[Elecraft] ESD

[Kurt Pawlikowski]

John,

    Interesting. The link is related to CMOS, which is extremely 
sensitive to ESD.

    Capacitors: I don't understand how a cap can be damaged unless ESD 
has a transient faster than the cap can charge or there is enough 
current to charge the cap beyond it's limits. But isn't that what the 
cap is supposed to do? Yes, once the voltage across the cap is exceeded, 
all bets are off!

    If you're talking about caps in tube equipment, I think the problem 
there would more likely be explained by degrading/defective components, 
or components that were exposed to high voltage, relatively high power 
discharges (i.e., not ESD).

    I can understand thin film resistors (the higher the resistance, the 
more likely an arc). Not sure about diodes. I'm thinking that if the ESD 
has a transient faster than the diode can handle, maybe. It just seems 
to me that if forward biased, it simply conducts. If backward biased, it 
acts like a zener (which conducts).

    Some interesting links...

    http://www.aiinet.com/documents/html/AI180hwman/m0699/aihxa.htm
    http://www.electrostatics.net/library/articles/ESD_damage.htm
    http://www.evaluationengineering.com/archive/articles/1102esd.htm
    http://focus.ti.com/lit/an/ssya010/ssya010.pdf
    http://www.ce-mag.com/archive/03/03/henry.html
    http://www.e-gizmo.com/ARTICLES/ESD/ESD2.HTM
    
http://electrostaticsolutions.blogspot.com/2005/06/are-capacitors-esd-suceptible.html

    Some of these have pictures (always interesting!). The last link 
talks about capacitors. One of the links is very IEEE technical. More 
fuel for the fire! {'-)

    Regards,

    kurtt

    Kurt Pawlikowski, AKA WB9FMC
    The Pinrod Corporation
    kurtt at pinrod.com
    (773) 284-9500
    http://pinrod.com
   
John Huggins wrote:
>
>
> John Huggins wrote:
>> While it is true caps can be relatively sturdy, capacitors are 
>> damaged by ESD if the high voltage appears across their leads despite 
>> what one might think of "charge time."  Any usual thinking of how 
>> caps work begins to break down once the peak voltage (not rated 
>> voltage, but whatever the much higher real peak voltage is - ie 
>> 400-1000V for a 100V ceramic)  is exceeded even with the low low 
>> power of an ESD event.  Audiophile Tube Stereo freaks recognize caps 
>> that have been zapped because they develop pinholes in their 
>> dielectric and begin to add pop and hiss to their "sound."
>>
>> Thin film resistors are also easily "hurt" by ESD.  Same with diodes.
>>
>> NASA is particularly anal about this (for obvious reasons) and have 
>> this to share...
>>
>>  http://workmanship.nasa.gov/wppr_comp_c2mos.jsp
>>
>> While it is true not all ESD events cause damage. The outcome of a 
>> discharge to a sensitive device or assembly will depend on many 
>> factors, including:
>> - device sensitivity
>> - severity of ESD stress
>> - actual strike site
>>
>> Some components handle ESD better than others, but none are entirely 
>> immune.
>>
>> If we are to assume Elecraft handles their parts with the care the 
>> parts probably received on their way to Elecraft (I hope this is so) 
>> and then delivered them to us with the same care, we should not break 
>> the chain of proper handling.
>>
>> ESD is so easy to do correctly why not treat all the parts with the 
>> same level of respect.  The chances of success are probably 
>> measurably better.
>>
>> John
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>