HALT is a rigorous methodology designed to push aerospace products beyond their operational limits, identifying potential weaknesses and failure modes that traditional testing methods might miss. By subjecting aerospace products to extreme stress conditions—far beyond what they would encounter in their normal life span—HALT provides invaluable insights into the inherent durability and reliability of aerospace components.

The beauty of HALT lies in its ability to reveal the unknown. It accelerates the aging process, simulating years of wear and tear in a fraction of the time, thereby uncovering latent defects and vulnerabilities. This preemptive identification allows for critical design modifications and enhancements, significantly reducing the risk of costly failures and recalls post-launch.

For aerospace manufacturers, the implications of HALT are profound. It signifies a commitment to excellence and represents a strategic investment in the product’s lifecycle. By integrating HALT into the development process, aerospace companies can confidently navigate the complex landscape of product reliability, ensuring that their products are not just fit for purpose but are built to last.

Aerospace Testing Laboratory: Advancing Product Reliability with HALT

In the quest for unparalleled aerospace product reliability, our aerospace testing laboratory offers organizations the use of Highly Accelerated Life Testing (HALT) methodologies. HALT represents a commitment to excellence and a testament to our dedication to advancing aerospace technology.

The HALT process within our aerospace testing laboratory involves a series of accelerated stress tests, including rapid temperature cycling, 6 degrees of freedom random vibration tests at varying frequencies, and combined environment tests. These tests are designed to expose products to conditions far more severe than they would ever encounter in service. By doing so, Delserro Engineering Solutions can identify potential failure points and address them long before they become real-world issues.

Key Advantages of HALT in Our Aerospace Testing Laboratory:

• Early Detection of Design Flaws: By applying stressors that exceed the normal operational limits, HALT helps uncover hidden weaknesses in product designs.
• Cost-Efficiency: Identifying and rectifying potential failures before products hit the market significantly reduces the risk of costly recalls and brand damage.
• Reduced Time to Market: Accelerated testing means faster validation of product robustness, enabling quicker transitions from design to production.
• Customized Testing Strategies: Our aerospace testing laboratory tailors HALT protocols to match the specific requirements and challenges of each aerospace product.

Through the strategic application of HALT, our aerospace testing laboratory supports the industry’s continuous drive toward innovation and reliability. We help our clients achieve the highest standards of performance and dependability in their aerospace endeavors.

Embrace the future of aerospace product testing with us. Discover how our HALT methodologies can elevate your products’ reliability to new heights.

The Impact of HALT on Aerospace Testing and Product Integrity

Highly Accelerated Life Testing (HALT) has significantly influenced aerospace testing practices, leading to more resilient and reliable aerospace products. HALT extends beyond traditional testing methods by focusing on identifying potential failure modes early in the product development cycle.

The practical benefits of integrating HALT into aerospace testing include:

• Early Detection and Rectification of Flaws: By pushing components beyond their operational limits, HALT helps uncover hidden weaknesses in the design and materials, allowing for early modifications.
• Comprehensive Stress Testing: HALT subjects aerospace products to a variety of stressors, including extreme temperatures and vibrations, to ensure they can withstand a broad range of operational environments.
• Support for Innovation: The rigorous demands of HALT encourage the exploration of new materials, designs, and manufacturing techniques, driving innovation in aerospace technology.
• Risk Mitigation: Identifying potential issues before products reach the market minimizes the risk of costly recalls and enhances the overall safety of aerospace missions.
• Streamlined Product Development: HALT can reduce the time required for product testing and validation.
• Stakeholder Confidence: Demonstrating a commitment to thorough testing and product reliability helps build trust among manufacturers, regulatory agencies, and users.

HALT’s role in aerospace testing is to provide a practical, systematic approach to improving product reliability and integrity. It’s about making informed decisions based on comprehensive data. Through the application of HALT, the aerospace industry can achieve a balance between innovation and reliability.

Improve Your Aerospace Products with HALT

Adopting Highly Accelerated Life Testing (HALT) for your aerospace products is a strategic move toward securing a competitive edge in the aerospace industry. By incorporating HALT into your product development process, you’re committing to the highest standards of safety, durability, and performance.

