I have written this for anyone new or inexperienced to the world of soldering. I worked many years at a couple of electronic companies as a certified soldering tech, and I want to share my knowledge with anyone out there that may need help. First, I have written a brief summary on how much is enough to spend on tools and supplies. The second part is a list of the tools, as well as descriptions and suggestions for the proper tool and why it should be used instead of something else. The last section, aside from some notes, covers a typical soldering operation in five steps.
Tools: [/b]Below is a list of necessary tools required for soldering electronics, at a minimum but adequate budget and inventory. Please try not to substitute or omit anything listed below, because soldering is something not to be short-cutted. If one takes short-cuts soldering, they will often find themselves soldering all over again. Let’s do it the right way the first time!
You may already have some of the tools listed below, but assuming that you do not, try not to spend over $65-70 for everything. That amount of money should last your entire lifetime in this hobby. Try and spend no more than $40 on the iron, $12 on solder, $6 for rosin flux, $3 each for the pliers and wire strippers, $4 for the insulation materials, and $3 on cleaning supplies. The small file or emory board and sandpaper can be found at the local dollar store. You may already have some of the tools mentioned below, and most likely chances are that you already have the cleaning supplies. Also, it never hurts to ask a friend to borrow the necessary tools, as long as they’re returned on time and are nice and clean.
Here are the required tools:
Soldering Iron:[/b] [/b]Avoid any iron less than 40 watts. Try and find a good one that has been made in the USA – for real; the quality of the iron and the quality of its tips made in the USA are significantly better than the quality and grade of metal they make in China or anywhere else, and the heating element and tip will not wear out as easily. Be sure to purchase an iron that has replaceable tips – if it doesn’t have it, shop somewhere else. Future regret will haunt you later on if you need to solder a part, only to discover that the tip is too large for the connect surface, for the sake of this argument. You should not have to spend more than $40 for this, but if you see a better deal, grab it.
Solder[/b] and Rosin Flux: [/b]There are many types of solder out on the market, and it is important to select the right one for your hobby. Look for lead-free solder for electronics, as this is the best type I have used throughout my many R/C hobbies. Buy a tube a rosin flux, and not the other types. Acid flux and regular flux emit corrosive gasses during the soldering operation, and may damage electronic circuits. Flux, for soldering, acts as a cleaner when heated, and is also a catalyst to help the molten alloy and the different metal bond together.
Pliers and Wire Strippers: [/b]Pliers are an invaluable tool for soldering. Not only do they keep you from burning your fingertips, they act as a third hand holding and assisting during the soldering operation. I sometimes use an elastic or rubber band to secure the handles and make sure that they have a strong yet delicate grip on the part. There’s no need to go out and buy a set of robo-grip mini vise action pliers; a simple set of flat grip needle nose pliers is more than enough for this hobby. That goes for the wire strippers too. It would be overboard to buy a set that has all the industry’s gauges preset on them. The strippers that look like angled shears are just fine.
Fine sandpaper and File: Some prep work may need to be done on the solder connect surfaces, and some fine sandpaper and a small file or emory board will speed up the work of exposing new metal for a surface for the solder to bond.
Insulation materials: [/b]You never know what you will need to patch up or cover after a soldering operation, so you need to have a minimum of at least a roll of electrical tape and a set of 2 inch assorted heat-shrink tubes. A roll of electrical tape and two feet of 12 gauge heat-shrink tubing cost about the same price at around $2.50 each.
Cleaning Supplies:[/b] I don’t like to leave all my solder work messy, and there are times when parts and surfaces need to be cleaned and prepped. A bottle of isopropyl rubbing alcohol and cotton swabs and cotton balls is a great thing to have while soldering and it’s friendly on electronic circuits because it evaporates rather quickly.
All of the above mentioned tools and supplies required for soldering can fit inside a shoe box or similar sized container, and shouldn’t take up much space on the workbench. Now that we have the parts that need soldering, and all the rest of the tools, let’s begin.
