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PULSE

EEWeb.c

Issue

April 17, 20

David ArthurSouthWest

NanoTechnologInc. (SWeNT)

Electrical Engineering Commun

EEWeb

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3/26EEWeb |Electrical Engineering Community Visit www.eeweb.com 3

TABLE OF CONTENTS

David Arthur 4SOUTHWEST NANOTECHNOLOGIES, INC.

Single Wall Carbon Nanotubes Enable 10Printed ElectronicsBY DAVID ARTHUR

Featured Products 13

Electric Overstress (EOS) and Its

Effects on Todays ManufacturingBY VLADIMIR KRAZ WITH ONFILTER

The Story of James Clark Maxwell 22

and Switched Capacitor FiltersBY PHILIP GOLDEN WITH INTERSIL

RTZ - Return to Zero Comic 25

How SWeNT is tapping into the unused potential of carbon nanotubes and creating a standardfor thin film production.

Interview with David Arthur - CEO

One-hundred years after their discovery, Maxwells switched capacitor filters revolutionized themodern analog circuit industry.

How this device-damaging phenomenon can be prevented by using EMI filters in the productionenvironment.

15

8/2/2019 Eeweb Pulse 2012 42


INTERVIEW

SouthWest NanoTechnologies, Inc.

Will you tell us about your25+ years of experiencecommercializing productsutilizing advanced materials?

I graduated with a BS in ChemicalEngineering from Tufts Universityin 1980. My first job was in R&D

with a specialty materials company,Rogers Corporation. During my14 years there, I worked in R&D,Manufacturing and Marketing. Mymain area of responsibility wascircuit materials for Microwave,RF and High Speed Digitalelectronics packaging. I wasactively involved with developingcopper-clad dielectric materialsbased on fluoropolymers filled with

glass microfibers and/or ceramicparticles. Dielectric constant wascontrolled over a range of about 2to 10 or so. These materials enabled

very low loss signal transmission athigh frequencies (10 GHz +), as

well as low cross talk and fast risetimes for digital packaging.

DDavid Arthur - CEO

avid rthurAI was also involved with working

with leading companies like IBMon developing novel fabricationmethods for making high densitymulti-layer printed circuit boardsfor high performance computingapplications. These circuit boards

were designed to enhance reliability

during thermal cycling of platedthru holes and also solder jointsof ceramic components surfacemounted to the circuit boards. While

working at Rogers, I attended theUniversity of Connecticut part-timeand received an MS in Chemical

Engineering in 1990.

8/2/2019 Eeweb Pulse 2012 42


INTERVIEW

In 1994, I joined A.T. Cross, a highquality writing instruments company.I was hired to lead the start-up ofCross Pen Computing Group. This

was part of a strategy to grow thecompany by diversification and alsoto address the risk that dramaticgrowth in e-communications wasreducing the use of conventional

writing instruments. After a fewyears of development, we launchedseveral products for pen computing.Our flagship product was theCrossPad, which was a personaldigital notepad. It enabled the userto write on conventional paper with

physical ink and capture all thepen strokes in the form of digitalink. This was accomplished bytransmitting an RF signal from thepen tip and receiving this signal in athin antenna grid discreetly mountedunder the pad of paper. The usercould then upload the notes to a PCfor storage, editing or translation totyped text. Handwriting recognitionsoftware was licensed from IBM.

The first Christmas selling season,we sold $25 million of CrossPads.This was a very busy time for me, asshortly after joining Cross, I became

VP of Engineering for the WritingInstrument side of the company.I also attended an executiveMBA program at Northeastern,graduating with an MBA in 1996.

In 1998, I took a CEO position at TPIComposites, a leading producer of

sailboats, including the J-Boat brand.TPI had a patented manufacturingtechnology (SCRIMP) that allowedlarge-scale structural compositesof complex shape to be fabricatedat higher quality, lower cost andlighter weight than alternativetechnologies. This process wasgreat for making sailboat hulls and

was also used to make wind blades,bridge decking and transportation

vehicles of various types (includinglarge refrigerated rail cars). Duringthe short time that I was there, weincreased the profitability of theboat business, completed an M&Adeal with Hardcore Composites(the merged company was called

I would not say that

I have any tricks.

Success comes theold fashioned way;

developing unique

skills, hard work,

personal integrity,

building relationships,

and not beingafraid to take risks

and innovate.

Composite Solutions) and startedup a new plant to build refrigeratedrail cars. After successfullyproducing the first dozen 72 foot

long rail car prototypes, we signeda very large contract with a leadingcompany in the rail industry. I lefta short time later, as the previousCEO and founder really wasntready for retirement and he cameback to more actively engage in thebusiness.

In 1999, I became VP of StrategicPrograms at Helix Technologies,a leading producer of cryogenic

vacuum pumping systems. Thiswas right around the time whendot coms were the rage. Helix

wanted to grow its service businesswith a disruptive technologyplatform called GOLDLink Support(Global On-line Diagnostic Linkto Customer Support). GOLDLinkallowed Helix provide remotediagnostic monitoring of sputteringand ion implantation tools usedin semiconductor fabs aroundthe world, enabling predictive

maintenance practices (eliminatingunscheduled downtime), improved

vacuum process control and lowercost of equipment ownership for thefabs. GOLDLink also enabled Helixto re-engineer its service deliverprocess, significantly improvingthe profitability of the servicebusiness. My main responsibilityat Helix was to lead the team tocomplete the development of the

GOLDLink platform and launchgoldlinksupport.com, which was amajor success for Helix. After a few

years, however, the semiconductorindustry went into another downcycle, which put a hold on the nextphase of our expansion plan. Atabout this time, nanotechnology

was the rage, so I decided toreturn to my roots (materialsscience) and seek opportunities innanotechnology.

In 2001, I became COO of Eikos,a developer of materials for theDOD and selected commercialapplications. I was asked to helpanalyze Eikos IP portfolio and figureout what opportunities there werefor commercializing productsbased on differentiated technology.

