Cost: > $0 – $100+
Tools Required: Soldering iron, solder, stand, wire cutters / strippers, cleaning sponge, flux, qtip or cotton swabs, tip tinner. Optional – heatsink, fine grain sandpaper, alcohol
Parts Needed: Something to solder
Difficulty Level: Moderate
Whether you fly an electric, nitro, gas or turbine RC helicopters, at one time or another you’ll come across parts that need soldering. It might be as simple as soldering on a battery connector or joining a broken wire together or something a little more complicated like replacing a component of a circuit board.
Something as simple as not soldering on your battery connector properly can lead to loss of power and complete devastation of your RC helicopter, so proper soldering is quite important in this hobby.
Whatever the need, soldering is also a great skill to have.
Besides your RC toys, there are a ton of other things around house that might need soldering. You can repair jewellery, fix kids toys, get an electronic device working again or even fix a leaky pipe.
Once you master the basics, you’ll find it’s kind of fun and not really all that difficult. So, in this ‘how to’ article, we’ll be discussing some basic soldering skills as well as some more advanced soldering tips and techniques to make soldering easier and ensure a solid connection every time.
Choosing A Soldering Iron
Regular cheap soldering irons cost anywhere from $5 – $15 and will generally run anywhere from 15 watts to 50 watts. The higher the watts, the hotter the iron usually gets and the more heat it can transfer to the parts being soldered. More expensive soldering irons usually have the ability to adjust the temperature depending on what you’re soldering.
For most jobs, a 25 watt or 30 watt iron will suffice, though more heavy duty soldering (like soldering deans plugs to a thick battery pack wire) will work best with a 50, 60 or 80 watt iron. I’ve never made the splurge to purchase an expensive variable heat soldering iron, but I do keep a bunch of different wattage ones on hand for different jobs.
(Soldering irons from left to right – 30 watt, 40 watt, 60 watt, 80 watt)
Tips Size & Selection
Always try to use a good quality tip. One of the first irons I owned cost under $10 from Radio Shack, but had a $15 tip from an electronics shop that outlasted the soldering iron by a long shot.
Lower quality tips won’t last and will oxidize and rust away in no time and need replacing, so in the long run, a good tip is a great investment. Solder also won’t stick to oxidized tips which can make soldering a lot more difficult than it needs to be – more on this later. Just be sure to get a good tip – even if you have a cheap iron.
Ideally, you want to as big as tip as possible, but not one that’s so big it’s larger than what you’re soldering to. A larger tip helps to transfer heat faster and acts as a larger reservoir of heat so the tips doesn’t cool off while the connection is being made.
For most soldering you’ll want to use a chisel tip. Chisel tips will also heat the surface you’re soldering to faster than conical tips because there’s a greater surface area available to heat the parts you’re soldering.
The only time a conical tip should be used is for fine circuit board work where you need a small point so as to not disturb any other joints besides the one you’re soldering.
If possible, always use 60 / 40 rosin core solder. The rosin core contains flux which is the stuff that helps it stick – you’ll see more on this later.
Solder comes is different diameters from super thin to super thick. I keep a roll of thin stuff and thicker stuff on had depending on if I’m soldering surface mount components on a circuit board or something a little larger that requires more solder.
The thickness doesn’t really matter too much – you just don’t want a big hunk of thick solder for delicate work and for more super-sized soldering, using thin stuff can take a while to build up enough solder to complete your work.
Also, despite common misconceptions lead based solders are best and it’s not going to poison you. The fumes from soldering are from the flux in the solder boiling, not the lead. Lead boils at over 3,000 degrees Fahrenheit while most soldering irons don’t exceed 750. Though, that doesn’t mean the fumes are good for you – over extended periods they’ve been know to cause asthma so try to avoid inhaling them if at all possible.
Lead free solder also takes longer to make a solid connection and it won’t cling to it as well which can lead to other problems.
How To Make Solder Stick
Probably the hardest part of soldering is getting the solder to adhere to the parts you’re soldering.
Put simply, solder won’t adhere to parts that are dirty, so make sure you clean what you’re working on (with water or alcohol and a cotton swab) and that it’s free from oil and dirt prior to soldering.
