How to determine NP0/C0G capacitors?

[terranigma]

Hello, is there any specific mark, shape, color on these ceramic caps helping to determine them? Or how can I sure that a cap is not NP0/C0G type? Tolerance? Price?

Thanks.

[Conrad Hoffman]

No, there may be no indication whatsoever. Or, they may be printed with NP0 or C0G. Ideally you should know what you bought! If you put the cap on a capacitance meter and heat it up with a hot air gun, the NP0s will change very little. Any others will change value significantly.

[jcx]

size is a clue too - compare with known NP0/C0G of the same value, V rating

the "bad" high K ceramics are used to pack more C in smaller packages

[DF96]

Some C0G caps may have a black hat. A coloured hat is a sign that it is not C0G. No hat tells you nothing.

[SY]

You can find out for sure very quickly using a cap meter and a heat gun.

[terranigma]

Originally Posted by Conrad Hoffman

If you put the cap on a capacitance meter and heat it up with a hot air gun, the NP0s will change very little. Any others will change value significantly.

Good point. I just tested some of ceramics with soldering iron using my LCR meter. Many of them dropped their half capacitance even keeping soldering iron near in just ~5 seconds. Some bigger but small valued ones just drop about %3~5 even if I touch soldering iron to them! I may put some pics later.

[terranigma]

Originally Posted by SY

You can find out for sure very quickly using a cap meter and a heat gun.

Yes I just find out. All replies in thread was very informative.

Thank you all.

[BrianL]

Though not a surefire indicator, usually the ceramic caps with poor dielectric have brown colored ceramic. Most C0Gs I've seen have a lighter color such as light green (Kemet).