HALT and HASS in IPC 9592A
HALT - Highly Accelerated Life Test
HASS - Highly Accelerated Stress Screen
IPC 9592A - Requirements for Power Conversion Devices for theComputer and Telecommunications Industries

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The information contained in this paper is copyrighted. No portion may be copied, modified,distributed or published without the express written permission of Qualmark Corporation or DLi
Labs. Portions of IPC’s standard 9592A used with permission from IPC. The complete standard isavailable at IPC’s website: www.ipc.org

HALT and HASS in IPC 9592A
by David Rahe
DLi Labs
andQualmark’s Senior Applications Engineers

THE HISTORY OF IPC AND IPC 9592A
In 1957, the Institute for Printed Circuits was formed. As its focus shifted and broadened over the years, theorganization changed its name to simply “IPC.” The mission of IPC is to represent all facets of the electronics
industry, including design, printed circuit board manufacturing, and electronics assembly. It is a member-driven
organization and is a leading source for industry standards, training, market research and public policy advocacy.

IPC-9592A: Requirements
for Power Conversion
Devices for the Computer
and Telecommunications
Industries

In 1995, IPC adopted “Principles of Standardization” as a guiding principle. IPC Standards
and Publications are designed to serve the public interest by helping to eliminate
misunderstandings between manufacturers and purchasers, facilitating interchangeability
and improvement of products, and assisting the purchaser in selecting and obtaining withminimum delay the proper product for a particular need. It is important to note that theexistence IPC’s Standards and Publications shall not in any respect preclude any member
or nonmember of IPC from manufacturing or selling products not conforming to such
Standards and Publication. Also, the use of these standards is not limited to IPC members,
but can be voluntarily used by any organization, domestic or international.

In 2007, IPC released IPC 9592, “Performance Parameters for Power Conversion Devices”.
The goal of this standard was to harmonize the supplier’s requirements for design,qualification, and production test practices. It included guidelines for Design for Reliability, Design andQualification Testing, Quality Processes and Manufacturing Conformance Testing ( See Figure 1).

IPC-9592 Standards
Design For Reliability

Design andQualification Testing

Quality Processes

Manufacturing
Conformance TestingSpecifying, designingand documenting
performance andreliability

Performance tospecification,
Performance in intended
environment
EST, HALT

Quality Management
Systems, Supplierand Sub-Tier Quality
Requirements

Burn-In, ORT,
HASS, HASA

Figure 1: The Four Main Sections of 9592

The Design for Reliability guidelines included Best Practices for specifying, designing and documenting
performance and reliability, such as Mean Time Between Failure (MTBF), Derating, Corrosion, Failure Modes andEffects Analysis (FMEA), Voltage Spacing and Moisture Sensitivity Level (MSL). The Design and Qualification
Testing section served two key purposes. First, it provided assurance that a product performed to specification,and second, that it would perform in the intended environment without failure.

HALT and HASS in IPC 9592-A© 2011 Qualmark Corporation • Accelerating Product Reliability • WWW.QUALMARK.COM

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To meet these requirements, this section defines specifications for:
•
•

•

•
•

Design Verification Testing (DVT)
Environmental Stress Testing (EST), including:•Highly Accelerated Life Testing (HALT)•
Temperature•
Humidity•
Bias (THB)•High Temperature Operating Bias (HTOB)•
Temperature Cycling (TC)•Power and Temperature Cycling (PTC)•
Shock and Vibration (S&V),•
Drop•
Corrosion•
Dust•
Solderability,
Electro-Magnetic Susceptibility (EMS), including:•Electrical Fast Transients (EFT)•Electro-Static Discharge (ESD)•
Immunity•
Emissions
Acoustic Noise
Product Safety