8/2/2019 Eeweb Pulse 2012 42


INTERVIEW

At that time, Eikos revenues wereprimarily R&D contracts and federalgrants. This led to the developmentof carbon nanotube ink technology,

which allowed transparentconductive films to be made usingspraying methods. These carbonnanotube films were more flexibleand more neutral in color thanIndium Tin Oxide (ITO). As partof the commercialization plan, Ihelped Eikos raise equity capitaland negotiate agreements withstrategic partners. It was at this timethat I met Professor Daniel Resascofrom the University of Oklahoma. I

was convinced then (and remain sotoday) that the CoMoCAT processthat he invented was the best way tomake single-wall carbon nanotubesof controlled structure at large-scaleand low-cost.

In 2005, Bob Praino and I co-founded Chasm Technologies,a consulting firm that helps itsclients commercialize productsthrough smart application ofmaterials science. The sweetspots for Chasm are projects thatinclude nanomaterials, roll-to-rollcoating, manufacturing processesand/or specialty equipmentdesign and build. There are ninepeople who work at Chasm andmost of them have several yearsexperience at Polaroid. SouthWestNanoTechnologies (SWeNT) wasone of Chasms first clients. Soon

after forming Chasm, ProfessorResasco contacted me to see if I

would be interested in being CEOat SWeNT. To make a long storyshort, I declined a few times, butafter meeting with him and thenChairman Skip Porter, I said yes.

At the time I joined SWeNT, the

organization consisted mainly ofpost-docs from Resascos teamand the scale of operations wasquite small (pilot scale). Over time,

we added several people to theteam with industrial experienceand we focused on scaling up themanufacturing technology. This ledto the construction of a large-scale18,000 SF manufacturing planton an 8-acre site in Norman, OK.This plant put SWeNT on the radarscreen of any serious developer ofcarbon nanotube enabled products.In 2009, SWeNTs material wasrecognized by NIST as the starting

material for its Standard ReferenceMaterial program for carbonnanotubes. This was an honor forus.

SWeNT is now

focusing on

commercializing

products that are

tailored for target

applications. One of

the things that sets

SWeNT apart is a

willingness and abilityto tailor products for

target applications.

In 2009, SWeNT also formalized itsstrategic alliance with Chasm, jointly

establishing a Carbon NanotubeApplications DevelopmentCenter at Chasms facility in theBoston area. This relationshipand this center have been key tocommercializing SWeNTs carbonnanotube products, especially forPrinted Electronics applications. In2010, SWeNT became the first USmanufacturing company to get aconsent order from EPA to make andsell commercial quantities of single-

wall carbon nanotubes. In 2011,SWeNT also received a consentorder from EPA for its specialty multi-

wall carbon nanotube products.

In 2011, SWeNT signed a licenseagreement with Chasms V2Vink technology, which enablesSWeNT to make and sell uniqueink products that allow carbonnanotubes to be printed at low-costusing standard industrial printingequipment. The combination ofSWeNTs unique ability to controlcarbon nanotube structure viaselective synthesis and SWeNTs

unique ink platform is opening thedoor to nice business opportunitiesin electronics materials. Also in2011, SWeNT commercialized itsSMW specialty multi-wall carbonnanotube product, which offersbetter ease of dispersion and higherconductivity versus traditional multi-

wall products. This is opening thedoor to great business opportunitiesin the composites materials area.

Will you tell us about someof your studies in synthesisof nanomaterials and thefabrication of nanoscalefeatures at a large scale?

I have been actively involved withsynthesis of carbon nanotubessince joining SWeNT in 2005.

While at Chasm, I have had the

8/2/2019 Eeweb Pulse 2012 42


INTERVIEW

opportunity to work alongside BobPraino and other team memberson several interesting projects thatinclude roll-to-roll printing andalso nanoimprint lithography forapplications in displays, pharmaand other industries.

What are your key attributesthat have helped you get towhere you are today?

I guess I have a nice combination oftechnical competency and businessskills that enable me to work well

with leading researchers and helpfigure out how to commercialize

technology to create a successfulbusiness. There are many verygood technical people and verygood business people, but muchfewer people that are good at both.

What is on your bookshelf?

Crossing the Chasm by GeoffreyMoore. This book is partly whatinspired us to form Chasm Tech-nologies. The Four Agreements: A

Practical Guide to Personal Free-dom by Don Miguel Ruiz. This bookhas helped me stay balanced. Forfun, right now I am readingDead or

Alive by Tom Clancy.

Do you have any tricks upyour sleeve?

I would not say that I have anytricks. Success comes the oldfashioned way; developing unique

skills, hard work, personal integrity,building relationships, and notbeing afraid to take risks andinnovate.

Do you have any note-worthyengineering experiences?

The past two years, I was honored bythe NanoBusiness Alliance as being

one of the most influential people inthe field of Nanotechnology. Over the

years, I have had the opportunity towork with some outstanding peopleand have accomplished some nicethings. A common theme for me hasbeen working on commercializingadvanced technologies to enabledisruptive product platforms. Two

very nice examples of this areGOLDLink and what we are doingat SWeNT right now. I also havemore than 25 patents on which I amlisted as an inventor.

Do you continue to have

an active role in productdevelopment? If so, how?

Yes, I am quite actively involved withproduct development at SWeNT. Ialso contribute in an advisory roleat Chasm on projects unrelated toSWeNT.

Can you tell us more aboutSWeNT, its goals and thetechnology its developing?

SWeNT is now focusing oncommercializing products that aretailored for target applications. Oneof the things that sets SWeNT apartis a willingness and ability to tailorproducts for target applications. Ourtarget markets include materialsfor electronics and materials forcomposite applications. We have

what you could call a sort of roadmapfor the particular segments that we

target. The segments we are goingafter are transparent conductivefilms (TCF) applications, which areused by various types of displays,lighting and solar applications.So we are actively pursuing thosetypes of applications for our carbonnanotubes. For that application

you need a nanotube product that

allows the customer to fabricatea thin film touch sensor pattern atlow cost with the right combinationof optical transparency andelectrical resistivity. There are a lotof materials that are conductive,a lot that are transparent, and afairly small number that are bothelectrically conductive and opticallytransparent. There is an even shorterlist of materials that are opticallytransparent, electrically conductiveand can be printed at low cost. Thematerial that dominates the industry,and has done so for the last fourdecades, is indium tin oxide (ITO).

