Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Extreme 220GHz+Broadband Silicon Capacitor X2SC 0201M 22nF BV11

pim.murata.com

Post reply on HN
Print view View original

21–30 of 34 posts

Re: Extreme 220GHz+Broadband Silicon Capacitor X2SC 0201M 22nF BV11

#21

Post by SV_BubbleTime »

IndrekR wrote: post #17
bri3d wrote: post #7

Earlier quoted context omitted.

Certainly not at these frequencies and corresponding high capacitance values; getting 22nF out of a PCB even with ECM would require quite a large surface area and at 220GHz you can't have that since your wavelength is so short; you'd just be making a giant resonator instead.

Length of this capacitor is close to half-wavelength of 220 GHz (in vacuum). Using siblings of this broadband capacitor (40 GHz, same package) in some designs. In assembly, those require decent process control. This 0201M package is closer to 01005 passives in pad size. Typically no solder paste is used, just flux. Solder mask alignment has to be very tight (thin web used as a dam only). Cost per cap is reasonable wh…

> Typically no solder paste is used, just flux.

Ah, so reflow the solder on the package ends then? And I assume they have a fancy precision process for “tinning” the ends?

Re: Extreme 220GHz+Broadband Silicon Capacitor X2SC 0201M 22nF BV11

#22

Post by kazinator »

thomasjb wrote: post #3

https://www.digikey.ie/en/products/detail/murata-electronics... A mere 2.40 euros each!

The temperature stability looks fantastic, but it has a voltage coefficient for capacitance which is worse than film caps.

From datasheet:

> Voltage That is significant: over just a 10V swing, it could be as high as 1%.

For a plain old polyester film cap, this is something like ±0.0001%/Volt, IIRC.

If you have an audio signal swinging over a -12 to +12 V range being coupled through a thing like this, there will be measurable distortion arising from ~ 0.1%/V variations in capacitance.

Not that you would want to necessarily do that in the first place, since this thing has an 11V breakdown voltage, nothing to write Mom home about.

There is no one-cap-fits-all; right cap type for the right job.

Re: Extreme 220GHz+Broadband Silicon Capacitor X2SC 0201M 22nF BV11

#23

Post by kazinator »

dlcarrier wrote: post #9

Someone's actually using nF, instead of 0.022uF or 22,000pF.

nF is used a fair bit in audio circuits. Nanofarad-range capacitors, typically from 1 to 100 nF, often appear in filtering circuits. From time to time, values down to around 300 to 500 pF may appear. Anything around 100 pF or less is typically for dealing with unwanted high frequencies in some way. On the other end of the scale, microfarad-range caps in the signal path appear as couplers into low-ish impedances, where good bass response is required. For doing things" with the signal, other than passing it through with bass intact and filtering out RF, the workhorses tend to be caps that are nicely measured in nanos.

In terms of brevity on a schematic, it about breaks even for two-digit nF values and wider as in 22n vs .022, and only when we have a blanket rule that when units multipliers are omitted from capacitors, they are understood to be μ. 2n is shorter than .002; and harder .0047 is easier to misread as .047 compared to 4.7n.

NOTE: You will may across audio schematics which do not write the "n"! It is assumed that any capacitance which is an integer like 33, or a real number >= 1 like 2.7, is nanofarads! Together with the convention that fractional capacitances are implicitly microfarads, so that 0.47 is microfarads.

In my local brick-and-mortar electronics shop, packages of capacitors 1nF and higher tend to be labeled in nF if they are film caps or ceramics. Electrolytics use μF; a bag of 0.1μF electrolytics would be labelled that, and not 100 nF, but the same-valued film cap will probably be 100 nF.

Re: Extreme 220GHz+Broadband Silicon Capacitor X2SC 0201M 22nF BV11

#24

Post by kazinator »

summa_tech wrote: post #18
PowerElectronix wrote: post #10

Earlier quoted context omitted.

