ESD Control Standards:
Setting up an ESD control program

Ryne C. Allen
Desco Industries Inc. (DII),
Employee Owned
February 1999

Reproduced with Permission, EE-Evaluation Engineering, February, 1999

 

INTRODUCTION

This paper will help an ESD Coordinator, Manager or Engineer apply the proper ESD standards when developing an ESD Control Program. For an ESD Control program to be effective it should be designed around the ElectroStatic Discharge Sensitive (ESDS) devices it is protecting; and most importantly, it should be supported at all levels within the company, from the company officers through all managers to the operators and technicians. This top-down approach, when fully adapted, ensures that all the elementary elements of the program are properly deployed.

One of the main reasons companies deploy an ESD Control program is to save money. Increased throughput and decreased scrap can yield a ROI (Return On Investment) of up to 3000% per year for successfully deploying an ESD Control program [1]. A secondary reason is to comply with their customers’ demands and ISO 9000 programs. Whatever reason, setting up and implementing an ESD Control program will almost always pay for itself within the first year.

There is an array of ESD Control products on the market. Which products should you choose when developing your ESD Control program? The products that you select are determined by how you have defined your ESD control program.

 

I STANDARDS from the Ground Up

ESD and Standards

There are about 60 of the more commonly used standards for ESD control listed in Tables I and II. These standards and specifications originate from many different organizations and serve different purposes, as are outlined below.

  1. ORGANIZATIONS
    1. Military & Government (FTM, MIL, OSHA)
    2. Commercial Organizations (AATCC, ANSI, ASTM, AT&T, CECC, IEC, IPO, ISO)
    3. Associations (EIA, ESDA)
  2. PURPOSE or FUNCTION
    1. Standard testing and classification of semiconductor devices
    2. Standard test methods
    3. Standards for qualifying ESD Control programs or items
    4. Standards for monitoring ESD Control programs or items
    5. Technical reports or advisories for understanding the standards or technology

If your company supplies various electronic components or is a board house, your customers may require you to follow certain prescribed standards to which they adhere. If you are establishing a new ESD control program then the Electrostatic Discharge Association’s Standards listed in Tables I through IV will aid you to establishing the proper criteria.

ESDA Standards

The Electrostatic Discharge Association (ESDA) standards are the most comprehensive and up-to-date industry accepted standards for the control of ESD. Their current standards are listed in Table I by application.

Six years ago, the ESD Association became an American National Standards Institute (ANSI) accredited standards development organization, and this attainment is reflected in some of the ESDA standards carrying the ANSI accreditation.

The first place to look for guidance in developing your ESD Control program would be from within the ESDA standards. As of February 1998, the ESDA has refined their definitions of standards by specifying the following categories.

  • Standard (S) is a precise statement of a set of requirements to be satisfied by a material, product, system or process that also specifies the procedures for determining whether each of the requirements is satisfied.
  • Standard Test Method (STM) is a definitive procedure for the identification, measurement and evaluation of one or more qualities, characteristics or properties of a material, product, system or process that yield a reproducible test result.
  • Standard Practice (SP) is a procedure for performing one or more operations or functions that may or may not yield a test result.
  • Technical Report (TR) is a collection of technical data or test results published as an informational reference on a specific material, product, system or process.

Furthermore, as a new standard evolves, it becomes ready for industry review and is classified as a Draft Standard and can be represented by the designation Draft Standard (DS), Draft Standard Practice (DSP), Draft Standard Test Method (DSTM), and Draft Technical Report (DTR). And lastly, an Advisory (ADV), which may be replaced by the Technical Report (TR), can be educational in nature and consists of general information and guidelines deemed helpful to the industry in understanding the use of standards and related technology.

The ESD Association has recently accepted the task of refining MIL-STD-1686 Electrostatic Discharge Control Program for Protection of Electrical and Electronic Parts, Assemblies and Equipment as a commercial document.

 

II Defining Your Program

The starting point of a sound program is to classify the sensitivity to ESD damage of the devices you need to protect. Classification of these devices should include all simulation models (HBM, MM, and CDM, refer to the ESD STM5 series in Table I) that will properly characterize the devices' sensitivity when handled at various locations within the facility.

