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約1年前 (2015/10/03)にアップロードinテクノロジー

Standardized Direct Charge Device ESD Test For Magnetoresistive Recording Heads I

- Electrostatic Discharge (ESD) Protection for a Laser Diode Ignited Actuator 約1年前 by Tsuyoshi Horigome
- Electrostatic Discharge Current Linear Approach and Circuit Design Method約1年前 by Tsuyoshi Horigome
- System-level ESD protection of high-voltage tolerant IC pins – A case study 約1年前 by Tsuyoshi Horigome

- Standardized Direct Charge Device ESD Test For

Magnetoresistive Recording Heads I

Tim Cheung (2), Lydia Baril (1), Albert Wallash (1)

(1) Maxtor Corporation, 500 McCarthy Blvd, Milpitas, CA 95035 USA

Tel.: 408-324-7067, fax: 408-894-3207, e-mail: lydia_baril@maxtor.com

(2) Previously at ReadRite Corporation, 44100 Osgood Rd, Fremont, CA 94359 USA

Tel: 805-967-8152, email: tocheung2u@yahoo.com

Abstract – The effects of the Human Body Model (HBM) Electrostatic Discharge (ESD) waveform on Giant

Magnetoresistive (GMR) recording heads is well characterized. This information has provided a starting point

for understanding ESD damage to magnetic recording heads but the HBM no longer reflect the reality of ESD

mechanisms along the production lines. Damage will most likely occur from metal contact to the MR

electrodes (metal) rather than from bare fingers. Direct Charged Device Model (DCDM) can be used to

simulate metal-to-metal contact discharge. A manual DCDM was characterized using disk capacitors. DCDM

manual ESD testing of grounded (suspension is grounded) and floating suspension (suspension is not connected

to ground) GMR heads was performed, and a DCDM breakdown voltage ranging from 3V to 9V was measured.

Pspice simulation was used to simulate the DCDM discharging events, the results agree well with the DCDM

manual discharge data.

I. Introduction

characterize the DCDM and understand how the

system behaves using disk capacitors, GMR heads,

It is well known the GMR heads are sensitive to

and Pspice simulations.

damage from an electrostatic discharge (ESD) event,

as the areal density increases dramatically in magnetic

II. Experimental Setup

recording industry, the magnetic recording heads

become more susceptible to electro-overstress (EOS),

The experimental setup consisted of the following

and electrostatic discharge (ESD) events. HBM no

components:

longer reflects the reality of ESD damage along the

manufacturing lines. ESD will mostly occur from

1) Manual DCDM test jig

direct charging the GMR head capacitances then

2) Tektronix CT-6 current probe

followed by metal contact to an input, MR+ or MR-,

3) Tektronix 3GHz TDS694C Digital Oscilloscope

of a GMR head. ESD damage to GMR heads during

4) HP Digital Control Power Supply

all stages of handling and assembly is a serious

5) Gold plated metal plate

problem in magnetic recording head manufacturing. 6) Disk capacitors

The GMR sensor will have a voltage if the sensor is

itself charged, or if it is in the electric field of a

nearby, charged insulator. Tribocharging during

High Speed

Power Supply

handling of a head gimbal assembly (HGA) with an

Oscilloscope

insulating Kapton flex circuit has often been the root

+

G N D

cause of severe ESD problems. ESD testing that

directly charges and then grounds the MR+ or MR- of

10M

CT-6

a GMR head, known as “DCDM” shows that if the

Disk

GMR sensor at about 4V is grounded, then the current

Short W ire

Capacitor

that flows through the GMR sensor is severe enough

Ground Plate

to change the sensor resistance. The discharge current

waveform from metal contact and DCDM to a GMR

Figure 1a. Schematic representation of the DCDM manual test jig

head are similar. The purpose of this paper is to

for disk capacitors. - The purpose of using a manual test jig is that it has

the ground wire to the top disk plate. During

very small parasitic capacitance and inductance.

discharge process, the manual contact must be very

Figure 1a shows the schematic representation of

fast and precise. The discharge current waveforms are

DCDM manual test jig. The inductanceless disk

detected with a CT-6 current probe and the

capacitors are made out of 0.8 mm thick FR-4 double-

waveforms are captured from a high-speed digital

sided printed circuit board (PCB). One side of the

oscilloscope Tektronix TDS 694C 3GHz and 10GS/s.