It is basically a ceramic thin-filmmaterial that is vacuum-depositedand then subtractively patternedusing photolithographic etchingtechniques. The carbon nanotubeinkss that we make are lessexpensive than ITO on a materialsbasis, but more importantly, when

you can directly print the touchsensor patterns versus having togo through the multiple steps of the

subtractive method. This will resultin significantly reduced cost.

Do you provide the corematerial for customers to use?

We have to control the structureof the carbon nanotube materialthat we make. We make two typesof nanotubes: one is called thesingle-wall carbon nanotube, whichhas one wall of carbon on a tiny

diameter of 1nm, with a length ofabout 1,000 times that. These are thehighest-end variety of nanotubes,and they are mainly used in thin-film applications for electronics.The other type, at the other end ofthe spectrum, is a material calledmultiwall carbon nanotubes.These are larger in diameter

8/2/2019 Eeweb Pulse 2012 42


INTERVIEW

about 10 timesand have usually10 or more walls, hence the namemultiwall carbon nanotubes. If youlook at these materials, youll seethat they are graphitic. Graphitelikes to be multilayered, so itsa lot easier to make a multiwallnanotube; its really what wantsto happen. In addition, the single-

wall is unique because its opticaland electronic properties can bechanged by manipulating diameterand orientation of the carbon inthe sidewall. The combination ofdiameter and orientation is calledchirality. Each combination of

diameter and orientation gives youa unique nanotube.

Is this a process that is easy tocontrol, or do you typically geta variety of nanotubes?

A variety. Its one of the big limitationswhen you dont know exactly whatresults you will get. Typically thereare certain chiralities or nanotubestructures that are preferred more

than others. Also, the coexistence oftwo different types of structures canresult in defects. One good exampleis another type of applicationthinfilm transistors (TFTs). With these,

you want to put a semiconductingthin filmnot necessarily aconducting thin filmbetweenthe source and drain electrodes,between which you do not want tohave any leakage current. You want to

have very well-defined on/off states.If you have a mixture of nanotubeswith metallic conducting electronicproperties, and nanotubes thathave semiconducting electronicproperties, you can end up witha very poor on/off ratio. So itsimportant to control the structure ofthe tube for electronics, and SWeNT

is better than anyone else at doingthat.

How reliable is the nanotubeprinting technology?

There is obviously a lot moreknowledge about the material (ITO)that has been industry standardfor the last four decades, so nomatter what we do, the provenand established material willinitially be more comfortable forprospective customers. But I wouldsay there are areas where ITO is

weak with respect to reliability,specifically because it is made

from a ceramic thin film, it is quitebrittle. So if there is any flexinginvolved, the ITO is very likely tocrack, which presents a reliabilityproblem. That has been a bigissue in touchscreens, for example,

where certain touchscreen designsrequire some flexing, and the mainfailure has indeed been crackingof the ITO. This is a weak point forthe ITO and a strong point for the

carbon nanotubes. However, thereis still a learning curve with carbonnanotubes; you have to recognizethat everything is a system. It isnt

just carbon nanotubes, but you mustalso know onto which substrateit is being printed, what opticaladhesive is being used to bond it tothe structure, and usually somethinghas to make electrical contact. Withall of these system parts, there

is a lot of learning that goes on.But because the cost-reductionpotential is compellingabout 80percentwe see that along with thelearning there is a lot of opportunity.

Were aiming to have our nanotubesbe a part of the rapidly growingtouchscreen movement.

In the TFT area, we have a joint

development project with PanasonicBoston Laboratory (PBL). Were

working together to qualify a single-wall carbon nanotube ink that willbe used as semiconducting thinfilm material for TFT backplanesin OLED TVs. OLED TV is a majorarea of focus for Panasonic, andit seeks a position of leadership.The biggest issue with this goalis the high current cost of OLEDTV technology compared toalternatives. So there is a desireto significantly reduce the cost ofthe TFT backplane by printing itinexpensively on plastic materials.

Using a significantly less expensiveTFT backplane will enable a morecompetitive price for OLED TV.

With regard to the printing, thetechnology has to be good enoughto print the features of a TFT

with a channel length of about 10microns or less. This is pushing theenvelope for a number of printingtechnologies. We are working withPBL first to establish the recipefor making a nanotube that meetsthe performance criteria. Second,

were formulating an ink andestablishing the printing systemfor it that is capable of printing therequired feature sizes printed overa large area. PBL is focusing on thelatter, and the formers is comingfrom SWeNT.

I believe that further down the road

printed transistors is going to be aneven larger market for us than touchtechnology.

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David Arthur -CEO Southwest NanoTechnologies, Inc. (SWeNT)

Single Wall Carbon

NanotubesEnable PrintedElectronics

Single wall carbon nanotubes(SWCNT) have long beenrecognized as having uniqueelectronic and mechanicalproperties that could enableimportant advances in electronicdevices, most notably for printingthin films for printed electronicsapplications, such as Thin FilmTransistors (TFTs) and TransparentConductive Films (TCFs.) Thispotential has not as yet beensignificantly exploited for severalreasons.

With respect to TFTs, the poten-tial advancements derive primarily

from the inherent electrical prop-erties of semiconducting SWCNT.SWCNT can be semiconductingor conducting, depending on thespecific structure or chirality ofthe nanotube1. Semiconduct-ing SWCNTs demonstrate greaterintrinsic mobility than any otherknown semiconducting substance,

and can be room tem-perature processed. Fur-thermore, the electronicband structure ofsemiconductingSWCNT facili-tates high on/off ratios. Amor-phous silica andorganic TFTs have both receivedconsiderable attention for TFTs, butboth exhibit comparatively low mo-bility and, in the case of amorphoussilica, high temperature process-ing is required. This situation wassummarized graphically by Sun, D.M. et al.2 as shown in Figure 1, who

used semiconducting SWCNT tomake TFT devices with on:off ratiosin the region of 106 and mobility be-tween 10 and 100 cm2 V-1 s-1.

With such desirable semiconductorproperties, why have semiconductordevices employing SWCNT notbeen commercially successful?

Typically, these resultshave been achieved usingSWCNT that have beenextensively purified to enrichthe semiconducting tube content.Indeed, Zhou et al.3 have shown thata minimum of 95% semiconductingtubes is desirable to obtain good
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PROJECT

TFT performance, as seen in Figure2. Statistically, as manufacturedSWCNT are expected to have67% semiconducting tubes and33%metallic tubes, this is indeedthe case for most manufacturingprocesses. To obtain SWCNTmaterial suitable for TFTs fromthese materials requires extensive

and expensive purification and tubeseparation processes to removethe metallic nanotubes, which canlead to degraded semiconductorproperties and very low yields.

