EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: NT0Z on April 18, 2024, 08:18:05 pm
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Hi, gang,
I'm getting ready to order a bunch of 1206 capacitors to stock my "junk box." Now, I know that we're supposed to use specialized caps for each and every application, but I want to go against the grain here if I can.
I mostly do ham radio stuff, so I'm thinking that I should just get NP0 caps (or C0G) to be safe, but what about materials? I don't want to switch "materials" every time I turn around (channeling my mother!) -- I just want to buy a big set of, say, NP0 caps and use them for everything: bypassing, front-end filters, crystal filters, coupling, AC, RF, whatever (assuming that physical size can handle the current, of course).
1206 is the smallest that I want to go, as I can barely handle that the way it is.
Would NP0 MLCC 1206s do the trick, or... ???
As always, thanks
--NT0Z
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NPO or COG ceramics are only available in the lower ranges. Say 1000 pF and below. Forget about getting the ubiquitous 0.1 uF or 1 uF caps. You will require X7R ceramics at the very least.
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NP0/C0G MLCCs can be used for almost any purpose, but they are not available with capacitance values as high as inferior dielectrics such as X7R or Z5U.
If you use the latter, read the data sheet for problems such as low Q and voltage co-efficient of capacitance, which do not occur with C0G.
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1206 package C0G capacitors are available at 100 nF, but a bit pricy.
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This is a crazy idea capacitor construction and sizes are extremely application dependent and the prices vary wildly.
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I mostly do ham radio stuff, so I'm thinking that I should just get NP0 caps (or C0G) to be safe, but what about materials? I don't want to switch "materials" every time I turn around (channeling my mother!) -- I just want to buy a big set of, say, NP0 caps and use them for everything: bypassing, front-end filters, crystal filters, coupling, AC, RF, whatever (assuming that physical size can handle the current, of course).
1206 is the smallest that I want to go, as I can barely handle that the way it is.
You need a binocular microscope, it really helps with 0805 and 0603 sizes ^-^ I am aged 70 and work with 0603 size parts, soldering by hand with a Weller 1010 station.
See this video from around 13 minutes in: https://youtu.be/eZtPR8_x0nc?feature=shared (https://youtu.be/eZtPR8_x0nc?feature=shared)
SMD capacitors can work out expensive if you want to hoard a wide variety of types. While I appreciate you wanting to stick with NP0, personally (as a fellow ham home constructor of SMD stuff) I would get a few 100n, 10n and 1n ordinary 50V ceramics. In addition a few aluminium electrolytics, perhaps 10uF, 47uF and 100uF in 25V rating.
I tend to order what I want for a particular project from Mouser, rather than buying a lot "just in case".
73 SJ
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This is a crazy idea capacitor construction and sizes are extremely application dependent and the prices vary wildly.
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1206 is the smallest that I want to go, as I can barely handle that the way it is.
Pop over to lcsc.com and enter 1206 and NPO/COG and you find you can get up to 220nF (higher if you do not mind larger cases)
Of course, common 100nF is much less than half the price of 220nF, so you may choose to skip that value. 8)
You can pay a bit more and get 1% or 2% tolerance in most values too.
Do not sort by voltage, as the lower values can be cheaper at 1kV than 50V, in the large 1206 case.
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Yes, I don't need bypass caps to be NP0, etc, and I have thousands of those in my junkbox already. :) I tend to use through-hole parts and SMD parts together, all on one side of an SMT board or Manhattan-style on a piece of copper-clad board.
I am looking into some kind of affordable USB assembly scope/stand with an LCD display. My eyesight isn't great for binocular solutions, as my left eye is awfully ornery. I use a magnification app as necessary on my Android phone, which is fantastic, but the camera lens aims down and the screen aims up, which is about 90 degrees away from useful when trying to solder. For inspection, no prob.
Although embracing it after 45 years, I do not have much experience with SMD. My trial by file was to replace SOIC8 and SOIC20 chips on the PCB of an obscure GPSDO unit. It worked (golf clap inserted here!) but it was really pushing my neurology. I have the aforementioned ornery left eye, a recalcitrant right eye, and ulnar nerve damage in my right (master) hand. What I really need is an SMD assembly robotic fixture from 20 years into the future!
I guess it comes down to wanting a good supply of "widely usable" parts on hand so I don't have to wait for delivery every time I want to build something (and pay shipping, and shipping, and shipping). I have lots of Rs, plenty or toroids to make Ls, and I have lots of through-hole Cs. I am hoping that I can sort of standardize on NP0/C0G 1206s for HF/RF stuff.
I recently ordered a couple hundred 600-V caps in the usual values for restoring tube amps and radios. Now, when I need something along those lines I have a pile of 'em on hand. Setting aside bypass caps, electrolytics, and audio stuff such as tantalums, I'm hoping that laying in a supply of NP0s will get me squared away for oscillators, filters, etc.