Our aerospace testing laboratory is equipped with state-of-the-art HALT technology and a team of experienced engineers dedicated to helping you achieve excellence in product development. Our aerospace testing laboratory’s ISO/IEC 17025 and ISTA accreditation are a testament to our capability to execute tests that are both precise and reliable. We understand the unique challenges of the aerospace sector and are committed to providing tailored testing solutions that meet your specific needs.

In the dynamic field of aerospace, staying ahead means continually pushing the boundaries of what’s possible. Partner with Delserro Engineering Solutions to harness the power of HALT and take your aerospace products to new heights.

Contact us today to learn more about how we can support your journey toward unparalleled reliability and success in the aerospace industry.

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In the fast-evolving medical device industry, the pathway to market success is marked by stringent standards. Delserro Engineering Solutions (DES) plays a pivotal role in this journey, offering expert testing services for both medical devices and their packaging. Recognizing that each product—from intricate surgical instruments to complex diagnostic machinery—requires rigorous scrutiny, DES employs cutting-edge environmental, vibration, HALT, and shock testing in its state-of-the-art facilities.

The comprehensive range of tests at DES is designed to address the specific challenges faced by medical devices in real-world conditions. By simulating various environmental factors and stressors, DES ensures that both the device and its packaging maintain integrity and functionality throughout their lifecycle. This attention to detail is crucial in the medical device industry where precision is paramount, and the smallest oversight can have significant consequences.

Our team delves into the nuances of each project, partnering with manufacturers to understand their unique needs and challenges. This collaborative approach allows for customized testing solutions that cater to the diverse requirements of the medical device sector.

Medical Device Testing: Meeting Rigorous Standards with DES

The field of medical device testing necessitates strict adherence to a variety of industry standards to ensure compliance. At Delserro Engineering Solutions (DES), we pride ourselves on aligning our testing services with these critical standards, assuring that medical device packaging meets the highest benchmarks of quality and reliability.

1. ISTA Compliance for Transportation Durability: As a certified testing laboratory, we conduct packaging tests that comply with International Safe Transit Association (ISTA) standards. These tests simulate the stress that packaging undergoes during transportation, ensuring that it can protect medical devices from damage due to shock, vibration, and other environmental factors.
2. ASTM Standards for Material Quality: Adhering to ASTM D7386 and other ASTM standards, we evaluate the material quality of packaging, assessing its durability and resilience under various conditions. These tests are crucial for determining if the packaging can maintain the sterility and integrity of medical devices.
3. ISO/IEC 17025 Accredited Testing: Our ISO/IEC 17025 accreditation signifies our technical competence in conducting standardized tests. This includes ensuring that medical device packaging meets specific environmental testing requirements crucial for maintaining product reliability throughout its lifecycle.
4. MIL-STD Compliance for Military-Grade Assurance: For products that require a higher level of robustness, such as those used in military applications, we ensure compliance with Military Standards like MIL-STD-810 and MIL-STD-202. This ensures that products can withstand extreme environmental conditions and rough handling.
5. Customized Testing Protocols: Beyond standard compliance, we offer customized testing solutions tailored to unique client specifications. Whether it’s assessing the resilience of packaging or devices under specific temperature conditions or evaluating its performance under unique mechanical stresses, our state-of-the-art facilities are equipped to handle diverse testing needs.

Navigating Challenges in Medical Device Package Testing

The journey from conception to market for medical devices is fraught with challenges, particularly when it comes to packaging. At Delserro Engineering Solutions (DES), we understand that the package is a crucial component that ensures device safety and efficacy during transit and storage.

With the medical device industry facing ever-tightening regulations, manufacturers must ensure their packaging can withstand a range of environmental stresses. DES’s medical device package testing services are designed to address these exacting standards, from simulating transportation conditions to mimicking the rigors of handling and storage.

