I usually use rosin flux for soldering or one with rosin core if the solder refuses to stick. I recently found this Goot BS-15 flux, but it says not applicable to PC boards. The label says hobby use soldering paste.
Unfortunately, the contents everything on the back of the container is in Japanese so I can't know for sure what this is intended to use for.
So,has anyone here come across this type of soldering flux and know what this might be used for?