From a fabrication stand point, microBGAs are finding
their way into more and more of the designs we are seeing.
They do challenge our capabilities. The flash memory stuff
is more moderate at .75mm and .65 mm pitch with lesser
I/O. The DSP stuff at .5mm pitch is real fun. Some of those
with higher I/O are being designed in with micro vias. These
are pushing line widths into the <.004" range. I have built down
to .002" so far. Have heard discussions down even smaller.
WhoooooHooooo. Those are a REAL CHALLENGE!
Micro Vias (blind versions) are generally in the .006" range
or less. Some techniques are in the .008" range. They can
made with some newer approaches/equipment. As mentioned,
IPC has a Conference fully focused on this. As far as the uglies......
These approaches are proving themselves with ATC. Typically
the aspect ratio is <=.7:1 (.5:1 preferred). For the laser drilled
approach,
success had been done using resin coated copper, woven FR-4,
aramid fiber, thermoplastics (film based dielectrics), screened on
or coated pure resins. Comingling....yep. It's being done.
Some other techniques to produce the blind (micro) vias are plasma
generated, photo defined, and electrically conductive polymers.
(I'm sure I forgot a few......sorry)
Assembly......can't help ya there. I know the CSP guys got it down.
Some assemblers are doing great jobs too. Maybe they can elaborate
some on this.

This is a hot topic. I'm sure more feedback will also accompany
this.


The above comments are of my own opinion, and
not necessarily that of my employer.

http:\www.hadco.com:8080

Dave Hoover (aka, Groovy)
NPI Mgr HADCO TC2
Watsonville, CA

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From: Dhawan, Ashok <[log in to unmask]>
To: [log in to unmask]
Subject: [TECHNET] FW: [TECHNET] microBGA's and CSP's