It is common to see the resist expand during reflow soldering and then pop like a balloon I would not see it as a big deal unless the mask is solid and prevents the stencil contacting the surface of the pads for second stage printing of paste in double sided reflow. Bob Willis Electronic Presentation Services 2 Fourth Avenue, Chelmsford, Essex CM1 4HA. England. Tel: (44) 01245 351502 Fax: (44) 01245 496123 Home Page: http://ourworld.compuserve.com/homepages/bwillis Email: [log in to unmask]