board is gold-plated etched to a circular disk, and the

Figure 2 shows that the grounded and floating

other is gold-plated ground plane. The capacitance

suspension GMR heads were tested on the same

depends on the size of a circular disk (the spacing is

DCDM manual test jig. A grounded suspension HGA

fixed). The larger the circular disk is the higher the

means that the suspension contacts the grounded

capacitance. Figure 1b shows four different sizes of

metal plate. A floating suspension HGA means that

disk capacitance, 0.5pF, 2.2pF, 4.4pF, and 11.5pF.

the suspension is isolated from the grounded metal

plate. A 10MΩ resistor is connected from a power

supply to the MR+ of a GMR head. Then, the

grounded short wire contacts the MR+ or MR- pad for

discharge the charged GMR head. The CT-6 current

probe captures the discharge current; the high speed

oscilloscope is used to monitor the discharge current,

and an Ohmmeter is used to measure the MR

resistance after each discharge event until the MR

Figure 1b. Four disk capacitors 0.5pF, 2.2pF, 4.4pF and 11.5pF.

resistance changed more than 1%. (Note: Use the MR

resistance failure for reference only, magnetic

High Speed

Power Supply

To Oscilloscope

Metal plate

Oscilloscope

+

GND

10 MΩ resistor

Power supply +

10M

CT-6

CT6

Short Wire

HGA

Short wire

Ground

Metal Plate

performance is more susceptible to ESD damage).

Figure 2. Schematic representation of the DCDM manual test jig

for GMR head.

Figure 1c. DCDM manual test jig for disk capacitors.

The bottom plate of the capacitor lies on a grounded

gold-plated metal. The grounded metal plate is gold-

III. Experimental Results and

plated for good contact between the bottom plate of

Analysis

disk capacitor and metal plate. A voltage source

provides voltage to the top plate of the disk capacitor

Figure 3 shows a simplified electrical equivalent

through a 10MΩ resistor. The voltage source is

circuit for DCDM manual test jig. The voltage source

continuously charging the disk capacitor. A short

is not shown in the circuit. Cdisk is the disk capacitor,

wire of about half inch long is connected to a

L1 is the inductance of the grounded wire, Cp is the

grounded metal plate through a CT-6 current probe parasitic capacitance of the circuit, Rspark is the spark

(See Figure 1c). The disk capacitor surface and the

resistance, which is created during the grounded wire

grounded wire must be cleaned. The discharge of the

contacts the charged disk capacitor.

disk capacitor is done manually contacting one end of - discharge current equation is given by:

L1

−α

I (t)

V

=

e

t sin(

ωt)

ω

(3)

L

2

1

R

where α = R/2L, ω = 2πf =

− ( ) ,

Rspark

LC

2L

Cp

Cdisk

I(t) is the discharge current and V is the voltage on the

capacitor. The equation (3) shows that the voltage on

SW

the capacitor is doubled, the discharge current is also

doubled. Figure 5b shows that the pulse width

decreases as the voltage on the capacitor increases.

The hypothesis for the decreasing pulse width at

higher voltage are the bandwidth limitation of a CT-6

Figure 3. Electrical equivalent circuit for DCDM manual testing

current probe and the lower spark resistance as a

for disk capacitor.

result of smaller change of time constant. Figure 5c

shows the discharge current saturated at high

Figure 4 shows an example of discharge current

capacitance. This is due to the smaller the

waveform for a disk capacitor 4.4pF at charging

capacitance, the higher the discharge path impedance,

voltage of 4V. The first peak current reaches 54mA

which limits the current. The magnitude of

and the pulse width is about 0.47ns. There is a second

impedance Z is given by:

peak of opposite polarity or undershoot. Its peak

current level is about –21mA. Waveforms obtained in

the same manner for the same capacitance and the

2

Z = R + (

ω ) 2

L ,

same charging voltage is mostly reproducible, i.e.

peak current and pulse width values are within +/-

10%. Waveforms were captured for a range of

where ω = 2πf, R is the equivalent resistance of the

capacitor values and charging voltages.

inductor L

1, the L is the inductance of the L1. Pspice

simulation will be used to verify this behavior.

