Capacitors and ESD

Capacitor divider. Run the numbers.

What's a human body, about 1nF and 10kV worst case? Not going to do much to anything over 0.1uF.

Tim

-- Deep Friar: a very philosophical monk. Website:

The common body model is 100 pF in series with 1.5K. That, charged to

I tested some 0603 16 volt ceramic caps to see when they'd fail. At

John

Yes, kinda, BUT if it's an electrolytic, it heals afterward, and if it's a ceramic, there isn't any permanent damage, and it goes back to 'normal' after a while (faster if it's hot).

Only the ultra-thin MOS capacitors of IC processes are really likely to take permanent damage from a little bit of charge.

Some of the high-density ceramics are piezoelectric, and those can turn nonlinear if you get 'em above the voltage rating. One manufacturer actually required the capacitance value to be measured BEFORE any verification of max sustainable voltage, so the units wouldn't fail incoming testing.

Of course, they'd be no good at bypassing at that voltage. The D-E curve (think B-H) is going to be flat as Kansas.

Tim

Why are you spoiling my fun?

John

Fun? You aren't having fun, the damn thing didn't even explode. ;-)

Tim

Ceramic caps are nonlinear enough that you could make a useful parametric amplifier from some.

Hmmm, and a fA-sensitive amplifier.

John

I recall HP already had made a leakage meter like that, using diode capacitance instead.

With pA-sensitive op-amps available these days, there isn't much point in doing that. Yeah, you said fA, but you'd be taking days to accumulate any charge to measure it. Unless it was a microscopic hunk, like if you got at a single cell of FeRAM. Ah, but a monolithic femtoammeter would perform well, wouldn't it? Still, it would be quite noisy. You might end up with a better thermometer.

Tim

Hello,

Yes ESD can destroy MLCC capacitors, even below the voltage breakdown limit. Try to locate "DC, AC and Pulse Load of Multilayer Ceramic Capacitors". This is a former PHILIPS document. You can probably find it on

If you can't locate it, please contact me.

Best regards,

Wim PA3DJS

Addition to text shown above:

The link to the document is:

Best regards,

Wim PA3DJS

Wim,

I just sat down and read the document:

I was hoping that if ESD was a problem for capacitors that I would be able to clearly understand that indeed there is an ESD issue. From what I have read and digested - it seems that there is not an ESD issue with capacitors.

Page 7 starts the section on ESD Pulses.

"The immunity of MLCCs to ESD pulses is not well characterized"

"When subjected to ESD pulses, low-capacitance MLCC's sometimes exhibited corona effects without internal damage"

"All products were resistant to at least 2.5 kV HBM [Human Body Model] and 1kV MM [Machine Model ]pules. 0805 and 1206 products showed the same behaviour."

There are two graphs Fig. 12 and Fig. 14 that show the experimental data on ESD immunity. I am not sure how to interpret these graphs. Are the areas that are shaded problem areas?

Thanks for any clarification.

-H

Please locate the waveform for the EN 61000-4-2 ESD gun. For the 8 kV pulse, the peak current is 30A. the I^2*t product is significantly higher then the product for the human body model as used in the document.

You should carry out I^2*t interpolation between the HBM, "your pulse" and the PHILIPS MM to figure out whether the selected capacitors will survive.

Therefore they did this investigation.

Depending on your environment, EN 61000-4-2 pulses can be up to 8 kV (contact discharge).

Lower edge of shaded area: first capacitor fails, so below the shaded area all survive Higher edge of shaded area: all broken or damaged, so above the shaded area all will be broken.

Because of the energy in the MM pulse, the pulse values in figure 14 are far below the voltages in figure 12.

Best regards,

Wim PA3DJS

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Comments like this make me appreciate Keithley 619 multimeters better.

Here's my ebay Keithley 610 measuring a surface-mount 100G resistor, soldered to the Pomona plug. This meter's full-scale ranges go to

ftp://jjlarkin.lmi.net/Keithley.JPG

And here's my home-made fA parts tester...

ftp://jjlarkin.lmi.net/99A260A1.JPG

ftp://jjlarkin.lmi.net/99A260A3.JPG

ftp://jjlarkin.lmi.net/99S260A.JPG

Turns out that some cheap transistor c-b junctions are better pA diodes than some official, expensive picoamp diodes.

I still want to demonstrate single-electron charge quantization at room temp using available parts. It should be just possible.

John

Thank you very much Wim!