Hi Carl! Here are my responses:
1. For 16 mil QFPs and uBGAs .65 I would like to see a different
surface finish (Immersion Silver?). What do you guys think?
*** I would highly recommend not using HASL. That leaves you with multiple
options:
Immersion tin, immersion silver, ENIG. All three alternatives are being
used with good
success by large numbers of assemblers. My favorite is immersion silver but
all three
finishes are tools to have in the tool box. You need to look at each finish
and see
which one best fits your manufacturing flow.
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?
*** We use type 3 paste and have no issues. In fact we just finished a DOE
on paste
deposit for 0201 components and found that the type 4 paste did not gain us
any advantages.
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.
*** Step stencils? Yuck, never liked trying to use those creatures. A 5 mil
thick stencil
and a 1:1 aperture has been shown to successful for many assemblers. Using
laser cut apertures
will also improve the stencil deposit consistency.
Good Luck!
(time to raid Doug Paul's Mt. Dew supply!)
Dave Hillman
Rockwell Collins
[log in to unmask]
Carlr Ray
<Carlr.Ray@SANMIN To: [log in to unmask]
A-SCI.COM> cc:
Sent by: TechNet Subject: [TN] 16mil QFP Process Issues
<[log in to unmask]>
02/17/2003 04:25
PM
Please respond to
"TechNet E-Mail
Forum."; Please
respond to Carlr
Ray
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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