Ok this topic has bugged the bajeebus outta me since I have been on these forums. Far too many internet bandwagoneers are perpetuating bad information, bad habits and just plain stupid and repeated advice when it comes to soldering. Specifically on Flight controllers and esc's.
WE ARE NOT SOLDERING PLUMBING. HIGH HEAT IS WRONG AND UNNECESSARY.
Those people here who keep telling people to turn up or use high heat please stop. You are WRONG. If that process works for you rock on but we are trying to help and teach so please stop perpetuating bad information. Stop telling people, specially those new to soldering to do this. You are only screwing them over in the long run as they will butcher their electronics and possibly ruin them completely.
Ok Rant off..
Just some back ground where this information I am going to pass on here comes from.. I worked in the Rochester area for nearly two decades in the electronics manufacturing industry soldering components, wires, making harnesses, sub assemblies for military radio systems, systems assembly and rework of complete telecom directory assistance gear. I worked for companies like E.N.I ( electronic navigation industries) Harris RF communications, Nexpress (joint venture between Kodak and Heidelberg digital) as well as a few others over that time.
Ok lets start by the soldering process so many have problems with. 90% of the time the issue is your soldering iron sucks. The other 10% is lack of experience, the wrong size tip, or the wrong solder. I say your soldering iron sucks because its either old, not temperature controlled WITH fast recovery or you have not taken care of it and done regular cleaning and maintenance.
First you need a temperature controlled iron that has a fast recovery circuit in it to keep a stable temperature as it leaches onto the work. There is a huge difference between one with that fast recovery and without. This is why some of you with temp controlled irons still have trouble soldering the main power leads on your builds. Naturally you THINK you need higher heat which is not the case.
You will need several size tips for the various things we solder in our hobby. You do not need to use a massive chisel tip to solder 22 gauge wire and you will struggle to do a power lead with a needle point tip. Use the right tool for the job.
Next is the solder you use. Forget all the hype about 63/37 as being better and dont even think about lead free for the little bit of work we do. Simple 60/40 rosin core solder is perfect for what we do. If you are picky you can get various diameter solder but I find a thin diameter best even on heavy wires you still use the same amount by weight even though it may look like you use a lot more. ZERO extra flux or solder paste or anything other then the rosin core solder is needed. Unless you are working with things pre 1970's then you MIGHT need extra cleaning.
Starting with a brand new iron:
When I get a new iron the first thing I do is find the minimum temperature to melt the most common size solder I use. ( you can still do this on your current iron) I start just lower then I know will melt it and then slowly raise it a bit until I am able to tin the tip for the first time. Once I have the tip tinned I will shut the iron off and mark on the dial that very minimum. Why you may ask.. I start my iron at that temp each time and tin my tip in preparation for the new task. This will also be a good indicator when it is time to clean or change the tip as over time the connection between the element and that tip will corrode causing resistance and thus requiring more power to heat. This will also greatly effect how stable the iron can keep the set temperature and that will show in how well your work turns out and how much effort it takes to do it well.
Soldering process:
Preheat and tin your iron. Wipe off the excess solder onto a damp not soaked sponge. Throw that brass scrunchy most irons come with away the damp sponge is best as it takes away the burnt flux as well as the excess solder. Those scrunchies do not remove the burnt flux good enough. After wiping look at the tip for any signs the solder is not sticking to the tinned tip over time. Tiny dark spots will start to show and this indicates time to clean or to replace that tip. Sometimes it can take several tinning and wiping attempts to completely tin a tip. Now you are ready to work.
With the iron set to that minimum temperature still you can tin the pads on where any connection you plan on doing is located. Do this by tinning the tip again but adding a tiny bit more so a solder bulb forms under the tip. THAT is what will do the work of transferring heat not the iron itself. The iron should only be holding the temperature steady. Take your solder wire and rest it on the pad you are going to tin. Touch the bulb of solder under the iron to the solder wire on the pad and it should instantly transfer heat to that which will in turn melt and flow over the pad. (SEE ATTACHED VIDEO) Do NOT set the iron on the pad and then feed solder to the iron. This is why everyone heats up and lifts pads. You will also have little solder splashes as the rosin boils if you use that feed method which with high heat will throw solder everywhere. This is also a big cause of failures with peoples electronics.
This same process now moves forward to wire work STILL at the same temperature setting. Strip your wire ends just long enough to cover the pad they will be joined to. Do not pull the wire off with your fingernails regardless of what the inter web gurus tell you. This stretches the casing which will pull back when heat is applied or shrink back over time exposing bare wire. If need be strip it long and clip it back to correct size after tinning. Again tin your tip and get that tiny bulb of solder. Using something to hold your wire steady rest the solder on the wire and set the iron on top of that it should melt into the wire quickly. Then to make sure its good touch the iron to the under side of the wire pulling solder all the way thru and drawing the excess solder off. The cool thing about solder is that it will follow the heat. What you want is a nice shiny coating that you can see the strands of wire thru.
Now the issue with power leads on esc / AIO flight controllers:
Given you use a "fast recovery" iron this should be a non issue but even so it is still doable with a normal temp controlled iron. Start with using the proper size tip. Here is where a chisel tip comes into play. One that has a flat tip the width of the wire gauge you are soldering will be perfect. Again find the minimum temperature needed to tin that tip then raise your temperature up a little. I usually just raise mine one number place higher on my solder station. Just dont go all Mr. Steele and launch temps into iron forge ranges.
This time when you tin the pads you will use a larger bulb of solder to make a good size lump on the pad. Tinning the bigger wire is same as little wires bigger bulb on the iron, rest solder on wire, touch iron to solder to melt into wire. Then heat from the bottom and pull it thru the strands. Air in between strands causes resistance in turn raising heat conduction under power and is the main reason for these wires getting hot enough to de-solder themselves in flight. The tinning should be nice and shiny and you should be able to see the shape of the strands in the wire thru the tin job. This is perfect. If your tin job looks like a ball on the wire you have too much applied and that will take more heat and time to bond when soldering to the pad. Reheat the wire end and tap it on the sponge tray to knock off the excess.
Time to attach the main wires. You have a good lump of solder on the pad from tinning, you can see the strands of wire thru your tin job. Now time to make the connection. Use something to hold the wire in place so it rests on the pad. Make sure it is relaxed enough to move a little as the solder melts. Tin your iron with a ball of solder that starts to look like it may fall off. Carefully rest that on top of your power lead NOT putting any pressure on it with the iron. Watch the wire and the pad as the heat transfers and you will see the wire relax down into the pool on the pad. If you did this correctly it should take less time then the high heat and pressure method everyone else propagates. Remove your iron and DO NOT BLOW on the joint to cool it.
Here is a video for proper tinning of pcb's
And here is a video using these practices to wire up a flight controller. Notice I do have a bit of struggle doing the power lead myself and is a perfect example of using the right tip for the job which was on my other iron a friend had borrowed at the time of doing that video.
Finally.. this is meant as a teaching thread not a how to solder debate. Any posts that do so will be removed. Questions are fine but what you do personally doesn't belong here.
