Unlocking the Mystery of Circuit Board Failures A Case StudyPresented By:

Alaa Arif

EDTC 560

January 15, 2007

Terms & Definitions

Board: Printed Circuit Board (PCB).

ESD: Electro-Static Discharge.

It is the release of a build up of charge, similar to the

shock some people experience when touching a metal

surface or another person.

Terms & Definitions

FPY: First Pass Yield.

The percentage of boards that pass the test during the

first trial.

NDF: No Defect Found failure.

Failure without any apparent cause.

Problem Statement

Boards Failures:

For the first time in the company’s history, a

newly released product failed to reach FPY goals.

Quantity of boards failures exceeded all

expectations.

Analysis

Analysis revealed that 2 types of failures

are mainly responsible for the low FPY:

0

5

10

15

20

25

30

35

40

August, 06 October, 06 November, 06

ESDNDF

ESD Failures

NDF Failures

Analysis - ESD

ESD Failures:Caused by unsafe

ESD practices.

ESD could

damage sensitive

components on

the PCB.

Increased over the

first 3 months.

0

5

10

15

20

25

30

35

40

August, 06 October, 06 November, 06

ESDNDFVF

Analysis - ESD

ESD Failures:Caused by unsafe

ESD practices.

ESD could

damage sensitive

components on

the PCB.

Increased over the

first 3 months.

0

5

10

15

20

25

30

35

40

August, 06 October, 06 November, 06

ESDNDFVF

Analysis - ESD

ESD Failures:Caused by unsafe

ESD practices.

ESD could

damage sensitive

components on

the PCB.

Increased over the

first 3 months.

0

5

10

15

20

25

30

35

40

August, 06 October, 06 November, 06

ESDNDFVF

Analysis - NDF NDF Failures:

Caused by

operator

error.

Malfunction

of test

equipment.

Decreased

over the first

3 months.

0

5

10

15

20

25

30

35

40

August, 06 October, 06 November, 06

ESDNDFVF

Analysis - NDF NDF Failures:

Caused by

operator

error.

Malfunction

of test

equipment.

Decreased

over the first

3 months.

0

5

10

15

20

25

30

35

40

August, 06 October, 06 November, 06

ESDNDFVF

Analysis - NDF NDF Failures:

Caused by

operator

error.

Malfunction

of test

equipment.

Decreased

over the first

3 months.

0

5

10

15

20

25

30

35

40

August, 06 October, 06 November, 06

ESDNDFVF

Solution - ESD

Addressing ESD Failures at each level:

Work station.

Operators.

Solution - ESD

Work Station:

Properly ground the

work station.

Coat floor with

ESD-safe material.

Cover workbench

with ESD-safe mat.

Solution - ESD

Operator:

Wears ESD-safe

smock.

Uses ESD-safe wrist

strap.

Cover shoes with

ESD-safe heel straps.

Solution - NDF

Addressing NDF at each level:

Test Equipment.

Operator.

Procedures.

Solution - NDF

Test Equipment:

Train maintenance

technicians.

Increase frequency of

preventive

maintenance.

Provide ample quantity

of spare parts.

Solution - NDF

Operator:

Share with operators the test

results.

Explain the consequences of the

excessive amount of boards

failures.

Train and re-train operators.

0

5

10

15

20

25

30

35

40

August, 06 October, 06 November, 06

ESDNDFVF

Solution - NDF

Procedures:

Document test procedure.

Add illustrations to test procedures.

Make test documents easily accessible.

Results

December test data showed improvement:

0

5

10

15

20

25

30

35

40

Aug. 06 Oct. 06 Nov. 06 Dec. 06

ESDNDF

Trend line

End of the Presentation!