Manual DCDM 4.4pF @4V

Manual Charging/Discharging on Disk Capacitors

6.0E-02

160

11.5pF

5.0E-02

140

11.5pF y = 17.786x - 5.5478

4.0E-02

120

4.4pF y = 12.151x - 3.4174

3.0E-02

100

4.4pF

2.2pF y = 5.1043x + 0.0087

2.0E-02

1.0E-02

0.5pF y = 2.1426x + 0.3652

80

0.0E+00

Peak Current (A)

60

-1.0E-02

-1.E-09

0.E+00

1.E-09

2.E-09

3.E-09

4.E-09

5.E-09

2.2pF

40

-2.0E-02

measured Ip (mA)

-3.0E-02

20

0.5pF

Time (ns)

Time (sec.)

0

0

2

4

6

8

10

Figure 4. Discharge current waveform of a 4.4pF disk capacitor at

DCDM Voltage (V)

4V.

Figure 5a. Charging voltage versus discharge current for four

Figure 5a shows the manual test discharge current for

capacitors.

four different capacitances and voltages. The - 1.2

1.0

L1

0.8

11.5pF

0.6

4.4pF

Rspark

0.4

2.2pF

V

CMR-to-grounded suspension

22pF

0.2

0.5pF

Peak Width at Half Amplitude (ns) 0.0

SW

0

2

4

6

8

10

DCDM Voltage (V)

Figure 5b. Pulse width versus charging voltage for four

capacitances.

Figure 7. Simplified equivalent electrical circuit model for

140

8V

grounded suspension GMR heads.

120

100

80

Figure 8 shows the discharge current of 51mA and the

4V

60

pulse width of about 2ns at 4V for the grounded

Ip (mA)

40

suspension GMR head.

2V

20

1V

Manual DCDM: Grounded suspension

0

Criteria: MRR > 1%

0

1

2

3

4

5

6

7

8

9

10

11

12

13

Capacitance (pF)

0.06

0.05

breakdown at 4V

Figure 5c. Discharge current versus capacitance for four charging

0.04

voltages.

0.03

0.02

0.01

Figure 6 shows an electrical circuit model of the

0

DCDM manual testing for grounded suspension GMR

Total discharge current (A)

-1.E-09

0.E+0 0

1.E-09

2.E-09

3.E-09

4.E-09

5.E-09

6.E-09

7.E-09

8.E-09

9.E-09

-0.01

heads. The capacitance from the MR leads to

-0.02

suspension is larger than other capacitance when the

Tim e ( n s )

Time (sec.)

suspension is grounded. The total capacitance of the

Figure 8. Discharge current waveform at 4V for grounded

HGA depends on the type of flexcircuit. In this

suspension GMR head.

particular flexcircuit HGAs, the total capacitance is

about 22pF from the MR leads to suspension. Figure

Figure 9 shows the electrical circuit model of the

7 shows a simplified equivalent electrical circuit of

DCDM, and the floating suspension GMR heads

Figure 6. Where 22pF is the total head capacitance,

(floating suspension means the suspension is not

L

connected to ground). The head capacitance is

1 is the total inductance of the MR lead and

inductance of discharge path.

dominated by the capacitance between the suspension

and the system ground.

5pF

5pF

10MΩ

MR pad+

2Ω

10MΩ

V

MR

2Ω

MR pad-

MR pad+

2

V

Ω

MR

2Ω

MR pad-

10nH

30nH

42Ω

30nH

10nH

30nH

42Ω

30nH

11pF

11pF

Rsp

5pF 5pF

11pF

11pF

40

100G

100G

5pF 5pF

33Ω

1G

1G

100G

100G

1G

1G

0.1pF

0.1pF

Bottom Shield

SW

Bottom Shield

SW

2pF

2pF

DCDM

10G

DCDM

10G

Substrate/Suspension

System Ground Substrate/Suspension

5pF

100G

Figure 6. Electrical circuit model of the DCDM manual testing for

grounded suspension GMR heads.

