Hi Gents-

I just did a prototype for a fairly simple board which had reasonably sized
parts. Several 0402's and everything else was significantly larger.
Except....

Except for a 100 lead 0.4mm pitch QFP. Based on most of the parts being
pretty sizable, I selected a 125 micron stencil. I found I could get solder
down into the apertures for the QFP, but it was WAY too much solder, and it
was clear that if I made the apertures any narrower, they wouldn't print.
Also, with the 125 micron deposit, the deposits tended to short together
anyway with that pitch.

I recall from somewhere that I saw someone use apertures that went
crosswise to the QFP leads, so a QFP would only have 4 apertures, shorting
all of the pins together. But my recollection is that still worked because
surface tension pulled the solder deposits away from each other. (I'm sure
you have to make sure the volume is not on the high side, which would
result in shorting.) But when I searched for advice on QFN apertures on the
web, nothing came up on this.

Anyone with helpful experience in this area?

Thanks,

Wayne Thayer