Direct Soldering vs Connectors

Direct Soldering vs Connectors

Posted by Lee McKenzie on 7th Oct 2016

Using connectors and header pins is a great way to start off with building drones, however in my experience, the cleaner and more compact a build is, the more reliable and durable it becomes. If you currently use header pins and connectors it might be time to step up to a more advanced level of building by direct soldering your components.

Why direct solder?

I'll take you back to my very first build. I had wires coming out the yin yan and my quadcopter looked like a bird had made a nest in the body of the frame. It flew well enough, however a few flights in I started having problems. My ESC servo connectors to the flight controller were coming loose, some pins had bent into each other and were shorting. My props had cut some of the wires and It was really not a fun quad to fly with all the issues I was having.

Sure it was easy enough to push the servo connectors back onto the pins, and bend them straight again. But at this stage I didn't have the confidence to cut wires shorter, and de solder electronic components without the fear of damaging the electronics.

My quad was an unreliable ball of crap. And a heavy one at that.

Direct soldering your electronics will take your builds to the next level. Not only will you learn some valuable skills but you will have a reliable, tidy racing drone that will perform well without unnecessary space and weight.

Where to start?

The key to learning how to direct solder well, is to learn how to desolder first. Desoldering gives you the confidence to remove and shorten wires and repair or remove connectors from electronics which can be a common failure point. Some Micro JST connectors can be really temperemental with intermittent connection or can come away from the PCB. 

Some of the items you need to desolder well are:

  • A good temperature selectable soldering iron with a fine pointed tip, and one which can heat up quickly.
  • Desoldering braid
  • A good quality solder sucker, cheap ones get stuck or don't suck the solder up.

Removing solder using these tools makes it easy. First heat the solder where you want to remove a wire. If the solder isn't softening, add a little bit of new solder to it to speed the process up. Once the solder has become a liquid, remove the wire from the pad and suck up the remaining solder with the solder sucker. You can resolder wires back onto the pad like this, however if you want to clean up every last remaining bit of solder, use the desolder braid to sap up the remaining solder. Be careful not to apply too much heat for too long as you can damage any electronic components.

The most common item I remove wiring from is the ESC's. I take off the heatshrink and remove all the wires and replace them with black wiring usually. Black seems to obscure the wires and make a build look really tidy. I am also able to use better quality wire and cut to the length that is required and nothing more. Extra wire can be exposed to damage and add weight when it is not required. I'll then add some new heatshrink to the ESC to protect it.

I also commonly remove the pins from X4R receivers so I can fit it in between a PDB and FC stack. And if I have any damaged micro JST connectors, I will cut them off, remove the remaining solder and pins, and then solder wires directly to the board where the micro JST pads were.

Removing the requirement to use connectors can really save space in your builds and allow for a tighter more compact quad. A reliable one too as the wiring is cut to length, routed properly and shouldn't be able to dislodge.

The next skill to learn is how to solder onto small wires and pads. This is relatively easy to do with the right heat settings, a pair of tweezers and a good angle of attack onto the pad. Practice here is the key, but in my experience more damage is done in the desoldering stage of a build. Or if you've had too much coffee and have the shakes lol.

To resolder wires onto pads, coat the pad in solder first (enough to consume the wire) and quickly pre tin the end of the wire. Liquify the solder on the pad with the iron while dipping the tip of the wire into the solder, letting it sit for a little bit and then removing the heat. Let the solder solidify. Don't apply too much heat with smaller wires for too long as the plastic can easily melt from around the wire. We are talking a matter of a second in some instances. For larger wires (12AWG etc) increase the heat settings on your soldering iron to about 400°c instead of the usual 350° for smaller wires. Larger wires can suck a heap of heat out of your iron and make soldering more difficult if your temperature is too low, or your iron can't reheat itself fast enough to recover.

If you bridge pads or drop solder onto other parts of the PCB, you have the skills to desolder, reset and start again. Don't feel that you have to use or try to modify a solder connection that went wrong. Resetting completely is usually a better strategy than trying to fix it. Common instances where resetting is required are bridged pads, too much solder, dry solder joints, solder spilt on places its not meant to be.

Hope these tips help you move your building to a more advanced level, the beauty of learning to desolder is you can now go through your first build and tidy everything up. Shorten wires, move components around and remove some connectors.

If you have any other tips, let us know in the comments.

Happy Flying