Hello,
 
I am wondering what are your experiences with the requirements on HASL finish
on 0.5mm PAD pitch devices. We have observed that variations in HASL finish
height will cause either opens or shorts on the 0.5mm pads. The shorts may be
attributed to having a poor gasket seal between the PCB and screen print
stencil. This seal is poor because of the variation in HASL finish within the
same footprint when using no snap off. During the screen printing process, the
solder paste tends to leak out the sides of the footprint and may result in PAD
to PAD shorts after reflow. We also experience opens again due to variations in
HASL finish height. We find that problems occur when PAD to PAD solder level
finish variation within the same device footprint is in the order of 400 micro
inches. We are putting down 6 thou of solder paste.
 
Has anyone out there had similiar experiences?
 
Rgds,
Tony.
(Supplier Quality Engineer PCB's).