Strongest solder for soldering copper to copper (vibration resistance) 1

[Z2TT]

Hello.

I have an alternator that I need to solder copper wire to the bridge rectifiers.
Now as this is being used in a vehicle, there will be vibration which may weaken the solder or cause it to fracture.

I need to know which solder will be able to give the strongest hold and be resistant to cracking under vibration,
What sort of combination of lead, tin and silver would be ideal?

Or would a solder that has no lead be a better option?

I have many different solders available at my supplier, so I want to select the one that would be best suited to this job.

Thanks.

 

[kingnero]

Have you already talked to a solder manufacturer?
They just might have tests done, or experience with this. I believe (but don't quote me on this) in aviation, solder isn't allowed because of vibration fatigue. Maybe there are exceptions, or alternatives, or again test results in this field.

 

[IRstuff]

I think you are overthinking the problem. People have been using standard electronics solder in automobiles, boats, planes, helicopters, missiles, and spacecraft, all with vibration and shock environments. Solders, by themselves, are not supposed to deal with constant flexure; you, as the designer, are supposed to design the wiring and component placement so that connection does not flex. Once that is done, the solder is almost immaterial.

TTFN
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[tbuelna]

My experience in aerospace is with mechanical systems, but it sometimes involves electrical components like wires and connectors. What kingnero said about avoiding soldered connections in aircraft wiring is partially true. Crimping is often the preferred method for attaching connector contacts to wires, because if done properly it is quicker, cleaner, and results in a more reliable connection. However, soldering is still widely used for electrical connections on things like circuit boards.

The key to preventing excessive stress at your solder joint is to provide proper clamping/strain relief of the wire close to the joint. The strain relief design should provide sufficient constraint of the wire to isolate the solder joint from dynamic forces acting on the wire length between. The strain relief should also provide enough compliance to prevent over-stressing of the solder connection from thermal expansion/contraction in the surrounding structures.

You can probably get a soldered wire connection to work well for your application if you pay attention to details and do a thorough job of designing the solder joint and component/wire attachments.

 

[berkshire]

Z2TT (Automotive)
If you are soldering diodes in alternators, you need to look at the original solder to see what it is composed of.
The diodes in an alternator can get pretty hot at full load , sometimes requiring a silver brazing type solder, instead of a tin lead type solder. The last thing you need is a solder failure at full load.
That said, for flexibility, and resistance to cracking , a 50/50 tin lead solder would be better. Most electrical ( wiring joint.) solders are 60/40 tin lead for their sharp melting point and quick freeze. If you are forced to use lead free then 95/5 95% tin 5% silver is usually specified. There are other lead frees with bismuth and other alloys also available.
B.E.

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