I am in the search of good flux. I have received IF 8300. It is not cheap, but if it is good then it is worth it.
The flux appears to be in a form of a very soft gel. It is so soft that it actually slowly flows when jar is tilted, so be careful.
As the manufacturer’s description states IF8300 has resin-like rheological properties. The odor is a little sweet. The odor actually resembles some medicine. It is completely halogen-free. It is not water soluble. PH is 3. It is considered to be “no-clean” flux and positioned as a BGA flux (which fact I simply ignore and plan to use for everything). People say that the residue is easily cleaned with Flux Off. Visually the flux resembles light liquid honey. Shelf life is 2 years (8300-4 and 8300-6 is 1 year). It is RE L0 type. Can be used with Pb and Pb-free soldering process. Suitable for manual soldering.
I have tested resistance of the flux using the device desribed in Solder Flux tester.
Open circuit voltage is 3.87V The test pcb is as before.
I have soldered the contacts using rosin flux, cleaned it thoroughly with flux-off and isopropyl alcohol. Then I have put a lot of non activated IF 8300 on the tracks and between.
Voltmeter showed: 3.87V
Then I have activated the flux.
Voltmeter showed: 3.87V
I have checked the device with another flux (TT): 1.3V right after activation.
Conclusion: the resistance of the flux in any state is at least more than the upper limit of the measuring device. This is really good! It really seems to be no-clean flux at least in a sense of resistance.
When touched with a solder iron the flux becomes liquid and flows very good. For normal usage one should put very little of the flux on the soldered surfaces. Surface wettability is excellent. Solder flows very good. The soldering iron tip retains its ability to pick solder. Odor is a bit strange. My wife said it resembles the camphor odor. It is a lot better than machine oil or alcohol smell. After soldering the flux remains in a little tacky transparent gel state. The best way to clean it is using FLUX OFF and rub it with a toothbrush or special cleaning brush, then clean what’s left with hot tap water and dry with a hair dryer. Isopropyl alcohol can also be used instead of FLUXX OFF, but the result is just a bit worse. Just hot water only spreads the flux all over the board. Soap or alike do not help either.
I have polished a piece of copper laminate, cleaned it and put activated and non-activated flux on two sides of it and put the piece on a shelf. We’ll see the result in 20 days.
It appears that I have the first candidate for the best and good-for-all soldering flux. I was a bit disappointed with tacky residue which absolutely needs to be cleaned, because dust will settle on it for sure. But what’s good is that it does not affect resistance. I also hope, that this residue will become solid after a while. We’ll see.
Economically this flux does not really cost that much. I have bough 30cc jar for 34$. Other good fluxes cost at least 8$ for 10cc. IF8300 costs around 11 for 10cc. But the main advantage is 2 year shelf life. I don't solder that much, so, I will not spend 30cc jar in a year, especially considering how little this flux must be put on the soldered surfaces. So, spending 34$ per 2 years is really not much.
Now I am waiting the result of the copper test.