Hello Carl,
It's hard to give advise without seeing the design.
But, like Kathy, I strongly recommend another board finish.
Never seen a HASL that was flat enough for 16 mil pitch.
ENIG is what we use for fine-pitch applications.
Hope this helps a little.
Jowan Iven
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Carlr Ray
Sent: maandag 17 februari 2003 23:26
To: [log in to unmask]
Subject: [TN] 16mil QFP Process Issues
Hey Techneters,
I have a couple of questions you guys maybe able to help with (at least
I want some advice). The questions below pertain to some assembles I
will be developing some processes for in the near future. These units
have the following technology: 16 mil QFP, uBGA .65 mil and 1 mil pitch,
multiple PBGA 300+ ball count, PTH components (radial and axial types),
double sided, HASL surface finish.
1. For 16 mil QFPs and uBGAs .65 I would like to see a different
surface finish (Immersion Silver?). What do you guys think?
2. Solder Paste. I have used type 4 powder mesh size (-400+635) in the
past but not much success. Who has had success with type 4 and who was
the vender?
3. Stencil Apertures. I know the industry recommends 4 to 5 mil stencil
for this application but what other techniques have you "wizards" tried
in the past? I have tried step downs, dog bones, bow tie, home base
plate, 10% and 20% reductions and various combinations. My biggest
concern is developing the process and stencil around the 16 mil
component. I also have seen success with Nickle plated aps to aid with
release for the super fine pitched devices.
Thanks in advance guys and gals!!
Carl Ray
Sr. Manufacturing Engineer
Huntsville, AL 35807
Phone: 256-882-4800 ext. 8845
Cell: 256-990-1990
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