Typical Steps for Soldering:[/b]
Step One: [/b]Set up all your tools and supplies on the workbench, and have any manufacturer’s instructions available for reference if necessary. Before turning on the iron, make sure that the tip is nice and clean. If not, then clean it with a sponge and some diluted rubbing alcohol with water. Turn the iron on, and wait at least 5 full minutes before use. Be sure to clean the iron’s tip before and after the iron is used for that day. When the tip is unusable or cannot efficiently transfer heat, then it must be replaced. Heat is very important for soldering, and I will emphasize that throughout this article.
Step Two: [/b]Pre-form all terminals and strip wire ends. Wire ends only need to be stripped away about 3mm; anymore and the wire may have a tendency to break. Please try to resist using a razor as a substitute for wire strippers, because you will cut away half the strands in small gauge wires. I do that once in a while, only if I am in a pinch, and I still cut off a couple of strands. The more the strands in the stack the better; after all, all the strands together make up the gauge of the wire!
Cut the heat-shrink tubing to a desired length if necessary, and pre-install them onto the relevant wires. Pull the heat-shrink tubing all the way down to the opposite end of the wire. Pre-fit and crimp any small terminals to small wires. FOR BATTERIES – WORK ON ONE WIRE LEAD AT A TIME TO AVOID AN ELECTRICAL SHORT – ESPECIALLY STRIPPING AND PREFORMING.[/b]
Also for wires, preform the strand ends by making sure that the whole stack is straight, even, and has a blunt end. When that is finished, gently twist the wire to make the whole stack of strands into a mild spiral, keeping the stack straight.
Step Three: [/b]Tin all solder contact surfaces; both terminal ends and wire strands. Tinning is a method used to create a pre-formed bonding surface to make soldering easy, clean and strong. Add a small dab of rosin flux to your finger, and cover the entire connection surface with it, and wipe away any excess. The result should be an even and thin coating on the entire area where the solder is going to bond. Heat up the surface that will be used for the solder connection for about 5-8 seconds. Once the surface has thoroughly been heated, add a small amount of solder to the surface. If the part is properly and evenly heated, the molten solder will flow evenly throughout the surface.
Be careful, because flat surfaces will tin faster than non-flat ones. There should be enough of a layer of solder on the surface to cover the whole area. A good example of tinning a flat surface would be about a layer of solder about half a drop of water in size and at least 0.5mm thick (a strong yet thorough coating). Pay attention to the amount of heat that you are applying to the surface; too hot, and you can destroy surrounding electronics and their own solder connection, and the solder you're applying may run off. Too cold, and you will not be successful. There is an industrial term known as a cold solder (a noun), which I will cover later.
Tinning a wire without a solder pot is still easy. Again, apply rosin flux to the entire strand stack and wipe away any excess, again looking for an even and thin coat throughout. Pay attention to the amount of heat that’s applied to the strand stack, holding the tip to it for about 8-12 seconds, and then add the solder. Let the molten alloy flow evenly through the stack, all the way down to the insulation. It is perfectly okay to let a little of the flow to go past the insulation; it actually helps prevent the wire from breaking in that area. Allow all tinning to cool on its own. Do not blow on it or cool it down any faster than it will on its own. This is the number one cause of a cold solder.
If smoke is getting in your face and burning your eyes, move your face farther away from the work, or turn a fan on and point it away from your work space. Put the fan on the side and not behind you as that will defeat the purpose. Don’t let the fan blow towards the work space as it may unevenly cool the part you’re trying to heat.
Wires and terminals usually need the assistance of the pliers, as you can imagine how fun it would be to burn yourself while juggling a strand of solder, the iron, and the part you’re trying to heat all at once. I would usually use the elastic or rubber band to secure the handles, so that my part won’t fall out if I bump the pliers with the iron.
