Hi Ray,
The aspect ratios you mention are mostly for uVia technologies, and even
that is being addressed to get to more layers. I've done some deisgns in
the past using "mechanically drilled" (same technology as thru holes,
same drills) .010" FHS holes. I've done boards going from layer1 to
layer2; layer1 to layer3; and layer1 to layer5, all on the same board
WITHOUT going to uVias. I've dealt with many fab shops that could do
this, and the cost isn't outrageous either. I haven't run into a fab
shops lately that's quivered at my designs. I like the technique much
better than uVia applications, especially regarding costs.
Hope this helps.
Mitch
---------Included Message----------
> Date: Fri, 22 Jun 2001 08:14:27 -0700
> From: "Ray Humphrey" <[log in to unmask]>
> Reply-To: "DesignerCouncil E-Mail Forum."
<[log in to unmask]>, "Ray Humphrey" <[log in to unmask]>
> To: <[log in to unmask]>
> Subject: Re: [DC] Burried via hole
>
> A major concern for blind vias is the aspect ratio; typically,
.7:1 for most
> PCB fab shops that can do them. (Notice that's less than 1:1
compared to
> 10:1 and greater for standard TH vias.) So, you will be using
some very
> thin prepreg between layers. If you also have controlled
impedance in the
> 50 -75 ohm range, it's a challenge.
>
> You can download or otherwise obtain the DFM manual from most
fabricators.
> Select the ones you will be considering to build your boards and
become
> familiar with what they can/cannot do. A good resource is the
Resource
> Center at Merix, http://www.merix.com/main_res.html. You should
also
> discuss your needs with the fab shop's tooling and engineering
department.
>
> Best of luck!
>
> Ray
>
>
> -----Original Message-----
> From: DesignerCouncil [mailto:[log in to unmask]]On Behalf
Of
> Flatfield, Cadcam
> Sent: Friday, June 22, 2001 2:35 AM
> To: [log in to unmask]
> Subject: [DC] Burried via hole
>
> Hi,
>
> I am looking for design specifications for blind and burried via
holes.
> Also am i looking for design specifications for flex and rigid
flex.
>
> Thank you,
>
> Gerard Goossens
> Flatfield multi print
> Tel :0344-622556
> Fax :0344 613652
>
> -----------------------------------
> Mail : [log in to unmask]
> Website : www.flatfield.nl
> -----------------------------------
>
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