I would like to contribute Ray, but I have only had to use blind/buried vias
once in my life.
I can tell you from a design point of view in Veribest it is effortless, you
just state the range of layers for each via type, use vias wherever you want
(whatever type you need) and the computer takes care of the rest (multiple
drill files, fab dwg layers, etc)

Its not that I am reluctant to use them, I just rarely see a need (yet).
We are using 1mm BGAs on .093 thick boards with no problems with regular ol'
vias

But I have absolutely no idea how to evaluate the cost difference, since
there is no way to get a "multiple quote" on a design that would prove
anything. Can't you just ask a couple of fab vendors what to use as a rule
of thumb for cost-adders?

It IS interesting that absolutely no one knows this,
or is willing to share anything about it, hmmm?

Good Luck,
(onward thru the fog)

Jack

-----Original Message-----
From: Ray Humphrey [mailto:[log in to unmask]]
Sent: Saturday, March 31, 2001 11:47 AM
To: [log in to unmask]
Subject: [DC] Blind and Buried Vias


In a recent posting, Your Opinoin Needed - Designers Learning Symposium, I
notice that blind and buried vias were included in the 'newer technologies'
category.  I also find that most designers are reluctant to use blind and/or
buried vias, for various reasons.  Blind and buried vias have been around
for over a decade, they are not new.  I have a great article from the March
1988 issue of PCD magazine talking about the use of blind and buried vias
down to 2 mils in size!  I am frustrated that PCB fabricators are failing to
keep up with the industry they support and continue to charge excessive
prices for such an old process.  Much of today's technology require the use
of blind and/or buried vias - I say it is time for designers to get over
their paranoia and for fabricators to stop taking advantage of it!

Several days ago, I posted this question to the DC forum, "Could someone
please give me a general guideline concerning the additional cost of using
blind vias on a PCB?  Perhaps there is someone out there in the PCB
fabrication business or a fellow designer that has done some extensive
research into this?"  To date, I have not received a single response.

Isn't it time we stopped considering blind and buried vias as a 'new
technology'?

Just my rant - I feel better, now.  :)

Ray

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