  1. Realize that there may be different sensitivities at different locations within the facility.
  2. The ESDA standards that aid the sensitivity testing process are ESD STM5.1-1998, ANSI/ESD S5.2-1994, ESD DS5.2-1996, and ESD DS5.3.1-1996. These documents are the most recent in the industry.
  3. The Military standards that can be used to determine device ESD sensitivity MIL-HDBK-263B, MIL-STD-883D Method 3015.7, MIL-STD-750C/4 Method 1020, MIL-STD-785
  4. The IEC standards to help classify device sensitivity are CISPR 24 (1997-09) and IEC-61000-4-2 (1995).
  5. ANSI has a document, ANSI C63.16, that can aid in device sensitivity classification.

If you do not classify the devices then you can assume the worst case for all 3 models, (Classes 0, M0, C0 - refer to the ESD STM5 series standards in Table I), making the program design critical and expensive.

III Program Design

Once the ESD device sensitivities for the various areas in the facility have been determined then this information can be mapped over the complete facility and will act as a guide to designing the ESD control program.

Now, the location/sensitivity map of the facility needs to be expanded upon by determining what standards you will use to evaluate the success and monitor the program’s progress. This map should also consider the transportation systems and traffic flow of the sensitive devices between various working areas. Additional design criteria to ensure device protection that needs to be broadened are listed as follows.

  1. Minimize voltage or field exposure (remove non-essential charge generators)
  2. Minimize voltage or field exposure (use of protective packaging during transportation or storage)
  3. Minimize voltage or field exposure (from machine to device contact, e.g., automated equipment)
  4. Exposed surfaces and their resistance (controlled discharge times and use of dissipative work surface materials)
  5. Grounding (power ground distribution) for common point grounds/work surfaces
  6. Grounding (floors – traffic areas)
  7. Grounding (personnel – wrist straps/foot grounders/smocks/gloves)
  8. Use of air ionization for essential non-grounded or insulative materials/equipment/tools
  9. Environmental controls (temperature and humidity)
  10. Training of employees within various affected areas (by far one of the most important factors)

 

 

 

 

IV Selecting General Product Criteria for each Area

Which standard(s) should you reference when building your ESD Control program from scratch, updating or evaluating your current program? When you look to build an ESD-safe workstation, you need to know what industry-wide acceptability criteria to comply with.

Table IV will help aid the design and development of an ESD control program for each area using either the ESD ADV-2.0-1994 or the MIL-STD-1686. The former is more recent at this time. Table III lists various ESD Control products and the associated ESDA Standards that can be used to qualify them.

As an example, an ESD Sensitive (ESDS) workstation that is designed for worst case criteria may have the following ESD Control products: an ESD floor; grounded floor mats with use of ESD footwear (such as foot grounders); grounded and monitored table mats covering all exposed surfaces; a common point ground with monitored wrist strap connections; and air ionizers covering all areas on the work surface to which the devices would be exposed. In addition, all exposed insulators and metal surfaces would be replaced with grounded dissipative materials; all non-essential items, especially insulators, would be removed the ESDS area; and most importantly, the ESDS workstation would have ESD Control Trained operator(s) at the helm.

 

  1. Floors

    Starting from the ground up, your floor would be the first place to start. One of the most important characteristics of an ESD floor is its ability to conduct charges to ground. The second most important aspect is its anti-static property. One of the main mechanisms of charge generation is triboelectric generation or tribocharging. Some examples of tribocharging are people walking along a floor and carts carrying sensitive devices rolling across a floor. Depending on where the materials in contact with the floor are in the triboseries, voltages of over 30,000 Volts can be attained. If a floor has the property of being anti-static, tribocharging becomes a much smaller concern. The standards documents to help choose a floor are ANSI/ESD S7.1-1994, AATCC Step Test - Method 134-1979, ANSI/EIA-625-1994, MIL-STD-1686, MIL-HDBK-263B, and the AT&T Electrostatic discharge Control Handbook.

  2. Mobility

    Typically protection on an ESDS device should start at receiving, continue to inventory storage, and then travel through its production flow usually from one workstation to the next before ending up in shipping. All throughout its handling, the device should be handled by grounded personnel. The easiest way to ground people who travel from one station to the next, delivering or picking up sensitive materials, is through mobile grounding. Wearing foot grounders (one on each foot) in conjunction with a conductive floor is one way to ensure that the operator is grounded and protected from delivering or receiving an ESD event. There are several ESDA standards to help in the testing and verification of foot grounders and shoes: ESD DSTM54.1-1997, ESD DSTM54.2-1997, and ESD S9.1-1995.

