I need to install an en electrical conductor through a piece of acrylic, and it seems that brass screws are ideal for this application. Question, can ordinary electronic solder (SN60PB40) be used to join a copper wire to a brass screw?

 

Copper to brass is a definite yes. I have done it many times, also brass to steel. All with leaded, rosin core solder. I have not tried bronze. Success with that might depend on the alloy.

 

Sure I've done it most of my life, soldering brass to copper. But depending on the size of the screw you might need more heat than a small electronics size iron can give. I have always used a Weller solder gun.

 

I have not tried bronze

The only bronze that I know of that would give trouble would be like an Oilite bushing, because of the oil in it.

 

If the joint receives any flexing I would look at low temp silver solder using a small torch. Especially if any significant current flow.
Max.

 

If the joint receives any flexing I would look at low temp silver solder using a small torch. Especially if any significant current flow.
Max.

Nah ... the joint will neither be flexed or suffer vibration. And the amount of current will be quite low, and also the voltage. That's why it's important that I don't use stainless steel for these screws, so as to keep power losses to a minimum.
There's a local supplier that sells copper screws, but not the size that I need. They do have more variety on brass screws, though. That's why I've asked if brass and copper solder well together.

 

Yes, they do, but it is not a good idea to do so. A sufficiently tightened screw should be enough to guarantee an airtight joint. Don't depend on solder to do this (as we have discussed many times here).

 

Yes, they do, but it is not a good idea to do so. A sufficiently tightened screw should be enough to guarantee an airtight joint. Don't depend on solder to do this (as we have discussed many times here).

Thanks for the advice, but I wasn't planning on doing things that way. My plan is to solder the wire to the head of the screw. The flat bottom of the screw's head will be pressing against the acrylic, with an o-ring between them acting as a sealant.

 

You asked about bronze. You DO know bronze is an alloy of copper and brass. Therefore, the answer regarding bronze would also be "Yes".

 

You DO know bronze is an alloy of copper and brass.

Ummm... not quite.

Brass = Copper + Zinc
Bronze = Copper + Tin

 

You asked about bronze. You DO know bronze is an alloy of copper and brass. Therefore, the answer regarding bronze would also be "Yes".

Actually, Bronze is an alloy of copper and tin, while Brass is copper and zinc.

It's the presence of tin and zinc in those alloys that had me wondering if they'd affect common electronic solder.

 

It's the presence of tin and zinc in those alloys that had me wondering if they'd affect common electronic solder.

Actually both tin and copper are solderable, so I don't see any problems with soldering bronze (provided the alloy is just those two elements).

 

Zillions of plumbing joints are copper soft-soldered to brass (mostly) or bronze (less common). Lead-free solder is now the standard for plumbing, and produces stronger joints. Though no longer true in plumbing, many brass alloys contain some lead, which acts as a sort of built-in machining lubricant.

Various brass and bronze alloys are extremely common in electromechanical devices such as relays. For example, the moving contacts in relays may be mounted on bronze alloy spring "fingers" which have wires soldered between them and the brass pins that get soldered to a PCB or plugged into a socket.

Model railroaders solder up all manner of things from brass.

About the only common metal that is very difficult to solder is aluminum. Stainless steel can be very difficult to solder if not prepared (freshly abraded to remove chromium oxide at the surface, which is what makes it stainless. I use 300 series welding filler wire for assorted things. As-is, no flux is adequate to allow it to be soldered, but a little work with 600 emery or the like will make it readily solderable with fully-activate rosin flux.). The wikipedia page on solderability give a rundown.

 

Actually, Bronze is an alloy of copper and tin

Oops. Yes. You're right. I'm wrong. Disregard my comment please.

 

It is easy to solder bronze, but for brass you need to use flux like this:
https://www.somersetsolders.com/zinc-chloride-flux-500ml/p292
After soldering wash thing with water.

 

It is easy to solder bronze, but for brass you need to use flux like this:
https://www.somersetsolders.com/zinc-chloride-flux-500ml/p292
After soldering wash thing with water.

Once again, Danko, you've reached the heart of my question.

Many, many thanks!

 

Once again, Danko, you've reached the heart of my question.
Many, many thanks!

You are welcome!
Here is flux from US supplier:
https://www.grainger.com/category/s...dering/welding/ecatalog/N-n9wZ1yzaqs0Z1z12456

 

Never never never solder stranded wire with zinc chloride flux unless you only need it to last for a short time. Molten flux will wick up among the strands where it is virtually impossible to remove by washing. Zinc chloride leads to a perpetual corrosion cycle - chlorine is a powerful oxidant and will react readily with the metal. The metal chloride can then react with carbon dioxide, producing metal carbonate and freeing up the chlorine to react with more metal in a process that continues as long as there is no more metal to destroy. Even the lead in solder is vulnerable to this. Somewhere out there there is a paper from one of the big solder manufacturers that describes this, but I can't find it.

I've soldered all sorts of brass things with ordinary electronic solder with activated rosin flux with no difficulty, provided the brass was properly cleaned. Clean brass is usually easy to solder even with RMA and no-clean fluxes. I just tested on some freshly cleaned thin sheet brass with 5 different kinds of electronic solders (RA, RMA, 3 no-cleans including one that is really "weak") and they all worked well. I have used brass tubing and washers as housings for in-line ultrasonic pre-amps and soldered them with RA-cored wire solder with no difficulty, though everything was always freshly cleaned. Microdot connectors were soldered to brazed-on brass nuts with the same solder. I designed in 10-32 brass machine screws with nuts as terminals for an industrial battery charger PCB. Both the head of the screw and the nut were soldered to the board during normal wave soldering (strategically-placed vias allowed the solder to flow to the top surface of the board to solder the nuts to keep them from turning).

 

(strategically-placed vias allowed the solder to flow to the top surface of the board to solder the nuts to keep them from turning).

Subtleties like that make my day!

 

Zinc chloride leads to a perpetual corrosion cycle - chlorine is a powerful oxidant and will react readily with the metal.

Thanks for the warning, somewhere in the back of my head that's information that I had already learned, many years ago. Thanks for bringing it back to the surface. On the other hand, it is magnet wire that I'll be soldering, so the effect that you're describing will not be a problem, and the joint is something that I can easily wash after soldering.