Moreover, DES’s commitment to staying ahead in an evolving industry landscape means continuously updating our medical device package testing processes in line with the latest regulations and standards. Our laboratory’s ISO/IEC 17025 and ISTA accreditation are a testament to our capability to execute tests that are both precise and reliable. We engage with the latest industry practices, ensuring that our clients’ medical device packaging is robust, compliant, and above all, safe for the end-user.

Recognizing that off-the-shelf solutions do not fit all, our engineers work closely with clients to develop specialized medical device package testing plans that match the unique needs of their products. Whether it’s fine-tuning temperature cycles to match specific geographic journeys or tailoring shock tests for delicate components, DES ensures that every aspect of packaging is scrutinized and optimized for peak performance. This meticulous attention to detail ensures that when a medical device reaches its destination, it does so with its integrity unblemished and its functionality assured.

DES embraces the challenges of medical device package testing with a blend of accredited procedures, advanced technology, and customized service. By doing so, we ensure that our clients’ products are not only compliant but exemplify the highest standards of the medical device industry. Contact us to learn more about how we can address the specific testing needs for your medical device packaging.

Proven Expertise in the Medical Device Industry at DES

At Delserro Engineering Solutions (DES), our expertise in the medical device industry is more than just a claim—it’s a commitment. With over three decades of experience, DES has established itself as a leader in providing comprehensive testing solutions for both medical devices and their packaging. Our deep understanding of medical device industry standards positions us uniquely to help our clients navigate the complexities of product testing and compliance.

Our team of skilled engineers and technicians is dedicated to delivering results that surpass expectations. At DES, we understand that the medical device industry is rapidly evolving, and staying ahead means being equipped to adapt to new challenges. We offer personalized service, working closely with our clients to understand their specific needs and providing tailored solutions that align with their goals. This partnership approach has made us a trusted name among industry giants.

In the medical device industry, where precision, quality, and reliability are non-negotiable, DES stands as a beacon of excellence. We invite you to experience the DES difference—where quality testing leads to quality products.

Contact us today to learn how our expertise can enhance the reliability and market success of your medical devices.

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1. Incorporate HALT in your Product Development Cycle

Highly Accelerated Life Testing (HALT) is a rigorous reliability test method that is used to expose product weaknesses. The goal of HALT is to proactively find weaknesses and fix them, thereby increasing product reliability. Because of its accelerated nature, HALT is typically faster and less expensive than traditional testing techniques. 

During product development, HALT can find design weakness when changes are much less costly to fix. By finding weaknesses and making changes early, HALT can lower product development costs and compress time to market. When HALT is used at the time a product is being introduced into the market, it can expose problems caused by new manufacturing processes. When HALT is performed after a product has been introduced into the market, it can be used to audit product reliability caused by changes in components, manufacturing or suppliers etc. The bottom line is that HALT can reduce product development time and cost, reduce warranty costs, improve customer satisfaction, gain market share, and increase profits.

More information about HALT can be found in the following blog articles:

Circuit Board HALT Testing Case Study

Rapid HALT – A Cost Effective Alternative to HALT

What Is HALT And Why Perform HALT?

What Is A Typical HALT Procedure?

What Equipment Is Used For HALT?

What Kind Of Failures Occur During HALT?

2. Perform Accelerated Life Testing (ALT)

Accelerated Life Testing (ALT) is a method used to simulate the life of a product in a short period of time.  The stresses are higher than normal to compress time.  The higher the stresses used in the ALT, the shorter the test time.  ALT is best applied to components or less complicated products to focus on specific failure modes.  Typical ALT models are the Arrhenius Model, the Arrhenius-Peck Model and the Coffin-Manson Model. 

Some benefits of ALT include:

• Determining if a product will have wear-out failures
• Estimating a product’s field life using testing.  The life determined through ALT can be compared to desired product life goals and analytical predictions and simulations. 
• Finding additional weaknesses not found in HALT

Some key differences between HALT and ALT are:

• HALT will not estimate product life whereas ALT will. 
• ALT Tests will use one or two different stresses and typically run longer than HALT tests.  Therefore, ALT typically produces wear out failures.   An example would be an ALT for a product that sees thousands of temperature cycles in its lifetime, but not much vibration other than from shipping.  The ALT would be focused on temperature cycling only and would likely expose it to a few hundred cycles or more.  The HALT would expose the product to much fewer temperature cycles, but also incorporates vibration stresses.   Thus, different types of failures could result from each test.  In HALT perhaps a weakness caused by vibration will occur that could show up during shipping and handling in the field.  In ALT, perhaps a failure caused solely by thermal fatigue would occur.  So if you only perform only one type of test, perhaps a potential field failure mode could be missed. 

