Astr2013 tutorial by mike silverman of ops a la carte 40 years of halt, what have we learned

40 years of HALT:What Have We

Learned?Mike Silverman

©2011 ASQ & Presentation SilvermanPresented live on Sept 12th, 2013

http://reliabilitycalendar.org/webinars/english/

ASQ Reliability Division English Webinar SeriesOne of the monthly webinars

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To view recorded webinar (available to ASQ Reliability Division members only) visit asq.org/reliability

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Mike Silverman, Ops A La Carte40 Years of HALT: What Have We Learned, Page 3 April 7, 2023 ASTR 2013 Oct 9-11, San Diego

Accelerated Stress Testing and Reliability WorkshopOctober 9-11, 2013 San Diego, CA

Accelerating Reliability into the 21st CenturyKeynote Presenter Day 1: Vice Admiral Walter MassenburgKeynote Presenter Day 2: Alain Bensoussan, Thales Avionics

Accelerating Reliability into the 21st CenturyKeynote Presenter Day 1: Vice Admiral Walter MassenburgKeynote Presenter Day 2: Alain Bensoussan, Thales Avionics

CALL FOR PRESENTATIONS: We are now Accepting Abstracts. Email to: [email protected].

Guidelines on website www.ieee-astr.org

For more details, click here to join our LinkedIn Group:IEEE/CPMT Workshop on Accelerated Stress Testing and Reliability


This is the 4th of a series of four webinars being put on by Ops A La Carte, ASTR, and ASQ Reliability DivisionEach webinar will also be presented as a full 2 hour tutorial at our ASTR Workshop Oct 9-11th, San Diego.

Abstracts for presentations are due Apr 30.www.ieee-astr.org

ASTR 2013 Oct 9-11, San DiegoMike Silverman, Ops A La Carte40 Years of HALT: What Have We Learned, Page 5 April 7, 2023

Introduction 5 min

Accelerated Reliability Growth Testing 45 min

Questions 10 min

Agenda


40 Years of HALT: What Have We Learned?

ByMike Silverman, CRE

Managing PartnerOps A La Carte

[email protected]


INTRODUCTION

HALT began 40 years ago with a simple idea of testing beyond specifications in order to better understand design margins.

Over the past 40 years, thousands of engineers around the world have been exposed to the concepts of HALT and have tried the techniques.

What have we learned in the past 40 Years?


INTRODUCTION

In this seminar, we will cover the following areas:1) What is HALT and What is Not HALT2) Basics of HALT3) Links between HALT and Design for Reliability4) New advances in HALT methodology5) What % of companies are doing HALT6) What lies in the future for HALT


1) What is HALT and What is Not HALT 2) Basics of HALT 3) Links between HALT and Design for Reliability 4) New advances in equipment 5) What % of companies are doing HALT 6) What lies in the future for HALT


WHAT IS HALT?

HALT: Done to ruggedize the product and obtain large margins over the expected in-use conditions. Uses all stresses which can cause relevant failures. Stresses are not limited to field levels or stresses.- “Accelerated Reliability Engineering: HALT and HASS”, Gregg Hobbs


WHAT IS HALT?

HALT: A design technique used to discover product weaknesses and improve design margins. The intent is to systematically subject a product to stress stimuli well beyond the expected field environments in order to determine and expand the operating and destruct limits of your product.- 50 Ways to Improve Your Product Reliability, Mike Silverman


WHAT IS HALT?

What do these definitions have in common: Greatly accelerated process Develop margins between spec and performance Not just measuring margins but improving margins Separating relevant from non-relevant failures Starts early in design Stresses are not limited to field stresses Stresses are not limited to temperature and vibration Power on and effective detection/monitoring Combined Environment Baby swimming (make more robust to real life later)


WHAT IS NOT HALT?

What are some classic HALT misconceptions: My product does not experience vibration so we can’t use it The spec for this component is 70C so we can’t go above that

in HALT We can’t drill holes in the product because it will change the

airflow We must mount it in the same direction as it will be mounted in

the field We don’t need to go above the first failure point because that is

what will fail first Run to preset levels (remember this is not a pass/fail test) Don’t stress beyond specifications Only perform HALT at system level Just perform HALT only when diags are fully ready


WHAT IS NOT HALT?

