have you ever seen silicon or teflon capacitors in anything? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: November 15, 2023, 01:21:41 pm
content: They exist. They have descriptions.Have you ever seen one inside of something? what was it?https://www.electronicsweekly.com/news/products/teflon-high-film-capacitors-can-tolerate-150c-without-derating-2021-09/https://eepower.com/technical-articles/beyond-mlccs-the-rise-of-the-silicon-capacitor/'where are they hiding?for the silicon cap, it looks like maybe the 1uF unit on mouser is the answer to the high value C0G capacitor.

author: Gyro
author_rank: Super Contributor
timestamp: November 15, 2023, 02:28:09 pm
content: Quote from: coppercone2 on November 15, 2023, 01:21:41 pmIn dusty warehouses in the former Soviet Union...https://www.ebay.co.uk/sch/i.html?_nkw=inkw=soviet+teflon+capacitor

author: coppice
author_rank: Super Contributor
timestamp: November 15, 2023, 02:40:12 pm
content: Teflon capacitors, teflon coax, and lots of other things teflon are common in high end RF applications.

author: themadhippy
author_rank: Super Contributor
timestamp: November 15, 2023, 03:16:51 pm
content: I had a teflon boss once,nothing would stick to him.

author: coppice
author_rank: Super Contributor
timestamp: November 15, 2023, 03:23:38 pm
content: Quote from: themadhippy on November 15, 2023, 03:16:51 pmYou haven't really seen a true one of those until you find one that has lost their employers at least a billion dollars. Loathed by everyone below them, and still being praised by those above.

author: moffy
author_rank: Super Contributor
timestamp: November 15, 2023, 07:54:12 pm
content: We used teflon capacitors as the integrating capacitors for precision accelerometers for the Tornado fighter/bomber. They were large and cylindrical, tied to the board with glued wedges to hold them in place. The accelerometers had a variable magnetic force applied to their displacement lever to hold it at zero through a couple of coils. The current was integrated in the teflon cap and a precision charge pulse was applied to reset the cap, which was how the A/D conversion was done and the force was measured.A story circulated around Ferranti about the Ariane rocket, for which we supplied the attitude measurement package. The French were the lead contractors and specified a supplier for these teflon caps for Ferranti. During environmental testing an inexplicable noise was found in the accelerometer loop, and it was traced to these teflon caps being vibration sensitive, acting as a microphone. Some fellows were dispatched to the supplier in Paris, who no one had heard of, and they found a factory that consisted of someones garage! The solution was to change suppliers.

author: coppercone2
author_rank: Super Contributor
timestamp: November 15, 2023, 10:10:02 pm
content: What is it not being wound tight enough?the ones for sale now seem to be a mica/teflon hybrid.

author: paul@yahrprobert.com
author_rank: Regular Contributor
timestamp: November 16, 2023, 11:59:44 pm
content: As I recall, in one of Bob Pease's "Pease Porridge" columns he singled out teflon capacitors for having very low dielectric absorption, which is important for precision integrators.

author: coppercone2
author_rank: Super Contributor
timestamp: November 17, 2023, 12:57:57 am
content: how about silicon capacitors? lots of them in space right now? oil rigs?

author: TimFox
author_rank: Super Contributor
timestamp: November 17, 2023, 03:57:14 am
content: The usual app notes for sample/hold circuits recommended Teflon due to its low "soakage" (dielectric absorption), and they are also recommended for RF purposes due to low loss.Besides the Soviet/Russian capacitors, and the audiophile units, there are manufacturers who make Teflon capacitors for high-temperature use.https://www.electrocube.com/pages/433d-high-temperature-polytetrafluoroethylene-ptfe-teflon-foil-capacitors-data-sheethttps://www.electrocube.com/pages/463d-polytetrafluoroethylene-ptfe-teflon-metallized-high-temp-capacitor-data-sheet

author: coppice
author_rank: Super Contributor
timestamp: November 17, 2023, 11:03:29 am
content: Quote from: coppercone2 on November 17, 2023, 12:57:57 amBillions of them are embedded in ICs.

author: coppice
author_rank: Super Contributor
timestamp: November 17, 2023, 11:08:14 am
content: Quote from: TimFox on November 17, 2023, 03:57:14 amThose are the key usage areas, although high temperature is misleading. Medium temperature might be more accurate. Teflon starts to emit toxic fumes at high temperature. It survives the normal usage of a frying pan, but that's about its limit. Teflon was banned from most airborne use because of this, although you'll still find small amounts in the RF equipment. Its great from day to day, but an over temperature incident could turn into a nightmare in a confined space.

author: TimFox
author_rank: Super Contributor
timestamp: November 17, 2023, 02:59:38 pm
content: Quote from: coppice on November 17, 2023, 11:08:14 amTeflon disintegrates above 250oC, which is higher than the other normal plastic films. Polysulfone is about 190oC.Don't take these temperatures literally: manufacturers of capacitors specify the actual temperature range.

author: ejeffrey
author_rank: Super Contributor
timestamp: November 17, 2023, 04:15:54 pm
content: Quote from: coppercone2 on November 17, 2023, 12:57:57 amI've mostly seen them in wire bondable / die bondable form factors integrated into packages or on interposers for high speed bypassing. Once you go out to a PCB they don't have much of an advantage over ceramic for bypassing. They can be an alternative to COG for applications that need stability and I have used them in cryogenic bypass applications where normal x5r types would loose too much capacitance.

author: Terry Bites
author_rank: Super Contributor
timestamp: November 17, 2023, 05:30:13 pm
content: Me too, and I slung plenty his way. Some people huh?

author: coppice
author_rank: Super Contributor
timestamp: November 17, 2023, 05:55:31 pm
content: Quote from: TimFox on November 17, 2023, 02:59:38 pmI think you missed the point. The key problem with telflon is the toxic fumes it generates when its hot, rather than not being able to tolerate the heat. The last time I worked on flight systems we used a lot of ETFE insulation. It takes pretty high temperatures, and decomposes in a less harmful way. Its a pain to work with, though, as it cracks quite easily.

author: TimFox
author_rank: Super Contributor
timestamp: November 17, 2023, 06:12:36 pm
content: Quote from: coppice on November 17, 2023, 05:55:31 pmA NASA test document about Teflon capacitors, up to 200oC:https://ntrs.nasa.gov/api/citations/19920010798/downloads/19920010798.pdf200oC is quite high: Silicon semiconductors fail at that temperature.PVC insulation is worse: depending on formulation, the max rated service temperature is only 90oC.Above that temperature, we are talking about extremely high temperatures.

author: coppice
author_rank: Super Contributor
timestamp: November 17, 2023, 06:19:05 pm
content: Quote from: TimFox on November 17, 2023, 06:12:36 pmWe fry on teflon at 250C, but it doesn't take much more than that. Semiconductors don't fail at 200C. They have a reduced lifettime, and you can't afford to dissipate much at 200C or the die really will reach a temperature where it fails. There are a number of parts available rated for operation at 210C (not sure why they use that specific limit) or higher. They are expensive, and you tend to have to go to specialist catalogues to find them, but things like down hole oil well electronics demands these parts.

author: PartialDischarge
author_rank: Super Contributor
timestamp: November 18, 2023, 07:51:55 am
content: The 3458A has a teflon coaxial line capacitor as sample hold

author: mqsaharan
author_rank: Regular Contributor
timestamp: November 19, 2023, 04:20:25 am
content: Fluke has been using variable Teflon capacitors rated for 2.0/1.7kV in their old handheld multimeters like 802XX, 806XA, 27, at the input for adjusting high frequency response at higher voltages.