More information about ALT can be found in the following blog articles:

Accelerated Temperature Humidity Testing Using the Arrhenius-Peck Relationship

Constant Temperature Accelerated Life Testing using the Arrhenius Relationship

Door Open/Close Accelerated Life Test Case Study

Accelerated Life Product Reliability Testing of a Carrying Handle

Accelerated Life Cycle Testing of a Case Handle

3. Perform Design Verification Testing (DVT)

Design Verification Testing is a comprehensive process to verify a product will meet all if its design requirements.  DVT is also referred to as verification or validation testing.  Obviously, this is done in the design phase before final production.  Examples of some of the parameters that are checked during DVT are:

• All product functions such as Electrical and Mechanical functions
• Product performance
• Climatic or environmental testing
• Electromagnetic compatibility (EMC)
• Safety testing
• Software validation

For example, a product could be exposed to specific types of climatic stresses such as salt corrosion, solar (UV), temperature-altitude stresses or water ingress.  These types of stresses would not commonly be used in a HALT or ALT.  Therefore, unique failure modes could be exposed in DVT. 

4. Perform Reliability Demonstration Testing (RDT)

The purpose of an RDT is to demonstrate the Mean Time Between Failure (MTBF) of a product.  Reliability Demonstration Tests are usually performed at a system level.  For example, a computer server that contains many components such as hard drives, fans, etc. is an example of a system level test.  RDTs are commonly performed on repairable systems.

RDTs incorporate a reliability percentage R and a confidence level C.  They are limited in using only the stresses the product will see in the field.  RDTs are focused on demonstrating the MTBF in the steady state portion of the bathtub reliability curve, where ALT’s are focused on wear-out.  Some manufacturers are required to show a minimum MTBF on their products before they can sell them to their customers. 

5. Incorporate a HASS or ESS Program

HASS stands for Highly Accelerated Stress Screening.  ESS stands for Environmental Stress Screening. Both are screening methods used to expose manufacturing defects that would cause a failure in normal field environments including shipping, handling and use.  Both HASS and ESS are performed during manufacturing on production products or components. 

The types of stresses used for HASS are similar to those used in HALT. HASS uses combined temperature cycling, random vibration and electrical loading/monitoring. HASS screens are performed in the same type of chamber that is used for HALT. The vibration in HASS is randomly applied over a broad frequency range producing energy to 10,000 Hz in 6 degrees of freedom.

ESS originated out of the military to improve the reliability of their complex products.  ESS typically uses temperature cycling and random vibration applied separately.  Products are normally electrically powered and functional tested during ESS.  Random vibration is usually preformed on and electro dynamic shaker.  “Environmental Stress Screening of Electronic Equipment”, DOD-HDBK-344, is a military handbook that provides guidelines for developing ESS programs. 

Both HASS and ESS are effective screening programs that yield more rugged/reliable products with less field failures and warranty expenses .  More information about HASS and ESS can be found in the following pages:

What is HASS Testing?

How to Implement a HASS Program

An Informational Guide to HALT and HASS

Environmental Stress Screening (ESS Test)

All of these test methods provide different benefits.  Not all of them have to be performed to produce a reliable product.  Contact DES to help determine what makes sense for your product. 

The post How to Make Your Product More Reliable Through Testing appeared first on Delserro Engineering Solutions.