And a few more… HALT is for electronic equipment only We can’t separate out this assembly because it will change the

thermal and vibration characteristics of the product We shouldn’t defeat protection circuitry because the product

will never experience higher than this stress. Performing each individual stress is the same as combined

stresses A G is a G 15C per minute is a limit of the technology

and my favorite… you can only perform HALT in a HALT Chamber

What other ones can you think of ?




16

Stre

ss

Start low and step up the stress, testing the product during the stressing

BASICS OF HALT


17

Failure

Gradually increase stress level until a failure occurs

Stre

ss

BASICS OF HALT


© 2008 Ops A La Carte

18

Stre

ss

Failure

Analy

sisAnalyze the failure

BASICS OF HALT



19

Stre

ss

Failure

Analy

sisImproveMake temporary improvements

BASICS OF HALT



20

Stre

ss

Failure

Analy

sisImprove

(incr

ease

)

Increase stress and start process over

BASICS OF HALT



21

Stre

ss

Failure

Analy

sisImprove

(incr

ease

)Fundamental Technological

Limit

BASICS OF HALT



22

Classic S-N Diagram(stress vs. number of cycles)

N0

S0= Normal Stress conditions

N0= Projected Normal Life

S1

S2

N1N2

S0

BASICS OF HALT



23

Classic S-N Diagram(stress vs. number of cycles)

N0

S0= Normal Stress conditions

N0= Projected Normal Life

S1

S2

N1N2

Point at which failures become non-relevant

S0

BASICS OF HALT



24

Product Operational

Specs

Stress

Upper Oper. Limit

Upper Destruct

Limit

Lower Destruct

Limit

LowerOper. Limit

BASICS OF HALT



25

Product Operational

Specs

Stress

Upper Oper. Limit

Upper Destruct

Limit

Lower Destruct

Limit

LowerOper. Limit

This is what the product spec distribution really looks like

BASICS OF HALT



26

Product Operational

Specs

Stress

Upper Oper. Limit

Upper Destruct

Limit

Lower Destruct

Limit

LowerOper. Limit

Operating Margin

Destruct Margin

BASICS OF HALT




HALT vs. DFR

DfR is knowledge-based engineering wherein, starting with capture of requirements and leading to assured reliability, a reliability plan is designed and executed using the full skills and knowledge of the project team. The goal of DfR is to work smarter through knowledge-based tailoring of the reliability plan.

HALT is one of the tools used during a DFR program to help improve and then prove the product reliability goals. It is one of the most effective tools but is still just one of the reliability tools used.

This is often forgotten by engineers.


HALT vs. DFR


Goal

Setting

Assess-

ment

Bench-

mark

FTAFMEA

Golden

Nuggets

Component

Selection

Predict-

ions

Thermal

Analysis

Derating

Analysis

POF

DOE Tolerance

Analysis

Preventive

Mainten.

EOL

Analysis

Warranty

Analysis

Test

Plan

HALT RDT ALT HALT-AFR

Calculator

FEA Software

Reliability

RCA CLCA

Vendor

Assessmt

HASS ORT OOBA

Lessons

Learned

Warranty

Returns

Reliability

Reporting

Statistics EDA for

Obsolesc

Out-

sourcing

Metrics

Reliability

Plan

CO

NC

EP

T

PH

AS

E

DE

SIG

N

PH

AS

E

MA

NU

FA

CT

UR

ING

PH

AS

E

PR

OT

OT

YP

E P

HA

SE

Gap

Analysis

Block

Diagrams


1) What is HALT and What is Not HALT 2) Basics of HALT 3) Links between HALT and Design for Reliability 4) New advances in HALT methodology 5) What % of companies are doing HALT 6) What lies in the future for HALT


NEW ADVANCES IN HALT

Along with improvements in chamber technology, there have been advances in the methodology as well. Harry McLean’s HALT Calculator

To determine “Guard Band” Limits during the HALT Plan

To determine AFR after HALT Using FMEA to determine specific areas to test for Linking HALT to ALT Using HALT for software/firmware issues


There are three different approaches to this problem

1) Physics of FailureDrawback: Too many variables/Model becomes too complex

2) Weibull models/make general assumptions about acceleration factors or plotting best fit curves.

Drawbacks:a) Acceleration factors incorrect/Cannot be generalized

b) Existing models are for constant stress and not step stressing

c) Not enough HALT failures for statistically significant data

3) Model using HALT and Field DataDrawback: requires a lot of data from many different types of products in many different industries to develop an accurate model. No one had access to this data…UNTIL NOW!