System Ground

Figure 9. Electrical circuit model of the DCDM and the floating

suspension GMR heads. - When the GMR head suspension is not grounded, the

M a n u a l D C D M : F l o a t i n g S u s p e n s i o n

capacitance from suspension to grounded metal plate

0.0 8

is approximately 5pF. Figure 10a shows the CMR-to-

Ip = 65mA @ 9V breakdown

0.0 6

suspension in series with the Csuspension-to-ground. The

PW50 = 0.8ns

0.0 4

total head capacitance can be calculated as follows:

0.0 2

C=(22pF)(5pF)/(22pF+5pF)=4pF

0

- 1 . 0 0 E - 0 9

0 . 0 0 E + 0 0

1 . 0 0 E - 0 9

2.0 0 E - 0 9

3 . 0 0 E - 0 9

4 . 0 0 E - 0 9

5 . 0 0 E - 0 9

6 .00E-09

7 . 0 0 E - 0 9

8 . 0 0 E - 0 9

9 . 0 0 E - 0 9

Total discharge current (A)

- 0 . 0 2

L1

- 0 . 0 4

Tim e ( n s )

3 . 0 5 V

4 V

4 . 5 V

5 V

5 . 5 V

6 V

6.5 V

7 V

7 . 5 V

8 V

8 . 5 V

9 V

2 . 5 4 V

Figure 11. Discharge current waveform at breakdown voltage of

Rspark

9V for a floating suspension GMR head.

22pF

Figure 12 shows that the comparison of the

CMR-to-suspension

breakdown voltage for the grounded suspension and

the floating suspension GMR heads. The grounded

SW

Csuspension-to-ground

5pF

suspension heads were broken down at about 3V to

4V, and the floating suspension head was broken

down at about 9V at the GMR resistance changing

more than 1%. The floating suspension exhibits

Figure 10a. Simplified electrical circuit model for a floating

higher breakdown voltage than the grounded

suspension GMR head.

suspension GMR head because the grounded

Figure 10b shows a simplified head capacitance from

suspension has a larger head capacitance than the

MR-to-ground for floating suspension GMR head. floating suspension GMR head reference to grounded

An equivalent head capacitance can be represented by

metal plate. The grounded suspension HGA has a

a single 4pF.

total head capacitance of about 22pF, and the floating

suspension HGA has a total head capacitance of about

4pF. The total head energy to damage to MR sensor

L1

can be calculated and compared as follows:

For grounded suspension HGA:

Rspark

A total head capacitance C of 22pF with a charging

V

voltage (V) at breakdown of 4V, then the total energy

CMR-to-ground

4pF

can be calculated based on the equation:

SW

E=1/2(C V 2 )=0.176nJ

For floating suspension HGA:

A total equivalent head capacitance C of 4pF with a

Figure 10b. Simplified electrical circuit model for a floating

suspension GMR heads with a total equivalent capacitance of 4pF.

charging voltage (V) at breakdown of 9V, then the

total energy can be calculated based on the equation:

Figure 11 shows the discharge current waveforms at

different charging voltages from 3V to 9V. The MR

resistance of this floating suspension head changed

E=1/2(C V 2 )=0.162nJ

from 42Ω to 54Ω at 9V breakdown. The peak current

Comparing the two total energies, the floating

amplitude at 9V is about 65mA, and the pulse width is

suspension HGA requires higher voltage to reach the

about 0.8ns.

same energy level as for the grounded suspension

HGA that can damage the GMR sensor (assume same

MR resistance for both type). This is due to the

floating suspension HGA has lower head capacitance

than the grounded suspension HGA reference to

ground. - the discharge current amplitude and wider the pulse

Manual DCDM: Grounded vs Floating suspension

Criteria: MRR >1%

width. Both the resistance and impedance of the

56

inductor L1 in the discharge path can affect the

54

Grounded suspension

Floating suspension

52

discharge current amplitude and the pulse wide.

Col 50

d

M

48

RR

46

The total resistance, Rt, in the discharge path is

44

approximately related by the following expression:

42

40

0

1

2

3

4

5

6

7

8

9

10

Rt = Rseries + Rspark + | Z | (4)

DCDM Voltage (V)

Hd1

Hd2

Hd3

Hd4

The magnitude of impedance Z is given by:

Figure 12. GMR resistance versus DCDM breakdown voltage for

2

grounded and floating suspension GMR heads.