For TCFs, the promise for bettertransparent conductive films derivesfrom the inherent high conductivity

of the material, the unusually highaspect ratio (~1,000) and extrememechanical strength. Theseproperties enable the manufactureof highly conductive, flexible filmsthat are also transparent. However,producing the best SWCNT for thispurpose has been limited by theavailability of consistent SWCNTof sufficient purity. Furthermore,most applications for conductivethin films, including touchscreens,flexible displays, sensors, etc.require the CNT to be patterned,and cost-effective ways of achievingthis with CNTs have not been

available.

SouthWest NanoTechnologies hasaddressed these concerns.

The CoMoCat process4 uses asupported catalyst in a fluidized bedreactor. This provides very preciseand uniform control of reactionconditions allowing the selectivegrowth of either semiconducting ormetallic enriched SWCNT. Thus,

by careful design and productionof the catalyst, together withprecise control of the reactionconditions, SWCNT material with> 95% semiconducting tubescan be realized directly from thereactor, negating or substantiallyreducing the need for expensivesecondary operations. Similarly,by modifying the catalyst designand varying the reaction conditions

tubes can be produced that are 70%metallic in nature, enhancing theconductivity of TCFs. This processproduces tubes of high purity with

very little evidence of other formsof carbon and minimal residualcatalyst. Figure 3 shows a TEMof the CoMoCAT product afterpurification to remove the residual

Figure 1: Comparison of On:Off ratios and Mobilities for TFTs made from differentmaerials2

Figure 2: Effect of proportion of semiconducting tubes in coating. (a) Schematic showingthat a small percentage of metallic tubes can be tolerated without creating a conductive pathand (b) Effect of removing metallic SWCNT on TFT performance.

Mobility(cm

2V

-1s-

1)

On/off ratio

100

10

1

0.1

0.01

Ref. 21

100 101 102 103 104 105 106 107 108

p-Si

a-Si

This Study

Other nanotube TFTs

p-Si, a-Si, oxide, organic

Organic27

Ref. 22 Ref. 17

Ref. 10

Ref. 13 Ref. 3Ref. 23 (LTPS)

Ref. 18

Ref. 26(organic crystal)

Ref. 25 (Organic)

Ref. 24(InGaZnO)

Ref. 5

Ref. 14

Ref. 20

Channel Length (m)Black = Metallic CNT Gray = SC CNT

On/OffRatio

10

8

6

4

2

00 2 4 6 8 10 12 1 4 16 18 2 0

Simulation

Measurement

Measurement

Separated Nanotubes

CVD Mixed Nanotubes

Simulation Nanotubes

Simulation

10

8

6

4

2

00 2 4 6 8 10 12 1 4 16 18 2 0

105

104

103

102

101

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0 20 40 60 80 100
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PROJECT

catalyst and catalyst support.

SWeNT has combined this synthesistechnology with proprietary inktechnology to allow nanotubes tobe printed by conventional means,such as screen, pad and gravureprinting. This V2V technologylicensed from our sister company

Chasm Technologies allowsSWCNT to be dispersed in anorganic vehicle without the use ofsurfactant. This dispersion is thencombined with an ink vehicle whichcontrols the rheological propertiesof the ink, which can be adjusted forthe requirements of different printingtechnologies. All components ofthe ink with the exception of theSWCNT are fugitive and easilyremoved by heating the ink in aforced air oven for a few minutes at100 to 120C. The process is shownschematically in Figure 4.

Thus, combining this ink technologywith the SWCNT synthesiscapability gives a practical solutionfor printing both conducting andsemiconducting electronics byconventional and well establishedprinting methods. To date, SWeNThas produced TCFs with surfaceresistance < 300 / at 90%T. Initialresults for TFTs show that on/off

ratios of 105 can be produced withthe current materials. With furtherdevelopment, its anticipated that anon/off ratio of 106 can be achieved.

References

1. Wilder, J.W.G.; Venema, L.C.;RinzlerA.G.; Smalley, R.E.;Dekker, C. Nature 391, 59(1998)

2. Sun, D.M.; Timmermans, M.Y.;Tian,Y.; Nasibulin, A.G.; Kaup-pinen, E.I.; Kishimoto, S.; Mizu-tani, T.; Ohno, Y. Nature Nano-tech. 6, 156 (2011)

3. Wang, C.; Zhang, J.; Ryu, K.;Badmeav, A.; De Arco, L.G.;Zhou, C Nano Lett. 9 4285(2009)

4. Resasco, D.E.; Alvarez, W.E;Pompeo, F.; Balzano,L.; Her-rera, J.E.; Kitiyanan B.; andBorgna, A. Journal NanoparticleResearch 4, 131 (2002)

Figure 3: TEM of CoMoCAT SWCNTShowing high purity long SWCNT bundles.

Figure 4: Schematic of V2V Ink Printing Process

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8/2/2019 Eeweb Pulse 2012 42


Vladimir KrazPresident, OnFILTER, Inc.

and Its Effectson TodaysManufacturing

Electric

Overstress

Electrical overstress, orEOS, is a phenomenon where elec-

trical signals applied to a circuit ora device exceed normal operatingparameters. These excessive elec-trical signals are abnormal by defi-nition and are not a part of normaloperation of the devices. Accord-ing to Intel1 , EOS is the numberone cause of damage to IC com-ponents. In the broadest terms,EOS also includes electrostatic dis-charge (ESD), however, commonly

EOS is used for excessive signalsother than ESD and this is how it

will be used in this paper. Here wewill discuss the effects of electricaloverstress on devices and equip-ment, the origins of EOS, its propa-gation, as well as mitigation of EOSin production environment.

EOS and ESD

Most readers are quite familiar withelectrostatic discharge (ESD) andits adverse effects on electronicequipment and components. EOS,

while technically encompassingESD, is differentiated from ESD in a

numberof ways:

Effect of

EOS on Devices

A typical semiconductor device canbe damaged by an ESD Event with

ESD Event EOS Event

Caused by a rapid discharge of accumulated

electrical charge. Once this accumulated

charge is consumed, ESD Event can no longer

manifest itself.

