Life TestingLife Testing

A Reliability Engineering A Reliability Engineering ConceptConcept

By: Nicole PanaccioBy: Nicole Panaccio

Life Testing OverviewLife Testing Overview

• What is Life Testing?What is Life Testing?• Life Testing in OrganizationsLife Testing in Organizations• How Does Life Testing Work?How Does Life Testing Work?• Who Uses Life Testing?Who Uses Life Testing?• Motorola’s ProcessMotorola’s Process• Paper Clip Life TestingPaper Clip Life Testing• SummarySummary

What is Life Testing?What is Life Testing?

• A process done under controlled A process done under controlled conditions to determine how and conditions to determine how and when a product will fail in its when a product will fail in its intended environment intended environment

• Improves a product’s reliabilityImproves a product’s reliability• Finds the weakest and strongest Finds the weakest and strongest

points of a product points of a product

Life Testing in Life Testing in OrganizationsOrganizations

• Design Life Cycle:Design Life Cycle:– Have an ideaHave an idea– Design itDesign it– Make a prototypeMake a prototype– Final definitionFinal definition– Design and evaluationDesign and evaluation– implementationimplementation

Life Testing in Life Testing in OrganizationsOrganizations

• Life testing design cycle:Life testing design cycle:

IdeaIdea Design Design Prototype Prototype

• Prototype is tested for failuresPrototype is tested for failures• Design cycle stops with prototypes Design cycle stops with prototypes

Life Testing in Life Testing in OrganizationsOrganizations

• Customers believe that quality is Customers believe that quality is inherent is all productinherent is all product

• Life testing validates this Life testing validates this assumption. assumption.

• Specific directions are followed in a Specific directions are followed in a uniform fashion uniform fashion

Three Types of TestsThree Types of Tests

• Type of tests performed:Type of tests performed:– Qualitative TestsQualitative Tests– ESS (Environmental Stress Screening)ESS (Environmental Stress Screening)– Accelerated Life TestingAccelerated Life Testing

Qualitative TestsQualitative Tests

• Gives the product tested the most Gives the product tested the most failuresfailures

• Failures produced by high and low Failures produced by high and low stressesstresses

• To pass the product must live To pass the product must live through the entire test without through the entire test without failure ¹failure ¹

ESS-Environmental Stress ESS-Environmental Stress ScreeningScreening

• Applies environmental stimulus to Applies environmental stimulus to products products

• Goal: ¹Goal: ¹– To find latent defects and eliminate To find latent defects and eliminate

themthem– To find defects not found with To find defects not found with

inspection or electrical testing inspection or electrical testing

Accelerated Life TestingAccelerated Life Testing

• Similar to Life TestingSimilar to Life Testing– Testing moves at a faster paceTesting moves at a faster pace

• Uses quantitative dataUses quantitative data• End results yield times-to-failure End results yield times-to-failure

datadata– Times-to-failure: how long it takes till Times-to-failure: how long it takes till

a failure is madea failure is made

Accelerated Life TestingAccelerated Life Testing

• Life distributions show how fast a Life distributions show how fast a product will fail ¹product will fail ¹

• Two methods used to get times-to-Two methods used to get times-to-failure information:failure information:– Usage rate accelerationUsage rate acceleration– Overstress acceleration Overstress acceleration

Usage Rate AccelerationUsage Rate Acceleration

• A test used for products that only A test used for products that only operate for small amounts of time ¹operate for small amounts of time ¹

• It increases the time to make It increases the time to make failures happen quicker than if it failures happen quicker than if it were used normallywere used normally

Overstress AccelerationOverstress Acceleration

• Backup to usage rateBackup to usage rate• Used if usage rate is not Used if usage rate is not

appropriate means ¹ appropriate means ¹ • Tests products that are constantly Tests products that are constantly

usedused• Uses stress levels that it would not Uses stress levels that it would not

normally encounternormally encounter

How Does Life Testing How Does Life Testing Work?Work?

• Majority of tests done on small Majority of tests done on small samplesample– 4 to 6 units 4 to 6 units

• Begin test with lowest level of the Begin test with lowest level of the product product

• Failures must be documented as Failures must be documented as they happen they happen

How Does Life Testing How Does Life Testing Work? Work?

• Soft failuresSoft failures occur when there is occur when there is damage made but the product damage made but the product returns to its normal statereturns to its normal state

• Hard failures Hard failures are permanent are permanent damages done to the product damages done to the product

• The difference The difference between soft and between soft and hard failures is the hard failures is the margin for stress ¹ margin for stress ¹

• Once the failures are Once the failures are found and fixed, the found and fixed, the margins have margins have reached their maxreached their max

• Maximized margins Maximized margins increase reliability increase reliability and the life of the and the life of the product product

Margins and ReliabilityMargins and Reliability

Who Uses Life Testing?Who Uses Life Testing?

