Direct electrical connection from wire to wireform spring...

[jamxb6]

I'm looking for suggestions on connecting wires to a wireform spring. Imagine a cotter key Link that needs to pass a current. My application is automotive, so 12V. I can either have an copper insert in a plastic injection part that will have interference contact with the spring and a spade terminal built in, or I was thinking I might be able to connect a spade terminal to the end of my spring. The spade connector I think is a very simple solution, but the wire is 2mm dia music wire ASTM A228, with hardness C41-60 (

http://optimumspring.com/technical_...rbon_steels/music_wire_228_spring_wire.aspx).

I don't know how well a spade terminal typically designed to grip a soft copper wire will do with hard music wire. Any thoughts on this? Or maybe soldering would be a viable option? Someone even mentioned stamping a spade terminal in the end of the spring might be an option, but I don't think that I agree. Any input is helpful. Thanks

 

[IRstuff]

You've not said how much current you're trying to conduct, but an unprotected connection like this in an automotive environment sounds like a recipe for failure. Dust, dirt, oil, etc., are all enemies of good conductivity. People do it and get away with it, mostly, but I would vote for soldering a connection directly, or even just soldering the pigtail from the mate to the spade terminal

TTFN
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[jamxb6]

The current will be <= 10A I think. I don't have the spec in front of me, but I'm comparing it against the equivalent fuse/circuit in my personal car. Sure it's an "open connection", but there are other existing solutions with similar connections, and they go through very rigorous thermal cycle testing, as well as humidity, corrosion resistance and salt spray testing. The connection won't be "sealed off", but it's in an enclosure and internal within the car. I work for a Tier 1 supplier to this particular customer.

Thanks

 

[IRstuff]

10A is a bit much for just a contact connection. I would think that you'd also run the risk of getting arcing and burning on the contact surface

TTFN
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[jamxb6]

IRStuff, correction. Something like 10mA goes through this circuit, to trigger a higher current (10A possibly) relay. Not that it matters, but it's not a constantly closed circuit either, i.e. it doesn't pass current all the time

 

[MacGyverS2000]

At low current, then you have to worry about oxidation... rubbing and preventing oxidation tend towards more expensive materials.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[VEBill]

Perhaps spot weld a solder-friendly metal tab or a suitable terminal onto the hard spring wire. Then you can take it from there easily.

If you're being cheap, then spot weld the copper wire straight on. A very common technique.

For reliability, you'd presumably have to be careful that movement and recurring stress is kept away from the spot welded section of the spring wire. In other words, that section of the spring wire (heat damaged by the process of spot welding) would be clamped in a fixed position, not flexing.