Re: [time-nuts] The ultraAtomic clock for home
On 4/7/17 3:45 PM, Charles Steinmetz wrote:
Bob wrote:
The epoxy over wire bond construction approach
is low cost, and not very experimenter friendly.
It is also extremely unreliable, particularly WRT environmental effects
such as temperature changes, humidity, and atmospheric pollutants. In
my view, it is unsuitable for use in anything but dirt cheap, purely
disposable devices like greeting-card audio players and disposable cameras.
Interestingly enough it is used in space flight hardware. It is much
less expensive, lighter weight and easier to inspect than thick film
hybrids and similar schemes.
You can can do a pre-cap inspection, then apply the potting material,
and then you could even xray it to see if the bond wires moved or something.
A flipchip with a blob is even better.
It's even reworkable (e.g. you can soften the blob & solder and scrape
the die off and bond a new one down).
I suspect that there is a wide variation in the material you blob on
there and so forth.
Hi
On Apr 7, 2017, at 7:19 PM, jimlux jimlux@earthlink.net wrote:
On 4/7/17 3:45 PM, Charles Steinmetz wrote:
Bob wrote:
The epoxy over wire bond construction approach
is low cost, and not very experimenter friendly.
It is also extremely unreliable, particularly WRT environmental effects
such as temperature changes, humidity, and atmospheric pollutants. In
my view, it is unsuitable for use in anything but dirt cheap, purely
disposable devices like greeting-card audio players and disposable cameras.
Interestingly enough it is used in space flight hardware.
Humidity does not tend to be a big issue once you get in space :)
Bob
It is much less expensive, lighter weight and easier to inspect than thick film hybrids and similar schemes.
You can can do a pre-cap inspection, then apply the potting material, and then you could even xray it to see if the bond wires moved or something.
A flipchip with a blob is even better.
It's even reworkable (e.g. you can soften the blob & solder and scrape the die off and bond a new one down).
I suspect that there is a wide variation in the material you blob on there and so forth.
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Jim wrote:
Charles wrote:
[blob over wire bond construction]
is also extremely unreliable, particularly WRT environmental effects
such as temperature changes, humidity, and atmospheric pollutants.
In my view, it is unsuitable for use in anything but dirt cheap, purely
disposable devices like greeting-card audio players and disposable
cameras.
Interestingly enough it is used in space flight hardware. It is much
less expensive, lighter weight and easier to inspect than thick film
hybrids and similar schemes.
Very interesting.
I suspect that there is a wide variation in the material you blob on
there and so forth.
No doubt. I suspect also that space flight hardware doesn't use blobs
on plain FR4. While one problem with the blob technique is the
permeability of the blob material, another is the permeability of the
substrate -- and FR4 is pretty bad in this regard.
It would not surprise me to find that space-qualified blob material is
very different from consumer-grade blob material, and is actually more
expensive than using consumer-grade packaged die would be (which would,
of course, defeat the purpose of using it for consumer circuits).
I suppose in the vacuum of space permeability to gasses and humidity may
be less of a problem than it is in Earth's atmosphere, so the blob may
need to be the primary means to prevent ingress of gasses and humidity
only from the time of construction until launch.
Makers of space flight hardware can also afford to spend more for
materials with similar coefficients of thermal expansion than makers of
consumer devices can.
Best regards,
Charles
On 4/7/17 6:25 PM, Bob kb8tq wrote:
Hi
On Apr 7, 2017, at 7:19 PM, jimlux jimlux@earthlink.net wrote:
On 4/7/17 3:45 PM, Charles Steinmetz wrote:
Bob wrote:
The epoxy over wire bond construction approach
is low cost, and not very experimenter friendly.
It is also extremely unreliable, particularly WRT environmental effects
such as temperature changes, humidity, and atmospheric pollutants. In
my view, it is unsuitable for use in anything but dirt cheap, purely
disposable devices like greeting-card audio players and disposable cameras.
Interestingly enough it is used in space flight hardware.
Humidity does not tend to be a big issue once you get in space :)
Bob
Yeah, but you sit for years on the ground waiting, in tropical areas no
less.
It is much less expensive, lighter weight and easier to inspect than thick film hybrids and similar schemes.
You can can do a pre-cap inspection, then apply the potting material, and then you could even xray it to see if the bond wires moved or something.
A flipchip with a blob is even better.
It's even reworkable (e.g. you can soften the blob & solder and scrape the die off and bond a new one down).
