High Accelerated Life Test : Translating Theory in to Design Solutions for the Implementation Tool

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High Accelerated Life Test Translating
Theory in to Design Solutions for the
Implementation Tool
m o r e t h a n t e c h n o l o g y
solid-edge design
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INTRODUCTION

• The Environmental Test Chambers are today
  compulsory for developing any product
  reliability,
• The one which is becoming more and more popular
  is the chamber for Highly Accelerated
  Environmental Test or HALT. The chamber is easy
  recognized by high environmental performance and
  integrated shaker, but this is not all what is
  required to an environmental chamber to perform
  accelerated tests

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ACCELERATED TESTING

• The theory behind the accelerated testing has
  been explored in many academic contexts, the
  advantages have been broadcasted all over the
  world for the benefit of every one
• The object is now how to translate the
  accelerated test requirements in the proper
  technical solutions for the tool which has to
  implement the test the environmental test
  chamber.
• basic philosofy for accelerating environmental
  tests to provide high stress to the product by
  rapid cycling between extreme environmental
  conditions and by strong stimulation of the full
  spectrum failure modes.

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HALT requires Outstanding Performance

• 1 - Extreme change rate chamber
• 2 - Multi-axis Random Vibrations
• 3 - Maximum Vibration Transmissibility
• 4 - Maximum Thermal Transmittance
• 5 - Adjustable Air Flow
• 6 - Reliability and Usability
• 7 - Supplier qualification

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1- Extreme Temperature Change Rates

• When temperature rate goes to extreme (20 - 30
  C/min), the cost effective solution for the
  cooling ramps is to use the evaporation of LN2
  (Liquid Nitrogen).
• Being the evaporation temperature at ambient
  pressure -196C and the calorific value 40-50
  Kcal/Kg, it gives the LN2 a very high cooling
  power to rapidly cool down the systems which
  include the air inside the chamber, the walls
  and components of the chamber and. the specimen.

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1- Extreme Temperature Change Rates

• Considering also a price which all over the world
  is under the 0.25 USD per Kg, the LN2 solution is
  convenient when the LN2 supply facility is
  already available in the laboratory. Traditional
  compressor refrigeration system for this
  application would require tenths of HP, even if
  the electrical energy consumption cost will save
  some money in comparison with the LN2 consumption.

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1- Extreme Temperature Change Rates

• As far as heating the solution refers to the
  traditional technology of electrical heat
  dissipation from resitors easy to implement and
  fast to be controlled. The associated power has
  to be adequately increased, for a 1 m3 chamber
  with 20 kg of electronic specimen to be heated at
  60C/min, the dissipated, and electrically
  supplied, power is in the range of 100 Kw !

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2 - Multi Axis random Vibration

• Accelerating the test means also to test "in
  parallel" as it can be done with a multiaxial
  shaker which wich avoids rotation of the specimen
  and test repeatition. Furthermore it has been
  demonstrated that some product failures are
  detected by
• - correlation effect of multiple axes vibration
• - application of a vibration signal which is
  random as far as possible (flat and extended
  frequency band).
• The cost-effective solution is to use multiple
  pneumatic actuators.

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2 - Multi Axis random Vibration

• This experimented system satisfy the technical
  requirements but also is available at costs which
  are considerably less than complex 6 DoF system
  which use different technology (i.e
  electrodynamic).
• Vibration levels
  up to 60 Gs.

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Multi-Axis Repetitive Shock Vibration

• The instateneous pressure
• of the supplied air controls
• the "movement speed" of each
• actuator, viceversa when the
• actuator works it affects the
• instaneous air pressure and
• consequently the "speed" of
• other actuators, pratically each of the actuators
  moves
• randomly and in different direction. Not only the
  intensity
• of the acceleration vector is random but also the
  direction

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Multi Axis random Vibration

• Wide frequency band in the PSD

A potential disadvantage is that the vibrations
are basically not controllable as far as spectrum
shape (they are random only) but they can be
controlled only in total rms level. Nevertheless
this is what HALT requires.
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3 - Maximum Vibration transmissibility

• Mounting products on Aluminum standoffs provides
  maximum transmissibility of vibration input from
  table

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4 - Powerful Airflow

• Thermal power is nothing without the ability to
  transfer the power to the the real subject of the
  test the specimen. One of the most important
  parameter affecting the thermal transfer is the
  thermal resistance between the air and
  specimen. It depends from material and shape of
  the specimen, density (temperature and pressure)
  and humidity of the air, airspeed.
• The factor controllable by the chamber is the
  airspeed the higher is the airspeed the lower
  is the thermal resistance and the most part of
  the thermal energy is transferred to the
  specimen.

