What solder to use?
 

Lead free?

60/40?

Does it matter?

I am talking mostly for the motor and batteries but also other misc wires on the car.

I've tried lead-free solder, and don't like it. I'm sticking with 60/40 multicore for as long as my supply lasts.

solder type
 

2 basic solder types: lead free and lead

lead comes in several types: 60/40 (tin/lead) 63/37 (tin lead) 60/37/3 (tin/lead/silver) and some other mixes of tin/lead/silver

lead free: 96/4 (tin/silver) or 100% tin and some other mixes of tin and silver

The difference: (lead vs. lead free solder)
Lead solder pros: flows better, requires less heat, easier to work with
Lead solder cons: LEAD is toxic, lead is a poor conductor (so 40% of your joint has resistance), lead joint is weaker

Lead-free pros: less resistance, much stronger
Lead-free cons: requires more heat and a better iron, doesn't flow as well so flux may be needed

I have used lead-free solder for several years. If you will be soldering and unsoldering the same joint many times, lead solder is better because it is easier to work with. If you use connectors, lead-free solder is better because it is much stronger and has less resistance. DO NOT USE lead solder around small kids, or let them play with your cars. Kids swallow strange things, and if your kid swallows lead solder, IT IS VERY HARMFUL.

If you use lead-free solder, the joint will not be shiny but a dull metal.

They are different and you solder with them slightly differently. Lead solder is already banned in europe, japan, canada, etc, and it is only a matter of time before it is banned in the us.

Lead-free needs more heat.
Could this be one cause of the current problem with "exploding" cells? As more people are using lead-free to solder their packs, more of them are exploding.......

Lead-free makes a stronger joint, but is it more prone to fracturing with continued heat cycling or vibration?

I was having soldering problems. My solder joints where not strong and always coming off.

A fellow racer looked at my setup and noticed I didn't have 60/40 solder. I bought some and used it. Bam, no more problems.

The problem is the solder I was using (don't know the mixture) needed a lot more heat to become soluable(melt). 60/40 is the best way to go and my joints are now staying together.

Hope this helps.

lead-free solder problems
 

If you are having problems with lead-free solder, you don't know how to solder with it. Again, you solder with it little differently. You need slightly more heat (30 or 40c higher,) and you probably need a better iron (60 watts minimum.)

Since it is only a matter time before you can't get lead-solder, learn how to use lead-free solder.

Since solder containing lead is mostly banned for sale in the EU i use Much More's racing solder. It's kind of overpriced but it's the only good solder containg lead i can come by :P

Audiophiles swear by Wonder Solder. Works wonders in RC too.

60/40 Rosin core. RadioShack sells it with their branding, its relatively cheap and readily available. Good stuff too.

Hankster that runs Hobbytalk.com used to sell 63/37 eutectic 5 core solder. Awesome stuff! It turns to a solid very quickly and makes an excellent joint.