aggressive flux electrical HELP !

[Tmoose]

We have to solder a large assembled crimped connection. 2-2-0 Stranded copper and nickel tin plated crimped lug.
The common electrical fluxes aren't getting us the wetting we need. Any suggestions ? We can do some cleaning and soaking afterwards.

 

[itsmoked]

Ow! I feel for you... When a joint decides against soldering it becomes nearly impossible. The best bet is to try to make sure its going to go the first try.

You do this by CAREFULLY dipping the prepped wire in a solder pot to "pre-tin it" Then pre-tin the inside of the connector barrel by soldering it or dipping it too. Then assemble the joint and crimp it. Next heat it with a large "soldering copper" [hundreds of watts] like what was used by roof gutter people. Or you can use a torch but only out on the end of the connector. The whole key then is to wait until ALL the pre-tinned stuff is fluid before adding more solder. Use the Weller yellow rolls of solder which is the most aggressive flux[not the water soluble stuff]. One warning: if you use a solder pot where a full shield because if there is any moisture in the cable the lead pot with explode[steam explosion].

 

[ScottyUK]

Nickel is not that easy to solder using resin based fluxes. You will need a fair bit of heat and an active flux. Most of the water-washable electronics fluxes are pretty aggressive, but you must get them off afterwards. Nickel is a common plating material in some areas of electronics. Some of the plumbing fluxes are really powerful: you need to find the non-resin based ones. Again you will need to clean it up afterwards. If all else fails, there are products like Baker's No. 3 Fluid for metalworking purposes but they are really corrosive so I'd leave this as a last resort. It would be really tricky to clean it all from a stranded conductor.

Anyway, why aren't you crimping the lug on? Soldered joints are usually weaker because the solder wicks up the copper and makes it rigid causing high stress in the material when the conductor bends.



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One day my ship will come in.
But with my luck, I'll be at the airport!

 

[itsmoked]

Tmoose Scratch the "Weller" comment I should have said
>-> Kester "44" Rosin Flux.

 

[itsmoked]

ScottyUK he might be doing boat work.. Often in that case joints are soldered for corrosion resistance.

 

[jraef]

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[itsmoked]

Me too.. I'm often astounded.

 

[ScottyUK]

Never throught of marine applications - better add me to the list of amazed people!

When I worked in the electronics industry we considered the rosin fluxes as relatively passive for 'easy' jobs. Most rosins are able to remain on the circuit after soldering i.e. they are 'no clean', whereas most water washable types of the day were really aggressive to the components and absolutely had to be removed. The water washable fluxes were much preferred for soldering awkward materials, but there was / is a lot more specialisation in the WW fluxes making them very good for certain materials or combinations and virtually impotent for others. We used a WW flux for die-substrate attachment on a line making integrated power modules for VSDs. The Direct Bonded Copper substrate was nickel plated, and I forget what the die metallisation was. We needed very low voiding beneath the die to prevent thermal fracture of the silicon so a high performance flux was required. Other processes at the plant were migrating over to WW technology as the CFC regulations gradually banned our flux-removing solvents of choice. Once the processes settled down the results were actually better than they had been in the good old days of Chlorothene, Trichloroethylene, Methylene Chloride et al.

I had a play last night making joints between a nickel plated housing for a thick film hybrid and a bit of copper wire. Heat was from a propane torch. I tried using both a rosin plumbing flux and a WW plumbing flux. The latter was Fry's Powerflux and it was far superior in both the profile of the finished joint and the ease with which it was established. Although I didn't measure it, I'm certain the highly active WW flux allowed the joint to be made at a lower temperature too. To crudely identify the fluxes, rosin-based flux is typically a light brown colour, while the WW fluxes are often pure white pastes. Pop the lid off some in the hardware store or plumber's merchants.

Multicore Solders - now part of the Loctite group - used to have an extremely knowledgable technical department. If you are really stuck you could contact them.


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One day my ship will come in.
But with my luck, I'll be at the airport!

 

[itsmoked]

ummmm Let me get this straight... You were using a TORCH on a thick film hybrid???!!

 

[ScottyUK]

Yeah, don't you make 'em that way? We always did.

It's an old housing for a military hybrid intended to mount to a heatsink. I think it was a single phase bridge driver from memory. I've got a collection of all manner of wierd crap built up from past employers that is in the 'useful one day' pile! The housing material is Kovar -an iron-nickel alloy - which has expansion properties which closely match alumina (hybrid substrate material), but Kovar is nary impossible to solder to and it rusts so the housings were plated with either gold or nickel. I just thought I'd try a practical experiment for the benefit of Eng-Tips!



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One day my ship will come in.
But with my luck, I'll be at the airport!

 

[itsmoked]

All the thick film hybrid's I've ever worked on were the size of postage stamps...

You know what "I" would do faced with your task? I'd get out my TIG welder and set it to 5 or 6 Amps.