In message 20100125.140436.3508.5.cdelect@juno.com, Corby Dawson writes:

The advent of CD's made polycarbonate ridiculously expensive and
priced them out of the market...

--
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.

Corby Dawson wrote:

0.1uF and 0.22uF NP0/C0G SMT caps are readily available, leaded versions
are also availble.
Polycarbonate film production ceased about 10 years ago.

Bruce

They're not quite dead yet...

http://www.polycarbonatecapacitors.com/

But I wouldn't use them unless forced to at gunpoint, since they are quite the
boutique item these days.

I too have had good success with the PPS capacitors.

--David Forbes

Seems that boutique item and time-nut might go together, if there was an actual performance advantage.  Besides, think of the bragging rights from some of this stuff.  It could be worse than audiophile craziness: My DMTD has capacitors made of genuine Lexan(r), not just any old polycarbonate, hand pressed to a thin film from the finest selected window glazing sheets using rollers machined from the finest steel puddled by English craftsmen in Sheffield using traditional methods.

In message <ECE7A93BD093E1439C20020FBE87C47FED2B80A552@ALTPHYEMBEVSP20.RES.AD.J
PL>, "Lux, Jim (337C)" writes:

Thanks for pointing that little shop out.

Did you notice this in their whitepaper:

From 1960s to 1980s, Electronic Concepts used Peter Schweitzer
(a Division of Kimberly Clark) manufactured film, the only
United States supplier of material, by license agreement
with Bayer. In 1984, Electronic Concepts acquired the Peter
Schweitzer film division, terminating the license, allowing
Bayer to market the film in the United States. For economic
considerations, Electronic Concepts started manufacturing
capacitors using a balance of Bayer and Electronic Concepts
film.

Does that sound like a run-of-the-mill business decisions made by
a small company which produces capacitors ?

No ?

Then how about this:

In 1990, the conclusion of a polycarbonate film capacitor
paper[1] stated, "both the orientation and crystal structure
of PC (polycarbonate) film affects its mechanical properties
and electrical dissipation factor". The paper was a cooperative
investigation by the Jet Propulsion Laboratory and Electronic
Concepts' film manufacturing division,

Why would JPL study obscure production details of polycarbonate
film capacitors in 1990, if they fell of the market six years earlier ?

Sounds fishy ?

Anybody know what this means ?

Electronic Concepts accumulated almost five hundred million
hours of testing military grade Polycarbonate capacitors;
and, currently meet established reliability failure rate
level "R."

Have you connected the dots yet ?

A fair number of the in-stockpile nuclear weapon designs are qualified
using polycarbonate capacitors and can't be retested, redesigned
or requalified...

Poul-Henning

--
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.

And if my recollection from my days running a product validation lab many
years ago is correct, the failure mode of most polycarbonate caps was
shorted and flaming.

Regards,

Tom Holmes, N8ZM
Tipp City, OH
EM79xx

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Poul-Henning Kamp
Sent: Monday, January 25, 2010 5:12 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Low temperature coefficient capacitors for DMTD

In message 20100125.140436.3508.5.cdelect@juno.com, Corby Dawson writes:

The advent of CD's made polycarbonate ridiculously expensive and
priced them out of the market...

--
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.

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We study all manner of obscure stuff here.  Comes from using 20 year old parts in spacecraft that will last another 20 years.  Consider Cassini.. launched back in the 90s, with equipment using "heritage" designs from the 80s.  Those designs probably use some peculiarity of the components available, and someone had a box of the parts stashed away which was used.

Every time someone proposes a new widget, they get asked in the design review: "can you use any of the parts we have in bonded flight stores to save money?", and someone says "Well, sure, but they're kind of old, I think we need to study whether they're any good".

(there are octal tube sockets in flight stores, as I recall.  Never know when you might need to refurbish a telemetry transmitter that uses them..<grin>))

It means that they had a raft of life test fixtures with thousands of capacitors running continuously for years (perhaps under accelerated life conditions).  There's a whole lot of research into figuring out failure scaling laws; e.g. does life scale with voltage to the 5.5 or the 7.5 power? Does it scale with temperature according to the Arrhenius equation? With what exponent?