I never understood why nF is less frequently used than uF or pF. To me, the logical thing is to express the capacity in units that are between 1 and 1000, like it's done with resistors and inductors.

I, too, had wondered; this seems particularly common in the US. My best theory is that in rough handwriting, n and u/μ can look pretty similar, and everyone sort of agreed to only use u to reduce ambiguity.

Another way to reduce ambiguity is to omit the suffix (unless it's p for picofarads) and let it be deduced from the numbers and symbols.

  47    ->  47nF (if next to plain double bar symbol with no polarity markings)
  47    ->  47μF (if next to polarized cap symbol)
  0.47  ->  0.47μF
  47p   ->  47pF
  10np  ->  np -> nonpolar -> electrolytic -> 10μF

Re: Extreme 220GHz+Broadband Silicon Capacitor X2SC 0201M 22nF BV11

#25

Post by kazinator »

nomel wrote: post #19
summa_tech wrote: post #18

Earlier quoted context omitted.

I, too, had wondered; this seems particularly common in the US. My best theory is that in rough handwriting, n and u/μ can look pretty similar, and everyone sort of agreed to only use u to reduce ambiguity.

I heard this, and have witnessed it. One of my first jobs included board rework. There were several times when I had to go ask if they wrote a uF or an nF. The response was always "obviously a uF", because nobody uses nF!

Nobody uses nF in, say, digital, where the only caps are power supply filter caps and bypass/decoupling caps next to ICs.

It's not customary to call a 0.1μF bypass cap 100 nF.

If someone wrote in 100 nF for a decoupling cap, I would tend suspect they are trying to discourage a substitution like 82nF or 150nF and want to find out why.

Whereas if it is 0.1μF, I know we can stick in a 0.2μF, if that's what we have on hand, and everything will be fine.

Re: Extreme 220GHz+Broadband Silicon Capacitor X2SC 0201M 22nF BV11

#26

Post by kazinator »

lisper wrote: post #4

Why is this a component? Couldn't you just make one of these out of PCB traces?

Not if it is to be 22 nF.

To make a 22 nF capacitor using a pair of copper pours separated by a 1.6 mm thick old school two-layer PCB, we would need something like 10 square feet! It would have to be an electronics art project, intended to be displayed on a gallery wall. :)

That goes down to something like 90 square inches if the separation is a 0.1mm thick layer of a thin four-layer PCB: still an impractically huge area.

Capacitors achieve their density in a small package by two tricks: extremely tiny dielectric gaps, and convoluted surface areas.

For instance, electrolytic caps achieve a big surface area due to using rough, anodized aluminum (or tantalum) for the anode (mnemonic: anodized aluminum -> anode). Then every ridge and crevice in that anode is available for capacitance due to using an electrolytic gel for the cathode. The roughness of the anode and the gel optimize for high surface area. Then the thinness of the oxide layer optimizes for a small gap size, also favoring high capacitance.

Re: Extreme 220GHz+Broadband Silicon Capacitor X2SC 0201M 22nF BV11

#29

Post by IndrekR »

SV_BubbleTime wrote: post #21
IndrekR wrote: post #17

Earlier quoted context omitted.

Length of this capacitor is close to half-wavelength of 220 GHz (in vacuum). Using siblings of this broadband capacitor (40 GHz, same package) in some designs. In assembly, those require decent process control. This 0201M package is closer to 01005 passives in pad size. Typically no solder paste is used, just flux. Solder mask alignment has to be very tight (thin web used as a dam only). Cost per cap is reasonable wh…

> Typically no solder paste is used, just flux. Ah, so reflow the solder on the package ends then? And I assume they have a fancy precision process for “tinning” the ends?

The (more common) package has very precise solder bumps. You can have a special order for one with ENIG finish as well, but this only makes sense if you have a really good use case (using Pb solder, wirebonding directly). Not sure what method is used to deposit this solder. Probably just stencil on wafer before slicing.
Post reply on HN