Caused by voltage and/or currents associated

with operation of equipment or with power

generating equipment. Lasts as long as the

originating signal exists. There is no inherent

limitation on its duration.

Characterized by a specific waveform. While

the waveforms of different models of ESD

Events (CDM, HBM, MM and others) certainly

differ in appearance, in general their properties

include rapid rising edge (within few

nanoseconds) and an asymptotic rear edge

lasting typically less than 100nS.

Can technically have any physically possible

waveform the sources of EOS are often

unpredictable. There are some major

categories, however, which will described

further in the text.

Non-periodic and non-repeatable

accumulation of charges cannot be guaranteed.

Mostly, but not always periodic and repeatable.
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TECHNICAL ARTICLE

magnitude of anywhere from 100Vto 250V CDM (of course, the overalldamage range is much wider).EOS-induced damage, however,occurs at much lower levels. IPC-

A-6102 (3.1.1) and IPC-77113

(2.11), the standards used by PCBassembly plants to control quality ofelectronic assemblies, recommendthat the EOS levels should bekept below 0.5V and in case ofsensitive assemblies below 0.3V.

Why is there such a discrepancyin damage voltage levels? Thishas to do with the waveforms ofexposure, not just absolute voltage

levels. Similar discrepancies existsbetween different ESD dischargemodels the same device may bedamaged by 2000V HBM model,

while being sensitive to 100V CDMmodel discharge.

The effects on the device froman ESD Event and an EOS Eventcan be very different. At the risk ofoversimplification, the followingexample can be helpful. An ESDEvent could be compared withemptying a cup of water on a floor.There is a resulting small puddle,but once the content of a cup (i.e.charge) is gone, there is no more

water coming and the damage fromthe spill is thus limited. An EOSevent, however, could be compared

with an open faucet. However littlewater it may drip in comparison withthe sudden pour of water from the

cup, with time this trickle may floodthe entire floor and cause significantdamage. The duration of typicalEOS Events is several magnitudeslonger than the duration of mostESD Events (microseconds or evenmilliseconds vs. nanoseconds) thousand or even a million timeslonger; therefore this comparisonholds water.

According to Craig Hillman , oneof the mechanisms of damage dueto EOS is thermal runaway from

Joule heating (excessive current).This is also systemic to ESD Eventsas well. While overheating due toESD requires a significant currentinjection over a few nanoseconds, amuch smaller EOS Event that wouldlast thousands or even millions

signature of EOS-caused damageis similar to that of the ChargedBoard ESD model (CBM) due to thesimilarity in energy of the event.

Figure 3 shows another example ofdamage due to EOS. High energy ofEOS Event melted the bonding wireof the device.

To the authors knowledge, at thepresent there is no establishedcorrelation yet available betweenthe levels of damage due to ESDand the ones due to EOS. This paperrecommends that such relationshipis examined by the experts inthe industry and, if possible, acorrelation is established for thebenefits of the industry.

EOS Effect on Equipment

Device damage is not the onlynegative effect of unwantedelectrical signals. Electronicequipment can be susceptible tonoise on power lines and ground.Transient spikes all too common

on power lines can add an extrapulse on digital lines (Figure 4) andcause numerous other problems anywhere from sensor misreadingto outright equipment lockup. Sincemost of production equipment todayhas significant electronic content,this problem cannot be ignored.Please see more on this subjecthere 4,5,6,7.

Types of EOS in

Production Environment

There is a large variety of typesof EOS occurrences in a typicalproduction environment. This paperoutlines the most common typesand provides brief description oftheir properties and their most likelyorigins.

Figure 2: EOS Damage of SemiconductorDevice. Source: Intel

times longer microseconds ormilliseconds may generate a

similar amount of heat.

EOS often causes massive damageof the device due to its high energy,as shown in Figure 2. Sometimes the

Figure 3: Damaged Wire Bond. Source:SEM Labs.
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TECHNICAL ARTICLE

Mains-Caused EOS

(AC 50/60Hz)

Voltage Induction

Since most equipment operates onAC power from the mains, it is notsurprising that the mains artifactscan be present in some tools. Poor

wiring schemes, lack of adequategrounding and ground loops areall contributors to this. There is astrong relationship between groundimpedance and the AC voltage thehigher the ground impedance, thehigher the resulting AC voltage8,9.

Neutral/Ground Reversal

It is an unfortunate (and unsafe)occurrence when neutral and

ground wires in the electrical outletor inside the tool itself are reversed.In the authors experience thishappens even in the best-runfacilities in the world. To complicatethe matters, conventional testerssuch as the ubiquitous three-lightchecker, which is obtainable fromhardware stores, cannot test for

this condition. In such a situation,the return current flows not throughneutral but through ground wire,creating voltage on ground, whichis never a good thing.

Current Induction

Whether in wires connected tomotors or other current consumersin the tool or within the motors,heaters and other devices, strongcurrents generate magnetic fields,

which can produce currents andvoltages in largely accidental loopswithin the same tools. Spreadingpower cables away from data

cables and wires and reducingloops mitigates this problem tosome degree.

High-Frequency Noise on

Power Lines and Ground

High-frequency signals, or electro-magnetic interference (EMI), onpower lines are usually parasiticin nature (an exception to this isoutlined below) and are a result of

transient signals generated by op-eration of equipment such as step-per and variable-frequency motors,solenoids, relays and the like. Thehigher the power consumption ofsuch a device the stronger the EMIsignal. Figure 5 shows a typicalsignal on power lines generated

by EMI. As clearly seen, it is any-thing but a continuous waveform.

When assessing EMI signals forthe possibility of EOS, it is impera-tive that instruments with the abilityto capture the peak signal are used.In the authors experience, it is notuncommon to encounter spikes ofup to 20V on ground and in powerlines. Figure 5 shows some typical

waveforms on power lines in a pro-duction environment.

There are cases, however, when thepredominant signal in cables and

wires is a continuous waveform.