  3. Work Surfaces

    The surfaces where ESDS devices are handled should be both conductive (in the dissipative range) and properly grounded to the equipment grounding conductor to be an effective ESD control element. There are several materials to choose from such as rubber mats, vinyl mats, both single and multi-layered and FRP and Micastat® for rigid or permanent bench surfaces. Conductive metal work surfaces should be discontinued or covered with a dissipative material because it is highly susceptible to causing an ESD event from a metal-metal contact. It is very important to control your discharge time by minimizing the energy transfer by employing resistive materials to ground [4]. The ESDA standards to help characterize a work surface are ESD STM4.2-1998 and ESD ADV53.1-1995.

  4. Personnel Grounding

    The human being can be the most dynamic part of a working environment and consequently should be considered one of the most important objects to ground. Wrist straps, a conductive wristband with a connecting ground cord, is the most popular and effective way to ground a person. Wrist straps should always be properly employed when working with ESDS devices. The ESDS standard EOS/ESD S1-1987 can aid in qualifying your wrist straps before implementation.

  5. Ionization

    Materials that must stay with the ESDS work area but are neither conductive nor groundable should be treated with air ionization. Ionizers come in several types, the most popular is the corona discharge air ionizer. Corona discharge air ionizers can have emitters that are powered by AC, DC or pulsing DC high voltage. Air ionizers can be qualified by applying the ESDA standards ANSI-EOS/ESD, S3.1-1991ADV3.2-1995, and ESD SP3.3-1998.

  6. Transportation & Packaging

ESDS devices should always be stored in an enclosed antistatic shielding bag or conductive closed tote or bin when not being handled. This includes inventory storage, transportation, and WIP. Further precautions during transportation include using dissipative carts with conductive wheels or drag chains in conjunction with a conductive floor when transporting ESDS devices in their shielded containers. The standards to help characterize and qualify packaging materials are ANSI/ESD S11.31-1994 for shielding bags, ANSI/EOS/ESD S8.1-1993 for proper use of package markings, ANSI/EIA-541-88 and ANSI/EIA-583-91 for packaging materials.

 

CONCLUSION

Determining the product sensitivities within the facility and then mapping this information helps in choosing the right materials to keep each work area under control. Using the ESDA or other related Standards will help your ESD Control program comply with industry-accepted requirements and procedures that govern the materials, products, systems or processes. Acceptability, repeatability, and dependability can be expected from an ESD Control program that employs a good design using the appropriate standards along with proper training and monitoring.

 

REFERENCES

  1. ESD Program Management, G. Theodore Dangelmayer, Van Nostrand Reinhold, NY, NY, Chpt. 14, 1990
  2. The ESD Association, 7900 Turin Road, Bldg. 3, Suite 2, Rome, NY 13440-2069, http://www.eosesd.org
  3. MIL-STD-1686B, Department of the Navy, Defense Printing Service Detachment Office, Philadelphia, PA, 31 December 1992
  4. R. C. Allen, "Controlling Workstation Discharge Times", Evaluation Engineering, Jan. 1998, pp. 88-92.

 

FOR EXTERNAL COLORED TEXT BOX (related info)

There is always some confusion between the terms conductive and dissipative. Conductive can imply at least two different things: (1) the basic property of being able to move charges along a surface and (2) the range in ESD Control that differentiates very conductive materials (classified as "conductive") from lesser conductive materials (classified as "dissipative"). A "dissipative" material is conductive in that it will move charges along its surface. A "dissipative" material also has more resistance to the charge flow and will move these charges slower than a "conductive" material will, but much faster than an "insulative" material. Figure 1 graphically displays the ESD Control resistive ranges of "conductive", "dissipative" and "insulative". In ESD Control, one of the main keys of this control is to control the charge flow (current) during a discharge. Increasing the time for an ESD discharge will result in a reduction of the peak energy transferred over any given point in time, which minimizes the chance for an ESD event to occur and cause damage to a sensitive device. This is best accomplished with a conductive material that has sufficient resistance. The resistance range considered for this type of control starts at the high end of the "conductive" range through a good part of the "dissipative" range, refer to Figure 1.

