I believe plumber's flux is typically based on zinc chloride. I always have to laugh when I pick up my tin of it from my plumbing kit and the can is labelled "no-corrode" and the can is almost rusted out(!). I think the chloride ions are pretty aggressive and can corrode metal if they are not completely removed. The key word is "completely". It is perfectly legit to solder boards with acid based fluxes ∗if∗ the cleaning is very very controlled and rigorous. For small board runs in non-industrial settings, mildly activated rosin flux is the safe way to proceed, IMHO. As I understand it, rosin has the desirable property of being active when melted, but basically traps the flux ions so they can't flow and corrode when it is cooled and is solid. This discussion always leads to "clean the rosin off" or leave it in place debate. I was taught to leave it in place...that cleaning it could lead to freeing the additives that "mildly activate it". For very sensitive work, there is so called "water white" rosin core...but without the activation ingredient(s), it requires virtually no oxides to be effective. Bottom line: if you use a "no corrode" plumber's flux, clean, clean, clean...
--- In Homebrew_PCBs@yahoogroups.com, "Rick Sparber" wrote:
>
> Wanliker,
>
> I'm trying to understand where the flux ends up after soldering. I scrub the
> bare copper with a 3M pad to remove oxides, brush it with plumber's flux,
> and then coat the board with solder. I would think that there is no flux
> between the copper and the solder. So if I then scrub the coated board with
> alcohol to remove the flux, wouldn't that be the end of it?
>
> Do understand that I am not using plumber's solder, just the flux. Maybe you
> are talking about acid core solder which IS nasty stuff.
>
> I agree about the lead free solder. I stick with 60/40.
>
> I remember and built Heathkit, Allied Radio, Lafayette, and Etco. Wonderful
> education and great products. But then, I'm just a kid at 62...
>
> Rick
>
> -----Original Message-----
> From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
> On Behalf Of wanliker@...
> Sent: Sunday, January 13, 2013 10:40 PM
> To: Homebrew_PCBs@yahoogroups.com
> Subject: [Homebrew_PCBs] Re: No HASL
>
> I have been reading comments abut plating circuit boards and types of fluxes
> used. I have always been told, and firmly believe that the only flux to
> ever be used on a PC board is Rosin, and I have seen the corroded results
> of plumbers solder. But remember I started before the Lead free solders,
> so I don't have anything to say about those materials.
>
> It has been years since I made PC boards, but for 55 years, I repaired them.
>
> The only solder I will use on any PC board, is about an .030 solder with a
> rosin core. the small diameter is easy to handle, and control the amount of
> solder being deposited. I will admit all of the solder I still use, and
> still have is a LEAD based solder. I absolutely hated the non lead solder.
> When I tinned the traces, I was usually repairing a broken or burned trace,
> and would deposit a nice thick film of solder for the extra current carrying
> ability.
> At times I would drag a piece of Solder wick with my iron on the top and it
> would leave a nice clean trace, as the wick filled up I would feed in more
> wicking under the iron, at times I would have 1-2 inch piece of wick
> saturated with solder.
> If you want to use just plain copper braiding, flatten it, then drag the
> braid across a piece of rosin, and it will absorb solder much better.
> I would use a wedge shaped iron, and the results would be a nicely tinned
> trace that was shiny, which is an good indication that it is clean.
>
> Just a bit of thought from a 77 year old man. To show my age, I taught all
> of the Fire control systems on the F-100, later I held a 2 nd Class FCC
> license when it meant something, and passing that test was an indication of
> your technical knowledge.
> I had been working for years before CB's came out. It was an exciting time,
> with Heathkit, Allied Radio, Lafayette, and many others all offering kits.
> I have a Lafayette KT 320 4 band radio I built in Nov 1963 from a kit.
> I was doing an alignment on it, when the first station came in with the
> announcement of Kennedy's Assassination. What a shock, no more alignment
> that day, stayed glued to that one station. PS, it still works.
> Enough rambling,
> oldman
>
> But that was Then, and we are here Now.
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
>
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