used to solder millions of these years ago when i worked for pision, you have to be very quick on the centre bit, else you will damage it
I understand and there's no problem with it - it is covered with some film, that sucks most of solder from the iron in a split second. The base metal however is exactly opposite.
The back part is white? Or are you talking about the center part(i.e. does it look like the one in the video)? Again, I've never soldered these, but rolling off and jumping back to the iron sounds like it's not hot enough. I'm getting a new iron in a couple of days, and if you're not successful by then, maybe I'll take a crack at it. If jonisonvespa has soldered millions of them though, I'd ask him for help.
The base metal is white (like stainless steel). I cranked my iron to 450-460c and the result was the same, plus the solder started to cover with oxide film and flux just burned black on touch
That piezo is dead for sure now (hint - buy a lot of 'em)
Edit: Ok! Still need too many tries to get it done while it's alive, but at least there's hope, so guess it's matter of practice from now. The recepie is to set iron to 240-270c and drag quickly across disc. If the temperature is less the solder seems to solidify too quickly and not adhere at all. The higher the temperature the shorter is the moment you can drag, as if the disc gets above solder melting point it starts repelling solder like wax&water. Piezo should be clean, so better don't touch it too much.
After some bit of solder is stuck to piezo there's a chance of sticking the lead to it in the same manner. It's harder to stick the lead directly as slight movement while solidifying tears it off.
Tried "yellow" piezos - they seem to adhere solder about twice as good. But maybe it's just me.
Thanks for replies! Hope someone will find this useful