Steve,

My $.02 on this subject:
There are MANY reasons I've seen for MicroVias. Here's just
a few.
1) Fine Pitch BGA. (Like CSP, FPBGA, DSP. Pitch's less that 1.0mm)
2) Via-in-pad.
3) Dropping a noisy clock/signal below a plane (to lyr 3)for EMI/EMC
   reasons.
4) Providing distributed plane capacitance right at the solder ball
   (no lead inductance which can degrade electrical performance on
    high speed devices)
5) Separating Logic types on the PCB.
   (Analog, Digital, RF, Control, or Microwave)
6) Connecting directly to planes for heat dissipation (or pwr)
   without "swiss cheesing" the plane(s).

That's just a few. It looks like when the PCB (or substrate) get's
greater than 130 Holes per square inch, then microvias (or
buried/blind vias) are necessary.

Groovy
-----Original Message-----
From: Steve Underwood [mailto:[log in to unmask]]
Sent: Friday, September 03, 1999 7:32 PM
To: [log in to unmask]
Subject: Re: [TN] Micro VIA's


Jim,

It seems there are quite a few fab houses doing the micro-via thing now.

Just out of curiosity, are the vias you are specifying finished
plated-through hole sizes?  These finished hole sizes can be acheived
through drilling with .008 to .0135 drill bits.  Do you have very thin
dielectric requirements?  Why are you specifying micro-via technology to
build these?

Steve U.

On Mon, 23 Aug 1999 15:49:41 -0600 Jim Kittel
<[log in to unmask]> writes:
>Fellow TechNetters,
>
>We are are moving into the assembly/design of circuit card assemblies
>using
>micro via technology and I need a lead on some PWB vendors that can
>fabricate boards with buried or blind micro vias.  These designs will
>require vias in the 0.004 to 0.008 inch diameter range with 0.004 inch
>trace
>widths.  I would like to find a supplier that can do the entire
>process in
>house.  The finish will be nickle/immersion gold, typically FR-4 or
>polyimide and we are talking small order sizes.
>
>Any ideas on who to contact?
>
>Jim Kittel
>
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