[SI-LIST] Re: some help needed: Re: Testing chips with system level specs
- From: "Grasso, Charles" <Charles.Grasso@xxxxxxxxxxxx>
- To: "Pommerenke, David" <davidjp@xxxxxxx>, <doug@xxxxxxxxxx>, <dcuthbert@xxxxxxxxxx>
- Date: Wed, 6 Sep 2006 14:49:24 -0600
Posted for David Pommerenke.
Best Regards
Charles Grasso
Compliance Engineer
Echostar Communications Corp.
Tel: 303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Pager/Short Message: 3032042974@xxxxxxxxx
Email: charles.grasso@xxxxxxxxxxxx;
Email Alternate: chasgrasso@xxxxxxxx
Charles,
On the "really fast discharges" using the Andy Hish simulatior I do not
have the data here, as I am in Germany right now.=20
But if you look at
http://web.umr.edu/%7Etiumr/davidjp/Jour_Estat__high_qual_1995.pdf
(the link has %7 in it, that is OK)
at figure 10 and figure 11. You see measurements of discharges at 10kV
having risetimes of about 100ps or so. That is very close to the limit
of the measuremetn system (SCD5000).
The physics of the very fast discharges in air discharge is explained in
http://web.umr.edu/%7Etiumr/davidjp/ESDForum_1993.pdf
(kind of old paper, but the physics have not changed).
Regards,
David Pommerenke
-----Original Message-----
From: Grasso, Charles [mailto:Charles.Grasso@xxxxxxxxxxxx]
Sent: Wed 9/6/2006 9:44 AM
To: Pommerenke, David; doug@xxxxxxxxxx; dcuthbert@xxxxxxxxxx
Cc: SI-List; emc-pstc
Subject: RE: [SI-LIST] Re: Testing chips with system level specs
=20
David,
Can you please enumerate what "really fast discharges" are with the
Andy Hish generator @ 25kV?=20
Using the conical probe, the most prevalent discharge type I have seen
measured is a slow (ns) rise time pulse at the first strike as the probe
approaches the UUT and then a fast (ps)secondary spike as the probe
completes the contact to the UUT.=20
Best Regards
Charles Grasso
Compliance Engineer
Echostar Communications Corp.
Tel: 303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Pager/Short Message: 3032042974@xxxxxxxxx
Email: charles.grasso@xxxxxxxxxxxx;
Email Alternate: chasgrasso@xxxxxxxx
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Pommerenke, David
Sent: Wednesday, September 06, 2006 7:04 AM
To: doug@xxxxxxxxxx; dcuthbert@xxxxxxxxxx
Cc: doug@xxxxxxxxxx; SI-List; emc-pstc
Subject: [SI-LIST] Re: Testing chips with system level specs
Doug,
it is all a matter or likelyhood. If you use rounded electrodes (no =3D
corona discharge) and dry air you will get really fast discharges up to
=3D
25k
V or so. We have measured such discharges usign the old Andy Hish =3D
simulator, but also with people.
If you look at the gemeotry of a memory card there are plenty of sharp =
=3D
edges. If we assume the card, or the cell phone or the camera is charged
=3D
to 8kV and you plug the card into the reader then there will be some =3D
corona. This corona will initiate the discharge over a larger distance =
=3D
(e.g, Paschen length for 8kV is about 2mm or so) and the discharge will
=3D
be soft. Without the corona the electrodes could approach further before
=3D
they the discharge is initiated. In summary, I agree that for such a =3D
geometry the likelyhood of sub-nanosecond discharges at 8kV is probably
=3D
low.
David Pommerenke
-----Original Message-----
From: Doug Smith [mailto:doug@xxxxxxxxxx]
Sent: Tue 9/5/2006 8:17 PM
To: dcuthbert@xxxxxxxxxx
Cc: doug@xxxxxxxxxx; Pommerenke, David; 'SI-List'; 'emc-pstc'
Subject: Re: [SI-LIST] Re: Testing chips with system level specs
=3D20
Hi David,
It is good to have lots of discussion on this. ESD is often only=3D20
considered when a gross problem surfaces. This discussion will help=3D20
bring the issue to the front.
What voltages were you using? Such fast events are common at low=3D20
voltages and rare at high voltages. I have personally measured =
edges=3D20
of <80 picoseconds at low voltages. For my chip example where slow=3D20
approach (say plugging in a memory card into a reader) is the norm, =
a=3D20
fast edge is probably not possible although I do not have=3D20
comprehensive data on this.
It seems one has to work at it to get a fast discharge at high=3D20
voltages, at least that is what I read through the lines. Hish =
et.al.=3D20
in a 1991 paper show three waveforms at about 10 kV, two slow and =
one=3D20
fast, but again they used a specific conical shaped tip with =
symmetry=3D20
that was required (that part was not spelled out clearly in the =
paper=3D20
but I was talking with a friend of Andy's). They said the =
likelihood=3D20
of the fast event was much smaller for a rounded tip.