The Quality Processes section of the standard defines supplier and sub-tier quality requirements through the useof Quality Management Systems (QMS), Sub-Tier Materials Traceability and Change Authorization & Qualification.
Finally, the standard defines Manufacturing Conformance Testing, such as Highly Accelerated Stress Screening(HASS), Highly Accelerated Stress Auditing (HASA), Burn-In (BI), Ongoing Reliability Testing (ORT), Safety and OBA.
The original release of 9592 defined these standards for Power Conversion Devices (PCD). PCDs are defined as AC
to DC and DC to DC modules, converters and printed circuit board assemblies. Within the document, these devices
are broken down into categories of internal DC output power supplies (AC or DC input), board mounted DC to
DC converters and external AC to DC power supplies (adapters & chargers). In addition, it defines two reliability
classifications for the devices. The General or Standard classification are for devices intended to function in acontrolled environment with an expected lifetime of five years. The Enhanced or Dedicated Service classification
is for carrier grade/high performance devices with a 15 year life
requirement.
9592A includes a
The original version of 9592 included a description of the use of Highly
Accelerated Life Testing (HALT) as part of the Design and Qualification
requirements. In 2010, IPC revised 9592 and released 9592A. In 9592A,
the description of HALT was significantly expanded, including greater
detail on its implementation. These changes came from a desire toclarify and specify a process that was not well defined in the industry.
It defines the process for HALT as well as for Highly Accelerated Stress
Screening (HASS). Revision A includes a requirement for HALT and arecommendation for HASS.

requirement for Highly
Accelerated Life
Testing (HALT) and arecommendation forHighly Accelerated Stress

Section 5.2.3 defines HALT (See Figures 2 and 3) as follows:

Screening (HASS).

“HALT is a series of tests performed on a product as part of the design
process to aid in improving product robustness. The principal idea of
HALT is to find design weaknesses as quickly as possible and then fix them. After improving one weakness, the next
design weakness is found and improved and so on until no design weaknesses remain that could result in field

HALT and HASS in IPC 9592-A© 2011 Qualmark Corporation • Accelerating Product Reliability • WWW.QUALMARK.COM

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HALT STRESSES
Stress (e.g., Temperature)

UDL
UOL
USL
Customer
Operating
Limits

Product
Operating
Limits

Product
Destruct
LimitsLSL
LOLLDL
USL/LSLUOL/LOL
UDL/LDL

Upper/Lower Specification Limits. Limits to which you guarantee operation of your product.
Upper/Lower Operating Limits. Limits to which product ceases to function, however can be
returned to USL/LSL and begin working again.
Upper/Lower Destruct Limits. Limits at which product fails catastrophically.
IPC-9592A, Figure d-1

Figure 2: HALT Identifies the Operating and Destruct Limits for a Product

Lower
Destruct
Limit

Lower
Operating
Limit

Product
Operational
Specs

Upper
Operating
Limit

Upper
Destruct
Limit

Destruct
MarginOperatingMarginStressCourtesy of Qualmark Corporation © 2011

Figure 3: The Goal of HALT:
Expand the Margins Between Specification and Actual Limits
failures. During HALT, a product is stressed beyond the product specifications… to quickly accelerate and identify
design weaknesses. … HALT is not a pass/fail test.”
Appendix D goes into greater detail on both the purpose and the process of HALT, as well as the equipment needed
to perform the testing.

HALT Lab Equipment and Power Supply Unit (PSU) Samples...a test system is requiredthat is capable of stressing
a product in a combined
thermal and vibration
environment, using
Repetitive Shock (RS) 6

To perform HALT as defined in 9592A, a test system is required that is capable of stressing
a product in a combined thermal and vibration environment, using Repetitive Shock (RS)
6 Degree Of Freedom (DOF) vibration. A vibration level of 50 gRMS minimum is specified,along with a wide thermal range of at least -80°C to +170°C. This thermal range, combinedwith thermal change rate requirements of at least 40°C per minute, demands the use of
direct injected liquid nitrogen cooling.
In addition to describing these chamber requirements, 9592A goes on to define the key
pieces of ancillary test equipment that are needed to set up an effective HALT lab. For a
PSU supplier that is new to HALT, this information helps insure success, as well as allowing
better cost analysis when setting up a lab.
The equipment list reflects the requirements in 9592A for careful and complete data

Degree Of Freedom (DOF) collection and reporting, as well as the extensive functional testing that is critical to an
vibration.

effective HALT. The ability to monitor and record multiple channels of thermocouple,
accelerometer, voltage and current measurements are required for the testing.