Z = R + (

ω L)2

, (5)

ω =

Discharge current occurs when the grounded wire is

where

2 f

π

, R is the equivalent resistance of the

brought near a charged disk capacitor, the electric

inductor wire and L is the equivalent inductance, f is

field between them increases to an extreme value. the frequency. The Rspark and the impedance can be

When the field exceeds the dielectric breakdown

calculated from the Equation (4):

strength of air, current begins to flow by an avalanche

process. Eventually a low resistance spark develops. Rspark + | Z | = Vc/Ip - Rseries

The spark resistance can be affected by the contact

conditions such as humidity, contact speed, grounded

where Vc is the charging voltage on the capacitor, and

wire/disk capacitor plate material, the size and the

the Ip is the discharging current.

shape of the grounded wire tip and the contamination

between the grounded wire tip and the disk capacitor.

0.1

No Rseries

0.08

The following setup can be used for initial spark

11 Ohms

0.06

51 Ohms

resistance study.

0.04

100 Ohms

0.02

Figure 13 shows the spark resistance test setup. A

0

low inductance surface mount resistor must be used.

Discharge Current (A)

-2.E-09 -1.E-09 0.E+00 1.E-09

2.E-09 3.E-09 4.E-09 5.E-09

6.E-09 7.E-09 8.E-09

-0.02

The purpose of using additional resistance in series

-0.04

Time (sec.)

with the discharge path is that the behavior of the

pulse width and the amplitude of the discharge current

Figure 14. Discharge current versus Rseries at charging voltage

of 4V.

can be observed. (See Figure 14)

Figure 15 shows the Rspark and the impedance Z as a

function of charging voltage. The manual DCDM test

High Speed

Power Supply

jig was used to perform this experiment (See Figure

Oscilloscope

13). The spark resistance plus the impedance Z

without adding the series resistance is 44Ω at 4V.

+

GND

Based on the experimental data, the Rspark plus the

impedance Z increase as the charging voltage

decreases. However, we expected higher spark

10M

CT-6

resistance with the increasing of the charging voltage.

Disk

More experiments need to be conducted and analyzed

Series resistor

Capacitor

in this area.

Ground Plate

Figure 13. Schematic representation of the spark resistance test

setup.

Figure 14 shows the discharge current waveforms

varying the different series resistances. The higher

the series resistance in the discharge path is the lower - used to observe the current flows through the GMR

sensor. Figure 17 shows the Pspice simulation of the

140

total discharge current (solid line), and the current

120

Series resistance 51 Ohms

100

flows through the GMR sensor (dashed line) for the

(Ohm)

Series resistance 11 Ohms

80

grounded suspension GMR head at breakdown

+ Z

60

Series resistance 100 Ohms

voltage of 4V. The discharge current of 22mA flows

40

spark

R

20

through the GMR sensor. The reason for the current

0

flows through the GMR sensor less than 50% of the

0

5

10

15

20

total current because the GMR sensor resistance limits

DCDM Voltage (V)

the current. The total discharge current using the

Figure 15. Spark resistance versus DCDM voltage

manual discharge (See Figure 8), and the Pspice

simulation (See Figure 17) for a grounded suspension

IV. Pspice Simulation

GMR head are comparable.

The Pspice simulated discharge current for the

The DCDM manual discharge behavior can be

floating suspension GMR head at the breakdown

confirmed by Pspice simulation.

voltage of 9V (See Figure 18) is comparable to the

Figure 16 shows the Pspice simulation of discharge

manual discharge (See Figure 11). The total

current waveform from discharging a disk capacitor of

discharge current is about 66mA; 22mA flows

4.4pF at 4V, inductance L1 of 10nH and spark

through the GMR sensor, and the pulse width is about

resistance of 24Ω . As can be seen, the DCDM

0.8ns.

manual discharge waveform and the Pspice simulation

waveform are comparable.

