>>> [log in to unmask] 02/17/03 04:25PM >>>
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?
** Agree HASL is not the finish you need. I like ENIG over silver.
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?
* Can't help there we have never had to resort to a grade 4 powder.
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.
* Haven't seen step downs used much anymore. The circuitry is too tight to allow the space on the stencil for a proper step down. For Fine pitch we have had good success with apeture width reduction and length elongation to keep the volume needed.
Not a lot of help but it's Monday!!!!
Kat
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<DIV><BR><BR>>>> [log in to unmask] 02/17/03 04:25PM
>>><BR>Hey Techneters,<BR>I have a couple of questions you guys maybe
able to help with (at least<BR>I want some advice). The questions below pertain
to some assembles I<BR>will be developing some processes for in the near future.
These units<BR>have the following technology: 16 mil QFP, uBGA .65 mil and 1 mil
pitch,<BR>multiple PBGA 300+ ball count, PTH components (radial and axial
types),<BR>double sided, HASL surface finish.</DIV>
<DIV><BR><BR>1. For 16 mil QFPs and uBGAs .65 I would like to see a
different<BR>surface finish (Immersion Silver?). What do you guys think? </DIV>
<DIV>** Agree HASL is not the finish you need. I like ENIG over
silver. </DIV>
<DIV><BR>2. Solder Paste. I have used type 4 powder mesh size (-400+635) in
the<BR>past but not much success. Who has had success with type 4 and who
was<BR>the vender?<BR></DIV>
<DIV>* Can't help there we have never had to resort to a grade 4 powder.
</DIV>
<DIV> </DIV>
<DIV>3. Stencil Apertures. I know the industry recommends 4 to 5 mil
stencil<BR>for this application but what other techniques have you "wizards"
tried<BR>in the past? I have tried step downs, dog bones, bow tie, home
base<BR>plate, 10% and 20% reductions and various combinations. My
biggest<BR>concern is developing the process and stencil around the 16
mil<BR>component. I also have seen success with Nickle plated aps to aid
with<BR>release for the super fine pitched devices.<BR></DIV>
<DIV>* Haven't seen step downs used much anymore. The circuitry is too
tight to allow the space on the stencil for a proper step down. For Fine
pitch we have had good success with apeture width reduction and length
elongation to keep the volume needed. <BR><BR>Not a lot of help but
it's Monday!!!! </DIV>
<DIV> </DIV>
<DIV>Kat<BR></DIV></BODY></HTML>
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Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
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