There are three different approaches to this problem

1) Physics of FailureDrawback: Too many variables/Model becomes too complex

2) Weibull models/make general assumptions about acceleration factors or plotting best fit curves.

Drawbacks:a) Acceleration factors incorrect/Cannot be generalized

b) Existing models are for constant stress and not step stressing

c) Not enough HALT failures for statistically significant data

3) Model using HALT and Field DataDrawback: requires a lot of data from many different types of products in many different industries to develop an accurate model. No one had access to this data…UNTIL NOW!

NEW ADVANCES IN HALTHALT Calculator


• It is a provisional patent Excel-based mathematical model that, when provided with the appropriate HALT and product information, will accurately estimate the product’s field AFR or Actual field Failure Rate.• Three acceleration models are used, linear, exponential, and quadratic.

• The AFR Estimator has been validated on almost thirty products from diverse design environments and manufacturers.

• It is a provisional patent Excel-based mathematical model that, when provided with the appropriate HALT and product information, will accurately estimate the product’s field AFR or Actual field Failure Rate.• Three acceleration models are used, linear, exponential, and quadratic.

• The AFR Estimator has been validated on almost thirty products from diverse design environments and manufacturers.



Complete MTBF prediction1. Use Telcordia, MIL-HDBK-217, or equivalent

2. Parts Count is acceptable

3. Ensure if you have a high failure rate item that you research and get supplier test/field data to replace handbook data. The calculator is very sensitive to single component weaknesses in HALT. Therefore, having prediction data for individual components.

4. If you don’t have access to MTBF Prediction, use default prediction value provided in model or use built in prediction estimator (model sensitivity to prediction is relatively low so a default value is acceptable).

Complete MTBF prediction1. Use Telcordia, MIL-HDBK-217, or equivalent

2. Parts Count is acceptable

3. Ensure if you have a high failure rate item that you research and get supplier test/field data to replace handbook data. The calculator is very sensitive to single component weaknesses in HALT. Therefore, having prediction data for individual components.

4. If you don’t have access to MTBF Prediction, use default prediction value provided in model or use built in prediction estimator (model sensitivity to prediction is relatively low so a default value is acceptable).

To Maximize Use of the ModelTo Maximize Use of the Model



Complete HALT using the following guidelines:

1. Sample size of at least three, preferably four units. Model can accommodate 1 to 6.

Realize that HALT sample sizes of three or less will dramatically affect the ability to detect product defects and hence, the statistical confidence is likewise, impacted.

2. Perform HALT at each phase of Product Development Process to expand limits as much as possible.

But use the results of your HALT later in product development when samples are more abundant. HALT early in development is a great idea but doesn’t give as good an input to the calculator.

3. Capture HALT Product Operational Response Limits.

Complete HALT using the following guidelines:

1. Sample size of at least three, preferably four units. Model can accommodate 1 to 6.

Realize that HALT sample sizes of three or less will dramatically affect the ability to detect product defects and hence, the statistical confidence is likewise, impacted.

2. Perform HALT at each phase of Product Development Process to expand limits as much as possible.

But use the results of your HALT later in product development when samples are more abundant. HALT early in development is a great idea but doesn’t give as good an input to the calculator.

3. Capture HALT Product Operational Response Limits.



Guard Band

Design

New End Use

Prod Spec

End Use

Guard Band, Spec & End UseGuard Band, Spec & End Use



• The model has not been validated on mechanical designs.

• The estimate is as good as the test protocol used in HALT and other reliability tests.

• HALT does not capture every possible design defect, i.e., humidity related issues, field operation beyond Guard Band limits, some wear-out mechanisms, etc.

Limitations of the ModelLimitations of the Model



PublishedSpec, C

Level Application Guard Band, C

0 to +40 1 Consumer -30 to +80

0 to +50 2 Hi-end Consumer -30 to +100

-10 to +50 3 Hi Performance -40 to +110

-20 to +50 4 Critical Application

-50 to +110

-25 to +65 5 Sheltered -50 to +110

-40 to +85 6 All Outdoor -65 to +110

Product Type & Guard BandProduct Type & Guard BandProduct Environment & LevelProduct Environment & Level



40


Actual Field Failure Rate Estimate - % of Failures/Year

Input MatrixCalculated MTBF (in Hrs) = 100,000

Product Thermal (Hot in °C) = 110Product Thermal (Cold in °C) = -80Product Vibration (in Grms) = 25

