We are holding a HALT Seminar at our premises in Nazeing, Essex, UK on Wednesday, 17th May 2006.

We are delighted to have Chris Peterson from ACS/C.Hanse Industries Inc., presenting this seminar.

For futher information or to reserve your place please contact Sharon Leake.

Below are the subjects and topics of Chris Peterson's presentation on HALT:

What is reliability?

  • The best quantitative measure of the integrity of a designed part, component, product or system
  • The probability that parts, components, products, or systems will perform their deigned-for functions without failure in specified environments for desired periods data given confidence level
  • Theoretical and practical tools

Discovery testing

  • HALT testing is a process that is for discovery, specifically looking for failures
  • It is NOT a life test
  • The true value of a life parameter is never known, only it's distribution about an expected value, so we cannot say when failure will occur. Sometimes we can say that the likelihood increases, but we can very rarely predict the time of failure.

Who should be involved in the Halt Test

  • Design Engineer
  • Product Engineer
  • Management
  • Customer or end user
  • It is important to remember that a HALT process should be continuously monitored, both by data acquisition equipment and by personnel.

What should be tested?

  • At least 3 samples as a minimum
    • Gold cards
    • Lemons
  • Products likely to have be exposed to and possibly suffer from temperature, vibration, power cycling, or some combination
    • Not a drop or classical shock test

Where should the HALT be performed?

  • Your lab
  • Another test lab in your company
  • An outside test lab

What is a failure?

  • Failure or the absence of failures is heavily dependent upon human actions and perceptions.
  • What may be a failure to one company may not be to another:
    • Scratched paint (Cisco)
    • Circuit boards (Honeywell)
    • Transients (Motorola)

Why perform HALT?

  • To get a better knowledge of your product
  • A single tool in the toolbox
  • To save ££££

Logic for use of Unrepresentative Stresses

  • The causes of failures that will occur in the future are often very uncertain
  • The probabilities of and durations to failures are also highly uncertain
  • Time spent on testing is expensive so the more quickly we can reduce the uncertainty gap the better
  • Finding causes of failure during development and preventing recurrence is far less expensive that finding new failure causes in use

When do you HALT?

  • Should be started as soon as the hardware is available for test
  • For action to be taken to analyse and correct failure modes before production
  • As a way of tracking down causes of field failures

How do you run HALT?

  • Actually A series of Tests
    • Cold only
    • Heat only
    • Vibration only
    • Temperature swings
    • Heat with vibration
    • Swings with vibration

Preparation for the process

  • Temperature:
    • Laboratory ambient
    • Expected usage temperatures
      • Operating
      • Transportation
      • Storage
    • Margins
    • Melting point

Understanding margin

  • Operating range
  • Shipping range
  • Storage range
  • Testing range

Ignoring failures outside the margins

  • Wrong question: At what stress do we decide that the level is so high that we can ignore the failures?
  • Right question: Could this failure occur in use?
    • On other items
    • After longer times
    • At other stresses
    • etc.

Additional preparation

  • Monitoring
  • Data acquisition
  • Time to market
  • Cabling suitable for test environments

Talk to people

  • Talk with end users
  • Find out how they expect to use the vehicles
  • Get horror stories on the worst things that have ever happened
  • Find out the things that they have been most satisfied with
  • An engineer and an end user will look at the same product or system in very different ways

Cold test

  • Least destructive environment
  • Start at room ambient
  • N2 will remove extra humidity
  • 10° steps

Cold chart

  • Start with 10 degree steps.
  • Bring temperature up at the first sign of failure to see if it may be intermittent because of certain temperature.
  • Control the return to room temperature since this may cause it's own failure.

Heat test

  • Still single environment
  • 5° steps for assemblies
  • Know melting limits ahead of time

Heat chart

  • Start with 10 degree steps.
  • Change to 5 degree steps as you get closer to suspected failure temperature (or melting point).
  • Bring temperature down at the first sign of a failure to see if it may be intermittent because of a certain temperature.

Vibration test

  • Single Environment but multi-axis random
    • On product
    • On fixture
    • On table near product

Vibration chart

  • Start with 2 g steps.
  • Keep temperature constant, preferably at laboratory ambient, so that vibration is your only stress.
  • Bring g level down at the fist sign of a failure to see if it may be intermittent because of a certain acceleration.

Temperature swings

  • Hot and cold Test
    • Cold first (removes humidity)
    • Hot first (retains humidity)
  • 5 or 10° steps depending on earlier results
  • Rapid ramps (thermal mismatch and conductivity effects)
  • Short dwells

Swings chart

  • Assuming a failure at 85 degrees we go 10 degrees lower
  • Give a 125 degree difference giving -50 as the cold range
  • According to Harry McLean in HALT HASS & HASA explained 3 to 5 cycles with 5 being preferred
  • According to Gregg K Hobbs in Accelerated Reliability Engineering he has not found any product to be rate sensitive so there is no need to limit the speed of the change rate

Heat with vibration

  • Heat
    • Start at laboratory ambient
    • Compare with heat only test
  • Vibration
    • Duration
      • Bursts
      • Full time
    • Level
      • Lower than failure rate
      • Higher than expect in real life

Heat with vibration chart

  • Assuming a failure at 85 degrees we start at 65° giving a margin
  • Assuming a failure at 14 gs we use 10 giving a margin
  • Vibration can be either pulsed or constant depending upon expected end usage
  • The same principal would work with a combination of cold and vibration
  • Thermal swings:
    • Closest to real world conditions
    • Compare to earlier results
    • Rapid ramps
    • Short Dwells
  • Vibration
    • Duration
      • Bursts
      • Full time
    • Level
      • Lower than failure rate
      • Higher than expect in real life

Swings with vibration chart

  • Use data based on baseline and earlier swing test
  • Assuming a failure at 50 gs we divide that into fifths (because of five swings) and increase with each vibration burst
    • 10
    • 20
    • 30
    • 40
    • 50 g's

Other environments

  • Humidity
  • Corrosions
  • Dust
  • Power cycling


  • Remember that testing is a form of experimentation
  • Good guesses are valuable but need to be backed with real data
  • HALT is a way of getting a lot of data in a little time and for a comparatively small cost