I've been finding from day one that adhesion is a challenge. Less so with reflow so long as the flatness of the pad enables good surface contact (although if the pad isn't flat then even simple items like 0602 resistors can have a very fragile bond). I've struggled with through-hole hand soldering but have been able to squeak by more or less. That was with the old solder wire.
Am trying out the new wire and am completely striking out. I cannot get it to wet onto a pad to save my life. The pad may as well be mask as far as the solder is concerned. I've tried adjusting temperatures, more flux, less flux, no flux (for tinning the pad). Nope. The solder globs up on the wire but is seemingly repelled by the pad.
I've tried turning my iron as low as it will go (150C) and the solder does seem to just barely flow at that temp. But the pads from the practice board look as though I used too hot an iron (and I most definitely did not apply heat for too long: 15-20 seconds at the very most):
The pads in the pic look white but that's the fault of the lighting and smartphone pic. They are silver and well-burnished. But you can see the results of my failed attempts (this is only three of many more). I can get the pad to barely tin, if at all, and the solder simply doesn't fillet around the wire. The topmost attempt had looked like it might work but broke with the slightest bit of pull on the wire.
What gives? I am still using my original ink cartridge, but it dispenses well and seems to cure and burnish just fine. I'm finding that I almost always having to use a new nozzle, which is a bit frustrating.
I love the concept of this device, and the silver-on-green boards look way purtier than the milled copper boards I've been doing with my Othermill. But if the ink won't take solder, or if it requires such a gentle touch that an entire board is scrap due to one failed pad, then I really have to think hard about the amount of effort I can put into mastering it.
That said, it does work very well for paste dispensing, and would be worth keeping around just for that . But I have yet to experience a smooth end-to-end workflow using ink.