Prod Published Spec Level (see below) = 2Number of HALT Samples = 6

Field Duty Cycle (in Percentage) = 80Confidence = 1

Steady State AFR, % (HALT Only) = 0.30Steady State Field MTBF, Hrs (HALT Only) = 2,893,373

Lower % HALT Confidence Limit = 1,829,861Upper % HALT Confidence Limit = 4,682,531



To determine “must meet” margins during the HALT Plan

To determine AFR after HALT Using FMEA to determine specific areas to test for Linking HALT to ALT

NEW ADVANCES IN HALTUse of FMEA


IEC 60601 3rd Edition mandates that you must understand your product risks before you can develop a test plan

This is especially true of HALT Understanding risks will help determine

What stresses to apply? What are the limits to technology? What test routines are needed to detect? Are there any prognostics that will indicate failures

before the test routines pick up a hard failure?

NEW ADVANCES IN HALTUse of FMEA



To determine “must meet” margins during the HALT Plan

To determine AFR after HALT Using FMEA to determine specific areas to test for Linking HALT to ALT

NEW ADVANCES IN HALTHALT vs. ALT


HALT cannot find all types of failures Mechanical wear failures Other long term degradations (UV, corrosion, etc) Failures due to process variations



An Accelerated Life Test (ALT) is the process of determining the reliability of a product in a short period of time by accelerating the use environment.

ALT is also good for finding dominant failure mechanisms.

ALT is usually performed on individual assemblies rather than full systems.

ALT is also frequently used when there is a wear-out mechanism involved.



Advantages of ALTInstead of stepping up to failure, we will pick a level that we know the product will survive at (within relevant failure area) and then run at this level until failure.This will characterize wear-out mechanisms



One key advantage of ALT over HALT is when we need to know the life of the product.

In HALT, we don’t concern ourselves with this much because we are more interested in making the product as reliable as we can, and measuring the amount of reliability is not as important.

However, with mechanical items that wear over time, it is very important to know the life of the product as accurately as possible.



Another advantage is that we often do not need any environmental equipment. Benchtop testing is often adequate.



FAILURE TESTING

HALT

OBJECTIVES1. Root Cause Analysis2. Corrective Action Identification3. Design Robustness Determination

TESTING REQUIREMENTS1. Detailed Product Knowledge2. Engineering Experience

ALT

OBJECTIVES1. Reliability Evaluation (e.g. Failure Rates)2. Dominant Failure Mechanisms Identification

TESTING REQUIREMENTS1. Detailed Parameters

(a) Test Length(b) Number of Samples(c) Confidence/ Accuracy(d) Acceleration Factors(e) Test Environment

2. Test Metrology & Factors(a) 4:2:1Procedure Or Other(b) Costs

ANALYTICAL MODELS1. Weibull Distribution2. Arrhenius3. Coffin-Manson4. Norris-Lanzberg



Cell Phone

Fan

Hard Drive

Infusion Pump

MedicalCabinet

Robot

These pictures are samples of products we have tested. These are not the actual products to protect the proprietary nature of the products we test.

Automotive Electronics



When wear-out is a dominant failure mechanism, we must be able to predict or characterize this wear-out mechanism to assure that it occurs outside customer expectations and outside the warranty period.

ALT is an excellent method for doing this

NEW ADVANCES IN HALTHALT vs. ALT - Summary




What percentage of companies use the HALT methodology? I estimate about 50% of all companies in the US

have some form of reliability program. I estimate about 50% of the companies that have

some form of reliability program are doing HALT. This is based on projects we have worked with in

the past 3 years (about 750 clients). Of course there are numerous companies that have no formal reliability program.

This is up from 5% in 1995.

WHO IS USING HALT ?




The number of companies performing HALT will continue to rise as more labs obtain HALT equipment

The need for more education will continue to increase Standards/guidance docs will gain more importance as

more companies and labs are doing HALT, many incorrectly.

Chambers will need to provide stresses in addition to temperature and vibration to keep up with the physics of the failures (especially due to smaller packages and MEMs devices).

Move away from people and move to process HALT as acronym will fade away Less HALT and more emphasis on DFR including

HALT

FUTURE OF HALT


CONCLUSION

In this presentation we took you through 40 years of HALT showed you advances that have been made pointed out areas where improvements are

still needed


THANKS!

QUESTIONS?

ANY QUESTIONS?


Mike Silverman

Ops A La Carte

Managing Partnerwww.opsalacarte.com

[email protected]

(408) 472-3889

Confidence in Reliability

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