avoiding esd damage in design and production - fhi · frits j.k. buesink, senior researcher emc 2 8...

Frits J.K. Buesink, Senior Researcher EMC

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Avoiding ESD Damagein Design and Production

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Avoiding ESD DamageTelecommunications

Engineering

Avoiding ESD Damage in Design and Productionoverview

How to pick up charge?

What’s the damage?

Measures to prevent ESD damage in production

Measures to prevent ESD damage by design

the threat

mechanisms

Current boundaries

cable protection

input protection

Testing



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Engineering

Static Discharge Accidents do happenusually you do not see the effects immediately



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Engineering

Tribo – Electric Seriesif two materials touch, charge is transferred.

Air

Teflon

Human Skin

Glass

Wool

Aluminium

Cotton

Steel

Gold

Polyester

Silicon

+++

- -

- --



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Engineering

Adhesive Tape demo

Electric Fields exert Forces on Other Objectsequal charges repel, opposite charges attract each other

++

+++++

++

++

+++

Mutualrepulsion

and: attractionto neutral or negatively charged objects



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Engineering

What to do if plastics cannot be avoided?discharge with an ioniser or keep your distance to charged objects

How to fight? 1. a flame

2. an ioniser…

With ionised air!

Risky alternative:Keep at least 30 cm distanceto (necessary) plasticsif there is no ioniser!



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Engineering

Electric charging by inductiondirect contact not necessary!

Teflon

+

+

+

+

+++

+ +

+

Wool

Printed Circuit Board

- - - - - - - - - - - - - - - - -+ + + + + + + + + + + + + + + +

1. Charging of an insulator

2. Insulated PCB on charged surface

- - - - - - - - - - - - - - - - - - - -

- - - - - - - - - - - - - - - - -



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Engineering

Electric charging by inductiondirect contact not necessary!

+ + + + + + + + + + + + + + + +

3.Touch or Ground PCB:negative charge disappears (spark)(PCB possibly damaged)

4. Lift PCB: voltage increases! More Sparks fly!

- - - - - - - - - - - - - - - - -

- - - - - - - - - - - - - - - - -

- - - - - - - - - - - - - - - - -

+ + + + + + + + + + + + + + + +

PCB

PCBPCB C

QV (CPCB decreases)



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Engineering

1 k

100 pF 100 pF

charged“person”

The Danger: Large Discharge Current, Fast Rise Timedirect damage to components or via inductive coupling into circuit loops

15 kV200 pF100 ns200 kW

Capacitancein soles orfloor covering

Human Bodyis a conductor



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Engineering






the threat

mechanisms

Current boundaries

cable protection

input protection

Testing



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Engineering

Trace evaporates: large current

Destruction mechanismsultimately, all damage is caused by current

Gate oxide puncture: high voltage

N NP

break down: 20 V gate oxide[insulator]



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Engineering

The person can be charged or the component or bothessential for an ESD event is the difference in charge voltage

1 k

100 pF 100 pF

charged“person”

+ + ++

charged“thing”



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Engineering






the threat

mechanisms

Current boundaries

cable protection

input protection

Testing



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Engineering

Part, handler and assembly: same potential!when in proximity, there can be no voltage difference!

Employee(M/F)

Employee(M/F)

ESD sensitivepart

ESD sensitivepart

Electronicsin cabinet

or: ESD-bag

Electronicsin cabinet

or: ESD-bagthese three objects must be continuously

interconnected during handling!



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Engineering

static dissipative

If there is charge? Get rid of it!but not too fast!

discharge time [s] (at 50% humidity)

thro

ugh

resi

stan

ce[

]

106

109

1012

10-4 110-3 10-2 10-1 102

750 kconductive

insulating

0.02

Standard: IEC 61340

safe for component

safe for people

acceptable

desired

too slowfast enough



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Engineering

ESD Protected Area (EPA)everything conductive and interconnected

Earth

ShoeShoe

ESD SensitivePart

ESD SensitivePart

EPA

Work Surface

possibly:wrist strap

Equipmentcabinet

(usually notin this area)

Equipmentcabinet

(usually notin this area)

ESD CoatESD Coat

“grounded”through cuff“grounded”through cuff

Employee(M/F)

Employee(M/F)

FloorFloor



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Engineering

Prevent charging of persons and furniturestandard: IEC 61340-5-1 specifies through-resistances



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Engineering

ESD shoes should contact the ESD floor….we are actually only interested in the maximum charge voltage

ESD STM97.2-1999

Presently : <100 VFuture : <20 V and lower!



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Engineering

ESD Protected Workstationemployee, work surface and electronics cabinet mutually interconnected

Earth

ESD Workstation

Employee(M/F)

Employee(M/F)

ESD SensitivePart

ESD SensitivePart

Equipment CabinetEquipment Cabinet

Electronicsin equipmentor: ESD-bag

Electronicsin equipmentor: ESD-bag

Work Surface

(Wrist Strap)

MarkingApprovedWorkbench



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Engineering






the threat

mechanisms

Current boundaries

cable protection

input protection

Testing



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Engineering

Better be prepared if your design is planned here!keep electronics protected in harsh environments



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Engineering

the ESD ThreatESD pulse from IEC 61000-4-2 immunity standard

0 2 10 8 4 10 8 6 10 8 8 10 80

5

10

15

20Contact discharge current IEC 61000-4-2

time [sec]

Curr

ent [

A]

I i( )

t i( )

The ESD contact discharge current waveform (IEC 61000-4-2)



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Engineering

Time to frequency domain conversiontwo characteristic frequencies appear related to pulse duration and rise time

A

50%

90%

10%

h

r

Fknee

h 1

r 1

r21

F1 F2

ampl

itude

log (frequency)

f1~

21~f



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Engineering

ESD pulse can be decomposed into two trapezoidsthis allows an estimate of the ESD current frequency spectrum

0 2 10 8 4 10 8 6 10 8 8 10 80

5

10

15

20Building blocks contact discharge pulse

time [s]

curr

ent [

A]

IS i( )

IF i( )

I i( )

t i( )

Short and long pulse added in the time domain

Fast pulse: r=0.7 ns; h=10 ns

Slow pulse: r=10 ns; h=60 ns

To convert the ESD pulseto frequencies, it can besplit into two trapezoids

To convert the ESD pulseto frequencies, it can besplit into two trapezoids



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Engineering

Spectra of slow and fast pulse can be addedthe resulting spectrum is used for shielding analyses

1 106 1 107 1 108 1 109 1 10101 10 10

1 10 9

1 10 8

1 10 7

1 10 6

1 10 5ESD current spectrum

frequency

curre

nt c

ontri

butio

n Iesd i( )

IesdS i( )

IesdF i( )

f i( )

Total current

SumFast pulse

Slow pulse



avoiding esd damage in design and production - fhi · frits j.k. buesink, senior researcher emc 2 8...

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