This is the kind of thing that spacecraft components people obsess about, because it allows them to estimate failure probabilities for something 25 years from now.

I, for one, hang onto my 70s and 80s era IC databooks, because those are the parts that are flying.  My grandchildren will thank me if they wind up working here. (Ohh.. I remember, grampa worked to get that radio working because it was a spare on a 1995 mission, before they used iton that outerplanets Oort cloud mission launched in 2011, and here it is at Pluto in 2040, and there's an inflight anomaly, so we better get the breadboard out of storage and see if we can fire it up)

Hi

My understanding is that it was part of a several decades long multi-billion dollar Coast Guard program to enhance the long term reliability of the Loran-C transmitter chains .....

Bob

On Jan 25, 2010, at 5:47 PM, Poul-Henning Kamp wrote:

Oh my.. a bit of research in Xplore finds that all the gory details were in the very section I work in at JPL (we build radios for deep space missions)

Well, the original incident triggering the study was in 1978 on Voyager 2, when they weren't able to get an uplink lock to the spacecraft.  The telemetry from the spacecraft indicated that the loop filter in the carrier tracking loop was having problems, most likely from leakage across the 75 uF capacitor. They figured out a workaround to estimate the best lock frequency using temperature and Doppler estimates, and Voyager continues on its happy way out of the solar system.  (FWIW, the carrier tracking loop has a bandwidth of a few Hz, I think.)

In fact, my office mate says that the former occupant of the chair I am sitting in as I type this spent months checking the best lock frequency of Voyager to develop that estimation approach.

Frank Ott (a coworker who retired a couple years ago) did the failure analysis and figured out a way to test the capacitors and published a paper in 1985 describing it, and that paper was the basis for the 1990 Yen and Lewis paper cited in the white paper.

So, JPL actually did the studying in the 80s, right around when the market for polycarbonate caps was going away.

Interesting conclusions in Ott's paper: "Conditions leading to a capacitor failure can occur without voltage being applied.  JPL believes the Voyager in-flight failure occurred during six months of non-operation."

The actual reference (from IEEE Xplore) is:
"Effect of structure and morphology on thermal and electrical properties of polycarbonate film capacitors"
Yen, S.P.S.    Lewis, C.R.
Jet Propulsion Lab., California Inst. of Technol., Pasadena, CA, USA;
This paper appears in: Power Sources Symposium, 1990., Proceedings of the 34th International
Publication Date: 25-28 June 1990
On page(s): 387 - 391
Meeting Date: 06/25/1990 - 06/28/1990
Location: Cherry Hill, NJ
ISBN: 0-87942-604-7
INSPEC Accession Number:4111725
Digital Object Identifier: 10.1109/IPSS.1990.145871
Current Version Published: 2002-08-06

Abstract
Research is reported to identify polycarbonate (PC) film characteristics and fabrication procedures which extend the reliable performance range of PC capacitors to 125°C without derating, and establish quality control techniques and transfer technology to US PC film manufacturers. The approach chosen to solve these problems was to develop techniques for fabricating biaxially oriented (BX) 2 μm or thinner PC film with a low dissipation factor up to 140°C; isotropic dimensional stability; high crystallinity; and high voltage breakdown strength. The PC film structure and morphology was then correlated to thermal and electrical capacitor behavior. Analytical techniques were developed to monitor film quality during capacitor fabrication, and as a result, excellent performance was demonstrated during initial capacitor testing

And the paper's first paragraph says why JPL would do this:

In March 1978, a 78 uF PC capacitor failed in a receiver tracking loop filter aboard Voyager I. This failure led to a series of investigations to duplicate the failure mode, determine the failure mechanism and establish a viable screening technique. The research was completed in 1982 [1-3]. Sporadic failures of metalized 2 micron polycarbonate (PC) film capacitors in low voltage high impedance circuits indicated lack of reliability above 100°C. Although the failure mechanism was not identified, a ramp test was implemented as a standard screening test[3], and 100°C was set as the upper temperature limit for full rated voltage use. For 125'C applications, a 50% voltage derating was recommended.