About the Author

Ryne C. Allen is the technical manager at ESD Systems, a division of Desco Industries, Inc. (DII). Previously, he was chief engineer and lab manager at the Plasma Science and Microelectronics Research Laboratory at Northeastern University. Mr. Allen is an NARTE-certified ESD control engineer and the author of 27 published papers and articles. He is a member of the ESD Association and an active ADCOM associate member of the Northeast Local Chapter. He graduated from Northeastern University with B.S.E.E, M.S.E.E., and MBA degrees. ESD Systems, 19 Brigham St., Unit 9, Marlboro, MA 01752-3170, (508) 485-7390,, e-mail: ryne.allen@esdsystems.com, URL: http://www.esdsystems.com.

Standards Summary Tables

TABLE I

Electrostatic Discharge Association (ESDA) Standards [2]

Standard Number

Standard Description

Type

Application(s)

ESD ADV3.2-1995

Selection and Acceptance of Air Ionizers

ADV

Air Ionizers

ESD SP3.3-1998

Periodic Verification of Air Ionizers

SP

Air Ionizers

ANSI-EOS/ESD S3.1-1991

Ionization

S

Air Ionizers

ESD ADV11.2-1995

Triboelectric Charge Accumulation Testing

ADV

Antistatic properties of materials

ESD STM12.1-1997

Seating – Resistive Measurement

STM

Chairs

ESD STM5.1-1998

Human Body Model (HBM) -

Component Level

STM

Device & Program classification, Device sensitivity testing

ANSI/ESD S5.2-1994

ESD DS5.2-1996

Machine Model (MM) –

Component Level

STM

Device & Program classification, Device sensitivity testing

ESD DS5.3.1-1996

Charged Device Model (CDM),

Non-Socketed Mode,

Component Level

STM

Device & Program classification, Device sensitivity testing

ESD ADV2.0-1994

ESD Handbook

ADV

ESD Control guide

ESD ADV1.0-1994

Glossary

ADV

ESD Definitions

ANSI/ESD S7.1-1994

Resistive Characterization of Materials, Floor Materials

STM

Floors finishes, floor mats, floor paint, floor tiles & carpets

ESD DSTM54.1-1997

Floor Materials and Footwear- Resistance Measurement in Combination with a Person

STM

Foot grounders, shoes, floors

ESD DSTM54.2-1997

Floor Material and Footwear – Voltage Measurement on a Person

STM

Foot grounders, shoes, floors

ANSI/EOS/ESD S6.1-1991

Grounding–Recommended Practice

S

Ground cords, common point grounds (CPG), grounding systems, grounding objects

ANSI/ESD S11.31-1994

ESD Shielding Materials - Bags

STM

Shielding bags

ESD S9.1-1995

Footwear – Resistive Characterization

S

Shoes

ESD STM2.1-1997

Garments

STM

Smocks, Lab Coats

ESD DSTM13.0-1998

Soldering/Desoldering Tools

STM

Solder Irons, desoldering tools

ANSI/EOS/ESD S11.11-1993

Surface Resistance Measurements of Static Dissipative Planar Materials

STM

Surface resistance of planar materials

ANSI/EOS/ESD S8.1-1993

Symbols – ESD Awareness

S

Symbols for ESD packaging/awareness

ANSI-EOS/ESD S4.1-1998

ESD Protective Worksurfaces

Resistive Characterization

S

Table Mats, planar worksurfaces

ESD STM4.2-1998

ESD Protective Worksurfaces

Charge Dissipation Characteristics

STM

Table Mats, planar worksurfaces

ESD DS11.12-1996

Volume Resistance Measurement of Static Dissipative Planar Materials

STM

Volume resistance of planar materials

ESD ADV53.1-1995

ESD Protective Workstations

ADV

Workstations

EOS/ESD S1-1987

ESD DS1.1-1996

Personal Grounding,

Wrist Straps

S

Wrist Straps, bands and cords, monitoring

 

TABLE II

Other Related ESD Control Standards

Standard Number

Standard Description

Type

Application(s)

U.S. Government (Federal Test Method & Military Standards)

MIL-STD-1686

(see ESDA)

Electrostatic Discharge Control Program for Protection of Electrical and Electronic Parts, Assemblies and Equipment

S

Defines ESD Control program

FTM STD. NO. 101C, Method 4046.1, 1982

Test Procedures for Packaging Materials

Electrostatic Properties of Materials

STM

Determine electrostatic properties of materials in film & sheet form

MIL-STD-750C/4,

Method 1020, 1983

Electrostatic Discharge Sensitivity Classification

STM

Device (semiconductor) sensitivity classification

MIL-STD-785

Electronic Component Failure Analysis

S

Device failure analysis

MIL-STD-883D,

Method 3015.7

Electrostatic Discharge Sensitivity Classification

STM

Devices - defining ESD sensitive

MIL-HDBK-263B

ESD Control Handbook for Protection of Electrical and Electronic Parts Assemblies and Equipment

S

Devices –defining ESD sensitivity. General ESD control program.