Tip: The oil from your skin is especially good at making solder not stick, so be sure to clean anything you touch before soldering.
Solder also won’t stick to cold parts, so be sure to use an adequately heated iron and heat up the parts briefly prior to applying the solder and make sure that you’re using the right sized iron.
When you’re ready to solder, you also need to make sure there is a good physical connection between the parts to transfer heat and melt the solder easily and evenly.
For example, if you’re soldering two wires together, twist them tightly first. If you’re soldering a component to a circuit board, bend the leads before soldering to help hold the part in place and clip it in advance. Clipping it afterwards can cause a crack in the joint and lead to a flaky connection.
You also need to make sure there’s no oxidation (similar to rust) on the parts you’re soldering or the soldering iron itself or the solder won’t adhere properly. If the surface is overly oxidized or extremely shiny, use a fine grit (600) sandpaper to rough it up a little. Be sure to wipe away the dust prior to soldering.
Here’s a pic of a tip that was so heavily oxidized, it took a couple of pairs of vice grips to get it out:
If it’s just a little oxidized, you can use a little flux. Flux is a weak acid that removes oxides and acts as a place holder to keep oxygen away until it’s replaced by solder. It also reduces the surface tension of solder to help it spread more evenly
Flux can also be purchased in paste or liquid forms and can be applied to the joint prior to soldering. For small jobs, it’s not necessary to use extra flux if your solder has a core of it, but for larger surface area’s it may be impossible to make the connection without adding a little extra flux.
To use it, just apply it to the surface you’re soldering, heat it up then apply the solder.
The other secret to soldering is keeping your tip tinned. Having a small amount of solder on the tip helps to transfer heat to the part you’re soldering and is essential to get it to stick.
Clean the tip every time you pick up the iron and always keep it tinned by adding a small amount of solder to the tip to prevent oxidation – even when you unplug your iron.
Soldering Tips & Techniques
When your iron is hot, the parts are clean and you’re all ready to solder, here’s how to do it:
When you’re ready to solder, clean the tip using the sponge, then tin the tip with fresh solder. Then use the iron to heat the solder joint and then touch the opposite side of the joint with the solder. Solder runs towards the heat and around the part to get to the iron and it ensures that the part is hot enough to make a good connection.
Never touch the solder directly to the iron when soldering. When the joint is hot enough, it will flow freely. If you put solder on the iron tip first, the flux boils off before the solder even touches the joint.
You want to use enough solder to clearly cover the joint, but not so much that you can’t see the outlines of the wires or sides
Solder each connection as quickly as possible… 2 to 5 seconds per joint should be more than enough. Keeping the heat applied to the joint for too long can destroy some electrical components from the excessive heat.
Just don’t push too hard, especially when working on circuit boards. Excess pressure can cause the little tabs to break off or pull away from the circuit board.
The solder should flow freely and make a smooth and shiny connection like this:
If joint is dull and solder isn’t smooth, chances are you have a cold solder joint where the solder didn’t meet smoothly and bond with the surface.
For this reason, it’s really important that you don’t move or disturb the joint while it is cooling.
After it’s cooled off, clean the parts you just soldered with alcohol (or water for water based flux) using the cotton swabs. The excess flux may corrode the connections over time and cause them to crack or come loose which in most cases isn’t good.
In cases when soldering sensitive electrical components such as transistors, you may want to use a heatsink (pictured at top of page) to dissipate extra heat.
To remove excess solder, you can use a copper wire braid or solder sucker (both pictured at top of page). I prefer the braid because it’s easier to use and more precise, but both will work. The solder sucker or de-solderer uses suction to suck up excess liquid solder. The copper braid sucks the solder through it and the solder adheres to the braid thereby removing it from whatever your de-soldering.
By the way, if you need help to hold things in place, you can use a helping hand type device. For things like soldering Deans plugs, I’ll often just take a pair or pliers and wrap a rubber band around it to hole the plug in place while I solder the connection to it.
You can also use electrical take to tape wires and such to the surface you’re working on while you solder the connection.
That’s mostly all you need to know. As always, if you have any questions, please feel free to ask by leaving a comment.
Here are a couple of video soldering demonstrations:
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