Voltage is just one factor in a half dozen or so contributors to CAF.

For example, you’re not out of the CAF woods with laser ablated microvia
holes, a poorly designed or executed siloxane process will still rear it’s
ugly head leading to glass/polymeric separation, mechanical drilling or
not.

On Thursday, September 5, 2019, Dwight Mattix <[log in to unmask]>
wrote:

>
> Anyone here running uVia CAF test vehicles?
>
>
> Bev,
> Thanks for that prompt reply/acknowledgement.
>
> In  our uVia area it has mostly been in shorter life, lower voltage apps
> (e.g. high end consumer, engineering ref designs etc) as compared to the
> days when we both played Base Station games (has it really been that
> long?). Those applications  allowed room to be casual (dismissive?) of CAF
> concerns in the uVia pwb.
>
> Now these uVia apps are finding their way into critical use case, and long
> term high availability, higher sustained temp/duty cycle applications that
> call for IMHO more attention to CAF now.  (Automotive, infrastructure)
>
> CAF risks in uVias has the advantage of laser ablated vias vs. mechanical
> drilling disruption of the laminate.  But the uvia drill edge to drill edge
> spaces run much tighter than in a mechanically drilled pwb. So…
> Then there's the voltages involved which tend to be lower and lower and
> would it seems work to reduce the CAF risks than in our bad old days with
> PTH only designs for infrastructure on  BUTS pwbs (big ugly thick suckers).
>
> re: Certainly for the materials, construction and suppliers used in those
> two projects, stacked microvias were not as robust as staggered.
> Yeah I/we have a bit more experience than the average bear with respect to
> uVia stacking (and uVia stacking on core vias).  We were early, very early,
> adopters -- some would say pioneered even.  Living on the leading node of
> pitch and pin count (and frequency/radio complexity) will do that to you.
> :)   In any case,  have a pretty good understanding of that Z-axis part of
> it;  where to put limits in design; and how to test/qualify/demonstrate
> reliability for our use case.
>
>
> -----Original Message-----
> From: [log in to unmask] <[log in to unmask]>
> Sent: Wednesday, September 4, 2019 3:43 PM
> To: 'TechNet E-Mail Forum' <[log in to unmask]>; Dwight Mattix <
> [log in to unmask]>
> Cc: [log in to unmask]
> Subject: [EXT] RE: [TN] CAF in a uVia world
>
> Dwight,
> Thx.
>
> After BlackBerry ceased making devices and sold off my lab by auction ☹, I
> went to run the CALCE Lab at the University of Maryland, but for a variety
> of reasons I was not happy there and resigned after four months and came
> home to Canada.  The last couple of years I have worked part time as a
> project facilitator for the High Density Packaging User Group, an
> electronics industry research consortium of about 50 companies.  So, I
> personally or through HDP, have not done any CAF testing on what you label
> ELIC. HDP does have two CAF projects, one looking at developing a new
> standard coupon that will be offered to the industry and another project
> looking to develop a new CAF equation.
>
> With regards to stacked microvias, HDP has completed two other projects
> (presented at SMTAI in 2017), is trying to start a third and is keeping a
> toe in the pool of the microvia turmoil that the IPC is trying to corral.
> Certainly for the materials, construction and suppliers used in those two
> projects, stacked microvias were not as robust as staggered.
>
> Regards,
> Bev Christian
> Project facilitator
> HDPUG
>
>
> -----Original Message-----
> From: TechNet <[log in to unmask]<mailto:[log in to unmask]>> On Behalf Of
> Dwight Mattix
> Sent: September 4, 2019 4:42 PM
> To: [log in to unmask]<mailto:[log in to unmask]>
> Subject: [TN] CAF in a uVia world
>
> Nice to see Bev back in the mix so I admit this post is mostly a bit of
> trolling for his input. :) But I know there are other veterans of the CAF
> wars so...
>
> For those of you working with full stacked uVia designs (aka ELIC: Every
> Layer Interstitial Connection) what have you done in terms of CAF testing?
>
> Use one or more of the standard IPC CAF thru via coupons with the hole
> edge/hole edge spacings down to ~10mils and call it good enough?
> Or do you go to custom CAF test vehicle designs that reflect the uVia
> stack and (tighter) spacing that is typical of uVia designs?
>
>
>

-- 
Bhanu Sood
Tel: (202) 468-8449