Off season skills: Learn how to Solder

Technical Electrical
1

Just got back from our learn how to solder day. Passed out 17 kits, only 15 stayed to build. Youngest was 10, oldest early 20’s but the average age was 14. Almost every builder had a parent to help. Combo of our VEX and FRC roboteers.

Final goal was to build this kit: Minimatrix 8*8 LED scrolling display

We spread the parts on the table (pick up a 1 gal re-closeable zip lock storage bag, put into the bag the following: practice resistors, practice capacitors, practice boards, 3 batteries, remote, Minimatrix kit, pliers, iron, length of solder, clippers, instructions, and a paper towel). Take all to table, take paper towel fold it into 1/8’s and get it damp.

Opened up with standard safety lecture on how hot the irons get, how hot solder really really hurts, etc. Then a quick demo on how to solder. (Heat the joint, then feed solder into it). Roboteers then practiced with resistors on a single sided protoboard. With 6 good connections they got promoted to a double sided board, 4 good connections they were on to the Minimatrix kits.

Most roboteers finished the test runs in 30 mins, and got the kit done in 20-35 mins. Three fails, one on not soldering the (-) connection on the battery, two with bent battery connectors. Easy fixes. All 15 roboteers left with working systems that they had programmed to spell out their names.

And only two other minor issues, one kid burned the table with an iron and one Mom got a minor burn by not thinking that the metal shaft also gets hot.

So all in all a successful day, roboteers were excited and had leaned a new skill. Thanks to parents that stayed to monitor/cheer on their roboteers and to Scott for supplying practice components and boards.

Total cost for items was $21 per kit, shipping adds another $6 per kit if you decide to reproduce our event. Battery life in the units is ~30 hours of active use, Digikey has 2032’s in stock for 30cents each, but shipping is expensive. The irons and tools came from Marlin P Jones in Florida, my goto guy for surplus stuff. Nick, the builder of the Minimatrix was great on geting a mixed order of displays over to me from England.

2

Awesome! My team has been looking into a soldering training class, as we(ok, mainly me) want to get more members involved with electrical. We taught a few students to solder when we made our own light-up team number signs for champs. It was a lot of work (over 700 solder joints) but everyone involved loved it. It was a good training opportunity and a great social opportunity for newer members.

(edit) anyone have suggestions for cheap soldering kits? Especially ones with medium to large joints like those that students will be using on the bot?

3

We do something very similar as part of our summer camp. Each kid spends two days (for a total of 4 hours) at each station. It’s not as focused as yours sounds - we spend time talking about the robot and how the electrical system goes together as well as making the our own kits (the camp is for prospective members, not just anyone).

We get our kits from http://www.apogeekits.com/ - I’ve had an excellent experience with them every time - twice now the kit we had at the top of our list wasn’t available in the quantities we wanted, and they offered a different (more expensive) kit at a discount to match the price of the original order. (Note: I have no affiliation with them other than as a customer with 3 orders over the past 3 years)

We have the kids practice soldering initially with small scraps of wire. They typically end up making themselves little “electrical bracelets” with different colors of wire they can wear the rest of the camp.

4

We only use solder for small joints on the bot such as sensors. Why would any medium or large joints be anything other than crimped?

5

Hopefully not using lead solder.

And as for lead free solder, I don’t use it. Ever. That stuff is terrible. Wrecks the tips of the irons too.

6

Agreed. We used to solder other joints, and we had many failures. Getting good crimpers was a very good investment.

7

Yes, all our solder is lead free. We’ve never had any issues with it doing its job. I have yet to have a good solder joint break on our robot… There have been a few cold solder joints, fixed with training and demonstrations, an a few wires that have broken past the joint from stress, but never an issue with the joint itself. Yes, the tips of the irons need to be replaced every couple of years… but we can afford a couple bucks for new tips when we need them.

8

For solder projects I like Sparkfun, Tindie, Adafruit. Ramsey Electronics for radios, and cool retro Nixie tube things.

I’m a big fan of building sensor things and putting them together on a board and making sure the connections are soldered.

But I’m also in the camp that says “things that carry power or can be flexed have crimps for connections.” So all the boat and robot things I play with have crimps.

So I would build my cool ARM / PIC controlled 9 way motion and realtime star sensor on a board and do my usual solder stuff. Off board would most likely be a screw compression connector or some type of RJ-xx connector that locks in place.

Both crimping and solder have their places. My Roboteers learned today how to solder and got a cool microprocessor with an 8*8 led matrix display they can control with a $4 remote. What I missed was the ability to spend another hour and go “this is how this works”.

The “jellybean” level of micro processors is pretty amazing. The board we built has a switch, battery holder, IR sensor, 8 bit processor and a R*C digital LED matrix. In 1974, that would have taken an whole board of 7400 logic chips and hand wire 64 LEDs In 1994 it would be down to a big chip and glue electronics, in 2013, it all fits in a 1" square.

9

Lead free solder is awful. I don’t use it. It’s much easier to end up with a cold solder joint. Have you every had a ps3/xbox fail on you? It’s probably because a lead free solder joint got too hot during operation, and got ruined.

10

We use solder with lead in it, lots and lots of toxic lead. As you and others mentioned, the lead-free stuff can be tricky.

This gives us a teachable moment: **Lead is toxic. **I instruct all students handling solder (in any manner) that they must wash their hands twice with soap, hot water, and vigorous scrubbing. And I enforce it very strictly.

