solder for flashlight kit

Hello,

I am a newbie CS teacher using your flashlight solder kits this year. At approx. the 5.30 mark in the intro video it talks about the “thicker core” solder:

https://youtu.be/ABzP8A4rSHA

Is this the solder he speaks of??

https://www.sparkfun.com/products/10243

It looks like the one linked at the bottom of the flashlight product page, but it looks to be a different diameter – if the diameter is what “thicker core” speaks to??

https://www.sparkfun.com/products/14877

The soldering process has been a VERY slow and frustrating process using solder we purchased from another vendor (lead free, 0.8 mm diameter, 2.2% flux), so we’re trying to figure out how to make the experience better.

We’ve tried adjustable solder irons that get hotter (~450 degrees & others that get up to ~750) than the single-temperature ones that were in the room when I came to the room. That works a bit better. We’ve tried wedge solder iron tips based on another video we watched. That doesn’t seem to make much of a difference. We have made sure we’ve followed the soldering process of not using the tip of the iron and heating up the annular ring and the component and then trying to apply the solder. But most still struggle to solder the complete kit in a reasonable amount of time. Most of the time it’s taking most of the students about 20-30 minutes or more to complete the kit, which is a very slow go for a class of 25-30. Or maybe that’s normal?? When they use the solder we have (lead free, 0.8 mm diameter, 2.2% flux), it “balls up” very quickly and students have to often remelt those balls and push them into the joint. Every once in a while a couple of students seem to go through the kit in about 10 minutes or so with nice solder joints, so we realize a lot of this is technique. But perhaps the solder has something to do with it? Is it because we’re using lead-free solder? Should we be using leaded solder (with gloves and a fan)? If so, the two links above are lead-free. Do you have similar that’s leaded?

Thanks in advance,

Gordon

I’d start with som good old fashioned 70/30 leaded flux core solder. It’s a ton easier to work with especially for someone learning how to solder.

A fan is nice but not necessary, there will be NO leas in the smoke created by burning flux. Gloves are OK but as long as nobody is touching their mouth or lips or eating before washing their hands they will be just fine.

Once you develop a good soldering technique you can try the lead free stuff. I’ve used sparkfun lead free solder and it’s pretty good but not as easy to use as leaded.

I haven’t watched the video but thicker solder has the advantage that you don’t have to feed in as much into a joint as the thinner stuff. That makes it a bit easier to use than the thinner stuff. The thin stuff is better for surface mount parts rather than through hole parts like you’re using.

As a warmup you might consider soldering pin headers into a solderable breadboard. That gives you plenty of practice with cheap parts so you can develop a good technique.

One last thing, heat the pad and the part lead with your soldering iron then apply solder to the pad and lead. (NOT the iron) You’ll find good joints are pretty easy this way.

Thanks for the reply. I’ll look for leaded with a larger diameter.

gordonb:
… so we realize a lot of this is technique. But perhaps the solder has something to do with it? Is it because we’re using lead-free solder?

You got it. Successful soldering is almost all operator technique with a little bit of equipment and solder sprinkled in.

For example, if the temperature is too low or the iron’s tip is too big or burnt up, it will be difficult to get good results. But setting that kind of stuff aside, it’s mostly getting some practice. The visual difference between solid and melted solder can be subtle. The way it flows across different kinds of joints and materials is, too.

I’d recommend getting some scrap electronics and practicing on some boards you don’t care about. Through-hole equipment is less common than it used to be but maybe find an old alarm clock, telephone or VCR at a thrift/resale shop/garage sale for some donor boards and wires.

Thanks for the reply. We’ll keep at it.

70/30 is not a standard alloy. For leaded solder, 63/37 is the best, but 60/40 also works.

/mike

Thanks for this.