Doug
David Cuthbert wrote:
> Doug,
>=3D20
> I've done some measurements of actual human body discharges into a 2 =
=3D
ohm
> current target. The rise time was less than 500 ps. I plan to continue
=3D
this
> work soon using a 2.5 GHz oscilloscope and a TDR. The human SPICE =3D
model I
> developed is quite interesting and I'll be refining it.=3D20
>=3D20
> I then built a circuit that quite accurately mimics the actual human =
=3D
body
> discharge. It is much more complex than the usual ESD gun =
network.=3D20
>=3D20
> Dave Cuthbert =3D20
>=3D20
>=3D20
> LINEAR TECHNOLOGY CORPORATION
> =3D20
>=3D20
> Internet Email Confidentiality Footer=3D20
>=3D20
> This e-mail transmission, and any documents, files or previous e-mail
> messages attached to it may contain confidential information that is =
=3D
legally
> privileged. IF you are not the intended recipient, or a person =3D
responsible
> for delivering it to the intended recipient, you are hereby notified =
=3D
that
> any disclosure, copying, distribution or use of any of the information
> contain in or attached to this transmission is STRICTLY PROHIBITED. If
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=3D
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manner.
> Thank You
>=3D20
>=3D20
>=3D20
> -----Original Message-----
> From: emc-pstc@xxxxxxxx [mailto:emc-pstc@xxxxxxxx] On Behalf Of Doug =
=3D
Smith
> Sent: Monday, September 04, 2006 11:15 AM
> To: davidjp@xxxxxxx
> Cc: SI-List; emc-pstc
> Subject: Re: [SI-LIST] Re: Testing chips with system level specs
>=3D20
> Hi David and the group,
>=3D20
> You have presented good data which you and others have presented =
in=3D20
> the various standards bodies we have attended together. However,
have=3D20
> you ever seen an air discharge with a 700 ps rise time at 8 kV? If so,
=3D
> what is the probability in the distribution of 8kV discharges? I=3D20
> measured a lot of discharges and none came close to that. Some had
a=3D20
> vestige of the initial spike, but it was not much larger that the body
=3D
> discharge after and its risetime was always much slower.
>=3D20
> If this concept was to be included in a standard, a lot of work
would=3D20
> be needed to determine the right amount of filtering.
>=3D20
> But, to apply this waveform (8 kV contact discharge) to a solid
state=3D20
> device like a flash memory card is not justified and will
needlessly=3D20
> increase device cost. I do agree that an 8kV contact discharge =
has=3D20
> uses in system level testing which what the 61000-4-2 standard =
was=3D20
> intended for.
>=3D20
> There is a LOT of work to apply that standard to devices, much =
more=3D20
> than the filtering I wrote about. There is no guidance in the standard
=3D
> as to how to apply the discharge and how it is applied will =
almost=3D20
> completely determine the results (other pins grounded or
ungrounded,=3D20
> if grounded how, and much more). If someone says their device
passes=3D20
> this test, the statement is meaningless at this point unless the
test=3D20
> method is documented.
>=3D20
> Doug
>=3D20
> Pommerenke, David wrote:
>=3D20
>>Group,
>>I like the idea from Doug to use a ferrite for reducing the risetime =
=3D
of a
>=3D20
> contact mode ESD generator. However, I do not agree to the statement =
=3D
that
> air discharge ESD will not show fast risetimes and high peak values at
> voltages above 4kV. The reference event for the ESD standard IEC =3D
61000-4-2
> is the discharge between a hand-held metal part and a large metallic =
=3D
surface
> (called "hand-metal ESD") in contrast to the IC-HBM standard that is =
=3D
based
> on a discharge from the skin.
>=3D20
>>The current has two maxima, an initial peak caused by the charges on =
=3D
teh
>=3D20
> hand and on the metal part and the later body waveform. If the initial
=3D
peak
> will show up depends on the resistance of the arc as a function of =3D
time. If
> the arc resistance drops quickly (let us say in less than 1ns) below =
=3D
the
> source impedance of the discharging person (without going into =3D
details,
> assume 100-300 Ohm http://web.umr.edu/~davidjp/paper/00478274.pdf ), =
=3D
then
> the inital peak will show up. If the arc resistance drops slowly, let
=3D
us say
> it reaches 300 Ohm in 5 ns, then the initial peak will not show up, as
=3D
the
> arc resistance is too high during this phase of the discharge.
>=3D20
>>So the quesion is: How fast does the arc resistance drop?
