EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: GreggD on October 04, 2017, 01:52:33 pm
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I got some 1% caps at Mendelsons surplus just to test my meters.
That got me thinking. Went to Digikey to see what they had.
Naturally I looked for 1% film caps as all the 1% I have ever has are film.
They only have ((one)) 1% in stock. I was shocked.
Then ceramic, plenty in stock. Sorted by value the bigest being 0.1uF NP0. Ok. But look at the prices $6.20 for one.
Ok 1000pF for $0.12 Qu-1, $0.023@Qu-1000 Thats nice.
https://www.digikey.com/products/en/capacitors/ceramic-capacitors/60?FV=ffe0003c%2Cc0001%2C1c0002&mnonly=0&ColumnSort=-2049&page=1&stock=1&pbfree=0&rohs=0&cad=0&datasheet=0&nstock=0&photo=0&nonrohs=0&newproducts=0&quantity=&ptm=0&fid=0&pageSize=25 (https://www.digikey.com/products/en/capacitors/ceramic-capacitors/60?FV=ffe0003c%2Cc0001%2C1c0002&mnonly=0&ColumnSort=-2049&page=1&stock=1&pbfree=0&rohs=0&cad=0&datasheet=0&nstock=0&photo=0&nonrohs=0&newproducts=0&quantity=&ptm=0&fid=0&pageSize=25)
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100nF @50V is a BIG, HUGE, ENORMOUS state of the art thing in an NP0 ceramic, no surprise that it is a little spendy, I am amazed that it exists at all....
The fact that you can get caps in values and tolerances useful for audio filters in NP0 is a nice surprise, that has come on a long way, and low value .
Regards, Dan.
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As films caps in SMT are a little temperature sensitive and limited, there is some demand for larger capacitance NP0 caps. With MLCCs it's just a question of size and price to make some.
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Polystyrene used to be a common part to get in 1% or better tolerance, but as they arre no longer being made they are only available as either NOS or used. However I have seen them in reasonably large values ( around 100n 160V, with 0.1% tolerances), and this was often used in telecoms as analogue filter values.
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Sure, 1% capacitors are available new -- just not from Digikey and Mouser.
Check out http://www.justradios.com/capacitors.html (http://www.justradios.com/capacitors.html)
They have 1% silver mica and polystyrene. Like Kleinstein says, not SMD-friendly. So that explains their disappearance from D&M.
Yeah, I still build through-hole stuff and use wire-wrap...
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Sure, 1% capacitors are available new -- just not from Digikey and Mouser.
Check out http://www.justradios.com/capacitors.html (http://www.justradios.com/capacitors.html)
They have 1% silver mica and polystyrene. Like Kleinstein says, not SMD-friendly. So that explains their disappearance from D&M.
Yeah, I still build through-hole stuff and use wire-wrap...
Digikey has through hole 1% mica capacitors in stock.
Mouser has through hole 1% film capacitors and both through hole and SMD 1% mica capacitors sitting in stock.
You might not like the prices but they are readily available.
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SMT film is a pain because of very tight process requirements, the window between "lead free solder melts" and "cap melts" is just too small for comfort.
CDW have some interesting mica SMT if you are doing big RF, lots of volts and a reasonable number of amps.
Regards, Dan.
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Cermics. Ok, it is obvious that Class 2 and 3 dielectrics are not going to be 1%. Class 1 though:
Resistance to Flexure : ±5% or ±.5 pF, whichever is greater
Thermal Shock : ? ±2.5% or ±.25 pF, whichever is greater
Load Life: ? ±3.0% or ± .3 pF, whichever is greater
Load Humidity :? ±5.0% or ± .5 pF, whichever is greater
You get the picture. As soon as you solder it, the value will change.
Source: http://datasheets.avx.com/C0GNP0-Dielectric.pdf (http://datasheets.avx.com/C0GNP0-Dielectric.pdf)