MIL-W-87893A

Workstation, Electrostatic Discharge Control

S

ESD Workstations

MIL-STD-454

Standard General Requirements for Electronic Equipment

S

Grounding

MIL-HDBK-773, 1988

Electrostatic Discharge Protective Packaging

S

Packaging

MIL-STD-129M, 1993

Marking for Shipment and Storage ESD Standard List

S

Symbols

Cenelec Electronic Components Committee (CECC)

CECC 00015/1

Protection of Electrostatic Sensitive Devices, Part 1: General Requirements

S

General ESD control protection for electronic devices & assemblies

EN 100 015/1-1991

Protection of Electrostatic-Sensitive Devices, Part 1: Minimum Requirements

S

General ESD control protection for electronic devices & assemblies

EN 61000-4-2, 1996

Test and Measurement Techniques – Section2: Electrostatic Discharge Immunity Test

S

Device sensitivity testing

IEC (International Electrotechnical Commission)

CISPR 24 (1997-09)

Information technology equipment - Immunity characteristics - Limits and methods of measurement

S

Defines the immunity test requirements for information technology equipment incl. ESD

IEC-61000-4-2 (1995)

Test and Measurement Techniques – Section2: Electrostatic Discharge Immunity Test. Basic EMC Pub.

STM

Immunity requirements for electronic equipment subjected to ESD

IEC-60093 (1980)

Methods of Test for Volume Resistivity and Surface Resistivity of Solid Electrical Insulating Materials

STM

Measure volume and surface resistance & resistivity

IEC 60417-1 (1998)

Graphical symbols for use on equipment - Part 1: Overview and application

S

Symbols

ASTM (American Society of Testing and Materials)

ASTM D-257-91

Standard Test Method for direct current (DC) Resistance or Conductance of Insulating Materials

STM

Measure resistance of insulative/dissipative materials

ASTM D-991-89

Standard Test Method for Rubber Property-Volume Resistance of Electrically Conductive and Antistatic Products

STM

Measure volume resistance of electrically conductive or antistatic rubbers

EIA (Electronics Industry Association)

ANSI/EIA-541-88

Packaging Material Standards for ESD Sensitive Items

S

Packaging materials

ANSI/EIA-583-91

Packaging Material Standards for Moisture Sensitive items

S

Packaging materials

ANSI/EIA-625-1994

Requirements for Handling Electrostatic-Discharge-Sensitive (ESDS) Devices

S

General ESD Control program

EIA-471

Symbol and Label for Electrostatic Sensitive Devices

S

Labels, symbols

American Telephone and Telegraph (AT&T and AT&T Bell Labs)

T1Y1/88-029

American National Standard Central Office Equipment – Electrostatic Discharge Requirements

S

ESD requirements

AT&T Electrostatic discharge Control Handbook

S

General ESD Program

ISO (International Standards Organization)

ISO 2878

Rubber, Vulcanized-Antistatic and Conductive Products, Determination of Electrical Resistance

S

Measure resistance of rubber based items <1E8 Ohms

American National Standards Institute (ANSI)

ANSI C63.16 – 1993

Guide for Electrostatic Discharge Test Methodologies and Criteria for Electronic Equipment

STM

Device sensitivity testing

ANSI Z41-1991

Footwear Resistive Characterization

S

Shoes

American Association of Textile Chemist and Colorists (AATCC)

AATCC Step Test, Method 134-1986

Electrostatic Propensity of Carpets

STM

Floors, Carpets

AATCC Test Method 76-1987

Electrical Resistivity of Fabrics

STM

Smocks, Lab Coats, Gloves, Coverings, other fabric products

National Fire Protection Association (NFPA)

NFPA 77-1983

Recommended Practice on Static Electricity

STM

Controlling Fire/Ignition Hazards from Static Electricity

Occupational Safety and Health Administration (OSHA)

OSHA 3075, 1988

Controlling Electrical Hazards

S

Personal safety

Institute for Interconnecting and Packaging Electronic Circuits (IPC)

ANSI/IPC-A-610, 1996

Acceptability of Electronic Assemblies

S

General ESD control practices

 

 

 

TABLE III

ESD PROTECTIVE PRODUCTS & RELATED ESDA STANDARDS

ESD CONTROL PRODUCTS

ESDA STANDARDS

Chairs

ESD STM12.1-1997

Floors: Finish, Paint, Mats, etc.

