Path: Xl.tags.giganews.com!local-2.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail
NNTP-Posting-Date: Mon, 15 Apr 2024 23:26:36 +0000
From: john larkin <jl@650pot.com>
Newsgroups: sci.electronics.design
Subject: Re: Predictive failures
Date: Mon, 15 Apr 2024 16:26:35 -0700
Message-ID: <pbdr1j11kj8sdfrtu4erc8c67s1g8dos9m@4ax.com>
References: <uvjn74$d54b$1@dont-email.me> <jg0r1j1r2cdlnhev0v1gaogd3fj0kmdiim@4ax.com> <0s1r1jhb5vfe7lvopuvfk4ndkbt54ud3d9@4ax.com> <rh7r1jhtvqivb43vmt3u9d0snah8fu4pjn@4ax.com>
User-Agent: ForteAgent/8.00.32.1272
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Lines: 81
X-Trace: sv3-qw79UbpP5kauHZ+cPvuDMijERrZhHWfU3QBA1SmJgMi2alsRJNpReV3dTXBl8ZYwRr5MMVST5RKImZi!pU6fiNZAsBosDCaFbeGOrs6tNHyudA+tRaNxo3zda5oDAkNXYd6UZfh0tCiEp9tPfGyvGEDgQJy4!Fiv+Xg==
X-Complaints-To: www.supernews.com/docs/abuse.html
X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html
X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers
X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly
X-Postfilter: 1.3.40
Bytes: 4228

On Mon, 15 Apr 2024 18:03:23 -0400, Joe Gwinn <joegwinn@comcast.net>
wrote:

>On Mon, 15 Apr 2024 13:05:40 -0700, john larkin <jl@650pot.com> wrote:
>
>>On Mon, 15 Apr 2024 15:41:57 -0400, Joe Gwinn <joegwinn@comcast.net>
>>wrote:
>>
>>>On Mon, 15 Apr 2024 10:13:02 -0700, Don Y
>>><blockedofcourse@foo.invalid> wrote:
>>>
>>>>Is there a general rule of thumb for signalling the likelihood of
>>>>an "imminent" (for some value of "imminent") hardware failure?
>>>>
>>>>I suspect most would involve *relative* changes that would be
>>>>suggestive of changing conditions in the components (and not
>>>>directly related to environmental influences).
>>>>
>>>>So, perhaps, a good strategy is to just "watch" everything and
>>>>notice the sorts of changes you "typically" encounter in the hope
>>>>that something of greater magnitude would be a harbinger...
>>>
>>>There is a standard approach that may work:  Measure the level and
>>>trend of very low frequency (around a tenth of a Hertz) flicker noise.
>>>When connections (perhaps within a package) start to fail, the flicker
>>>level rises.  The actual frequency monitored isn't all that critical.
>>>
>>>Joe Gwinn
>>
>>Do connections "start to fail" ?
>
>Yes, they do, in things like vias.  I went through a big drama where a
>critical bit of radar logic circuitry would slowly go nuts.  
>
>It turned out that the copper plating on the walls of the vias was
>suffering from low-cycle fatigue during temperature cycling and slowly
>breaking, one little crack at a time, until it went open.  If you
>measured the resistance to parts per million (6.5 digit DMM), sampling
>at 1 Hz, you could see the 1/f noise at 0.1 Hz rising.  It's useful to
>also measure a copper line, and divide the via-chain resistance by the
>no-via resistance, to correct for temperature changes.

But nobody is going to monitor every via on a PCB, even if it were
possible.

One could instrument a PCB fab test board, I guess. But DC tests would
be fine.

We have one board with over 4000 vias, but they are mostly in
parallel.


>
>The solution was to redesign the vias, mainly to increase the critical
>volume of copper.  And modern SMD designs have less and less copper
>volume.
>
>I bet precision resistors can also be measured this way.
>
>
>>I don't think I've ever owned a piece of electronic equipment that
>>warned me of an impending failure.
>
>Onset of smoke emission is a common sign.
>
>
>>Cars do, for some failure modes, like low oil level.
>
>The industrial method for big stuff is accelerometers attached near
>the bearings, and listen for excessive rotation-correlated (not
>necessarily harmonic) noise.

Big ships that I've worked on have a long propeller shaft in the shaft
alley, a long tunnel where nobody often goes. They have magnetic shaft
runout sensors and shaft bearing temperature monitors.

They measure shaft torque and SHP too, from the shaft twist.

I liked hiding out in the shaft alley. It was private and cool, that
giant shaft slowly rotating.