• MotorolaMotorola– Mission to produce cell phones with Mission to produce cell phones with

“virtually no defects”“virtually no defects”– Use accelerated life testing to Use accelerated life testing to

accomplish mission accomplish mission – Helps to validate their six sigma Helps to validate their six sigma

corporate standard corporate standard

Motorola’s Process Motorola’s Process

• Determine environmentDetermine environment• Perform life testing in all Perform life testing in all

environments.environments.– Four to six weeks of testing is required Four to six weeks of testing is required

¹¹

Motorola’s ProcessMotorola’s Process

• Drop Testing ¹Drop Testing ¹– Samples are dropped on different Samples are dropped on different

surfaces of the phone multiple times.surfaces of the phone multiple times.• Hot and Cold Temperatures ²Hot and Cold Temperatures ²• The phones receive extreme The phones receive extreme

temperatures of hot and cold. temperatures of hot and cold. – Testing simultaneously with audio Testing simultaneously with audio

quality and simulated calls quality and simulated calls

Motorola’s ProcessMotorola’s Process

• Electro-Static Discharge ¹Electro-Static Discharge ¹– Zap products with an electric pulse at Zap products with an electric pulse at

“discharge” points “discharge” points

• Dust Exposure ²Dust Exposure ²– Products are placed in dust chamberProducts are placed in dust chamber– Dust is shaken all over the product Dust is shaken all over the product

and then left to settle and then left to settle

Motorola’s ProcessMotorola’s Process

• Vibration Testing ¹Vibration Testing ¹– Horizontal and vertical vibration testing.Horizontal and vertical vibration testing.– Placed into vibration table and controlled by Placed into vibration table and controlled by

tester tester – The tests vary in the extremes of vibrations The tests vary in the extremes of vibrations

given given – During the test it places a call and must be During the test it places a call and must be

stable throughout the process stable throughout the process

Motorola’s ProcessMotorola’s Process

• Environmental Aging Tests ¹Environmental Aging Tests ¹– Temperature cycling: moving from low to Temperature cycling: moving from low to

high heat and coldhigh heat and cold– Temperature shockTemperature shock

• Certification Testing ²Certification Testing ²– Sudden Impact Testing Sudden Impact Testing – Endurance Testing Endurance Testing – Package Drop Testing Package Drop Testing – Transport Simulation Transport Simulation

Motorola SummaryMotorola Summary

• Life testing cuts Motorola’s costs Life testing cuts Motorola’s costs • Less return of products that fail for Less return of products that fail for

the customerthe customer• Their design exceeds customer Their design exceeds customer

satisfaction with “virtually no satisfaction with “virtually no defects”defects”

Paper Clip Life Testing Paper Clip Life Testing

• Follow these directions to Follow these directions to determine how fast a paper clip will determine how fast a paper clip will break using the life testing break using the life testing methods. ¹methods. ¹

Follow These StepsFollow These Steps

• With one hand, hold With one hand, hold the clip by the longer, the clip by the longer, outer loop.outer loop.

• With the thumb and With the thumb and forefinger of the other forefinger of the other hand, grasp the hand, grasp the smaller, inner loop.smaller, inner loop.

• Pull the smaller, inner Pull the smaller, inner loop out and down 90 loop out and down 90 degrees so that a degrees so that a right angle is formed right angle is formed as shown.as shown.

Follow These StepsFollow These Steps

• With one hand, With one hand, continue to hold the continue to hold the clip by the longer, clip by the longer, outer loop. outer loop.

• With the thumb and With the thumb and forefinger of the forefinger of the other hand, grasp other hand, grasp the smaller, inner the smaller, inner loop. loop.

Follow These StepsFollow These Steps

• Push the smaller Push the smaller inner loop up and in inner loop up and in 90 degrees so that 90 degrees so that the smaller loop is the smaller loop is returned to the returned to the original upright original upright position in line with position in line with the larger, outer loop the larger, outer loop as shown.as shown.

Follow These StepsFollow These Steps

• This completes one cycle.This completes one cycle.• Repeat until the paper clip breaks. Repeat until the paper clip breaks.

Count and record the cycles-to-Count and record the cycles-to-failure for each clip.failure for each clip.

SummarySummary

• Quality is inherent in most products Quality is inherent in most products • Life Testing allows the consumer to have Life Testing allows the consumer to have

reliable information because it is reliable information because it is consistent throughout the testingconsistent throughout the testing

• Some life testing can cause permanent Some life testing can cause permanent damage, and some aspects of the damage, and some aspects of the testing do not testing do not

• Prototypes are used to test because it is Prototypes are used to test because it is cheaper and easier to run tests on cheaper and easier to run tests on samplessamples

SummarySummary

• Life Testing can be done with ease Life Testing can be done with ease or tremendous detailor tremendous detail

• Any way it is done it will yield the Any way it is done it will yield the same informationsame information

• The tester must document what The tester must document what and how they do thingsand how they do things