Static Sensitivity of Devices by Class
July 1999

Ryne Allen

 

Devices have various levels of sensitivity.A chart from MIL-STD-1686 and reprinted in the ESD Awareness Guide from ESD Systems will give you a partial list of various devices and their sensitivity levels.

 

 

DEVICE SENSITIVITY TO

ELECTROSTATIC DISCHARGE

Human Body Model (HBM)

 

ESD Class 0-1C: 0 to 1999 volts

Text Box: DAMAGE YOU CAN’T FEEL The following devices or microcircuits were identified by test data as class 1:

Microwave and high frequency devices

(Schottky barrier diodes, probe contact diodes, other detector diodes)

Discrete MOSFET devices

SAW

JFETS

CCDs

Precision voltage regulator diodes

OP AMP

Thin film resistors

Integrated circuits

Hybrids utilizing class 1 parts

VHSIC

SCRs

 

Text Box: DAMAGE YOU MIGHT FEEL ESD Class 2: 2,000 to 3,999 volts

Devices or microcircuits when identified by appendix A test data as class 2:

Discrete MOSFET devices

JFETs

ICs

VHSIC

Precision resistor networks (type RZ)

Hybrids utilizing class 2 parts

Low power bipolar transistors

 

Text Box: DAMAGE YOU CAN PROBABLY DETECT AS A SPARK WITH YOUR OWN BODY ESD Class 3A-3B: 4,000 to over 8,000 volts

Devices or microcircuits when identified by appendix A test data as class 3:

Discrete MOSFET devices

JFETs

OP AMPS

ICs

VHSIC

All other microcircuits not included in class 1 or class 2

Small signal diodes

General-purpose silicon rectifiers

Opto-electronic devices (LEDs, photo transformers, opto couplers)

Resistor chips

Piezo electric crystals

Hybrids using Class 3 parts

 

ESDS classifications are from U.S. Department of Defense, MIL-STD-1686C, 25 October 1995.

Refer to this document for Machine Model (MM) and Charged Device Model (CDM) ESDS classifications.

 

 

A revised level of sensitivity for ESD sensitive components is shown in the ESD Association document ESD-STM5.1-1998 (Electrostatic Discharge (ESD) Sensitivity Testing) on page 2.It is reprinted here because it is important information when you determine the level of your ESD program

 

 

HMB ESDS Component Classification

Class

Voltage Range

0

<250

1A

250 to <500

1B

500 to <1000

1C

1000 to < 2000

2

2000 to < 4000

3A

4000 to < 8000

3B

> or + 8000

 

 

 

Normal activity within a production facility regarding triboelectric charging levels of operators and objects given in voltages and dependent on relative humidity.

 

Table 1

TYPICAL ELECTROSTATIC VOLTAGES*

EVENT

RELATIVE HUMIDITY

10%

40%

55%

Walking across carpet

35,000

15,000

7,500

Walking across vinyl floor

12,000

5,000

3,000

Motions of bench worker

6,000

800

400

Remove DIPs from plastic tubes

2,000

700

400

Remove DIPs from vinyl trays

11,500

4,000

2,000

Remove DIPs from Styrofoam

14,500

5,000

3,500

Remove bubble pack from PCBs

26,000

20,000

7,000

Pack PCBs in foam-lined box

21,000

11,000

5,500

 

 

 

Difference in component sensitivity between through-hole and surface mount devices is dependent on the architecture and technology packaged.Typically, surface mount devices have much smaller architecture making them even more susceptible to ESD than through-hole packaged devices.

 

 

 

 

 

Technology Trends

 

1995

1998

2001

2004

2007

Feature size (mm)

0.35

0.25

0.18

0.12

0.10

Voltage (V)

3.5

2 - 3.5

1.50 – 1.9

1.0 – 1.5

1.0

Source: Terry Welsher, Bell Labs, Lucent Technologies, 12/2/97

 

 

 

For IC packaging, the I/O count has climbed from 600 to 1,000 to well over this now.

Ball Grid Array Chips are replacing through hole pin chip technology.

 

A typical electronics company looses 5% of revenue from all causes of product failure.Even with all ESD programs in place.

Cost avoidance is the biggest issue.

21% of failure analysis is due to electronics and most are ESD.

 

ROI

The ROI on an ESD control program is 95:1.For every one-dollar invested in ESD control, ninety-five dollars comes back as money saved.