DES president Gary Delserro is featured in an article published in Assembly Magazine on July 9, 2021.  Titled “Accelerated Life Testing,” the article discusses different types of manufacturing life testing and quotes Gary with reference to highly accelerated life testing (HALT):

“Companies have reported savings in the millions after using HALT,” claims Delserro. “The test can accelerate a product’s aging process from actual months into test minutes, and it can help you discover weaknesses in your product during the design stage. Combined vibration, temperature and electrical stress variables, as well as internal fluid pressure, are typically used during HALT to induce failures and uncover fault points. By using combinations of loads, we can uncover design or manufacturing process flaws before they reach your customer.”

The entire article can be found on Assembly’s website. 

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Customer Goal

A customer approached DES looking to perform Highly Accelerated Life Testing (HALT) on a new circuit board design.  DES and the customer agreed to test the circuit boards using DES’s traditional HALT test procedure which calls for hot/cold temperature steps followed by rapid temperature ramping, vibration steps and combined temperature and vibration stresses.  HALT testing on electrical componentry is quite common across industry to expose design weaknesses; both mechanical and electrical (What is HALT and Why Perform HALT?).  Typical failures include poor solder connections, overheating, component failure, etc. (What Kind Of Failures Occur During HALT?)

Results

The hot/cold temperature steps exposed soft failures such as power resets and lack of communication for the circuit boards.  One hard failure was also exposed during this stage which proved to be a recurring problem and thus an area of weakness in the product design.  The units functioned properly during the vibration steps and rapid thermal ramping stages.  The combined temperature and vibration stage, however, revealed the same issue as seen in the first stage on two other units.

The circuit board featured potted componentry for purposes exclusive to the customer.  This potted feature cracked on multiple units throughout testing and caused all sorts of communication issues for the units.  In 3 days the customer was able to expose a product design weakness that would most likely have caused a number of warranty and reliability issues.  In the words of the customer:

“The results from this testing have identified strong and
more importantly weak areas in our design.”

– Customer

HALT testing is a necessity for products with electrical circuity in terms of preventing field failures and high product return rates.  Problems such as these can be really damaging to a company’s bottom line if not addressed early in the design process.  Fortunately this customer has had experience with HALT in the past and chose to perform HALT before finalizing the product design.  DES has over 20 years of experience performing HALT testing on a variety of medical, commercial, industrial and military products.  Schedule your next HALT test with us by contacting us or call us at 610.253.6637.

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• What is HALT Highly Accelerated Life Testing and why perform HALT?
• What is a typical HALT procedure?

A Rapid HALT is an abbreviated HALT, typically one day of tests, making it a great cost-effective solution for those seeking faster qualitative results.  Exposing a product to a Rapid HALT early in the design process can help reduce product development time and cost by enabling manufacturers to identify flaws or areas of improvement before it’s too late.

Rapid HALT’s are a good tool for assessing the reliability of different suppliers of components but can also be used to assess the reliability of less complicated products.  For example, DES has performed Rapid HALT’s to evaluate the reliability of different suppliers of power supplies, cooling fans, and LED’s.  DES has also performed a Rapid HALT to study different fastening methods in order to determine which was more robust.

Rapid HALT profiles may vary slightly depending on the product.  Figure 1 illustrates DES’s standard Rapid HALT profile.  Vibration levels are ramped up concurrently with hot and cold temperature cycles.  The stresses are increased until the practical limits of products have been reached.  Examples of practical limits include the melting temperature of solder joints or excessive softening of plastics.  These stress levels are obviously well beyond the scope of most product designs and that is ok.  The purposes of any HALT is time compression by applying higher-than-normal stress levels.  The user should not necessarily focus on what level of stress caused the problem, but should focus on improving the weak points in their product.

Many times our customers are surprised with the Rapid HALT results because the less expensive components perform better.  Thus our customers are able to apply a significant cost reduction to their products.  This results in increased profits and reduced warranty costs.

For more information on HALT or other testing services, contact DES or call 610.253.6637.

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A customer approached DES looking to find an accelerated test solution for an AC powered cooling fan used in one of their products.  The product had been established in the marketplace and the company was now looking for ways to reduce cost by looking at different cooling fan suppliers.  Most fans, however, have a mean life rated for over 20,000 hours, so a typical accelerated life test would require a significant amount of time and money. 

