </p>
<p>i will be your friend :)</p>
Thanks, I needed this for my Home Economics class!
<p>you'll fail </p>
<p>Hello! Thank you for your post. Can you comment on the use of soldering flux-types, dangers or relative importance.</p><p>Thanks.</p>
<p>Absolutely! ;)</p>
<p>Thanks for explaining things so clearly! The whole article has given me a great insight and also explained where I had been going wrong in the past.</p><p>I will leave the desert island survival tips alone for a while, but its good to know just incase!</p>
<p>Thanks for the guide! I also wouldn't recommend stripping wire using teeth. Some plastic wire insulation can contain lead. Here's a CDC account of someone getting lead poisoning from chewing the plastic: http://www.cdc.gov/mmwr/preview/mmwrhtml/00020984.htm</p>
<p>More of a problem with biting the insulation would be chipping your teeth, as I have done over the years of removing insulation that way.</p>
<p>He chewed the plastic wire coating for 20 years and has a slight lead poisoning in the article. That's a huge difference from biting off the tips and spitting them out. </p><p>Lets not go overboard comparing apples to planets.</p>
<p>You shouldn't twist the wire. You don't need to and its amateurish. You should just position the two wires parallel and solder them that way. That way you can make a nice tight joint and can easily fit heatshrink sleaves over the joint. Regardless of what people might think.. twisting the wires together does NOT make for a better joint. The solder is more than enough to take any stress from the wire being pulled or twisted afterwards. It does not need to be twisted together beforehand. </p>
<p>Hi I've just finished a little soldering project but unfortunately its not working, I've just read your comment about not reheating solder, which I think I did a few times, how crucial is this and could this be the reason my circuit won't work? do you think I should start again? Thank you</p>
<p>@<a href="http://www.instructables.com/member/sjones98/" rel="nofollow">sjones98</a> Hey there. Fixing that wouldn't be a problem. I've reheated solder many, many, many times on the same project while I was learning and I never had an issue. It cleans easily, remelts cleanly and often looks 10x better when I'm finished. The best advice I could give with regards to fixing your soldering is to do one small area at a time. Reheat the solder and wick most of it away, make sure you are using the right kind of solder. Find some that is specific to electronics. It will have mostly a silver base as opposed to lead and is very thin. A thin point tip on your soldering iron will help as well. It keeps the solder neat and reduces the solders habit of spreading to other holes.</p><p>When you are ready to resolder your board, only use a very tiny amount of solder. It takes barely any to make a nice solid connection. It's human nature to want to gob it in, because more is better right? In most cases, no. Just a dab will suffice. The right amount will surround the pin and be barely larger than the hole.</p><p>I hope this helps! Cheers.</p>
<p>I see that this is a bit late but the problem seems to be the soldering done on the board. There are a few areas where leads seem to overlap, which, of course, causes short circuits. I'm not the greatest at soldering myself, and I've done worse quite a few times; sometimes involving unpleasant explosions. </p>
<p>FLUX...the secret of flow</p>
<p>One very undersold product at the Shack was the Velleman kits. I've done a couple of them, and they seem more like useful items than the Arduinos and Bone stuff. For example, Velleman had a USB breakout kit you could build that gave a variety of real world contact closures and sensors out... and in. I have a couple of them going in a remote control project or two where you can uVNC to a PC somewhere, and turn things on and off, take readings, and so forth for equipment nearly a hundred miles away. I didn't have to learn an entire micro-language or buy/build complex processors, masks, and all that like it appears i would have to with Arduino. I dunno about the rob you clean bit... I'm old enough to think of names like Heathkit, Archer, Optimus, Uniden and the like in Radio Shack stores. Yes, sometimes expensive... but nearly always rebuildable and nearly all that stuff I've bought over the years is *still* running.</p><p>Like my Optimus 100X6 Tuner Amp. yup. 6 big transformers in it and it drives 15&quot; drivers to about 128dB @ 35 - 12k frequencies.</p>

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