ANSI/ESD S7.1-1994

Foot Grounders

ESD DSTM54.1-1997, ESD DSTM54.2-1997

Ground Cords

ANSI/EOS/ESD S6.1-1991

Ionizers

ANSI-EOS/ESD S3.1-1991, ESD SP3.3-1998

Labels

ANSI/EOS/ESD S8.1-1993

Shielding Bags

ANSI/ESD S11.31-1994

Shoes

ESD S9.1-1995

Smocks, Lab Coats, etc.

ESD STM2.1-1997

Solder Irons, Desoldering Tools

ESD DSTM13.0-1998

Table Mats

ANSI-EOS/ESD S4.1-1998, ESD STM4.2-1998

Wrist Straps & Cords

EOS/ESD S1-1987, ESD DS1.1-1996

 

TABLE IV

ESD Control Program Requirements [3]

ELEMENTS

ESD ADV-2.0-1994

14

14.2.1 & 17.3

14.3.1 & 17.3

10

14.2 & 6.4.3.3

14.2.3

14.4.4

16

15.3.1

6 & 11.6 & 15.3.6

15

17.4.3

MIL-STD-1686

5.1

5.2

5.3

5.4

5.5

5.6

5.7

5.8

5.9

5.10

5.11 - 5.12

5.13

ESD Control Program Plan

Classification

Design Protection

Protected Areas

Handling Procedures

Protected Covering

Training

Marking of Hardware

Documentation

Packaging

QA Requirements, Audits & Review

Failure Analysis

FUNCTIONS

Design

X

X

X

X

X

 

X

X

X

X

X

X

Production

X

 

 

X

X

X

X

X

X

X

X

X

Inspection & Test

X

 

 

X

X

X

X

X

X

X

X

X

Storage & Shipment

X

 

 

X

X

X

X

X

X

X

X

 

Installation

X

 

 

X

X

X

X

X

X

X

X

 

Maintenance & Repair

X

 

 

X

X

X

X

X

X

X

X

 



FIGURE I

GRAPHICAL REPRESENTATION OF SURFACE RESISTANCE

TITANIUM DIOXIDE <1.0 E18 Ohms-cm

I

1.0 E17 OHMS

N

S

1.0 E16 OHMS

U

L

1.0 E15 OHMS

A

T

1.0 E14 OHMS

I

V

1.0 E13 OHMS

SURFACE

SURFACE

E

RESISTIVITY

(RESISTANCE)

1.0 E12 OHMS

|

|

V

V

1.0 E11 OHMS

1.0 E12 OHMS/SQUARE (1.0 E11 OHMS)

D

1.0 E10 OHMS

I

S

1.0 E9 OHMS

^

^

S

^

STATIC DISSIPATIVE

|

I

1.0 E8 OHMS

S.D.

ESD PROTECTIVE

ESD SHOES

P

ESD

|

WORK SURFACES

[ESD S9.1]

A

1.0 E7 OHMS

FLOORS

FOOT GROUNDERS

v

(1E5 - 1E9) Ohms

|

T

[EIA-625]

(1.0E6 - 1.0E8) Ohms

WRIST STRAPS

[EIA-625]

v

I

1.0 E6 OHMS

|

(7.5E5 - 1.0E7) Ohms

|

V

|

^

v

E

1.0 E5 OHMS

v

|

1.0 E4 OHMS

1.0 E5 OHMS/SQUARE (1.0 E4 OHMS)

C

1.0 E3 OHMS

O

N

1.0 E2 OHMS

D

U

1.0 E1 OHMS

C

T

1.0 E0 OHMS

I

V

1.0 E(-1) OHMS

E

1.0 E(-2) OHMS

1.0E-2 OHMS/SQUARE (0.0E-1 OHMS)

NOTE: COPPER = 2E(-5) Ohm-m