DES Solution

Performing a quantitative accelerated life test on cooling fans presents challenges because they have such a long lifespan.  Reasonably speaking, the shortest quantitative solution for determining the lifespan of a fan could take as long as a couple months.  DES proposed a qualitative solution, a Rapid HALT.  A Rapid HALT (Highly Accelerated Life Test) is designed to apply a variety of stresses, concurrently, to a product in order to significantly time compress a product’s lifespan.  A typical Rapid HALT lasts only one day which is extremely convenient for companies that need results quickly.

Results

A sample size of 3 cooling fans were tested for 4 different fan suppliers.  We will refer to these suppliers as Supplier A, B, C and D.  All 12 fans were placed in the chamber together and a Rapid HALT was conducted.  None of the four suppliers survived testing without some issues but the results were still differentiating.  Supplier A had no electrical issues in any of its samples but the fan blades on all 3 samples vibrated off the armature.  Fans of Supplier B, all experienced sputtering of the fan blade and eventually saw two of its fans current levels drop to 0.  By the time testing was completed, none of the fans were functioning.  Supplier C fared slightly better than A and B.  One of Supplier C’s fans lost current at the most extreme step and never recovered.  The other two however, experienced fan blade sputtering but were functioning normally upon final inspection.  Supplier D performed the best out of the four suppliers and thus would be considered the most durable of the suppliers tested.  Only one of the fans experienced any issues, in which it lost current at the most extreme step.  Upon final inspection all of the fans were functioning normally.

There are other factors to consider such as price and accessibility but these results were able to successfully assist our customer in differentiating between the reliability of the four fan suppliers.  While a HALT is qualitative and will not produce an actual estimated fan lifetime, it is a great comparison tool to evaluate the reliability of different suppliers faster and less expensive than traditional testing techniques.

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If the product fails to operate, the temperature or vibration will be changed toward ambient room conditions followed by a short dwell period to see if the product recovers. If the product is non-operational after dwelling at ambient conditions, trouble shooting will take place to find the failed component. The failed component will then be removed, repaired or replaced with a new component (as is practical) in an effort to expand the test stresses.

Relevant Failures

All HALT failures are relevant unless it is determined that the failure was caused by a condition external to the product which is not a test requirement. Relevant failures may include, but are not limited to the following:

• Design and Workmanship Failures
• Failures caused by Poor Manufacturing
• Component Part Failures
• Multiple Failures
• Intermittent Failures
• Built-in-Test Failures

All relevant failures represent an opportunity for improvement and should be thoroughly investigated to determine their root cause. All relevant failures should be evaluated as to whether or not they can be corrected with a reasonable amount of effort and cost. However, all failures that prevent a product from functioning in its normal environment should be fixed! Figures 1 through 3 show examples of relevant HALT failures.

In Figure 1, the mounting tabs used to hold a power supply in place failed during vibration. Larger tabs with better stress relief grooves should be used in this case to better withstand the vibrations. The capacitor leads in Figure 2 failed due to repeated fatigue stresses from vibration. Improved mounting such as placing an adhesive under the capacitor could be used to prevent this type of failure which is common for large components connected by thin metal leads.

In the case of temperature related failures such as seen in Figure 3, the temperature at which failure occurred should be well outside of the expected operating range of the equipment.

Even in this case, an evaluation should be performed to determine if a component with an improved temperature rating can be economically substituted because the failing component may be a weak point in the product design.

Non-Relevant Failures

Failures listed below may be considered as non-relevant:

• Failures directly attributable to erroneous product manufacturing or operation.
• Failures resulting from improper test setup or procedure.
• Dependent failures, unless caused by degradation of items of known limited life.
• Failures occurring during test “down-time” such as during troubleshooting on the bench unrelated to the HALT Procedure.

Care should be taken when determining if a failure is non-relevant as this may result in missing an opportunity for product improvement.

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Specialized test chambers are needed to perform a HALT. Typical HALT chambers are shown in Figure 1. The specification for HALT chambers is typically the following:

Liquid nitrogen (LN2) is used to cool the air temperature in HALT chambers. This allows for very rapid temperature changes of 60°C per minute and a cold temperature extreme of -100°C.

