# How to solder in a spring?



## yellow (Jun 4, 2007)

have to enter a spring on one side and some part to raise the contact point for the batt at the other (flat top li-Ion)...

no problem with that normal thing, some metal and just solder it on the battery contact of board or switch, or just do a solder blob there.
But the spring just seems not to be able to be soldered, the solder just does not grab it.

Dunno what to do, anyone has a solution?


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## IsaacHayes (Jun 4, 2007)

Sand the spring a little so it's roughened up a bit. Then tin the spring separately from what you want to solder to. Then try to solder it to the part you are soldering it to. I've had good luck with this in the past. Also the spring will act like a heatsink and cool down the iron so you may have to hold it there for a while to get it hot.


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## cy (Jun 4, 2007)

besides ruffing up surface and/or make sure surface is perfectly clean. 

use correct sized soldering gun with correct tip to part. meaning unless you have a high end solder gun that reacts to temp at tip. for larger parts... use a higher wattage gun like http://www.weisd.com/store2/WELD550.html

first heat larger part to temp, before attempting to solder wire to spring. if you cannot get base metal up to temp. you will not get a good bond. always use a high quality flux. 

on charging clamp pic below... note brass contacts are soldered to 14 gauge wire. this job required a large solder gun to get brass hot enough to stick.


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## rufusdufus (Jun 18, 2007)

I think maybe some springs are made of materials that cannot be soldered.


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## cy (Jun 18, 2007)

good point.... what I do is get solder to stick to spring first. before flowing on wire. 
some materials would be hard if not impossible to stick. 



rufusdufus; said:


> I think maybe some springs are made of materials that cannot be soldered.


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## Illum (Jun 18, 2007)

I'd try a solder glob that encloses the base of the spring and hold it down in that manner.

the spring itself is solderable, as some springs attach easily after sanding, but most are :sick2:


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## LuxLuthor (Jun 20, 2007)

What everyone said here. I was able to do it reliably after sanding and using flux and a hot enough iron.


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## yellow (Jun 20, 2007)

Illum_the_nation said:


> I'd try a solder glob that encloses the base of the spring and hold it down in that manner.


solved the problem like Ilum_the_nation, no chance the spring bonded with the solder

(maybe that SF LA spring I used is not solderable?)


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## cy (Jun 20, 2007)

surefire doesn't solder to their springs, but uses a spot welder like lux posted about recently ($1,000 min)

this is part of reason Surefire bulbs are tougher than others. better construction!



yellow; said:


> solved the problem like Ilum_the_nation, no chance the spring bonded with the solder
> 
> (maybe that SF LA spring I used is not solderable?)


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## 65535 (Jun 20, 2007)

You could buy a spring from the shoppe or you could get a 99cent light and use that spring.


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## yellow (Jun 20, 2007)

too large or not working

I tried several I had here, from battery holders and such. All got warm at 1 A draw, except the small one from the SF LA's (and I still have a few blown LA's here. Like to use the springs for some time now but every time with a solder blob holding it, not really soldered in place)


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## 65535 (Jun 21, 2007)

If they can't handle the current than attach soft copper wire to both ends creating a low resistance path. It's a common incan low resistance mod and should do wonders.


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## Illum (Jun 21, 2007)

I think theres tin on the spring or used to make the spring....tin doesn't mix too well with solder which is probably why its applied to solder guns


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## LuxLuthor (Jun 21, 2007)

Another strategy is loop wire or copper desoldering braid around the wire and solder the end closing the loop tightly around the spring.


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## HarryN (Jul 6, 2007)

I have used silver filled 2 part epoxy with success. You can get it through McMaster-carr. Use the "flexible" type if available - it is really tough.

Clean parts with rubbing alcohol before bonding.

Not the cheapest method, but it works. Around $ 20 for a single use tube.

Don't bother with the circuit trace stuff. It has no mechanical strength.


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## wykeite (Jul 7, 2007)

Illum_the_nation said:


> I think theres tin on the spring or used to make the spring....tin doesn't mix too well with solder which is probably why its applied to solder guns


 
I always thought something like 60/40 solder was the ratio of lead to tin, in which case tin would seem to alloy perfectly with solder. I suggest the reason that solder will not adhere is that the spring is coated with a passivated zinc compound that will not accept solder. Filing some of this coating away will allow the solder to join steel to copper if the temps are right. The coating penetrates the steel and rejects the solder, which is why you have to remove a very slight amount


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## doc_felixander (Jul 22, 2007)

Right....with the new lead-free regulations here in Europe, solder even consists of ~99% tin.

Chrome is usually very hard to solder. Needs lots of heat and flux. I assume that spring is chrome plated...


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## Mark620 (Jul 22, 2007)

Springs like other chrome plated and high chrome materials should be etched before soldering...
You can use regular rosin core electronic solder to do this; but, you have to use zinc chloride based flux like Ruby-Fluid or Stay-Clean.


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## StefanFS (Jul 22, 2007)

I sand the spring, pretin the spring, make a substantial solder blob for the spring and then I set my iron on max and hold the spring in place with some thick leather work gloves. I believe that holding the spring firmly in place during the soldering is crucial for this to work.


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## GarageBoy (Jul 24, 2007)

Yea, steel sucks for taking solder (and aluminum)


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