Not always..  A guy I worked with was pulling a ceramic 40 pin dip out of a socket when it broke...  sliced his finger to the bone.  There was initially some concern that it was a BeO ceramic.  Checking with the manufacturer showed it was not.  I checked the socket afterwards, and it seemed normal and had no problems releasing other chips.

Hi all

Yes some industrial ceramics are very tough but the few I have
encountered as substrates for electronics were delicate and
brittle. ("Hybrid" circuits like pressure transducers or ceramic IC
packages as below).

John

Mark Sims holrum@hotmail.com writes:

--

John Devereux

What can account for this difference between your and my experience
and what Chuck said?

On Wed, Apr 12, 2017 at 1:11 PM, John Devereux john@devereux.me.uk wrote:

Simple, ceramic is a generic term, like car.

And, ceramic substrates are available in all manner
of different thicknesses, densities, and materials.

Like every other engineering material, you decide what
characteristics are important to you, and you pick the
appropriate material that meets those characteristics.

If you work outside of the envelope of that material's
capabilities, the results will be disappointing.

You were opining that ceramic was too brittle, and
breakable and shouldn't be used for metrology work, I
disagreed, and attempted to enlighten you with tales of
some ceramics that you would be hard pressed to break,
even with repeated blows from a hammer.

I could tell you of transparent ceramics that are
amazingly hard, and strong.

I could go further and tell of other ceramics where you
can crumble brick sized blocks with light finger pressure.

And I could tell you of still other ceramics that you can
heat white hot with a torch, and then in a fraction of a
second, press the glowing section against your arm without
it even feeling warm.

Which could lead some to say: ceramics are cool!

But as they say, you can lead a horse to water, but you
cannot make him drink.

-Chuck Harris

cheater00 cheater00 wrote:

Ceramic plates are even used in armor to stop armor piercing projectiles.

Lots of applications.

----- Original Message -----
From: "Chuck Harris" cfharris@erols.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Wednesday, April 12, 2017 5:04 PM
Subject: Re: [volt-nuts] PCBs with ceramic substrates

Hi Chuck

But the context is "PCBs with ceramic substrates". Are any of those
tough? They may well be, perhaps you know of some? It does not help us
with the subject much if there are ceramics with these amazing
properties if they are not available as PCBs.

There is also the question of exactly what properties of FR4 are
limiting for "metrology" use.

John

Chuck Harris cfharris@erols.com writes:

--

John Devereux

In message 87inm44nl4.fsf@devereux.me.uk, John Devereux writes:

FR4 are certainly not without its own problems, in particular
with respect to mechanical/electrical phenomena (bending, tempco etc.)

And saying "Ceramic" isn't really narrowing down what we mean
anyway, pretty much anything in the Rogers catalog is in game:

https://www.rogerscorp.com/acs/products.aspx

I suspect only experiments would be able to tell which of many
possible desirable properties are most beneficial ?

The real question is if the mobile devices have brought the volume
up so that running small series for specialty use is affordable?

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

Hi John,

I am not advocating ceramics in place of FR4, or vice versa.
That was someone else wondering why ceramics weren't used in
metrology...

As to what you can use that isn't brittle, that is up to your
imagination.  Unlike common FR4 materials, ceramics don't do
well with the usual FR4 process of thermally bonding a thin
sheet of copper to each side, masking, etching, and being happy.

Ceramic PCB's, in my experience, are more of a silk screen
a silver ore gold bearing "glaze" on the surface of the ceramic,
and fire in a kiln process.

Any ceramic you can get in a thin sheet the thickness you desire,
and in the shape/size you desire is a candidate.

Some ceramics might not do well with drilling, or other machining
processes, so may have to be formed, drilled, etc. while in the
greenware state.

I shudder to think what machining ceramic armor plate, as is
used for the breastplate in a "bullet proof vest" might be like.

There are some ceramics that would eat tungsten carbide drills
for breakfast, so diamond tooling is probably essential.

-Chuck Harris

John Devereux wrote:

"Tungsten carbide drills? What the bloody hell is tungsten carbide drills?"
https://m.youtube.com/watch?v=rQDeU6dHX-c

(Sorry, just couldn't resist :) )

⁣Met vriendelijke groet,
Rob Klein

verstuurd vanaf mijn smartphone​

Op 16 apr. 2017 15:41, om 15:41, Chuck Harris cfharris@erols.com schreef:

On Mon, 10 Apr 2017 20:06 Poul-Henning Kamp, phk@phk.freebsd.dk wrote:

incompetence.

Indeed your friend would have told you that the materials to be had are
Al2O3, AlN, BeO, Si3N4, or ZrO2.

The first is commonly found on old cooking pots or bicycle parts, and you'd
know that the whiteish film, while resistant to water, is easile malleable.
It has low fracture resistance, sometimes even if sintered. Its
monocrystalline version, sapphire, is not commonly used in manufacturing.
While it has excellent electrical properties, any experimental chemist will
tell you that sapphire windows, tiny bits of (synthetic) sapphire, are
prohibitively expensive and have to be handled with care; the largest ones
affordable to a well funded university are a couple inches across. Sintered
Al2O3 is used in spark plugs. I think it needs to be sintered into form and
cannot be milled or otherwise machined. Spark plugs also have huge gaps in
the metal casing due to different thermal expansion between ceramics and
metals such as say copper traces placed on a pcb. So even if you can solder
the board without fracturing either the substrate or the traces, just
keeping it in variable weather will fracture either one due to them working
all the time.

