Hi, I am Joyce, I have been doing prototype boards and small production runs for the last years and usually have very good results, but still struggle with 0.5mm QFP.
I use Loctite GC10 paste and reflow oven. The stencil is are stainless steel, both framed and non-framed. I have issues when placing parts by hand and also when using the PnP.
Way too many QFP need rework, I rarely encounter a single IC without a solder bridge.
For the boards, I use 4mil solder mask expansion. In theory, this should leave a 0.3mm solder mask strip between the pins. Hover looking at the bridging under the microscope shows the bridges are not necessarily at the end of the pins (where they touch the board) but often 'higher up' and closer to the IC. Too much paste?
I don't have the same problems with 0.5mm QFN..
Any suggestions on what I might try to optimize my process?
Thanks