You can find the paper in NASA Technical Reports Server (NTRS) at ntrs.nasa.gov... The record there says it's not copyrighted, but the electronic copy I have has the IEEE copyright notice on it.

NTRS has another paper listed "Review of the NASA Voyager spacecraft polycarbonate capacitor failure incident"
Summary: The premission failure of a Voyager spacecraft capacitor has prompted an investigation into the use of polycarbonate capacitors in high impedance circuits, during which capacitor failures were induced by thermal cycling together with extended periods at high temperature. Measurement of leakage path temperature coefficients indicates that there are two distinct leakage types whose mechanisms are complicated by movement within the capacitor during temperature changes. A novel system for pulse detection during capacitor burn-in and ramp testing has proven to be beneficial.
Feb 1, 1985
IEEE Transactions on Electrical Insulation (ISSN 0018-9367), vol. EI-20, Feb. 1985, p. 47-54.

Frank Ott, the lead author on the latter, retired about 2 years ago, and coauthored a NASA Tech Brief on a technique for "determining internal connections in capacitors" in 1986 (presumably from the same incident).  NPO-16499 and a "Capacitor Test System" (NPO-16485) which was a microprocessor controlled system simultaneously monitoring 80 capacitors (which is how they got those millions of hours).

Finding an old 1992 MTT paper by Mysoor, et al., that describes the design of the Deep Space Transponder (DST), which is what's in Voyager..

There's a second order lowpass filter in the tracking PLL. The two time constants are 3556 seconds and 0.0556 seconds (time constant of the pole, timeconstant of the zero, respectively), the loop gain is 2.2E7 1/sec.

The loop bandwidth is about 9 Hz for weak signals and 90 Hz for strong signals (50dB above threshold).

There's a fair amount of information on the tradeoffs made for phase noise and Allan deviation in the papers.  The Allan deviation was predicted to be 2.5E-11 for 0.01 second, 2.6E-13 for 1 second, and 2.5E-15 for 1000 seconds. (that's the incremental deviation, assuming a perfect input signal)

This is, of course, an all analog transponder design.  These days, we do all the loop tracking in the digital domain with a sampled signal and regenerate the carrier with an NCO.  Don't have to worry about those 75 microfarad capacitors in the loop anymore (but, on the other hand, we have other things to worry about now...<grin>)  We can probably do about an order of magnitude better on ADEV these days, with a digital radio, and maybe 2 orders of magnitude better with an all analog design.

James Lux, P.E.
Task Manager, SOMD Software Defined Radios
Flight Communications Systems Section
Jet Propulsion Laboratory
4800 Oak Grove Drive, Mail Stop 161-213
Pasadena, CA, 91109
+1(818)354-2075 phone
+1(818)393-6875 fax

Jim,

I was one of the guys who suffered from the incident while in the DSN.
If my memory doesn't fails, the loop bandwidth became smaller, one Hertz
or less (we routinely used 12 Hz BW in the downlink receivers so it was
quite smaller) making the spacecraft unable to track the Doppler rate of
our uplink.  The spacecraft problem forced us to continuously and slowly
sweep the transmitter to compensate the Doppler and avoid spacecraft rcv
lock loss.  The S/C receiver resting frequency was periodically measured
ramping the uplink and observing the lock-in and lock-out times.
Fortunately enough, we had the (then) new Block IV receiver/exciters
just installed, which had a programmable synthesizer, able to ramp at
very slow and precise rates, because the previous set, the Block III,
used a monster HP synthesizer (I don't remember the model, but
frequencies were entered with a huge matrix of pushbuttons) which could
not be ramped and all needed ramps were done manually (or "fingerly"),
moving a VCO frequency.
Even with the Block IV an operator has to stay there updating the ramp
rate to the Voyager II every few minutes.

Oh good old days ...
Ignacio Cembreros, former DSS 61-63 guy.

Lux, Jim (337C) wrote: