binding Au to stainless steel

[cosmicdust]

I am looking for a method to bind high purity (99.999) Au foil to a stainless steel substrate. We have tried the brute force method of scoring the stainless steel surface and pressing the Au, but this leaves the Au surface very rough (due to the roughened stainless steel surface). I am wondering whether it is possible for Au to form an alloy with stainless steel directly or by using an intermediate soldier. Ideally this would be done with relatively low T (< 260 C). Any advice is appreciated.

 

[btrueblood]

Why not just electroplate?

 

[EdStainless]

Would glue be acceptable?
You can solder. I would start by plating the stainless with Cu or Ni and then looking for a solder to use.

What shape are you working with? If you are working with strips of metal you could roughen the stainless (blast and piclkle) and the roll bond them. If the finish roll is polished you will get a good finish on the gold.

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[cosmicdust]

I should explain that we are making sample mounts for electron microscopy and mass spectrometry analysis. The Au needs to be high purity (99.999) - is this possible by electroplating?

Another requirement is that the binding agent is conductive, so glue is not acceptable.

The stainless steel substrates are 1 cm disks that are a few mm thick. The gold is 0.003"-thick foil cut into 0.1" wide squares. We us a sapphire plate to press the Au into the substrate.

 

[gaufridus]

I read somewhere, some years ago (say 10+) of a technique called "explosive bonding" where Al sheet was "joined" to a parent metal by holding/clamping the two pieces slightly apart over a container. An explosive charge in the container forced the Al to close bond with the parent metal. I don't know what became of the method but its just a suggestion you might explore, try a web search.

 

[NickE]

Sputter coating?

it might take a long time to build up .003" but it would be clean.

Nick
I love materials science!

 

[btrueblood]

Yes, a good plater, using clean fresh solutions and careful control of cleanliness (both parts and tanks/equipment) can achieve very high purity of deposited gold; but then we were satisfied at 2- or 3-9's purity for the optical properties. As Ed said, a typical process starts with a copper "strike" layer, followed by nickel, then gold plating. This is to ensure a good metallurgical bond (no blistering). The same sequence of layers may help in trying to form a diffusion (mechanical) bond using foil.

 

[EdStainless]

Platting will not be pure enough vor you. I tried it on sample holders for an X-Ray spectrometer.
You could gold plate and then mechanically bond. Work with 1/2" wide strips a foot long or so. Find a small rolling mill in a lab to use for the bonding.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[kenvlach]

Ed is right about electroplated gold purity -- the highest commercially available, for the semiconductor industry, is 99.95%.

I suggest polishing the SS strip, electroplating with nickel (no copper, just a Wood's nickel strike), then roll bonding followed by baking to improve adhesion.

Does the Au foil really need to be 0.003" thick?
If not, just gold coat the Ni-plated SS by evaporation.

 

[unclesyd]

Your answer might be here. I'm not familiar with the process but it sure looks good. I believe its worth giving them a call with your problem. You may be able to directly bond the gold to substrate.

I ran across this while investigating Nickel Aluminide as possible solution to your problem.

http://www.rntfoil.com/

http://www.llnl.gov/str/October05/pdfs/10_05.1.pdf#search="nanofoil"

 

[unclesyd]

Here is one of the RNT papers that has essentially your setup, a gold plated contact bonding to a copper plated PCB. I think any other metal will work. If that isn't possible you could go with the Au/Sn solder.

http://www.rntfoil.com/_assets/pdf/RNT-2004-Agilent.pdf#search="Au/Sn solder"

 

[GRoberts]

What about glue with metal filler so that it is conductive?