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4 - Powerful Airflow

• High airspeed for a given volume requires
  powerful fans (2 - 4 HP of total power), likely
  two fans which in combination with a flexible
  configuration of air ducts give a good airflow
  distribution.

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5 - Adjustable Airflow

• Precise control of air direction provides faster
  product change rates
• Up to four ducts can direct air onto different
  products

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Adjustable Air Flow

• Air slot can be open or closed
• When slot is closed, air is directed to the ducts
  allowing air to be directed onto the product
• Allows flexibility in controlling airflow to
  maximize air velocity across the product

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Adjustable Air Slot
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6 - system reliability safety Vibration

• Top of the line Teflon Coated Impactors for long
  life and high MTBF

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6 - system reliability safety CE Mark

• The system has to comply with the latest
  requirements of the European Community.
• The package includes
• proper grounding procedures,
• specified components,
• screw type terminal connections,
• Electromagnetic shielding/immunity
• as well as filters for the heating system to
  reduce electrical noise

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6 - Usability

• Convenient Table Height
• Front and Rear doors for unrestricted product
  access
• 18 X 18 Windows for observation
• Access Ports for product interconnect, and
  product monitoring sensors
• Access Panels

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7 - Supplier Qualification

• Broad product line and experience in
  environmental chambers
• Turn-Key System chamber, controls, and
  vibration system.
• Local Sales and Service. Provide factory trained
  professionals.
• In house design and manufacturing of the system,
  from sheetmetal to electronics, electrical
  subsystems, etc. This assures full control of
  the production.

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Efficiency considerations

• Saving energy is today an "ambientalist" issue
  but also affect very much the money budget to run
  a particular chamber like an accelerated test
  chamber which use 100 kW of electrical power and
  hundreds of kg of LN2.

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Efficiency considerations

• do not waste energy special care has to devoted
  to
• - minimize the thermal capacity of the chamber
  internal elements in order do not absorb useless
  energy especially during the temperature
  transients
• - minimize the thermal capacity of the chamber
  walls and of the shaker table having the
  necessary thermal insulation
• - improve the thermal transfer characteristics
  with an adequate airspeed and good air
  circulation around the specimen

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Efficiency considerations

• - minimize the pressure drop and turbolence along
  the airflow circuit in such a way to reduce the
  dissipated power, the fan motor power and its
  heating transferred inside the chamber.
• Careful consideration the above points can
  considerably reduce the energy consumption

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Chamber Typical Performance

• Temperature Range -100C / 200C
• Temperature variation rate 60C/min cooling
  from 150C to 60C 60C /min heating up
  from 60C to 150C
• Air speed 20 m/sec
• Acceleration Up to 60 grms
• Frequency range Up to 10000 Hz
• Vibration table size 36 x 36 inches
• Chamber internal dimension 1000 litres
  (adjustable)
• Vibrator features The system provides vibration
  using impact excitors with 6 degrees of
  freedom equally distribuited il all 3 axes
  and in all 3 rotations
• Heating 100,000 Watts by Nicrome heaters
• Cooling Liquid nitrogen expansion
• Noise pressure level 76 dB(a)

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HALT HASS ChamberMod.UHS 300
UHS 1200
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HALT HASS ChamberMod.UHS300

• Temperature Range -70C / 150C
• Temperature variation rate 30C/min cooling
  from 120C to 40C 30C /min heating up
  from 40C to 120C
• Air speed 5 m/sec
• Acceleration Up to 60 grms
• Frequency range Up to 2000 Hz
• Vibration table size 24 x 24 inches
• Chamber internal dimension 300 litres
• Vibrator features The system provides vibratio
  using impact
• excitors with 6 degrees of freedom equally
• distribuited il all 3 axes and in all 3
  rotations
• Heating Nicrome heaters
• Cooling Liquid nitrogen expansion
• Power 45 kW