I teach them to think of their hands as dirty or sticky as soon as they handle solder, and to maintain that thought until their hands get washed. Some say it helps remind them.

11

I’m not sure what size is meant by “medium” or “large” joints. But from experience I’d recommend soldering Anderson Powerpole connectors instead of / after crimping them; doing a poor crimp job is easy and leads to failures. Adding a bit of solder instead of / after each crimp gives a little bit more protection.

Not to pull this thread into a tangent, but another (surprising) thing I’ve found that contains lead are light strands that people put up for holidays. The more you know, I guess.

12

Are you referring to tinsel?

*Lead foil was a popular material for tinsel manufacture for several decades of the 20th century. Unlike silver, lead tinsel did not tarnish, so it retained its shine. However, use of lead tinsel was phased out after the 1960s due to concern that it exposed children to a risk of lead poisoning. In the United States, the Food and Drug Administration (FDA) concluded in August 1971 that lead tinsel caused an unnecessary risk to children, and convinced manufacturers and importers to voluntarily stop producing or importing lead tinsel after January 1, 1972. The FDA did not actually ban the product because the agency did not have the evidence needed to declare lead tinsel a “health hazard.”

Modern tinsel is typically made from polyvinyl chloride (PVC) film coated with a metallic finish and sliced into thin strips. Coated mylar film also has been used.[3] These plastic forms of tinsel do not hang as well as tinsel made from heavy metals such as silver and lead.*

When my brother and I were kids back in the late '50s, we used to roll the lead tinsel into a ball as we were taking it off the tree and then tightly compact it with our molar teeth to make lead “marbles”. Probably explains a lot :frowning:

13

I think he’s referring to the wires in some light strings–or rather, the coatings of the wires. I want to say I’ve seen some of those warnings, but can’t remember anything specific.

14

Yep, this.

Safety labels are important to read, even if you think there isn’t much to know about the product.

15

Given that lead-free solder always has a higher melting temperature than lead solder, I can’t see the logic of this statement.

16

A cold solder joint results when the wire hasn’t been heated up enough for the solder - you can melt the solder because the iron is hot, but it won’t adhere to the wire properly if the wire is too cold. The most common way I’ve seen this done from my students is to put the solder directly on the iron, then touch the iron to the wire. It appears to work quicker, as the solder melts immediately and then is transferred to the wire… but the solder can then be pulled off very easily as it’s mostly just sitting on the surface.

That’s why it’s important to always put the iron on the wire first, then feed the solder into the wire, not the iron. It takes a bit longer than the “easy” way, but you’re guaranteed a good joint, and you can actually watch the solder flow through and all the way around a stranded wire.

That’s also why working with lead solder is easier… the lower melting point of lead makes it easier and quicker to get the wire to the correct temperature for that solder.

17

The “lead free” solder bashing is dumb. Let me harken back to the years of heating an iron with an external source, putting flux on the joint with a small brush and then heating it with the now hot iron, waiting the right amount of time and adding solder to seal the joint.

Purpose of classes is to TEACH people how to do it right. Right tools, right skills, right training, learning how to do it right.

Sorry you don’t have an iron that reaches the right temperature, sorry that you didn’t buy solder that has the right mixture of flux and metal. Sorry that you didn’t learn to heat the joint first, then apply solder. Sorry you didn’t learn to clean the tip and reflux/re-tin it every so often between joints.

And I can carry the “sorry parade” to other items: drills, saws, punches, welders, 3D printers, flux-capacitors, photon-tubes,warp coils, Transmogrifiers, and of course the center of all IFI and Andy/Mark parts, unobtainium.

Mostly sorry that I keep forgetting that CD is a whine fest of people that can’t pull together the right skills :rolleyes: while most of us go “Ok, that didn’t have a happy ending, how do I fix that.” Lead free solder is here, deal with it.

18

My first post was not clear. I’m not trying to say that lead free solder can not be used well, but that it is much harder to have a high school student who has never seen a soldering iron before do a good joint with lead free solder. If you take the time, it is definitely possible to cause the lead free solder to flow and make a good connection. But it is very easy for an inexperienced student to just get the solder to form into a cold solder blob.

Also, in commercial electronics it is a proven fact that lead free solder is inferior and has a significantly higher rate of failure.

19

Bigger joints, like the ones used to mount wires on Banebots. I don’t know how other teams do it, but our joints are pretty heavy duty. We don’t do too many small joints, as we have plenty of adapters and splitter cables from previous seasons.

Congratulations on winning at IRI:)
Couldn’t agree with sanddrag more. Leaded solder has a lower melting temperature, meaning the iron will take less wear when using it. This is because metal has a tendency to oxidize faster at higher temperatures. Tin is brittle and weak(for a metal), while lead is malleable and holds to itself very well. This is why an iron in storage will be preserved better if it is tinned using Leaded solder. If you are using the iron and solder properly, Leaded solder is no more dangerous than lead-free. As long as you don’t set your iron above 600F or so, the fumes from lead solder will be all flux.

efoote, I have never heard of soldering the anderson connectors. We have a special set of crimpers designed for powerpoles and, when used properly, they work extremely well.

20

That is true that the heat of the xbox/ps3 doesn’t cause the solder joints to fail, but the misconfiguration of the BGA soldering machines which caused the lead free solder joints to be cold and fail early. Same issue as some Macbooks had with Nvida integrated GPUs a while ago.