I was looking for an stencil design for a 0.5mm pitch uBGA. Pad size is 0.38mm in diameter. We have been using 5mil stencil with type 3 no clean paste. What size aperture should we be using? Any suggestions?
We've just set up a couple of products with 0.5mm pitch uBGA devices on them, i went for 5thou thick, laser cut nickel (to aid paste release) square pads same size as the diameter of the uBGA pads. Or you could go to a 4 thou nickel stencil, better paste release on this but you might need to switch to a type 4 paste as you'd get more metal in the apertures to make up for the reduction in paste volume if you've got some larger parts on the board. You could also use a stepped stencil but i'd be carefull with that, not so easy to work with.