I suspect that there is a wide variation in the material you blob on there and so forth.
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On 4/7/17 7:10 PM, Charles Steinmetz wrote:
Jim wrote:
Charles wrote:
[blob over wire bond construction]
is also extremely unreliable, particularly WRT environmental effects
such as temperature changes, humidity, and atmospheric pollutants.
In my view, it is unsuitable for use in anything but dirt cheap, purely
disposable devices like greeting-card audio players and disposable
cameras.
Interestingly enough it is used in space flight hardware. It is much
less expensive, lighter weight and easier to inspect than thick film
hybrids and similar schemes.
Very interesting.
I suspect that there is a wide variation in the material you blob on
there and so forth.
No doubt. I suspect also that space flight hardware doesn't use blobs
on plain FR4. While one problem with the blob technique is the
permeability of the blob material, another is the permeability of the
substrate -- and FR4 is pretty bad in this regard.
We fly a fair amount of FR4 - sure, we might do some coupons or get
source traceability. And it depends on the mission - a billion dollar
mission to Europa is different than others.
It would not surprise me to find that space-qualified blob material is
very different from consumer-grade blob material, and is actually more
expensive than using consumer-grade packaged die would be (which would,
of course, defeat the purpose of using it for consumer circuits).
Not necessarily - the market for "custom hi-rel" stuff is getting
smaller every day and a lot of times it just isn't available at all. You
might want to choose a material with the right properties, but stuff
that's made in large volumes tends to be pretty consistent - a mass
market product can't have a huge dead on arrival rate. I'd say
automotive applications probably have the most stringent, yet cost
sensitive, requirements.
I suppose in the vacuum of space permeability to gasses and humidity may
be less of a problem than it is in Earth's atmosphere, so the blob may
need to be the primary means to prevent ingress of gasses and humidity
only from the time of construction until launch.
But that is a fairly long time - launch delays are pretty common.
It's not unusual for something to be launched 5-6 years after being
built (and, of course, spares for mission 1 get used on mission 2,
coming along behind).
Sure, we're not doing salt spray tests or condensing humidity - but most
space electronics sits in a regular old airconditioned room for years.
(The days of ashtrays built into the test console are long gone)
Makers of space flight hardware can also afford to spend more for
materials with similar coefficients of thermal expansion than makers of
consumer devices can.
True enough - but then even for cheap commercial stuff, the CTEs are
published. It's pretty easy to get the right materials. (barring buying
your raw materials on eBay from unknown vendors, but then who knows what
you're getting.. it's one step from a guy in an alley saying "hey, I've
got some nice 2 part epoxy here, in the original package, fell off the
back of a truck, I can let you have it for a good price, as long as it's
cash"
The real issue with CTE these days is large ceramic packages (e.g. those
1000+ pin BGA/CGA packages) vs the boards (whether FR-4 or polyimide) -
given that we're not using anywhere near 1000 pins, a few dozen bond
wires on a the die seems like a great idea.
ANd bonding the die to the board is a lot better thermal transmission wise
Hi
On Apr 7, 2017, at 10:10 PM, Charles Steinmetz csteinmetz@yandex.com wrote:
Jim wrote:
Charles wrote:
[blob over wire bond construction]
is also extremely unreliable, particularly WRT environmental effects
such as temperature changes, humidity, and atmospheric pollutants.
In my view, it is unsuitable for use in anything but dirt cheap, purely
disposable devices like greeting-card audio players and disposable
cameras.
Interestingly enough it is used in space flight hardware. It is much
less expensive, lighter weight and easier to inspect than thick film
hybrids and similar schemes.
Very interesting.
I suspect that there is a wide variation in the material you blob on
there and so forth.
No doubt. I suspect also that space flight hardware doesn't use blobs on plain FR4. While one problem with the blob technique is the permeability of the blob material, another is the permeability of the substrate -- and FR4 is pretty bad in this regard.
Unless you are building a thick film on ceramic, or a thin film on glass, the rest of the likely substrates are pretty permeable.
It would not surprise me to find that space-qualified blob material is very different from consumer-grade blob material, and is actually more expensive than using consumer-grade packaged die would be (which would, of course, defeat the purpose of using it for consumer circuits).
I suppose in the vacuum of space permeability to gasses and humidity may be less of a problem than it is in Earth's atmosphere, so the blob may need to be the primary means to prevent ingress of gasses and humidity only from the time of construction until launch.