Plus, it's still shocking how little space SMD parts-caches take up!
Thanks for all of the advice. I appreciate it,
--NT0Z
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In a perfect world that's true. But this is far from the craziest idea I've had! :)
--NT0Z
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NPO or COG ceramics are only available in the lower ranges. Say 1000 pF and below. Forget about getting the ubiquitous 0.1 uF or 1 uF caps. You will require X7R ceramics at the very least.
Well upto about 10uF in fact, here's a 1206 2.2uF 50V C0G capacitor for example:
https://www.mouser.co.uk/ProductDetail/KYOCERA-AVX/12065C225MAZ2A?qs=%252BdQmOuGyFcHTCKX3VuI2YA%3D%3D (https://www.mouser.co.uk/ProductDetail/KYOCERA-AVX/12065C225MAZ2A?qs=%252BdQmOuGyFcHTCKX3VuI2YA%3D%3D)
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Well upto about 10uF in fact, here's a 1206 2.2uF 50V C0G capacitor for example:
https://www.mouser.co.uk/ProductDetail/KYOCERA-AVX/12065C225MAZ2A?qs=%252BdQmOuGyFcHTCKX3VuI2YA%3D%3D (https://www.mouser.co.uk/ProductDetail/KYOCERA-AVX/12065C225MAZ2A?qs=%252BdQmOuGyFcHTCKX3VuI2YA%3D%3D)
Have you looked at its datasheet? (It has 'X7R series' in a shop description too, beside with 'COG'). Shops sometimes make mistakes.
Once I have seen 1500 uF 450V rated 'film' capacitor of electrolite type.
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My basic component stock is 0805 resistors and capacitors, with capacitors being C0G up to 1nF, X7R beyond there, and larger chips (1206, 1210) in the larger values (couple uF up). Resistors more diverse than capacitors of course, and capacitors at least 1, 2.2, 4.7 series. And of course I've collected many other values over the years, for specific needs, from client projects, etc.
You don't actually -- or not necessarily, anyway -- want parts as low-loss as C0G for bypass. A little loss helps dampen out supply fluctuations and keeps PDN (power distribution network) impedance flatter; anywhere you have resonances in the PDN, you have valleys that are lower ("better"), yes, but you have complementary peaks where the impedance is higher.
It's not a big deal anyway for RF circuits, where impedances are fairly modest to begin with (50 ish ohms), or logic circuits of similar nature (single chips draw comparable switching currents). Unless of course they're not, in which case more work is necessary: an SoC or FPGA will generally need many bypasses in parallel, many supply pins, and wide pours; an RF power amp may use resonant traps (1/4 wave between subsequent blocks of bypasses; staggered values/chip sizes) to optimize PDN attenuation / isolation at the center frequency.
And so the question becomes: not whether you need some amount of capacitance, or ESR, but how much. Of both. Ceramic caps are generally quite low ESR, so you have that corner covered; higher ESR can always be obtained by adding more externally (at some expense to ESL, as the body length of C+R+traces adds up), or using [selected*] polymer, or tantalum or electrolytic, types.
*Al poly are generally quite low impedance, but they are available in a wide range, including fairly mid ESR values. Dry tantalum cover a wide range as well, averaging mid, with some low values available.
It's worth remarking on, or contemplating, just how low ESR C0Gs really are. Qs are typically 1000s, with 3k, 10k even, not being unusual. ESR is so low that it's difficult to measure, even with precision equipment. It's so low that connections you would normally think innocuous, are actually prone to resonance. Chip parts in parallel, adjacent on the PCB, resonate with the few nH between them. Even power components (10s nF say), which can contribute EMI peaks in the 10s MHz range.
As long as such resonances aren't a problem in the application, or can be dampened by connected components, that's fine. Just to be aware of it, and quickly model or test to verify it.
Tim
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I use a magnification app as necessary on my Android phone, which is fantastic...--NT0Z
Good Morning NT0Z, sorry to interupt your thread, but you mentioned a phone app that I think I could find useful....can I bother you for a link to it, or a name I could search for without having to paw through the bad ones? Thank you. :-+
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The Android magnifier app that I use daily is called "Magnifier and Microscope," and I found it in the usual Google Play App Store.
It used to be called Cozy Magnifier. The author is "Hantorm."
You can download "frozen" images, and I use it to take many close-up photos, even for the magazine articles that I write.
It's free, with unobtrusive inline advertising.
Best of luck,
NT0Z
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@Tim: It IS interesting that NP0/C0G might not be "sloppy" enough for the most effective bypassing...and to avoid unwanted resonances.
I love learning esoteric things...just before I mostly hate accommodating the thing I just learned. :)
Thanks, as always,
--NT0Z