Some examples are signals fromservos and variable frequencymotors. Their fundamentalfrequencies lie typically below20kHz. Another source is RFIDreaders. Passive RFID tags requirestrong magnetic field to power themup which results in strong inducedsignals into anything resemblinga conductive loop, which arenot difficult to find in productiontools. The resulting voltage, witha typical frequency of 13.56MHz,then propagates through wiresthroughout the facility. While thesesignals are intentional and are usedfor specific purposes, when theyspread outside of the equipmentinvolved they are liable to createEMI-related problems.

Figure 5: Typical Noise Waveforms on Power Lines

Equipment turning on and off Switched Power Supply Thyristor Control (dimmer)

Figure 4: Noise on Power Line AffectingEquipment

Noise Disturbance

An Extra Pulse
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Ground Bounce

This phenomenon deserves specialconsideration for high frequencysignals. Though mostly attributed toICs and PCB layout issues, groundbounce is a significant factor forfactory-scale signals. This paper6

provides adequate background of

the phenomenon of ground bounce.In short, when ground wire has sub-stantial impedance at high frequen-cies, current passing through this

wire from noise-generating equip-ment to ground produces voltageacross this wire thus floating what

was supposed to be the ground ofthe tool see Figure 6. According tocalculations in this paper7, this volt-age may reach several volts at justa few milliamperes of current. This

should trigger considerations for aproper grounding scheme.

Cases of EOS in Production

Now that we discussed whatphenomenon can cause EOSexposure, lets examine some of thecases of EOS in real-life productionenvironment and match them to

the physical phenomenon which ismanifested in each case. Only veryfew of such sources are outlined inthis paper due to limitation of thescope.

Soldering Irons

The tips of soldering irons touch themost sensitive electric components,therefore it is under the most scrutinyfor EOS exposure. Some standards(MIL-STD-2000) require the tip ofsoldering iron to produce no morethan 2mV of signal, which is quiteunrealistic in most environments,especially given that the document

does not limit the signal to only lowfrequencies. Papers such as thisone8 were written on the subject. A

voltage on a tip of a soldering ironcan inject EOS signal into a sensitivecomponent during soldering anddamage it. Lets take a look at whya soldering iron tip has voltage tobegin with.

Bad Grounding

Loss of Ground

If a soldering iron loses ground, thetip of the iron can have any voltageup to of the supply voltage to theiron. The voltage due to ground lossis usually AC 50/60 Hz. DC voltageon the tip would be contributed toother phenomenae, usually causedby a defective power supply in theiron itself. In the very best case,the voltage at the tip of the iron

due to loss of ground would beequal to voltage on neutral which,as discussed before, is not zeroand is typically several volts of AC.Loss of ground can occur withinsoldering irons themselves or inpower outlets. Raytheon9 reportedan occasion of massive failure ofground in power outlets which led

to EOS and resulting damage insensitive circuit. Reversal of groundand neutral also leads to excessive

voltage at the tip.

Noise on Ground

Whatever signal is present onground, it will be present on thetip of the iron. Noise on groundcan be quite high as discussedbefore. When the voltage on thetip is measured with a multimeteror an off-the-shelf iron checker,it will easily miss high-frequencysignals and especially spikesthat are typical in the production

environment. It is imperative tobe able to measure voltage withinstruments that are capable ofmeasuring high-frequency spikes.

A high-speed digital oscilloscopeor a dedicated meter with high-frequency capabilities should beused.

Noise on Power Line

Noise is propagated not only via

ground but via power lines as well.Transformers and power suppliesconverting mains voltage to 24V,for example, are often transparentto high-frequency spikes whichend up on the soldering iron tip.Spikes caused by commutation ofequipment (e.g. heat gun, etc.) canalso propagate through the powersupply. The effect is similar to that

which is caused by noise on ground

and the signal should be measuredin a similar fashion to what ismentioned above. Power line filterscan help to reduce this noise.

Power Tools

Power tools such as electricscrewdrivers commonly used inelectronic assembly may not always

Figure 6: Ground Bounce

I Z V
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have good grounding of the tipsduring rotation. Grounding viaball-bearings during rotation doesnot work since the lubricant in thebearing is insulative. In addition,some mains-powered screwdriversmay not have dedicated groundingsince they may be using doubleinsulation to satisfy safetyrequirements. Resulting voltage onthe tip of the screwdriver may bequite high. The author observed107V AC on the tip of a screwdriverused in the assembly of mobilephones in a 220V region.

Even the screwdrivers used inequipment for such a sensitiveprocess as assembly of disk drivescan generate significant voltage. Asdescribed in this paper10, voltageinduced into a screwdrivers ground

wire by simply being routed in thesame bundle as the wires to thestepper motor generated significantspikes (Figure 7)

Mitigation of EOS in ProductionEnvironment

Good grounding with less than 1Ohm impedance usually resolvesmost of 50/60Hz issues. High-frequency noise, however, is quitea bit more challenging. The mosteffective way to deal with noise onpower lines is EMI filtering whichis included with recommendationsby Intell in the abovementioned

document. EMI filters allow mainssignals (50/60Hz 120/250V) topass through, but greatly reduceextraneous noise. In addition tothe power lines, it is also highlydesirable to filter noise from groundas well, as it may carry a significantamount of noise throughout thefactory.

Some equipment at your factory mayalready have some sort of EMI filterbuilt in equipment manufacturersdo it in order to comply withemission regulations, such as FCCand CE. While such built-in filtershelp to reduce noise on powerlines in the laboratory environment,they are much less effective inmanaging noise on a factory level,

where the length of power linesand their complex network are

very different from a sterile and

predictable laboratory environment.Sometimes, built-in EMI filters canamplify the noise signal in a factoryenvironment rather than suppress it.Figure 8 shows noise on power lineamplified by a regular built-in EMIfilter. This paper11 presents moredetails on this phenomenon

Suppression of noise on power linesin a factory environment requiresspecial considerations which are

very different from those required forregulatory compliance. This showssuppression of noise by a speciallydesigned filter for such applications OnFILTERs CleanSweep powerline filter AF series. As shown inFigure 9, the transient signals on

power line are reduced to the pointof insignificance.

Connecting an EMI filter is quitesimple, as shown in Figure 10 pluga filter into an electrical outlet andplug your equipment into the outleton the filter. Now your equipment isprotected against noise on powerlines.