0.08

Solid line: total discharge current = 66mA

0.06

Dashed line: discharge current through MR = 22mA

PW50 = 0.8ns

0.06

Dashed line: simulated, Ip=54mA, PW50=0.47ns

0.04

0.05

Solid line: manual tested, Ip=54mA, PW50=0.47ns

0.04

0.02

0.03

0.02

0

Discharge Current (A)

0.0E+00 1.0E-09

2.0E-09

3.0E-09

4.0E-09 5.0E-09

6.0E-09

7.0E-09

8.0E-09

9.0E-09

0.01

-0.02

0

ischarge Current (A) -0.01

0.0E+00

1.0E-09

2.0E-09

3.0E-09

4.0E-09

5.0E-09

-0.04

D

-0.02

time (sec.)

-0.03

time (sec.)

Figure 18. Pspice simulation of discharge current for a floating

suspension GMR head. Dashed line is the current through GMR

Figure 16. DCDM manual testing (solid line) and simulation

sensor.

(dashed line) comparison using 4.4pF at 4V.

Figure 19 shows the Pspice simulation of discharge

current per charging voltage (mA/V) relationship for 4

different disk capacitors. The simulation results agree

0.06

Itotal=52mA

well with the DCDM manual discharge.

0.05

0.04

PW50=2ns

0.03

Pspice Simulated V vs I vs C

IMR=22mA

180

0.02

160

0.01

y = 16.208x + 0.1125 11.5pF

140

0

y = 11.13x + 0.5917 4.4pF

-1.E-09 0.E+00 1.E-09 2.E-09 3.E-09 4.E-09 5.E-09 6.E-09 7.E-09 8.E-09 9.E-09

ischarge Current (A)

120

-0.01

D

y = 8.1211x - 0.275 2.2pF

100

-0.02

y = 2.7734x + 0.125 0.5pF

80

Ip (mA)

time (sec.)

60

Figure 17. Pspice simulation of discharge current for the grounded

40

suspension GMR head at 4V. Dashed line is the current through

20

GMR sensor.

0

0

2

4

6

8

10

12

DCDM Voltage (V)

The total current flows through the GMR heads can be

measured but the current flows through the GMR

sensor can not be measured. Pspice simulation can be

Figure 19. Pspice simulation of peak current versus DCDM

voltage. - Figure 20 shows the Pspice simulation of discharge

current pulse width as a function of DCDM voltage

0.035

0.03

10 Ohms

for 6 different disk capacitors. The spark resistance,

0.025

0.02

inductance and capacitance are no changed. The

0.015

60 Ohms

pulse width maintains constant throughout the

0.01

0.005

charging voltage ranging from 1V to 16V. However,

0

0.0E+00

2.0E-09

4.0E-09

6.0E-09

8.0E-09

1.0E-08

1.2E-08

1.4E-08

the simulation conditions and the experimental

-0.005

-0.01

condition is slightly different. The experimental data

Discharge Current thru MR (A) -0.015

-0.02

shows that the spark resistance changes as varying the

Time (sec.)

charging voltage.

Figure 22. Pspice simulation of discharge current flows through

the GMR sensor at the charging voltage of 4V with varying the

0.8

spark resistance Rsp of the DCDM from 10Ω to 60Ω .

0.7

11.5pF

0.6

Figure 23 shows that if the DCDM module varies the

0.5

4.4pF

discharge path inductance from 5nH to 65nH, the

0.4

2.2pF

energy (not shown) increases about 23% at 65nH.

0.3

PW50 (ns)

0.2

0.5pF

0.1

0.03

5nH

0

0.025

0

2

4

6

8

10

0.02

65nH

Charging Voltage (V)

0.015

0.01

0.005

Figure 20. Pspice simulation of discharge current pulse width

0

versus charging voltage.

-0.005

0.0E+0 2.0E-09 4.0E-09 6.0E-09 8.0E-09 1.0E-08 1.2E-08 1.4E-08

0

Discharge Current thru MR (A)

-0.01

Figure 21 shows the discharge currents are saturated

Time (sec.)

as increasing the capacitance. The experimental data

and simulation data are comparable.

Figure 23. Pspice simulation of discharge current flows through

the GMR sensor at the charging voltage of 4V with varying the

140

discharge path inductance from 5 to 65nH.

