A recent blog pot in IPC website clarifies the confusion over the
definition of Microvia

http://blog.ipc.org/2014/01/10/new-microvia-definition-seeing-broader-usage/

*New Microvia Definition Seeing Broader Usage*

*In 2013, IPC changed its definition of a microvia. Before then, a microvia
was defined as any printed board with holes that have a diameter of equal
to or less than 0.15 mm [0.006 in]. Over time, that size became common,
while more challenging geometries emerged to alter the definition of
microvia structures.*

*IPC decided it was pointless to continue setting strict size parameters
that would need to be updated continually.*

*Now, microvia structures are being defined by the aspect ratio of a hole,
which is the ratio of the length or depth of a hole to its preplated
diameter. This approach acknowledges that a hole diameter of, say 0.10 mm
[0.004 in] will be challenging to adequately plate with copper on a
10-layer board (high aspect ratio), while the same size hole will be
comparatively easy to plate if the board has two layers (low aspect ratio)
that use the same materials in the 10-layer board.*

*This definition has until recently been found only in IPC-T-50K, Terms and
Definitions for Interconnecting and Packaging Electronic Circuits,
published in June 2013. The new definition is now being phased into printed
board design and performance standards. IPC-6013C, Qualification and
Performance Specification for Flexible Printed Boards, published in
December 2013, is the first to cite this definition.*

*This year, additional standards and handbooks will migrate to the
revision. That will make life simpler for companies that want to
differentiate microvia capabilities and requirements as technology
continues to evolve.*

Again its best to talk to your fab house to make sure if they align to the
same or not.

-Ragesh.


On 14 March 2014 15:09, Nagaraj Shanmugam <
[log in to unmask]> wrote:

> Experts,
>
> I ran into misunderstanding often on via classification on PCBs  and like
> to have clear understanding on this forum.
> As layout designer I classify vias
>         - based on drill depth as Blind via(external to internal), Buried
> via(with in internal) and through hole via (external to external).
>         - based on via stack as Stacked via(Blind/Buried vias placed at
> same locations) and staggered via (blind/buried via placed apart may have
> pad overlaps)
>
> I am fine and clear up to hear.
>
> Now, as I discuss with latest technologies /package
>         - on tighter pitch BGAs say 0.4mm pitch BGA's the VIP(via in pad)
> come into role and need via filling.
>         - high power ICs with thermal pad which needs thermal vias for
> heat dissipation, these via need plugging
>
> Here the discussion starts with Fabricator's and lead to misunderstanding
> on via definitions
> - They call  Microvia to plate and shut copper
>         What micro via means?
>                 a) Some refers to  Blind via but with limitation in the
> depth that the can only go one layer down from external layers with drill
> size less than 6mils.
>                 b) some inform they are Via in Pad using blind vias which
> is of drill size 6mils and less
>                 c) some refers to any via of drill size less than 6mils
> and is laser drilled called Microvia and the via doesn't matter
> blind/buried/through hole
>                 d) few other says its HDI(- High density interconnect) via
> and this includes Blind and buried but not through hole via
>
> I am totally lost here - Please help to understand the via terminologies
> in Fabrication world specifically Microvia.
>
> Thanks in advance for your inputs.
>
> Thanks,
> Nagaraj.
>
>
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