My main concern was you trying to get a refund for flux because of it not meeting the claimed conductivity specs, even though you hadn’t reflowed it. That’s not fair unless they specifically said it was nonconductive in a non-reflowed state.
That's 50/50, I would say. They never said that a full reflow profile was required for the loss of conductivity, either, and they advertised the flux as purposed for general repair work. Many other fluxes with similar claims have resistance on the order of gigaohms before heating, and that sounds fair and reasonable to me. Obviously I will prefer those over the more conductive ones.
These two, however, conduct in megaohm range, and that's a completely different story.
It’s only whatever flux has flowed far away that is of concern.
That's the point. Unless you heat entire board, you can't guarantee that the still conducting residues do not get trapped in some high impedance circuitry where it can cause trouble. I agree that it's not very likely, especially with almost exclusively digital circuits like laptop or smartphone boards, but it may be an issue with sensitive analog devices.
You should reconsider. Reflow in an oven is exceedingly efficient. (And practically mandatory for many modern packages.) A simple $50 toaster oven is enough for basic use.
I don't doubt that. I just won't have any use for it. I don't do repairs, I don't assemble complex boards (or any boards for that matter) on a regular basis. I mostly make one-off devices to try one idea or another, implement something that is of interest to me at a particular time, basically just what a hobbyist does.
You make it sound as though that’s some crackpot theory… No, it’s how no-clean fluxes are designed to work.
However, I would be leery of your proposed methodology, because it’s quite possible that it wouldn’t heat it evenly enough to draw any conclusions.
As I mentioned, it was an idea of a quick and dirty test to get a first rough estimate. It actually worked: I confirmed that heating at least one particular flux greatly reduces its conductivity. It was reduced in all areas that were heated to different temperatures.
Of course, proper testing would require a more complex setup with a corresponding reproducible temperature profile and a board (or whatever) designed to retain a given initial amount of flux in place as it's being heated to be able to measure it in a controlled and reproducible way.
And considering this:
Remember: there are TWO temperature thresholds to reach. The first (lower) one activates the flux, the second (higher) one neutralizes it again. If you heat to a temperature that reaches the activation temperature, but not the neutralization temperature, it may be left in a more conductive, more corrosive condition than the unheated state! So the only fair test of this “claim” is to actually get it hot enough to melt solder, since that’s what it was designed for.
...I don't think I'm gonna be bothered. It's calling for a much more complex test setup that I'm willing to use, and that, in addition, would serve no purpose for my practical application of fluxes.
Yes there is a certain probability that a comparison of unheated fluxes cannot be extrapolated to the same fluxes heated partially or fully. This is a disclaimer that has to be made.
Empirically, however, I've been observing, so far, that partially heated or fully heated fluxes are not worse than unheated ones, and if that is true, then testing unheated fluxes represents the worst case scenario, which I am happy with.
If someone wants to extend testing to partially and fully heated fluxes, it will be wonderful. But not me... at least for the time being :).