Figure 7: High-Frequency Noise atthe Tip of Power Screwdriver. Current atcontact reached 180mA

Figure 8: Noise Amplification fromRegular EMI Filter

Figure 9: Reduction of Noise after

specially-designed power line EMI filter

Motor Coil

Zs

Vs

-V

Tool Tip

VI

Component

Tool

(grounded)

1

Raw signal on power line

After typical EMC filter

Raw signal on power line

After OnFILTER CleanSweep Filter
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There are two fundamental

methodologies to consider. One is toreduce a generation of EOS-causingsignals; another one to preventEOS signals reaching sensitiveequipment and components. If youknow the culprits that cause mostof the noise in your environment,then the first approach may help.However, because there can be

so many pieces of equipment in asingle production environment andthe difficulty in identifying noisesources, it is a much more practicalapproach to use EMI filters fornoise-sensitive equipment as they

will suppress noise regardless of itssource. OnFILTERs CleanSweepEMI filters suppress noise in bothdirection, assuring that noisegenerated by filter-protectedequipment itself wont pollute thepower network as well.

To conclude, the use of powerline EMI filters is the most cost-

efficient and the most effective wayof improving uptime by reducingEOS in production environment,reducing downtime and improvingreliability of sensitive components.

References:

1. Intel Packaging Databook,Chapter 6 Intel, 2000

2. IPC-A-610-E, Acceptability ofElectronic Assemblies, 2010

3. IPC-7711 Rework, Modificationand Repair of ElectronicAssemblies, 2003

4. Temperature Dependence ofElectrical Overstress, CraigHillman, PhD, DfR Solutions

5. EMI Issues in the ManufacturingEnvironment, V. Kraz,Conformity Magazine, January2007

6. Ground Bounce Basics and BestPractices, Phil King, AgilentTechnologies

7. How Good Is Your Ground?,V. Kraz, P. Gagnon, EvaluationEngineering, May 2006

8. EOS Analysis of Soldering IronTip Voltage, Baumgartner, G.;Smith, J.S., Proceeds of EOS/ESD Symposium, 1998

9. EOS from Soldering IronsConnected to Faulty 120VAC

Receptacles, W. Farwellet.al., Raytheon Corporation.Proceeds of 2005 EOS/ESDSymposium

10. EOS Exposure of Magnetic

Heads and Assemblies inAutomated Manufacturing

11. EOS Damage by ElectricalFast Transients on AC Power,

A. Wallash, V. Kraz, Proceeds ofEOS/ESD Symposium, 2010

12. CleanSweep AC Power LineEMI Filters, OnFILTER, Inc.http://www.onfilter.com

About The Author

Vladimir Kraz is a founder and a

president of OnFILTER, Inc. Priorto founding OnFILTER he startedand was a president of CredenceTechnologies, Inc., a manufacturerof ESD and EMI instrumentation,

which was acquired by 3M. Mr.Kraz holds 22 U.S. Patents and isactive in ESD Association andSEMI Standards activities. He has

written a number of papers on thesubject of ESD and EMI physics

and management, many of whichcan be found at www.onfilter.com/library.html

Figure 10: Connection ofCleanSweep Power Line EMI Filter

EMI Filter

Component
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21/26

Low Power Ambient Light and Proximity Sensor with

Internal IR-LED and Digital Output

ISL29043The ISL29043 is an integrated ambient and infrared

light-to-digital converter with a built-in IR LED and I2C Interface

(SMBus Compatible). This device uses two independent ADCs

for concurrently measuring ambient light and proximity in

parallel. The flexible interrupt scheme is designed for minimal

microcontroller utilization.

For ambient light sensor (ALS) data conversions, an ADC

converts photodiode current (with a light sensitivity range up to

2000 Lux) in 100ms per sample. The ADC rejects 50Hz/60Hz

flicker noise caused by artificial light sources.

For proximity sensor (Prox) data conversions, the built-in driver

turns on an internal infrared LED and the proximity sensor ADC

converts the reflected IR intensity to digital. This ADC rejectsambient IR noise (such as sunlight) and has a 540s

conversion time.

The ISL29043 provides low power operation of ALS and

proximity sensing with a typical 136A normal operation

current (110A for sensors and internal circuitry, ~28A for

LED) with 220mA current pulses for a net 100s, repeating

every 800ms (or under).

The ISL29043 uses both a hardware pin and software bits to

indicate an interrupt event has occurred. An ALS interrupt is

defined as a measurement that is outside a set window. A

proximity interrupt is defined as a measurement over a

threshold limit. The user may also require that both ALS/Prox

interrupts occur at once, up to 16 times in a row beforeactivating the interrupt pin.

The ISL29043 is designed to operate from 2.25V to 3.63V over

the -40C to +85C ambient temperature range. It is packaged in

a clear, lead-free 10 Ld ODFN package.

Features Internal LED + Sensor = Complete Solution

Works Under All Light Sources Including Sunlight

Dual ADCs Measure ALS/Prox Concurrently

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T

he impact of switched capacitor filters onintegrated filter design in the late 1970s was

truly revolutionary, and is still considered one ofthe most significant inventions in the history of ICs [1].Suddenly the painfully large time constants needed forlow frequency signal processing were realizable in a

very compact fashion, and in addition became triviallyprogrammable via the clock frequency. The directemulation of resistors enabled switched capacitor filterdesigners to utilize a wealth of design techniques that

were already in use for active RC filters. This was themost critical attribute of the new technology because itenabled the veritable explosion of switched capacitordesign activity in the late 70s and early 80s. Perhaps themost impressive feature of this new technology, however,

was how beautifully it jibed with the CMOS technologiesthat would come to dominate analog design. Timeconstants could now depend on capacitive matchingstill the most tightly controlled matching parameter of anyanalog component in a CMOS process. This didnt justhold at nominal conditions either, these time constants

were predictable over the process, temperate andvoltage corners that were the scourge of active RC filter

designers. Utilization of switches, capacitive matching,and digital clocks made switched capacitor circuits feel

less like just a new idea, and more like destiny.Sure, switched capacitor filters have some trickyaspects. The switching introduces aliasing of boththe signal and anything that can interfere, includingnoise; approximations to continuous time filters haveinaccuracies due to finite clock speed, and there are allsorts of switch non-idealities to contend with. Additionally,simulation of these filters required such additionaloverhead that new custom simulators were developed[5]. Nonetheless, it is clear from the sheer number ofswitched capacitor filter publications in the decade

following 1978 that these issues were not proving to betoo troublesome. Switched capacitor filters were aboutas sexy as it gets in the analog circuits world.

