Solder resistant plating

[BradC]

I have an Aoyue desoldering station. I make adapters for this that fits Hakko tips, and I generally turn this out of a bit of 1/2" copper bar. The problem is two-fold.

1) The copper oxidises badly, so I have to clean it every time I change tips; and
2) The solder sticks to the interior of the adapter and slowly dissolves it until it gets so thin it breaks.

I've made a couple, and I've been looking at plating but never thought it about it much more.

I initially thought about electro-less nickel plating, but nickel tends to be easy for solder to adhere to. So I'm fishing for ideas. Admittedly Nickel will stop the copper dissolving, but is there something else I can do at home that'll both plate the copper *and* reject the solder?

Anyone? McFly?

[Ian.M]

Could you use aluminum for the adaptor?

Most solder-resistant metals aren't at all easy to plate with.   It would be possible to chrome plate your parts (over the Nickel layer), but due to the high toxicity of chromium compounds, you should strongly consider sending them out to be plated rather than DIY.

[BradC]

Could you use aluminum for the adaptor?

It had crossed my mind. I have some ally bar somewhere. Certainly worth a try.

Most solder-resistant metals aren't at all easy to plate with.   It would be possible to chrome plate your parts (over the Nickel layer), but due to the high toxicity of chromium compounds, you should strongly consider sending them out to be plated rather than DIY.

I did think about Chrome plating, and I certainly have no intention of playing with hexavalent chrome or cyanide.

Might give the aluminium a try. I suspect given the difference in thermal expansion might require some adjustment in the dimensions.

[SeanB]

How about just using thin steel, and then treating the surface with phosphoric acid to create an oxide layer that will not be wettable by the solder.  either a iron phosphate layer, or simply blue it to make it relatively inert. Cheap, and you can do a few at a time, even make them from appropriate sheet bent to the right diameter, or slit thin wall tube.

[Gregg]

Titanium nitride coating would fit the application but may be expensive in small batches.

[Benta]

Professional solder/desolder tips are iron/steel with a copper core for better heat transfer. They hold up well.

[BradC]

How about just using thin steel, and then treating the surface with phosphoric acid to create an oxide layer that will not be wettable by the solder.  either a iron phosphate layer, or simply blue it to make it relatively inert. Cheap, and you can do a few at a time, even make them from appropriate sheet bent to the right diameter, or slit thin wall tube.

I don't think steel is going to give me the thermal conductivity required to do the job. The copper does work very well, it just doesn't last as long as one might like.

[bitter_mike]

Hi Brad,

Nickel plating is actually not a bad choice here. Freshly plated nickel is wetted by solder, but over time, it forms a rather tenacious oxide layer and passivates. This makes solder not stick to it. It's the same reason most steels don't solder very well. I would go for electrolytic nickel as opposed to electroless nickel. Electroless nickel deposits an alloy of nickel and phosphorus which is harder and more corrosion resistant, but it also makes the passivation process slower. SeanB's suggestion about the phosphoric acid passivation will also work on nickel, though I am not sure how resistant to flux it will be.

[David Hess]

Nickel plating with high phosphorus content repels solder very effectively but I am not sure how feasible it would be to do this yourself.

[tkamiya]

Whatever plating UHF plug (PL259) from Radio Shack was using, it was very difficult to solder.  Maybe someone knows what it was....  I had to file that off before it will take to solder.

[BradC]

Hi Brad,

Nickel plating is actually not a bad choice here. Freshly plated nickel is wetted by solder, but over time, it forms a rather tenacious oxide layer and passivates. This makes solder not stick to it. It's the same reason most steels don't solder very well. I would go for electrolytic nickel as opposed to electroless nickel. Electroless nickel deposits an alloy of nickel and phosphorus which is harder and more corrosion resistant, but it also makes the passivation process slower. SeanB's suggestion about the phosphoric acid passivation will also work on nickel, though I am not sure how resistant to flux it will be.

I might have a go at it. The reason I was looking at electroless nickel is being able to effectively plate inside the hole. The only way I could see to properly electroplating the bore would be to thread a tiny electrode through the middle and I was having issues imagining how that might work. With electroless I can just push fluid through it to allow the plating to occur.

I've started to think about things like heating the resulting product to 400 degrees and slowly pushing oxygen through the bore to accelerate building up an oxide layer, but now I'm getting ahead of myself.

Anyway, due to circumstances I'm now going to be 3,500KM away from my Lathe until November, so it's all theory up until then.

[bitter_mike]

The thickness distribution of electroplating is, as you say, no where near as good as electroless, but as long as there's electrolyte in there, you'll get some nickel to deposit. Just plate at lower current for longer. There's also the fact that mixing up a respectable nickel electroplating bath only involves 3 ingredients, whereas an electroless nickel bath is a substantially more complicated beast. If you need some advice on it, do reach out. Electroplating is one of the few things about which I am qualified to speak.