HALT and HASS in IPC 9592-A© 2011 Qualmark Corporation • Accelerating Product Reliability • WWW.QUALMARK.COM

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The functional testing for HALT is described in section 5.2.3.6. The recommended sample size is outlined in section
5.2.3.5 (See Figure 4). A sample size of three units for each stress is defined, although in many cases units that were
tested under one stress and did not fail can be used for another test.

Table 5-1 Minimum Sample Size for HALT Tests

All Classes
andCategories

Low
Temperature
Step Test

High
Temperature
Step Test

Rapid
ThermalCycling
Test

6-DOF
RandomVibration
Test

Input
Voltage
Test

OutputLoad
Test

Combined
Stresses
Test

3

3

3

3

3

3

3

Note 1: For Categories 1 and 3 (Power Supplies/Adapters), users have the option of starting with less than 21 samples and reusing samples which survive a given sequence of testing. Users are cautioned that some HALT failures require extensive repairs
after failures during early testing and may not be suited for subsequent testing. Category 2 (BMPM) must begin with 3 newunits for each test sequence, except for units which have not failed a HALT test when the equipment capability limits have beenreached. These units may be used in the next test rather than replacing them with new units.
IPC 9592A Table 5-1

Figure 4: Table 5.1 From Section 5.2.3.5 Defining HALT Sample Sizes

The HALT Process
9592A describes a HALT process that incorporates the thermal and vibration stresses common to classic HALT
(See Figure 5). It includes the application of these stresses separately, then in combination, with each stressbeing applied in a step-wise fashion. Reference 9592A Appendix D, section D.1.1 for a detailed description of therecommended step stress process.

Cold Thermal Step
StressHot Thermal Step
StressVibration Step
StressRapid Thermal
StressCombined
Thermal and Vibration
StressFigure 5: Sequence of Environmental Stresses Typically Used in HALTIn addition to these standard HALT stresses, 9592A describes input and output loading stresses that are unique to
PSU testing (See Figure 6). They are first applied in conjunction with the thermal limits identified in the thermal
step stressing, then finally the PSU is subjected to combined thermal, vibration, output and input stresses. These
additional stresses make the HALT test much more effective for PSU testing than simply using the thermal andvibration stresses alone.
A well written and comprehensive HALT report is very important to a successful and valuable HALT. 9592A
addresses this in Section 5.2.3.7. It states that the report should include the basic, typical items that are common
to most test reports – descriptions of test equipment used, calibration verifications, identifications of units tested,
etc. However, it also puts emphasis on some of the report requirements that are particularly important in HALT,HALT and HASS in IPC 9592-A© 2011 Qualmark Corporation • Accelerating Product Reliability • WWW.QUALMARK.COM

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including software and hardware revisions of both the units under test and the test equipment and detailed
descriptions, with supporting photos, of the fixture details and the thermal and vibration monitoring points. In
HALT, it is not unusual to repeat a test after corrective actions have been implemented. The report should provide
all the details described in 9592A, since the fine points of accelerometer placement or software revisions can affectthe outcome of the test, resulting in invalid data when the test is repeated.
Another important use of this detailed report is to provide clear documentation that the testing was done, and was
performed in accordance with the procedure laid out in 9592A. Many times, a PSU manufacturer will perform HALT
in response to a requirement from a customer. With a good HALT report in hand, the manufacturer can alleviate
any concerns on the part of the customer about the testing done, and leave a good impression of the validity of theresults of their testing and their dedication to quality design.