Given this state of affairs, it may seem somewhat odd thatthe core idea behind switched capacitor technology wasinvented a century before this eruption of publicationsand it was published in one of the most famous scientificbooks of all time. So it is reasonable to assume that atleast a few people read it.

James ClarkMaxwelland Switched Capacitor Filters

The Story ofPhil Golden

Design Engineer
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As such, the history of switched capacitors is one of thebest illustrations imaginable of the general principle thatinnovation is the combination of creativity and value. Inother words, to really make a splash, you need to not onlyhave a great idea, but also to have people who want touse it [2].

In 1873, James Clark Maxwell published an ideaexplaining that he wanted to measure the value of acapacitor, or a condenser as it was then often referred

to, as a result of its ability to store a higher density ofelectrical charge than a typical conductor. On pages 374375 of A Treatise on Electricity and Magnetism, Volume2, [3] Maxwell describes connecting the capacitor tobe measured in a circuit to charge it. He then quicklyreverses the polarity of the capacitor connection usinga commutating switch. Following this, he demonstratesthat if this is repeated with a frequency of f, the averagecurrent flow will be equivalent to that of a resistor of value1/(f.C). He uses the fact that he can measure resistance(using any of the methods described previously) to

substitute in a resistor, measure it, and thus calculate thecapacitance of the condenser. Here then, in one of themost celebrated technical volumes of all time, is the coreidea of switched capacitors (i.e., emulating the averageresistance of a continuous time resistor by switchinga capacitor). It is laid out in black and white (actuallyblack and sepia), with a clear accessible descriptionand simple equations to better illustrate the principal. So

why did it take almost exactly one hundred years for thisidea to catch on?

The simple reason, of course, is that not very manypeople were interested in determining condenser

values, which was Maxwells stated value of thetechnique. It is probably a mistake to think that it was notconsidered to be a creative idea. The issue was muchmore likely that it simply was not considered much at allbecause people did not have a pressing need or use forit. Fast-forward to the 1970s and this is the fundamentalchange, because suddenly the world was calling for thistechnology. Incidentally, at this point it was effectively re-

invented, being described as a rather interesting andpreviously unrecognized concept in Frieds seminalAnalog Sample-Data Filters IEEE Journal of Solid StatesCircuits paper in 1972 [4].

So what can this story teach us about how to innovate?Here we have one of the most famous scientists of alltime, writing in one of the most famous scientific booksof all time, describing what would become one of themost revolutionary ideas in the history of analog circuits,and no one noticed. This reminds us that designers

working in isolation from their potential customers maystruggle to produce innovative products that really addvalue. And this holds even if they are really smart, andtheir ideas are good. This in turn suggests why one ofthe key challenges for many semiconductor companiesis to connect a deep understanding of underlying marketneeds with internal technology capability. Neither istypically trivial to assess.

Figure 1: How switched caps improve filter accuracy.

R2 C2

C1

CR1

VinVinVout Vout

C

+

BW3db1/2R2C

R2C product typically has

+/20% accuracy

C2/C typically has

+/0.2% accuracy

BW3dbC2fclk/2C

+
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[1] B. Murmann, Signal Conditioning Circuits,Stanford University Course EE315a, availableonline at https://ccnet.stanford.edu/cgibin/course.cgi?cc=ee315a&action=handout_download&handout_id=ID126954294624704

[2] J. Paap, Using Competitive Technical Intelligence toStimulate Innovation, available at http://www.jaypaap.com

[3] J. C. Maxwell, A Treatise of Electricity and Magne-tism, Oxford Clarendon Press, 1873, vol. 2, pp 374-375

[4] D. Fried, Analog Sampled Data Filters, IEEE JSSC,August 1972

[5] K. Kundert, Simulating Switched Capacitor Filterswith SpectreRF, available at http://www.designers-guide.org/Analysis/sc-filters.pdf

About the Author

Phil Golden is a principal design engineer and projectmanager at Intersil Corporation, specializing in circuitdesign and signal processing. He was educated at

Stanford University, where he was a graduate fellow fromlate 2003 until spring 2005, and the University of Dublin.
http://bit.ly/zVvNIshttp://bit.ly/zVvNIshttp://bit.ly/zVvNIshttp://bit.ly/zVvNIshttp://bit.ly/zVvNIshttp://bit.ly/zVvNIshttps://ccnet.stanford.edu/cgibin/course.cgi?cc=ee315a&action=handout_download&handout_id=ID126954294624704https://ccnet.stanford.edu/cgibin/course.cgi?cc=ee315a&action=handout_download&handout_id=ID126954294624704https://ccnet.stanford.edu/cgibin/course.cgi?cc=ee315a&action=handout_download&handout_id=ID126954294624704https://ccnet.stanford.edu/cgibin/course.cgi?cc=ee315a&action=handout_download&handout_id=ID126954294624704https://ccnet.stanford.edu/cgibin/course.cgi?cc=ee315a&action=handout_download&handout_id=ID126954294624704http://www.jaypaap.com/http://www.jaypaap.com/http://www.jaypaap.com/http://www.jaypaap.com/http://www.designers-guide.org/Analysis/sc-filters.pdfhttp://www.designers-guide.org/Analysis/sc-filters.pdfhttp://www.designers-guide.org/Analysis/sc-filters.pdfhttp://www.designers-guide.org/Analysis/sc-filters.pdfhttp://bit.ly/zVvNIshttp://www.designers-guide.org/Analysis/sc-filters.pdfhttp://www.designers-guide.org/Analysis/sc-filters.pdfhttp://www.jaypaap.com/http://www.jaypaap.com/https://ccnet.stanford.edu/cgibin/course.cgi?cc=ee315a&action=handout_download&handout_id=ID126954294624704https://ccnet.stanford.edu/cgibin/course.cgi?cc=ee315a&action=handout_download&handout_id=ID126954294624704https://ccnet.stanford.edu/cgibin/course.cgi?cc=ee315a&action=handout_download&handout_id=ID126954294624704

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