I am using the smallest sized readily available lead paste I could find (15-25 micron size) and printing using a metal stencil with the smallest pitch being .5mm pitch qfns. Reflow is with a SMTmax oven, with max temp around 240C.
The problem I am having is leftover solder bb's, which can be washed off with denatured alcohol, albeit with difficulty. The joints seems secure, even though they don't look right. Adding flux and reflowing with my benchtop reflow doesn't reflow these bb's, even getting it much hotter than the oven.
Could this just be a bad batch of solder?
Is this typical of fine screen solder paste?