Bonding aluminium foil to stainless steel foil for electrical conduction

[asimpson]

I wish to join alu. foil to ss foil by soldering or welding.

I would like to keep join low profile so a riveting or clamping is not suitable.

Foils are about 50 micron thick and 12 mm wide.

So far soldering with 60/40 solder has proved unsuccessful. Especially with SS.

I am sure the correct flux and solder is called for however I have not been able to get help from suppliers.

I have seen some brazing materials on the web however they are for heavier materials and I am concerned the thin foil would oxidize or melt in the temperatures required.


Thanks

 

[berkshire]

asimpson
one of the major problems you are going to have is the thickness of those foils. Most Aluminum soldering is done with solders containing zinc, and often involve scrubbing with a wire brush to break the oxide film, this may do terrible things to your foil. Most stainless steel fluxes are also very aggressive containing hydrochloric acid, Sal ammoniac, and other ingredients to break the oxide film. You can try electroplating the aluminum with nickel to get a more easily soldered substrate, or, you may be better off using resistance welding in an inert atmosphere i.e. spot welding. Alternatively if the tensile strength and flexibility can be sacrificed a little, you could join with a conductive epoxy.
B.E.

You are judged not by what you know, but by what you can do.

 

[MikeHalloran]

You can tin aluminum with solder by scratching it with a glass brush which is submerged in the molten solder pool. You will probably need some flux, too.

I suspect you can similarly tin stainless steel.

If you can, then you can sweat the two together.

I suspect you will be frustrated by process sensitivity, and by the labor content.



Mike Halloran
Pembroke Pines, FL, USA

 

[berkshire]

Tinning of stainless steel is done by heating ,adding a piece of solder to the fluxed surface , then scrubbing with a stainless steel " toothbrush".
The preferred solder for stainless is 95/5 tin silver or tin antimony, which wets out better than 60/40 tin lead, however it has a higher melting point than 60/40 that may oxidize the back of your stainless foil.
B.E.

You are judged not by what you know, but by what you can do.

 

[Compositepro]

What is it that you really want to accomplish? Trying to bond aluminum to stainless foil does not sound like it will result in anything useful. Copper foil can be hard or soft. Even gold foil might be a better option.

I've got some zinc rods for aluminum repairs but have never had a chance to use them.

Here is a video of soldering aluminum to SS.

https://www.youtube.com/watch?v=xQOC2BwiJDU

 

[MikeHalloran]

Stainless foil in that thickness is sold for wrapping steel for heat treating.
It is thin enough to cut with very sturdy and very sharp shears, but it is still stiff enough to resist bending, and the sheared edges (as well as the unsheared edges) can give you nasty, deep lacerations.
I.e., it's a nightmare to work.

But I suppose you could pierce it in multiple places and fold the pierced metal over on the aluminum and crimp it, probably giving some conductivity for a limited time in a benign atmosphere. I think I have seen foil strips joined that way in high current applications, so there may be commercial tooling available.





Mike Halloran
Pembroke Pines, FL, USA

 

[asimpson]

Many thanks

 

[dvd]

How about starting out with thicker bonded material and drawing it to the desired thickness? The thickness of the stainless would need to be less than the thickness of the aluminum, possibly by the ratio of Young's moduli. Also, sort of seem like a roughened up stainless surface would let the aluminum flow into it during this process, and adhesive bonding might not be necessary.

 

[MikeHalloran]

Thanks dvd for refreshing my memory.
Stainless and aluminum can be bonded by explosive welding.
... at least at plate thicknesses.
... which leaves you the option of rolling the resulting bimetal to foil-ish dimensions, or calling the guys who are already doing detonation welding/ explosive welding, to find out how thin they can go.




Mike Halloran
Pembroke Pines, FL, USA

 

[EdStainless]

Either explosive bond or roll bond, how do you think that they make clad cookware?
That is all roll bonded SS/Al/SS.
You can start with medium thickness plate, they pickle it, stack, seal the edges while pulling a vacuum, and cold roll the heck out of it.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[MintJulep]

Have you considered vacuum PVD of aluminum onto the stainless substrate?

 

[racookpe1978]

1, In a vacuum, flash deposit (spray) the cladding onto the base foil. (I don't know the two metals well enough to determine which is the easier foil to work with as a base metal, and which deposits easier.

2. With a 3D modeling machine (again, probably in a vacuum) use the 3d system to deposit the 2nd metal onto the base metal foil. The base metal does not need to be 3D modeled, just the coating. If a full-sized CAD part can be built up one droplet at a time, then a single thin layer can get deposited to the required thickness if the base metal is clean enough.

 

[berkshire]

racookpe1978
If you are going to all that trouble , you could just electroplate it.
B.E.

You are judged not by what you know, but by what you can do.

 

[racookpe1978]

True.

 

[winstonsk]

Have you considered ultrasonic joining? You'd have to buy equipment for this, but it can form very reliable joints between dissimilar metals for electrical applications. It avoids many of the problems of oxide displacement because mechanical wipe during the ultrasonic vibration displaces surface oxides. It also generates relatively little heat.