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 Silverman
Presented live on Sept 12th
, 2013
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Mike Silverman, Ops A La Carte
40 Years of HALT: What Have We
Learned, Page 3 September 12, 2013ASTR 2013 Oct 9-11, San Diego
Accelerated Stress Testing and Reliability Workshop
October 9-11, 2013 San Diego, CA
Accelerating Reliability into the 21st
Century
Keynote Presenter Day 1: Vice Admiral Walter Massenburg
Keynote Presenter Day 2: Alain Bensoussan, Thales Avionics
Accelerating Reliability into the 21st
Century
Keynote Presenter Day 1: Vice Admiral Walter Massenburg
Keynote Presenter Day 2: Alain Bensoussan, Thales Avionics
CALL FOR PRESENTATIONS: We are now Accepting Abstracts.
Email to: don.gerstle@gmail.com.
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 Division
Each 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 Carte
Learned, Page 5 September 12, 2013
♦ Introduction 5 min
♦ Accelerated Reliability Growth Testing 45 min
♦ Questions 10 min
Agenda

40 Years of HALT:
What Have We Learned?
By
Mike Silverman, CRE
Managing Partner
Ops A La Carte
mikes@opsalacarte.com
www.opsalacarte.com

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 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

 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 ?

Stress
Start low and step up the
stress, testing the product
during the stressing
BASICS OF HALT

Failure
Gradually increase
stress level until a
failure occurs
Stress
BASICS OF HALT

© 2008 Ops A La Carte
Stress
Failure
Analysis
Analyze
the failure
BASICS OF HALT

Stress
Failure
Analysis
Im
proveMake
temporary
improvements
BASICS OF HALT

Stress
Failure
Analysis
Im
prove
(increase)
Increase
stress and
start
process
over
BASICS OF HALT

Stress
Failure
Analysis
Im
prove
(increase)Fundamental
Technological
Limit
BASICS OF HALT

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

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

Product
Operational
Specs
Stress
Upper
Oper.
Limit
Upper
Destruct
Limit
Lower
Destruct
Limit
Lower
Oper.
Limit
BASICS OF HALT

Product
Operational
Specs
Stress
Upper
Oper.
Limit
Upper
Destruct
Limit
Lower
Destruct
Limit
Lower
Oper.
Limit
This is what the product spec distribution really looks like
BASICS OF HALT

Product
Operational
Specs
Stress
Upper
Oper.
Limit
Upper
Destruct
Limit
Lower
Destruct
Limit
Lower
Oper.
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
CONCEPT
PHASE
DESIGN
PHASE
MANUFACTURING
PHASE
PROTOTYPE
PHASE
Gap
Analysis
Block
Diagrams

 4) New advances in HALT methodology

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 Failure
Drawback: 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 Data
Drawback: 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!
HALT 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.
HALT Calculator

Complete MTBF prediction
1. 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
HALT Calculator

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.
1. 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.
1. Capture HALT Product Operational Response
Limits.
HALT Calculator

New End Use
Prod Spec
End Use
Guard Band, Spec & End UseGuard Band, Spec & End Use
HALT Calculator

• 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
HALT Calculator

Published
Spec, °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 Band
Product Environment & LevelProduct Environment & Level
HALT Calculator

HALT Calculator
Actual Field Failure Rate Estimate - % of Failures/Year
Input Matrix
Calculated MTBF (in Hrs) = 100,000
Product Thermal (Hot in °C) = 110
Product Thermal (Cold in °C) = -80
Product Vibration (in Grms) = 25
Prod Published Spec Level (see below) = 2
Number of HALT Samples = 6
Field Duty Cycle (in Percentage) = 80
Confidence = 1
Steady State AFR, % (HALT Only) = 0.30
Steady State Field MTBF, Hrs (HALT Only) = 2,893,373
Lower % HALT Confidence Limit = 1,829,861
Upper % HALT Confidence Limit = 4,682,531

well.
 To determine “must meet” margins during the
HALT Plan
Use 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?
Use of FMEA

well.
 To determine “must meet” margins during the
HALT Plan
HALT vs. ALT

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

♦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.
HALT vs. ALT

Advantages of ALT
♦Instead 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
HALT vs. ALT

♦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.
HALT vs. ALT

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

FAI LURE TESTI NG
HALT
OBJECTI VES
1. Root Cause Analysis
2. Corrective Action I dentification
3. Design Robustness Determination
TESTI NG REQUI REMENTS
1. Detailed Product Know ledge
2. Engineering Experience
ALT
OBJECTI VES
1. Reliability Evaluation (e.g. Failure Rates)
2. Dominant Failure Mechanisms I dentification
TESTI NG REQUI REMENTS
1. Detailed Parameters
(a) Test Length
(b) Number of Samples
(c) Confidence/ Accuracy
(d) Acceleration Factors
(e) Test Environment
2. Test Metrology & Fact ors
(a) 4:2:1Procedure Or Other
(b) Costs
ANALYTI CAL MODELS
1. Weibull Distribution
2. Arrhenius
3. Coffin-Manson
4. Norris-Lanzberg
HALT vs. ALT

Cell Phone
Fan
Hard Drive
Infusion Pump
Medical
Cabinet
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
HALT vs. ALT

♦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
HALT 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 Partner
www.opsalacarte.com
mikes@opsalacarte.com
(408) 472-3889
Confidence in Reliability
CONTACT INFO

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