Testing of Digital Systems - Introduction 1

stems

les

(ESLAB)

/test/index.html

Zebo Peng, ESLAB, LiTH

Testing of Digital Sy

Zebo Peng and Petru E

Embedded System Laboratory

Linköping University

http://www.ida.liu.se/~zebpe/teaching

Testing of Digital Systems - Introduction 2

m testing.

synthesis.

Zebo Peng, ESLAB, LiTH

Contents

☞ Basic principles and practice of digital syste

☞ Design for testability techniques.

☞ Integration of test consideration with system

☞ Testing of system-on-chip.

Testing of Digital Systems - Introduction 3

ipants.

edman, “Digital Systemcience Press, 1990.

Zebo Peng, ESLAB, LiTH

Cour se Organization

☞ General lectures.

- Lecture notes and selected papers.

☞ Seminars and discussions, led by the partic

- M. Abramovici, M. A. Breuer and A. D. FriTesting and Testable Design,” Computer S

- Seminar notes by the participants.

Testing of Digital Systems - Introduction 4

tion

Zebo Peng, ESLAB, LiTH

Lecture I: Introduc

1. Basic definition and terminology

2. Classification of test

3. Test process

4. Test cost and its reduction

Testing of Digital Systems - Introduction 5

t

Zebo Peng, ESLAB, LiTH

Design ver sus Tes

Testing of Digital Systems - Introduction 6

g its resulting response tohe manufacturing or opera-

g its resulting response to

nctions correctly.

Zebo Peng, ESLAB, LiTH

What is T esting?

☞ Process of exercising a product and analyzincheck whether faults are introduced during ttion phase.

☞ Process of exercising a product and analyzincheck whether it functions correctly.

☞ Process of determining whether a product fu

Testing of Digital Systems - Introduction 7

e

esting

TestPreparation

ionn

onon

Zebo Peng, ESLAB, LiTH

Hardware Lif e Cycl

Specification

Design

Implementation

Manufacturing

Production Test

Operation andMaintenance

TSystem Integration

System Test

VerificatValidatio

Simulati

ReviewInspecti

Testing of Digital Systems - Introduction 8

ital Systems

Physical faults

Zebo Peng, ESLAB, LiTH

Causes of Incorrect Function of Dig

• Design errors usually consistent

• Fabrication (manufacturing) errors

- often consistent, e.g., wrong components

- usually operator errors

• Fabrication (manufacturing) defects

- inconsistent, e.g., impurity of materials

• Physical failures

- wear-out

- environmental factors

Testing of Digital Systems - Introduction 9

F aults

urrence.

rvals.

y a temporary change in

Zebo Peng, ESLAB, LiTH

Classification of Ph ysical

☞ Permanent always present after their occ

☞ Intermittent existing only during some inte

☞ Transient a one-time occurrence cased bsome environmental factor.

Testing of Digital Systems - Introduction 10

of CUT (circuit under test)

meter is changed (e.g.,

Zebo Peng, ESLAB, LiTH

Another Classification

☞ Logic (functional) faults the logic functionis wrong.

☞ Parametric the magnitude of a CUT parapower and current).

Testing of Digital Systems - Introduction 11

est

Zebo Peng, ESLAB, LiTH

Principles f or Digital T

Testing of Digital Systems - Introduction 12

ple

Zebo Peng, ESLAB, LiTH

A Boar d Testing Exam

Testing of Digital Systems - Introduction 13

ut pins.

e so as to make contact

M application).

Zebo Peng, ESLAB, LiTH

Test Head Fixtures

• Edge-connector via the normal input/outp

• Bed of nails.

• Wafer prober a set of micro-probes arrangwith the bonding pads of a chip.

- Bare chip test for known-good die (for MC

- Wafer-level screening.

• Probes:

- Mechanical probe.

- Electron-beam probe.

Testing of Digital Systems - Introduction 14

ting

impossible.

st data.

Long test application time.

r/sensor mechanism and

opment efforts.

gn process.

Zebo Peng, ESLAB, LiTH

Main Difficulties in T es

• Miniaturization -> Physical access difficult or

• Increasing complexity -> Large amount of te

• Number of access ports remains constant ->

• High speed -> High demand on tester’s drivemore complicated failure mechanism.

-> Testing accounts up to 50% of product devel

☞ The key to successful testing lies in the desi

Testing of Digital Systems - Introduction 15

FT)

ing the design process so.

ble.