Cold Thermal Step
StressHot Thermal Step
StressVibration Step
StressRapid Thermal
Stress

Input Voltage Step
Stress

Output Load Step
StressCombined Thermal,
Vibration, Input
and Load Stress

Figure 6: Incorporation of Product Specific Stresses into HALT Environmental Stresses

Post HALT Requirements
The completion of the actual HALT test, including the identification of failure modes precipitated during the test,is only the beginning of the work to be done in HALT. The most important part of the process is to perform root
cause failure analysis and implement corrective actions. Section 5.2.3.8 of 9592A states “All failures found during
HALT tests shall be analyzed to their root causes.” As stated earlier in the document, the key output of HALT is failuremodes. If these failure modes are ignored, poorly understood or insufficiently responded to, then much of thebenefit of HALT can be lost. As part of the process to ensure the proper response to failure modes, this same section
also states that the root cause analysis process must be documented, along with the results and corrective actions
taken.
It is also important for designers incorporating the PSU to understand the corrective actions taken. Section 5.2.3.8
states that PSU users shall receive a report with the cause and effect for all corrective actions. It is possible that a
failure mode found in HALT can be safely ignored, without corrective action taken. However, this conclusion can
only be arrived at after a failure analysis is completed, and the logic understood and approved by the user as well.

HASS and HASA in 9592A
The original version of 9592 included a description of Highly Accelerated Stress Screening (HASS) and the Highly
Accelerated Stress Audit (HASA). These are production tests, with HASS being performed on 100% of the units
shipped, and HASA being performed on a sample of the units. These tests were included to mitigate the risks ofmanufacturing related errors and the resulting negative effects for the users.
HALT and HASS in IPC 9592-A© 2011 Qualmark Corporation • Accelerating Product Reliability • WWW.QUALMARK.COM

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HASS STRESSES
Stress (e.g., Temperature)

UDL
UOL
USL
Customer
Operating
Limits

Product
Operating
Limits

Product
Destruct
Limits

HASS
LimitsLSL
LOLLDL
USL/LSLUOL/LOL
UDL/LDL

Upper/Lower Specification Limits. Limits to which you guarantee operation of your product.
Upper/Lower Operating Limits. Limits to which product ceases to function, however can be
returned to USL/LSL and begin working again.
Upper/Lower Destruct Limits. Limits at which product fails catastrophically.
IPC-9592A, Figure d-1

Figure 7: HASS Limits are Based on Limits Found in HALT

Figure 8: A Typical Profile

IPC-9592a-d-13

9592A expands the description of HASS and recommends it as more effective than Burn-In. It also states thatthe supplier can choose between HASS and Burn-In. Section 7.3.2 in the standard defines HASS and HASA, while
Section D.2 of appendix D expands that description and discusses the process of implementing HASS.
The vibration and thermal limits that are used in a HASS are based on the operational and destruct limits identified
in HALT (See Figure 7). HALT must be performed before HASS in order to define those limits. The starting point forthe screen, as well as the Proof of Screen (POS) process that is used to demonstrate the safety and effectiveness ofthe screen are defined in section D.2 as well, and is largely unchanged from the original 9592. It follows the method
most commonly recommended in industry descriptions of the test process. See Figure 8 for a typical profile.
The equipment needed for HASS is very similar to the equipmentused for HALT, but there are a few key differences. Because the limits
for HASS are, by definition, lower than those found in HALT, the
HASS system may not need the extreme temperature range, rates ofchange or high vibration levels defined for the HALT system. While
the standard does state that the testing “…must be performed inindustry standard HALT/HASS chambers”, it reduces the thermalchange rate requirements to 30°C/minute. Also, a system withgreater table surface area will improve the efficiency/through-put ofthe process.