Remember – gravity is also your ally, and if the tin flow isn’t reaching an area where you want it to be, just tilt the part in the direction you want the flow to go. After the part has been properly tinned and cooled, the solder connect surface should look shiny and even throughout, and have a thin layer of solder coating all over the connect surface.
When the surface is cooled, clean it with a cotton swab and rubbing alcohol, and let it completely dry before moving on.
Step Four:[/b] Reflow and/or solder the connections. If you tinned two parts together, you can solder the connection together using a method called Reflow. Put the parts together as they should be, either via manufacturer’s instructions or obvious sense, and hold the tip of the iron to the middle of both parts, right where they join, and hold the tip there for around 5-8 seconds. Flip the parts over and repeat on the reverse side. The solder will re-flow (hence reflow) and thin layer of alloys with melt together and into each other, creating a conductive and mechanical bond between the two parts.
After the parts have cooled properly, test the joint by gently twisting or wiggling the two parts. If they move, add heat again as described above, and add a small amount of solder right at the joint where the two parts meet, and in a place where the solder will go inside both parts. Let it cool down and test it again.
For small wires and terminals that may need a solder joint, apply some rosin flux to the area that needs solder, and this time it’s okay to not wipe all the excess away – wipe away about half of it. Apply heat to the preformed connection for no more than 5 seconds, then immediately add a very small amount of solder. The result should be a nice flow that gets sucked right into the end of the terminal and wire.
After you let it cool down, clean up all the solder joints and connections with the rubbing alcohol and swabs or cotton balls.
Step Five: [/b]Install the terminals into their housings; insulate any exposed areas with the heat-shrink tubing or electrical tape as necessary. BE SURE TO CHECK THE POLARITY OF THE TERMINAL AND HOUSING BEFORE SEATING IT IN FOR GOOD! Typically, a terminal is correctly seated into the housing when you feel a pop or hear a tick, depending on the type of terminal. Use a small flat blade screwdriver to assist the terminal and get it seated.
I use a cigarette lighter to shrink all my heat-shrink tubing, and I use a small dab of shoe goo at the end of the piece of electrical tape to keep it on there (although I know electrical tape is for temporary use).
Lastly, take a once-over look at all the soldering work done, and clean any left-over rosin flux or smoke burns from the heat-shrink tubing with rubbing alcohol and a cotton ball. Looks professional, eh?
Cold Solder - a cold solder joint occurs either when the alloy is just hot enough to flow but then cools when it travels away from the heat source (the solder is not hot enough), or when the soldering surface becomes cooler than then molten alloy. This results in very tiny fissures and pits in the joint, which makes it very weak. These cold solder joints can be corrected immediately by a reflow operation, but pay attention to the amount of heat that is applied! Let the area cool itself down to be safe before the reflow.
I do want to note that there are many, many other tools used for soldering, such as solder suckers, hot plates, solder pots, silk screening and solder paste, wave machines, and so on. We don’t really need those things when we need to solder in this hobby, and for those on a budget, the simplest of the tools will do just fine for the job.
Another important note to mention is that some connectors and plugs come with the terminals pre-molded into the housing. A perfect example would be a set of W.S. Dean’s plugs. My best advice is to pay attention to the amount of heat that’s applied because if the plastic gets warm, the terminals will move and get out of their proper alignment. One solution to that problem is this: Connect the set of plugs together, after they’ve been cleaned and prepped. This way, the housing on the far end of the solder work will help hold the terminals in their proper alignment. This does not mean you get to ignore the heat. Any pre-molded connector will be prone to softening from a soldering iron. Pay close attention to how you are holding the iron too, and keep the heating element that’s under the tip away from your soldering operation.
I sure hope that this article is helpful to those who are looking for some good soldering tips and pointers. I typed out a similar article and tried to post it, but my session timed out and I lost the whole thing, and had to re-write it all over again. If you have any questions, problems or comments related to soldering in this hobby, feel free to post it here, and if you need any more help please PM me and I will help you out the best I can, aside from hitching a ride to you and showing you in person 8)