8V

120

100

V. Data Summary

80

60

4V

40

Table 1 shows the rise time of discharge currents for

2V

20

Peak Current (mA)

four capacitors at charging voltage ranging from 1V,

1V

0

2V, 4V and 8V. The experimental (exp) and

0

1

2

3

4

5

6

7

8

9

10

11

12

13

simulation (sim) results are closed.

Capacitance (pF)

Figure 21. Pspice simulation of discharge current versus

0.5pF

2.2pF

4.4pF

11.5pF

capacitance for four charging voltages.

tr (ns)

exp

sim

exp

sim

exp

sim

exp

sim

V

Figure 22 shows that if the DCDM module varies the

1

0.25

0.177

0.21

0.203

0.39

0.215

0.53

0.32

spark resistance from 10Ω to 60Ω during ESD testing,

2

0.18

0.17

0.25

0.197

0.31

0.226

0.42

0.32

75% less energy (not shown) flows through the GMR

4

0.17

0.175

0.26

0.209

0.29

0.225

0.4

0.32

sensor at 60? .

8

0.14

0.175

0.19

0.192

0.34

0.228

0.44

0.32

Ave

0.19

0.17

0.23

0.20

0.33

0.22

0.45

0.32

Table 1. Discharge current risetime comparison for four

capacitances at charging voltages ranging from 1V, 2V, 4V and

8V. - Table 2 shows the sensitivity of discharge current per

charging voltage (mA/V) for four capacitances. There

REFERENCES

is about 9% different between experimental and

[1] Socket Device Model Testing, ESD Association

simulation results for both 11.5pF and 4.4pF.

technical report TR 08-00

[2] The SDM Test Method: Past, Present, and Future.

Michael Chaine, Ion Barth, Tilo Bordeck, Leo G. Henry,

0.5pF

2.2pF

4.4pF

11.5pF

Mark A. Kelly, and Tom Meusen Compliance Engineering.

exp

sim

exp

sim

exp

sim

exp

sim

Ce-mag.com 09-10/2001

mA/V

2.14

2.8

5.1

8.1

12.2

11.1

17.8

16.2

[3] Charge Device Model. ESD Association standard test

Table 2. Discharge current per charging voltage sensitivity

method. ESD STM5.3.1-1999

comparison for four capacitances.

[4] Standardized Direct Charged Device ESD Test for

Magnetoresistive Recording Heads II. Lydia Baril, Tim

Table 3 shows the pulse width for four capacitances at

Cheung, Albert Wallash. Submitted to EOS/ESD

charging voltage ranging from 1V, 2V, 4V and 8V. Symposium 2002

The experimental and simulation results are close, but

[5] “Direct Charging” Charge Device Model Testing of

the simulation data are slightly less than the

Magnetoresistive Recording Heads. Tim Cheung,

experimental data. Selection of component values for

EOS/ESD Symposium 1997

simulation can affect the results.

0.5pF

2.2pF

4.4pF

11.5pF

PW50

exp

sim

exp

sim

exp

sim

exp

sim

V

1

0.37

0.2

0.44

0.33

0.65

0.46

1.00

0.72

2

0.35

0.2

0.42

0.33

0.58

0.45

0.95

0.72

4

0.34

0.2

0.39

0.33

0.49

0.45

0.85

0.73

8

0.25

0.22

0.43

0.33

0.49

0.46

0.79

0.73

Ave

0.33

0.21

0.42

0.33

0.55

0.46

0.90

0.73

Table 3. Discharge current pulse width comparison for four

capacitances at charging voltages ranging from 1V, 2V, 4V and

8V.

VI. Conclusion

We have learned from the manual testing, and Pspice

simulations, the spark resistance; parasitic capacitance

and inductance of the DCDM system can change the

characteristic of a DCDM discharging current

waveform. The Pspice simulation and experimental

data are comparable. The data shows the grounded

suspension GMR head is more sensitive than the

floating suspension GMR head. The spark resistance,

the DCDM parasitic inductance and capacitance can

affect the results of ESD testing. More spark

resistance experiments need to be conducted and

analyzed. It is a big challenge for the test equipment

vendors to design a DCDM tester with very small

parasitic inductance and capacitance.