HALT chamber heating is provided by high power resistive heating elements that can produce changes of 60°C per minute and a hot temperature limit of +200°C.

HALT chambers produce random vibration in 6 DOF simultaneously using pneumatic air hammers attached to the bottom of the chamber table. This means random vibration energy is applied simultaneous along three orthogonal translations and three rotations which is very unique to HALT chambers. Sometimes the vibration produced in HALT is called repetitive shock because pneumatic air hammers are used to produce vibration.

Random vibration accelerations up to 60 Grms and frequency content to 10,000 Hz are common. It is important to understand how the how HALT chambers compute Grms. DES’s HALT chambers calculate Grms using a 5 kHz bandwidth. Some chamber manufactures use a 10 kHz bandwidth which approximately doubles the computed Grms, but in reality the resultant vibrations are about the same! More information about random vibration can be found in our blog article Sinusoidal and Random Vibration Testing Primer

It is important that HALT chambers can be run in automatic or manual modes of operation. Temperature and vibration profiles are programmed to run automatically during parts of the HALT procedure. This allows the temperature rate of change to be accurately controlled during temperature transitions. The chamber can also be run in manual mode with the operator controlling the temperature and vibration set points. This is useful for other parts of the HALT procedure such as when operational or destruct limits are being determined.

Fixtures

DES’s has many stock channel fixtures that can be used for products with a flat top and bottom. Examples of DES’s stock channel fixtures are shown in Figure 2.

Custom-designed fixtures can be fabricated on a case by case basis. Figure 3 shows examples of custom-designed test fixtures. The fixtures must have a flat base with holes to enable them to be bolted to the chamber vibration table. Customers or DES can supply the fixtures used to attach the test units to the vibration table inside the chamber.

When performing HALT, it is desired to change the temperature of internal components as fast as possible. If products have existing vent holes or cooling fans, then air ducts can be placed to blow air through them as seen in Figure 2. Products with a sealed enclosure or case should be modified whenever possible to allow for internal airflow. This can be done by removing covers when practical or drilling holes in the enclosure. Air ducts can then be placed near these openings to direct air flow internally into the product.

Instrumentation and Monitoring

Monitoring can be accomplished with either digital recording instruments or by manually recording gauge readings or by visual observations. Monitoring sensors are usually thermocouples and vibration accelerometers. Reference thermocouples are placed at various locations on the product to measure the response temperatures on the product. Also, during the vibration step part of the HALT procedure, reference vibration accelerometers can be placed on the product to measure its vibration response. Therefore a digital temperature data recorder is needed and a vibration spectrum analyzer or Grms recorder is useful. HALT chambers will typically provide basic digital recording of the chamber temperature and table Grms. DES provides the equipment for recording all of the temperatures and vibrations. Many times the customer provides the equipment for monitoring the specific performance of their product. However, DES has the capability to provide all of the monitoring equipment and instrumentation if desired. DES has extensive experience in setting up custom monitoring to record many different parameters such as voltage, current, pressure, etc.

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Stage 1 is used to determine the HALT Operational Limits for temperature. The goal is not to cause destruction in Stage 1, but sometimes the operational and destruct limits occur simultaneously. The HALT Destruct Limits for temperature and vibration are typically found in Stages 3 to 5.

Temperature Step Stresses – Stage 1 (Figure 1)

Stage 1 is started with Cold Step Stresses. Testing is started at 10ºC and is decreased in 10 ºC increments until the lower operating limit is determined or the chamber minimum temperature of -100 ºC is reached.

The dwell time at each step is defined as the point when stabilization and saturation of the device and its components is achieved which is typically 15 to 20 minutes. Functional testing will occur during this stabilization period. The dwell time will be determined from temperature measurements obtained from thermocouples placed on the product. Thermocouple data from individual components that can be a source of heating or cooling are not used to define the dwell time.

The second part in Stage 1 is Hot Step Stresses. Testing is started at 40 ºC and increased in 10 ºC increments until either the upper operating limit is determined or the chamber maximum temperature of +200 ºC is reached. The dwell time will be established using the same procedure as for the Cold Step testing segment.

