Spot annealing of beryllium copper

[murwood]

I have some custom printed circuit board battery holders made from beryllium copper and hardened for spring temper. After hardening the clips are nickel plated. The mounting solder tabs do not hold well enough and need to be bent over. Being hardened the tabs crack and break. Anyone have ideas on how to soften just the solder tabs? Tabs are about 0.25mm thick, 2mm wide, and 3.5mm long. Simple hand butane torch heating to dull red and water quench softens, but destroys the solderability of the nickel.

Anyone have some ideas?

 

[technocrat]

Flux the nickel

 

[blcksmth]

If parts can be removed, immerse in water leaving the tab exposed and heat until soft. Leave it be until cool.

Bob
WB8NQW

 

[Joe Gwinn]

With copper alloys, which are precipitation-hardened, one quenches to anneal.

I'd look at heat-treating data from such as Brush-Wellman.

https://beryllium.com/about-materion

 

[Modelman]

If you are having the clips made the obvious solution is to have them spot annealed before plating.

 

[murwood]

I had 500 pcs made off shore, at 1/10th the cost I was quoted in the States. Initial idea was to just solder the mounting tabs. Turns out solder is not enough, the joints crack and the clip pulls up. Flux alone (and I am talking acid based plumbers flux) is not strong enough to overcome the tin oxide formed when annealing.

The process I have worked out to anneal is a tray of water, with a slab of metal laying in it. Fill the water level up to the base of the tabs with the clips on their back on top of the metal slab. Light the torch (with a #0 tip), turn off the lights, heat until just starts to show dull red, then push clip off metal slab into deeper water to quench. This does soften enough so the tabs do not crack or break off when bent, but they are now un-solderable!

I have been polishing off the oxide and solder plating, but that is time consuming.

 

[trevj]

With copper alloys, which are precipitation-hardened, one quenches to anneal.

I'd look at heat-treating data from such as Brush-Wellman.

https://beryllium.com/about-materion

My understanding was that the heat cycle anneals (solution heat treatment) the quench locks the material in it's annealed state, and artificial aging/precipitation, was used to return it to hardness.

I wonder at using a spot welder or similar high current,low voltage source as the heat?

Seems I saw a battery terminal welder made with a Rasberry Pi microcontroller used to control the timings to rather a fine degree.

Also seems to me that you might get a second order, made the way you need, with less dicking about with the fiddly work.

Could you brush plate anything on them that will stay, and that the solder will stick to?

 

[Peter from Holland]

I had some luck with flux for SS for soldering oxidised materials

 

[mnl]

The danger with that is SS fluxes are highly corrosive and if not completely neutralized can cause problems down the line.

 

[Joe Gwinn]

My understanding was that the heat cycle anneals (solution heat treatment) the quench locks the material in it's annealed state, and artificial aging/precipitation, was used to return it to hardness.

I'm not a metallurgist, but that sound right to me.

I wonder at using a spot welder or similar high current,low voltage source as the heat?

Seems I saw a battery terminal welder made with a Rasberry Pi microcontroller used to control the timings to rather a fine degree.

Could be. So long as the temperature curve is what the manufacturer recommends, it makes little difference how that curve is achieved.

Also seems to me that you might get a second order, made the way you need, with less dicking about with the fiddly work.

Second order?

Could you brush plate anything on them that will stay, and that the solder will stick to?

I think that clean BeCu alloy is easily soldered. If rosin flux fails, try plumbers grease flux. If that fails, tinner's or stainles-steel flux. In all cases, clean the flux residue of, and then wash the workpiece with hot water. The corrosive stuff is all water soluble.

 

[mnl]

BeCu solders beautifully, it sounds like the plating doesn’t. It will probably need an active acidic flux. The best bet is to neutralize with baking soda as part of the rinse. Also don’t solder near anything you card about. The micro-spatters travel an amazing distance.

 

[mnl]

Another question, are you trying to solder with SAC (lead free) or good old PbSn solder. SAC is much more brittle.

 

[cyanidekid]

"acid based plumbers flux" sounds like soft solder flux, that's not going to work at the temps annealing requires. in fact I think it breaks down the zinc chloride into nasty gases and evil vapors like hydrochloric acid and maybe chlorine gas.
a borax based brazing flux like "handy flux" is what you want, but it forms a glass like coating (that's how it works). that requires boiling off. t also pulls away if you overheat it and gets even harder to remove, as anyone who has silver "soldered" can attest.
not sure it would even work with your setup, the water boiling adjacent to the tabs will strip off the flux before it gets to annealing temp.
I think you'r just stuck cleaning them up after
. a scotchbrite wheel should clean it up in a few seconds without taking too much metal away if you choose the right grade.

 

[jim rozen]

Probably the acid based flux being discussed is muriatic acid. AKA tinner's fluid. It's muriatic killed with Zn.

 

[Joe Gwinn]

Probably the acid based flux being discussed is muriatic acid. AKA tinner's fluid. It's muriatic killed with Zn.

Yes, exactly.

 

[mnl]

Like RubyFluid stainless flux. Superior makes another flux that was better for tin.

 

[trevj]

I'm not a metallurgist, but that sound right to me.


Could be. So long as the temperature curve is what the manufacturer recommends, it makes little difference how that curve is achieved.


Second order?


I think that clean BeCu alloy is easily soldered. If rosin flux fails, try plumbers grease flux. If that fails, tinner's or stainles-steel flux. In all cases, clean the flux residue of, and then wash the workpiece with hot water. The corrosive stuff is all water soluble.

Re: Second Order. He said he sourced these cheap overseas, IIRC, he said it was a fraction of the price.

Which leads me to suggest re-ordering and making the required changes. Loses some time, but still cheaper than ordering locally. And avoids a lot of fiddly hand work.

 

[murwood]

The flux I am using is acid based plumbers flux, and I am cleaning the PCB well after! Solder used is good old 37/63 BpSn. I love that lead free junk, keeps me in business repairing failed equipment due to the solder cracks....

Also the no clean flux, love the way it becomes conductive over time if there is any moisture present.

After I polish off the tin oxide I can solder the tabs, I was looking for a way to get the oxide off without all the polishing.

The Borax based fluxes I have looked at work at much higher temperatures than used in soldering PCBs. I use a 700 deg F tip, borax fluxes generally are for 1200-1400 deg F temps.

 

[murwood]

Just had a brain fart moment... The parts are nickel plated, not tin plated. I need to find a local source for a nickel oxide remover.