>>
>>This depends mainly on:
>>
>> - Voltage at the moment the discharge starts
>> - Gap distance at the moment the discharge starts
>>
>>The smaller the gap, the faster the arc resistance will drop. The gaps
>=3D20
> will in most cases not discharge over distances given by the =3D
Paschen-law,
> but at smaller distance. This is a result of the speed of appraoch and
=3D
the
> statistical time lag ().
>=3D20
>>In general the behavior is as follows:
>>
>> Fast rise times --- Slow rise times
>> =3D20
>> Fast approach slow approach
>> Dry air Moist iar
>> Clean surfaces Dirty surfaces
>> Oxid layer, or paint =3D20
>>=3D20
>>The effect of environmental conidtions on the discharge are very =3D
strong.
>=3D20
> Humidity dominates over all other influencing factors (I can email =3D
papers on
> this topic on request). It is not possible to state: Above XYZ kV =3D
discharges
> will not have an initial peak.
>=3D20
>>To provide further evidence I attached a set of measurements that show
=3D
the
>=3D20
> peak current as a function of voltage having the arc length as =3D
parameter.
> The data is from D.Pommerenke, ESD: Transient fields, arc simulation =
=3D
and
> rise time limits, Journal of Electrostatics, 36, 1995, 31-54.
>=3D20
>>However, the likelyhood of having fast risetimes (e..g, less than =3D
200ps)
>=3D20
> decreases above about 6-10 kV. Nobody knows the distribution of ESD
> intensity in reality very well. There are a few studies, but they only
=3D
help
> to answer the question of voltage distribution, not of rise time
> distribution or field strengths distribution.
>=3D20
>>Overall, I warn against changing the pulse parameters above some =3D
voltage
>=3D20
> without having strong evidence that the reduction in protection level
=3D
is
> acceptable, the 0.7ns-1ns risetime is already providing only partial
> coverage.=3D20
>=3D20
>>Products that may see many ESDs or support critical functions should
>=3D20
> certainly not be tested at a different waveform. The 0.7ns - 1ns rise
=3D
time
> standardized contact mode waveform certainly does not cover the faster
=3D
ESD
> events.
>=3D20
>>Regards,
>>
>> David Pommerenke
>>
>>
>>
>>-----Original Message-----
>>From: si-list-bounce@xxxxxxxxxxxxx on behalf of Doug Smith
>>Sent: Sun 9/3/2006 11:03 PM
>>To: SI-List; emc-pstc
>>Subject: [SI-LIST] Testing chips with system level specs
>>=3D20
>>Hi All,
>>
>>I have been writing and recording again, this time on applying
system=3D20
>>level ESD tests to devices. If you are involved with either =
devices=3D20
>>that can be handled by people (for instance a USB thumb drive for=3D20
>>flash memory card) or the equipment they plug into you will find =
my=3D20
>>latest article and podcast of interest. Any standards people out =3D
there?
>>
>>This month's Technical Tidbit describes a method to simulate air=3D20
>>discharges at voltages above 4 kV in a repeatable way using a modified
=3D
>>contact discharge. This method is especially useful in ESD testing
of=3D20
>>solid state circuits using IEC 61000-4-2.
>>
>>Abstract: Contact discharge is used in ESD testing to improve =
test=3D20
>>repeatability, yet air discharge has significantly different=3D20
>>characteristics at higher voltages. A test method is described =
that=3D20
>>uses a modified contact discharge to simulate the characteristics
of=3D20
>>an air discharge but with improved repeatability.
>>
>>The link to the article is the picture of the experimental test
setup=3D20
>>at the bottom of the home page at http://emcesd.com . Or just click on
=3D
>>this link:
>>
>>http://emcesd.com/tt2006/tt090106.htm
>>
>>There is also an audio discussion of this article on my podcast
site:=3D20
>>http://emcesd-podcast.com where the direct link to the audio file is:
>>
>>http://emcesd-podcast.com/2006/september/2006-0904.mp3
>>
>>Can't download mp3 files? Download the following instead:
>>
>>http://emcesd-podcast.com/2006/september/2006-0904.dcs
>>
>>After download, change the extension from .dcs to .mp3 and the =
file=3D20
>>will then be able to play on most computers.
>>
>>Doug
>>
>=3D20
>=3D20
--=3D20
------------------------------------------------------------
___ _ Doug Smith
\ / ) P.O. Box 1457
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D Los =
Gatos, CA =3D
95031-1457
_ / \ / \ _ TEL/FAX: 408-356-4186/358-3799
/ /\ \ ] / /\ \ Mobile: 408-858-4528
| q-----( ) | o | Email: doug@xxxxxxxxxx
\ _ / ] \ _ / Web: http://www.dsmith.org
------------------------------------------------------------
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