...suppliers are required togenerate their own testing
profile based on actual
product performance andphysical characteristics.

A key part of the equipment needed for HASS/HASA is the HASS
fixture. A description of the design and validation of a HASS fixture is beyond the scope of this paper, and is beyond
the scope of 9592A as well. The standard simply states “HASS/HASA fixture should be designed and fabricated to
HALT and HASS in IPC 9592-A© 2011 Qualmark Corporation • Accelerating Product Reliability • WWW.QUALMARK.COM

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support the product through-put testing and provide proper vibration transmissibility, thermal uniformity and abalanced thermal rate of change.”
The abbreviated description of the HASS fixture design and qualification reflects a necessary restriction in the
HASS/HASA portion of the 9592A standard. The ‘Purpose’ section of section D.2 states “This document is to serve
as a general guideline and a reference... Since it is only a general guideline, suppliers are required to generate theirown testing profile based on their actual product performance and physical characteristics.”
Because PSUs differ so much, it is impossible to provide a specific HASS/HASA procedure and9592A defines ... thefixture that will work in all cases. As is the case throughout the industry, the implementationof HASS/HASA on a PSU requires careful thought with appropriate consideration given to theunique characteristics of the specific product being tested.
production maturity,

production quantities,
and field and factory
failure rates that justify
the implementation of
HASA.

9592A discusses the implementation detail of HASS and HASA and focuses on the uniquerequirements specific to PSU manufacture. Functional testing requirements for both HASS and
Burn-In are distinctly specified.
The move from HASS to HASA can provide a significant savings to a PSU supplier. However,
the move must be done intelligently. 9592A addresses this issue by clearly defining the
production maturity, production quantities, and field and factory failure rates that justify the
implementation of HASA. A sampling plan is also specified.

Failures found in HASS/HASA are treated in the same way as HALT failures. Root cause analysis
and corrective action must be conducted. This is particularly important in HASA. The standard
states that “Failures that occur in a sample population require immediate Root Cause FA/CA…”Summary
The increased emphasis placed on HALT, HASS and HASA in the revision from 9592 to 9592A reflects the value ofthe methods by IPC, as well as the perceived need for a defined process for the testing. The document includes
descriptions of the most important requirements for successful implementation of the test methods, including
the criticality of Failure Analysis and Corrective Action, the need for the use of product specific stresses and fullfunctional testing during the process, and the importance of detailed reporting. By implementing HALT, HASS
and HASA as outlined in this new revision, a supplier will realize the maximum gains in product reliability andreductions in warranty costs that the test methods can provide.
......................................................................................

Excerpts of IPC 9592A, Requirements for Power Conversion Devices for the Computer and Telecommunications
Industries, have been used with permission by IPC, the Association Connecting Electronics Industries ®. Licenses
for IPC 9592A can be purchased online at the association’s website: www.ipc.org.

HALT and HASS in IPC 9592-A© 2011 Qualmark Corporation • Accelerating Product Reliability • WWW.QUALMARK.COM

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Accelerating Product Reliability

Qualmark is the largest global supplier of accelerated reliability testing systems for performing HALT (Highly Accelerated Life Tests) and
HASS (Highly Accelerated Stress Screens) that improve product quality. Qualmark technology and services help companies in automotive,
aerospace, medical, electronics and other manufacturing industries to introduce new products quickly, boost product reliability, slash warranty
costs, and build lasting consumer relationships based on quality products.

www.qualmark.com
sales@qualmark.com
303.254.8800
The information contained in this paper is Qualmark proprietary information and is copyrighted. No portion may be copied, modified, distributed or
published without the express written permission of Qualmark Corporation.

DLi Labs provides a unique blend of testing and reliability services to our customers. We will execute your pre-existing test plan, or help you
to develop one tailored to your product. We believe that thorough testing is the best way to ensure a quality product gets to market. The righttesting drives down warranty costs, raises reliability and protects brand reputation

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