Note that the upper and lower temperatures may be reduced if material limitations, i.e., solder melting or plastic softening are exceeded. Also, it is good practice to perform a functional test of the product at room temperature or 25 ºC before starting a HALT to get baseline measurement on its performance.

Temperature Ramps – Stage 2 (Figure 2)

During this Stage, temperature cycles with rapid transition rates (ramps) will be applied to the product. The chamber air temperature will be changed at 60 ºC/minute. The hot and cold temperatures will typically range from 10 ºC above the lower operating limit to 10 ºC below the upper operating limit. These 10 ºC reductions are to allow for over shooting caused by changing the temperatures extremely fast. The dwell time, established in Stage 1, will normally be used at each hot and cold temperature. Five cycles are applied.

Vibration Step Stresses – Stage 3 (Figure 3)

A broadband vibration spectrum will be applied through the HALT chamber table. The HALT chamber table should apply random vibration energy to 10,000 Hz in 6 DOF (degrees of freedom). Vibration step stresses will start at 10 Grms and increase in 5 Grms steps until either the operating, the destruct limits, or the chamber maximum vibration level of 60 Grms is reached. At 40 Grms levels and above, the vibration step will be returned to 10 Grms for 1 minute to detect failures that could be hidden by extreme forces occurring at higher vibration levels. Dwell time at each step, will be approximately 15 minutes to accumulate fatigue damage. Grms is measured with a 5 KHz bandwidth. This test is performed at room temperature of approximately 20 to 25 ºC.

Combined Temperature & Vibration Stresses – Stage 4 (Figure 4)

Combined temperature and vibration stresses are applied in Stage 4. During this Stage, the chamber air is changed at 60 ºC/minute. The hot and cold temperatures are the same as those used in Stage 2. The dwell time at each hot and cold temperature will be the same as used in Stage 2. Vibration level is fixed during each temperature step and begins at 10 Grms and increases in 10 Grms steps until either the operating or destruct limits or the chamber maximum vibration level of 60 Grms is reached.

Temperature Destruct Limits – Stage 5 (Figure 5)

The cold temperature destruct limit is found by starting at the lower operating limit (found in Stage 1) and decreasing the temperature in 10 ºC increments until either the low temperature destruct limit or the chamber minimum temperature of -100 ºC is reached. The hot temperature destruct limit is found by starting at the upper operating limit (found in Stage 1) and increasing the temperature in 10ºC increments until either the hot temperature destruct limit or chamber maximum temperature of 200 ºC is reached. The dwell time established in Stage 1 is used typically, however dwell times may be reduced if the product stops operating or if failures occur. If the product fails to operate, the temperature will be reduced or increased towards 20 ºC to see if the product recovers. If the unit is non operational after stabilizing at 20 ºC, the product will be repaired (if practical) so that the test temperatures can be expanded. If it is not practical to repair the product, Stage 5 will be terminated.

Power On/Off Cycling

Powered on/off cycling is recommended at every temperature or vibration step to create additional electrical stresses. These power cycles will be conducted quickly but sufficient time will be allowed so as not to create artificial excessive overloads and failure modes. Powered on/off cycling may not be appropriate for every product as it may create artificial stresses and failure modes, or the product may take too long to power up.

Test Samples

The typical number of products tested simultaneously is 1 to 4 as practical based on the cost and size of the products. Additional spare parts or backup units (not under test) may be needed for spare parts to repair and continue with testing if a non-repairable failure occurs.

Test Reporting

High quality test reports written by DES will contain, at a minimum, plots similar to those shown in Figures 1 to 5. These plots will include measured chamber control temperature, vibrations and product response temperatures, vibrations along with an indication of where each failure or significant event occurred during the HALT. Additionally plots of test voltages, currents, pressures or other applicable parameters will be included as applicable. The report will also contain identification of samples, a list of test equipment and personnel, photographs of the test setup including response sensor locations, photographs of any physical failures and a summary of the test procedure and results.

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