YES!
(ok, I'm smiling... thanks for the response, Dwight)
On Mon, Mar 5, 2018 at 11:59 AM, Dwight Mattix <[log in to unmask]>
wrote:
> Oh sure, just when your company jewels are on the line, it pays to know if
> the standard works in your case. Esp if you tend to design/build to the
> right edge of the bell curve.
>
> How many years were we shipping 10:1 and greater aspect ratio vias when
> the std classifications stopped at (was it?) 9:1?
>
>
>
> *From:* Jack Olson [mailto:[log in to unmask]]
> *Sent:* Monday, March 5, 2018 9:48 AM
> *To:* Dwight Mattix <[log in to unmask]>; TechNet <[log in to unmask]>
>
> *Subject:* Re: [TN] Non Functioning pads
>
>
>
> I hear ya, brother. and don't think I am arguing with the value of doing
> the work,
>
> but (here I go anyway)
>
> One of the major benefits of having the IPC in our industry is that every
> new circuit board designer that comes along, who doesn't know whether to
> put that note on his fabrication drawing or not, can learn from the
> experience of others here. He doesn't have to repeat expensive tests just
> to verify what is already understood by the consensus of other members that
> have already contributed time and effort and resources to study the issue.
>
> (but I hear ya!)
>
>
>
> Jbro
>
>
>
> On Mon, Mar 5, 2018 at 10:51 AM, Dwight Mattix <[log in to unmask]>
> wrote:
>
> Yeah, I blew past the thread to busy to contribute last week.
>
> All else being equal retaining non-functional pads tends to increase time
> to barrel wearout from circumferential cracking at/near the midline. One
> notion being that the pads make for a local lower resin content region
> around the via (less expansive dielectric acting on the copper column to
> wear it out).
>
> Non-func pads don't seem to have much bearing on the actual post
> interconnect reliability. Multiwire anyone? (speaking of dinosaurs).
>
> But back to the barrel wearout thing... All things are rarely equal. So
> if you actually build it and test it (due diligence? That's crazy talk. Who
> has time or money for that anymore?), I'd wager you'll get mixed results.
> A lot depends on factors like the fabricator's drilling and hole prep
> skill, the aspect ratio, material involved, copper weights of the included
> NF-pads etc.
>
> Leaving non-func pads in, increases the drilling challenge. That increases
> things that disrupt the hole and factor in to it's ultimate reliability.
> For example, a rougher hole wall is very likely to be part of the effect of
> leaving NF pads in. That introduces stress risers in the holewall
> topography that can accelerate copper wearout and crack propogation.
>
> So all of that say the original question, "It depends." :)
>
> Do your due diligence. If it really matters, build it and test it. Better
> yet, build it both ways and test it. Even better, build both ways at more
> than one fab and test it. You'll be illuminated and smarter at the end of
> the exercise than 99 of 100 veteran pwb tech people seen walking the floor
> with tacky polo shirts, broken down posture and done-lops last week at
> IPC/APEX.
>
> cheers,
> dw
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson
> Sent: Monday, March 5, 2018 7:49 AM
> To: [log in to unmask]
> Subject: Re: [TN] Non Functioning pads
>
> I must be behind-the-times on this one.
> Werner Englemaier used to talk about this all the time, and from my memory
> an analogy might be similar to comparing a simple rivet to a "rivet with
> ribs". If your goal is a robust product (which a lot of Class 3's are) then
> it seems like you would want the extra support. (I'm not making a
> statement, I'm repeating what I was taught). I'm pretty sure I've heard
> Gary Ferrari recommend keeping them in at least a half a dozen times in his
> seminars. Aren't the most common failures in boards related to vias?
>
> Maybe I have more learnin' to do on this one, but I'm surprised that NO
> ONE responded in favor of keeping the unconnected internal pads
>
> Well, since we are talking about vias, I was also advised to require 1mil
> hole wall plating, even though the standard is 0.8 (I think). But for the
> same reason, the stronger we can make our vias, the less "most common"
> failures we will have, right? (At Caterpillar, we want the most robust
> product we can get for the money) Am I sounding like an old dinosaur now?
>
> but really, is EVERYONE removing unconnected inner layer pads?
> Is "increasing the longevity of drill bits" the dominant theme now?
>
> onward thru the fog,
> Jack
>
>
> .
> On Tue, 27 Feb 2018 11:12:22 -0600, Larry <[log in to unmask]> wrote:
>
> >Is there any reason I cannot remove non functioning pads on the inner
> layers for an Class 3 PCB?
> >
> >Many thanks,
> >
> >Larry
>
>
>
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