Zebo Peng, ESLAB, LiTH

Design f or Testability (D

☞ To take into account the testing aspects durthat more testable designs will be generated

☞ The design is changed to make it more testa

☞ Advantages of DFT:

- Reduce test efforts.

- Reduce cost for test equipments (ATE).

- Shorten turnaround time.

- Increase product quality.

Testing of Digital Systems - Introduction 16

(fault site and fault type).

ce manufacturing errors).

):

ossible faults.

: based on the erroneousould produce it.

Zebo Peng, ESLAB, LiTH

Test vs. Dia gnosis

• Test Detection of faults.

• Diagnosis Detection and location of faults

- Repair.

- Manufacturing process optimization (redu

- Re-design.

• Cause-effect analysis (external fault location

- Build a fault dictionary.

- Use dictionary look-up to determine the p

• Effect-cause analysis (internal fault location)response, determine directly the faults that c

- Ex. guided-probe testing.

Testing of Digital Systems - Introduction 17

idual products to checkufacturing phase.

environment to ensure thatther components.

duct in the filed for diagno-

faults during the system

Zebo Peng, ESLAB, LiTH

Types of T esting

• Production (manufacturing) test test indivwhether faults are introduced during the man

• System test test a product in its operatingit works correctly when interconnected with o

• Operation and maintenance test test a prosis or "preventive" purpose.

• Prototype test testing to check for design development phase. Diagnosis is required.

• Different levels: chip, board, or system.

• On-line, off-line, or concurrent testing.

Testing of Digital Systems - Introduction 18

t’ d)

ation with respect to its

, such as open, stack-at,

e internal nodes.

endent parameters, such

ing analog measurements circuit when all nodes are

Zebo Peng, ESLAB, LiTH

Types of T esting (Con

• Functional test validating the correct operfunctional specification.

• Structural test testing of structural defectsand short-circuit.

• Static v. at-speed testing.

• In-circuit test the tester gains access to th

• Parametric test testing of technology-depas power consumption.

• IDDq test testing the entire circuit by makof IDD which is the current flows in a CMOSin the quiescent state.

Testing of Digital Systems - Introduction 19

Zebo Peng, ESLAB, LiTH

Test Classification

Testing of Digital Systems - Introduction 20

t’ d)

Zebo Peng, ESLAB, LiTH

Test Classification (Con

Testing of Digital Systems - Introduction 21

ess

anufacturing

esign

st Mechanism

Zebo Peng, ESLAB, LiTH

A Typical T esting Pr oc

Test Strategy

Test Generation

Test Evaluation

Test Application

Analysis and

Selection

Diagnosis

M

D

Te

Testing of Digital Systems - Introduction 22

Costs

ections.

n and analysis).

"burn-in" purpose).

Zebo Peng, ESLAB, LiTH

Composition of T esting

• Cost of test equipment (hardware):

- A test controller (usually a computer).

- Interface drivers/receivers and cable-conn

- System of probe-contacts.

- A controlled environment.

• Cost of software supports:

- Test pattern generation programs.

- Test evaluation procedures (fault simulatio

• Testing time

- Test development time.

- Test application time (maybe very long for

Testing of Digital Systems - Introduction 23

of T ens”)

Field

>$500.00

Zebo Peng, ESLAB, LiTH

Cost of Finding Def ects (“Rule

Chip Board System

$0.50$5.00

$50.00

Testing of Digital Systems - Introduction 24

uction

ation, which decreases de-

, i.e., lower fault levels and

t equipment and supports

r functional test which has

st cost.

Zebo Peng, ESLAB, LiTH

Methods f or Test Cost Red

☞ DFT simplifies/automates test pattern genervelopment cost and lead times.

☞ DFT facilitates more efficient production testshorter test application times.

☞ BIST can reduce the need for expensive tesfield test.

☞ Better design verification reduces the need folong test application time.

☞ Statistics-based methods reduces overall te

Testing of Digital Systems - Introduction 25

nd is becoming more diffi-hips, especially systems-

cost.

ical faults introduced dur-.

lts!

Zebo Peng, ESLAB, LiTH

Summar y

☞ Testing is an expensive and complex task, acult with the development of more complex con-chip.

☞ It takes typically 30% of the total production

☞ Hardware testing is mainly used to find physing the manufacturing and operation phases

☞ Testing does not guarantee the absent of fau