158C ROHS solder paste, SP-50

[Emil]

Does anyone have experience with the SP-50 solder paste from Relife/Sunshine? Or the newer SP-X which appares to be the same product(?)

Why do I care? Because it's much nicer running the reflow oven 70 degreees colder than I need for SAC305. Less smelly, shorter cycle time, less chance of damaging connectors etc. On the other hand the melting point is not low enough to be a problem in most cases.

I have tried SP-50 and has a few observations:
-The melting point of 158C appares to be correct.
-It produces nice shiny joints when used with ENIG, similar to 63/37.
-Uneven joints when used with leaded HASL.
-It's strong, in my test the copper came of the board before the solder failed. Also not brittle.
-The shelf life appares to be short. Old paste becomes dry. If I mix with extra flux leaves unmelted solder balls around the joints.

And a few questions:
-Does anyone know what's in this paste?
-Does anyone know if it's really ROHS compliant and not some mix of lead or something even worse.
-Anyone got good results with this paste when it's more than a few months old? If so, how?