AlN is commonly used as a structural support in cheap heating elements, eg.
the dreaded "drop your iron and it's dead" soldering tip heating elements.
It's the reason everyone, including cheap Chinese manufacturers, moved to
including the heater directly in the tip as one exchangeable part. I've had
a tile stove with AlN heating elements inside and after 5 years the beads
housing the heating wire started falling apart on their own, without having
been touched once, while placed on a solid concrete base. This is likely
due to thermal shock, and goes to show objects out of AlN will have a
mechanically fragile structure on the interface of separate crystals that
make them up. But since ceramics are all porous they will all eventually
include other substances that will break the crystalline structure.

BeO is highly piezoelectric /and/ pyroelectric, which is just fuuun for
standards. This is due to its Wurtzlite crystalline structure, which it
shares with AlN. What it doesn't share with aluminum nitride is its ability
to give you cancer. It's so common it has its own name, berylliosis.

Si3N4 is ok. Except it covers in SiO2, silica, which is a thermal
insulator, so your chips can be nice and cozy. It's also nicely
piezoelectrical, which is why it's used in quartz oscillators. Quartz is
another name for silica. Si3N4 is also very hard, therefore fragile. So if
you shock mount it, it might be ok, otherwise just the thermal expansion of
whatever it's mounted to rigidly might stress it. Such as the copper
traces, which you have to balance out on both sides, or you're risking
fracture. It is commonly used in ball bearings. It can't really be milled.
So you only get the pre-made sizes. If you keep the board in SF6 or mineral
oil all the way from manufacture through use, it might be good, but don't
quote me on that.

Anyone who's ever owned one of those cheap tomato knives out of white
ceramic knows how easily ZrO2 chips when it is in a thin structure.

To know most of this stuff you'd have to have cooked for yourself or been
outside on a bike a few times, and googled for the other stuff, but I guess
making padding for a mail sig takes its toll, so I won't attribute this one
to malice.

A big issue with ceramics of all kinds is their thermal expansion
coefficient. It is incompatible with copper. Here's a company extolling
their revolutionary copper cladding process:

"Unlike the fragility of thick and thin film circuits, the DBCu circuits
allow rough handling and can endure repeated eutectic bonding temperatures.
The selection of the ratio of copper thickness to ceramic thickness is an
important consideration in the initial design of the circuit. One sided
bonding on thin substrates can cause severe camber conditions that can
degrade the bond with repeated temperature cycling due to shear and
bimetalic type bending forces or lead to ceramic fracturing. These effects
can be reduced by double sided bonding to equalize the forces between
opposite faces of the ceramic. Leaving copper in non-electrical areas will
not only improve lateral heat .spreading but also minimize bending stresses
during temperature cycling."

This is a new thing, so apparently neither wide spread nor available back
them fragile ceramic pcbs encountered by people on the list were being made.

Another issue is that they are porous. So anything floating in the air will
find its way into the inside of the crystal lattice, and because that is
ridgid it will wedge the ceramic apart, like an axe. This is my guess as to
why old ceramic boards fail. Note all ceramic pots are glazed. Glazing
wasn't always known. If you go to a museum and look at artefacts you will
only find glazed ceramics and no unglazed ceramics from that same period.
It's not because people suddenly stopped making unglazed ceramics - glazing
was expensive - but because the unglazed ones disintegrated over time,
unlike glazed ones. It's really lucky when you find unglazed ceramics, and
it's usually due to them sitting for a few centuries in some sort of mud
that was chemically compatible with them. Usually the same local mud they
were made out of. This should tell you a lot about the lovely long term
robustness of porous ceramics. They have nothing on dense organic layers
such as used in the manufacture of "normal" pcbs.

Watch this video to see a guy who's handy at repairing stuff find a ceramic
pcb isn't the "toughest material, pretty much on all parameters":
https://youtu.be/_x8ii58-W_Y (it's around 13:20). This is just cheap HP
junk which lost nothing in a metrology lab, but still. I guess a
manufacturer who actually cares about quality would have made the board out
of sapphire.

Al2O3, AlN, BeO, and Si3N4 substrates can be had in sub $50 MOQ from
alibaba, and you can get Zr2O3 bricks, so go for the experimental route
Paul. As far as experience goes hands on is loads better than arm chair.

I've investigated both ceramic guns and engines that were brought up
earlier.

I quickly remembered the only ceramic gun is the Glock 7. I live near the
Glock factory. The Glock 7 is a fully ceramic gun used to avoid detection
by metal detectors in Die Hard 2. It doesn't exist outside of Die Hard 2.

The thermal expansion coefficient, britlleness due to lack of plasticity,
and thermal insulative character are all reasons why we have no ceramic
engines. The only search result talking about fully ceramic engines as a
practical idea is a crackpot site called "why ceramic rotary engines" that
lists different kinds of ceramic materials and brings up a pish tosh of
random nice facts about them, many of which don't even apply to building
engines, such as thermal shock resistance. Unless you expect your engines
to be jet engines that is, in which case I guess that is right, because
NASA once made a ceramic jet nozzle that was a few inches big.

Google is indeed a good friend, but I guess he's shy to bring stuff up with
people who use a royal "we".