The other feature it provides is vibration protection for the wire bonds during launch. One would hope the device is stored in a low humidity package or dry box for the time (possibly years) between manufacture and launch.
Makers of space flight hardware can also afford to spend more for materials with similar coefficients of thermal expansion than makers of consumer devices can.
As long as the interface materials (mounting cement and die coat) are a bit elastic, you can get some pretty good thermo cycle performance out of the normal mismatches.
Bob
Best regards,
Charles
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Mike you may have missed it in the thread. I made a mistake its not the
cme8000 chip.
Thats a classic am decoder. You want the ES100. Thats a true wwvb bpsk
decoder. Contact La Crosse and ask if they have a model.
Regards
Paul
WB8TSL
On Fri, Apr 7, 2017 at 1:18 PM, Mike Seguin n1jez@burlingtontelecom.net
wrote:
Does anyone know of a clock with digital readout that uses the CME-8000?
Tnx,
Mike
On 2017-04-07 13:03, Tom Van Baak wrote:
Very good catch it is not the cme8000 chip. Thats a classic am receiver.
It is the everset chip. Sorry for mis-leading.
Hi Paul,
I can confirm (from talking with the guys backing it) that, yes, it's
the EverSet ES100, in die form (CoB). I believe you and I have both
used the early Xtendwave dev kits with the ES100 as SMT part. It's
nice to see the chip still lives and finally made it to a product!
I uploaded more ultrAtomic info and tear-down photos:
http://leapsecond.com/pages/ultratomic/
I encourage those of you who just bought these clocks to do some
experiments. The obvious ones are:
-
See how long it takes to acquire the correct time, at all sorts of
different and difficult environments, compared to the traditional WWVB
clocks. Check for off-by-one second, or minute, or hour errors. -
See how accurate they really are. For clocks like this I use a
variety of piezo sensors (feel the tick), acoustic sensors (hear the
tick), optical sensors (see the tick), and mostly electrical sensors.
Some of these are passive (non-destructive) timings and good enough.
Others require some level of disassembly but are more precise. For a
stepper motor clock it's easy to tap onto the coil connections and get
a sharp pulse every second or two. Then use a time interval counter,
or picPET, or TICC, or PC-based PPS-capture to collect readings. Note
the signal level is usually low power and below typical TTL levels,
and they do NOT drive 50R!
If all goes well, we can soon talk about a time-nuts special where we
get someone to make a timing board or disciplined timing board based
on the ES100 chip. The bad news is that at the same price it would be
like a million times worse than GPS. The good news is that lots of
applications need only ms level timing; there are places where WWVB is
receivable and GNSS is not; and then there's the redundancy and
low-power factor.
/tvb
----- Original Message -----
From: "paul swed" paulswedb@gmail.com
To: "Discussion of precise time and frequency measurement" <
time-nuts@febo.com>
Sent: Friday, April 07, 2017 5:08 AM
Subject: Re: [time-nuts] The ultraAtomic clock for home
Tom
Very good catch it is not the cme8000 chip. Thats a classic am receiver.
It is the everset chip. Sorry for mis-leading.
Regards
Paul
WB8TSL
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73,
Mike, N1JEZ
"A closed mouth gathers no feet"
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On Fri, 7 Apr 2017 21:30:18 -0700
jimlux jimlux@earthlink.net wrote:
No doubt. I suspect also that space flight hardware doesn't use blobs
on plain FR4. While one problem with the blob technique is the
permeability of the blob material, another is the permeability of the
substrate -- and FR4 is pretty bad in this regard.
We fly a fair amount of FR4 - sure, we might do some coupons or get
source traceability. And it depends on the mission - a billion dollar
mission to Europa is different than others.
Yes, it depends a lot on what the project is about. We have done a
project where whe choose PCBs from Eurocircuits because they offered
better quality over price than some space qualified manufacturer
and the mission was not critical (only flying up a space station.
If it breaks, you can send up a replacement part). Even a lot of
the chips on the board were just industrial grade plastic packages.
On others, any plastic was a total no go (optics in space, aka any
outgasing will condensate on the lens) and everything had to be
super-duper-space-quality (aka a simple 2N2222 suddenly costs 100€
or more and comes with a few binders full of documentation.. not
to forget the ITAR declaration).
Also, which techniques can be used in a specific mission highly depend
on the contractor who does the assembly. Some have no problem with
BGA packages, while others aren't going to solder any package where
they cannot visually inspect every solder joint (e.g. like QFN).
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson