In every field, there are always newcomers. The business environment has shifted due to the economic conditions over the past year or so. Many individuals are choosing early retirement when available. Due to significant layoffs, people are being required to perform tasks they have never handled before. Mergers might result in acquiring equipment that is unfamiliar. Additionally, there will always be individuals entering a field by choice, such as recent college graduates or those transferring from different departments.   Engaging with HALT presents an exhilarating challenge. For more than ten years, I've been thoroughly engaged in this process. I've encountered numerous engineers who possess a strong grasp of the process, but recently, I've noticed many individuals who are not very familiar with it and are eager to learn. Additionally, there's a group that prefers to argue over semantics rather than focus on the task at hand.   To begin, it's important to note that there isn't a single correct method to conduct HALT. Let's take a moment to examine what HALT is and what it is not. Usefulness of Accelerated Testing   Regardless of the perspective, business is challenging at the moment. Customers, whether they are individual consumers, government agencies, or internal departments, are demanding more for less. They seek high reliability, low cost, cutting-edge technology, and durability.   Admittedly, satisfying everyone is tough. You need to outpace your competitors to market while ensuring your product's longevity. How can you achieve this?   An effective way to address many of these challenges is by expediting the testing process. Waiting 20 years to see if a light bulb will last that long in your neighbor’s kitchen is not feasible. You need to accelerate the process.   While you can make a light bulb fail by dropping it, this only confirms that gravity works. A more logical approach is required, one that "accelerates" time to simulate potential failures. Various computer programs and scientific formulas can help correlate potential lifetimes, allowing you to identify likely failures in the field within days instead of years.   Why is this crucial? One significant company expense is warranty issues. When Ford Motor Company identifies and resolves a weakness before a part reaches a car on the road, their accounting department highlights the savings achieved by Engineering. Detecting issues early can save millions and enhance customer confidence. You benefit by reducing costs and increasing revenue through repeat business.   Starting Temperature The optimal way to begin the test is at laboratory ambient. Why do I use this term, you might ask? As a member of several IEC (International Electrotechnical Commission) working groups, I've observed that the term "ambient" has evolved to mean different things to different people over the years. Traditionally, ambient referred to the chamber temperature surrounding the product at any given time. However, most people now interpret it as the room temperature where testing occurs. By specifying "laboratory ambient," I aim to ensure that testing starts at approximately room temperature, avoiding confusion with the temperature from the previous chamber test. It's better to be cautious!   Always monitor the product continuously. Ford Electronics, before becoming Visteon, publicly reported that 50% of intermittent failures would not have been detected without constant monitoring. It's insufficient to merely take a reading at the start and another at the end.   A Series of Tests Considering that there isn't a single perfect method to conduct a HALT, here are some fundamental ideas to remember. HALT consists of a series of tests. Ideally, you should have multiple units available for testing, with one designated for each test in the series.   From a purist perspective, it's best to begin by testing in individual environments, then proceed with combined environments for comparison. We recommend the following six standard tests, although there are other possible approaches:   Cold only Heat only Vibration only Heat with vibration Temperature swings Temperature swings with vibration   Additional factors can certainly be included. If you're concerned about lower temperatures, consider adding Cold with vibration. If humidity is a worry, conduct a humidity-only test before combining it with other conditions like thermal and vibration. Power cycling can also be highly advantageous. Before testing begins, it's crucial to thoroughly understand the product being tested. Familiarize yourself with the end environment where it will be used and test accordingly. Remember: End users are always harder on a product than anticipated, yet they will expect it to function regardless. Step by Step After selecting the environment, how do you begin? The key is understanding your product. Is it as small as a PCB or as large as a tank? How long will it take to stabilize at a certain temperature? Are some components more prone to failure? How do you determine if your product has stabilized at temperature? Consider the example of what I'm testing today: a vehicle console nearly as wide as the van's ceiling. It's impossible to choose one representative spot and assume uniformity across the unit. The rule of thumb is: the larger the product or the more diverse its components, the more thermocouples are needed. Control should still be based on one main thermocouple, placed where it best represents the unit or on the most sensitive component, depending on your primary concern. A good starting point for all tests is laboratory ambient, typically around 25°C. If necessary, fixture your product and connect any required wiring. Remember, your wiring or cabling will experience the same extremes as your product! The order of tests is entirely your choice. However, starting with single environments before moving to combinations provides a solid baseline. For instance, if your first test combines heat and vibration and a failure occurs, can you tell which caused it? Or was it the combination? If you've already conducted separate heat and vibration tests, it's easier to identify whether a specific environment or the combination caused the failure.   What is a Failure? Different companies evaluate failures in various ways. I visited a company where they set aside products due to pinpoint scratches in the paint job. For them, this was considered a significant "failure" that prevented them from shipping the product to a customer. Some consider the first intermittent failure as the limit they are willing to accept. Others prefer to reach a complete failure. This is something to consider when planning your test—what will you define as a failure? The Tests Having reviewed the key points to consider before testing, let's examine the tests themselves. It's important to understand that more is involved than simply pressing the "Run" button on the computer. You've already seen the need for advance planning. We'll explore the different considerations for each test and the reasons for conducting them. Cold Step Test Cold temperatures tend to be the least destructive among single environments, making them a good starting point for testing. You can determine the size of the steps based on your product knowledge. If you are concerned about cold effects, use smaller steps. If you seek baseline data, start with larger steps and reduce them if a premature failure occurs. Many engineers are comfortable starting with steps of a 10°C per minute change rate in cold conditions. After deciding on your ramp rate, determine your dwell time. How long should your product remain at a certain temperature before ramping again? The general consensus is to keep the dwell time to the minimum necessary to stabilize the product. For a PCB, this might be only five minutes, while an assembly might require a longer time. Again, rely on your expertise to decide.     Take a look at the following graph: The chart above shows an example of what could be used.  Starting at laboratory ambient and holding until stabilization, the test lowers 10°C as quickly as possible, and then holds for ten minutes.  These steps are continued until there is a failure. Heat Step Test The heat test follows a similar procedure, but in the opposite direction. It relies on the same principles as the cold step test. Start by stabilizing at the laboratory's ambient temperature, then proceed with ramping and dwelling. Since heat is generally more damaging than cold, you might opt to increase the temperature at a rate of only 5°C per minute rather than at a faster pace.     I once had the opportunity to work with a company whose product was intended for use in a hospital setting. Their first significant failure occurred at just 2°C above the typical laboratory temperature. Initially, they weren't worried, thinking that hospitals are air-conditioned and the surrounding air would never become too warm. I shared with them my experience of an extended hospital stay where the temperature was controlled based on the time of year. The heating was activated due to the date, not necessity, resulting in patient rooms reaching nearly 30°C. The company redesigned the board, and their product is now the market leader. Moral: Ensure there is a margin between expected usage conditions and what your product can actually withstand. Consider the worst-case scenario and then add a safety margin. In essence, if something can go wrong, it will.   Vibration Only Test You've completed the simpler tests, such as heat and cold. You've monitored and recorded the data. You've implemented any changes you deemed necessary. Now, you're prepared for vibration testing. Begin with the temperature set to laboratory ambient conditions once more. This ensures that temperature will not influence the test. While this may not reflect a real-world scenario, our focus is solely on the vibration for now.   The standard method for measuring a vibration test is by using the g level. But where should we measure the g from?   Measuring from the bottom of the vibration table primarily indicates the table's activity, which may not accurately reflect your product's behavior. The ideal location for the accelerometer is on or near your product. Some opt to attach the accelerometer to the fixture securing the product, which is completely acceptable. If attaching it to the product or fixture is not feasible, mount it near the fixture on the table's surface. This will provide a reasonably close approximation of what the product experiences.   Unlike temperature, vibration needs to be managed in very small steps. It can be challenging to control precisely, so we recommend starting at 2 g’s and increasing by 2 g’s incrementally. The dwell time depends on your understanding of your product. Allow sufficient settling time, often ten minutes. Continue increasing until you observe what you consider a failure, while monitoring and recording data throughout the process. Combinations Now comes the exciting part. You've finished the tedious steps. You've gained more insight into your product and the reactions of your team members. ("You're doing what to my design?") Thermal Swing Test You've completed tests for cold, heat, and vibration. The next logical step is the thermal swing test, which combines the heat and cold tests. Adjust the chamber to start at the laboratory's ambient temperature and let the product acclimate. Choose whether you prefer to increase or decrease the temperature initially. Introducing nitrogen into the chamber air will aid in eliminating any residual humidity in the product, so this should be factored into your decision.   Choose the ramp increment, usually 5 or 10°C at a time, and determine your dwell time. Then begin.   As illustrated in the chart, each step expands. Suppose you decide on 5°C increments with a starting temperature of 25°C. You’ve opted for 5-minute dwells and prefer to increase the temperature first. Here is the basic scenario: Continue testing until a failure occurs.   Note:  It's common for a product to fail at very low temperatures and then start working again once it's warmed up. If you encounter a failure during the cold phase of this test, it's recommended to proceed to the next hot phase to see if it resumes functioning.   There are valid reasons for conducting the swing test. The difference in thermal coefficients can cause parts to separate from each other, sometimes leading to cracks. By applying these changes rapidly, we are stressing the unit beyond normal conditions. Some argue that you will rarely experience a temperature change of over 30°C per minute, but consider the following:   I live in Michigan. While not the coldest state in winter, it's common to experience a wind chill of -40°C at least once each winter. Imagine my car gets stuck in the snow about a mile from home. I decide to walk (we Michiganders are a resilient bunch).   My cell phone goes from about 25°C to -40°C as I hold it to my ear to call my husband and inform him of my predicament. Since he's on the road, I have to use my reliable palm computing device to find his number.   I arrive home, shivering, turn up the heat, and stand by the heater—still using my trusty phone. The phone and computer warm back up to 25°C as the hot air blows on them. By this time, not only have the electronics been stressed, but so have I! I'm sure you can think of other extreme situations where we subject electronics to stress. Heat with Vibration Test Let’s conduct some shake and bake. Not for dinner – although that’s been done! It’s time to combine heat and vibration to test your product.   What vibration level will you select? Suppose you know your product failed at 10 g’s in a previous vibration-only test. Since you already know this is the failure point, there’s no need to reach that level. You want to discover what occurs when thermal factors are combined with vibration.   Most engineers I have worked with opt for a level around 80% of the failure point. In this case, that would be 8 g’s. What is the optimal method for conducting a combined heat and vibration test? You should rely on your expertise once more. It's advisable to closely follow the original heat test you performed, beginning again at laboratory ambient. This will provide a reference point for anticipating where your product might exhibit a heat-related failure. If the temperature was very high, you might consider omitting some of the lower temperatures. For example, if your product didn't fail until 110°C, you might want to start at around 60°C and proceed from there.   The chart example above illustrates ten-minute dwells, with vibration applied (below failure level) for two minutes every five minutes. Pulsing can lead to failures, but so can continuous operation. It's your decision on the optimal way to conduct the test.   This is where comparison becomes intriguing. Typically, the product will fail at a slightly lower temperature when vibration is introduced compared to using heat alone. However, there are always exceptions. This particular test should provide valuable insights into how your product will withstand a combination, which it will likely encounter in real-world usage. Thermal Swings with Vibration Test Utilize the insights gained from your heat and vibration tests to apply similar principles to thermal variations and vibration. If your failure was significantly beyond laboratory conditions, consider skipping several steps.   I discovered something intriguing from a machine design magazine article: some companies use extremely cold temperatures to "de-stress" equipment destined for high-vibration environments. Typically, we learn that any action taken on a product reduces its lifespan. However, after implementing the article's principles, I conducted experiments with customers across various product types. In every instance, combining vibration with cold temperatures allowed the products to endure more vibration than at ambient conditions. You might observe similar results during your swing test with vibration. Additionally, consider including a cold test with vibration if your product needs to withstand low temperatures. Now What? With all these numbers and failure times, what should you do next? What are your goals?   There's no need to over-engineer. If your product meets real-world requirements with a reasonable margin, you might not need to make any changes. For example, Microsoft extended their mouse warranty from one year to three after testing, without worrying about warranty issues.   Not breaking something doesn't mean failure on your part. It likely indicates a robust product ready for market. If you do encounter a failure, view it positively. HALT is a learning tool, helping you identify premature product end-of-life quickly, avoiding prolonged learning through warranty replacements. No Magic Bullet Will a HALT test predict the exact market lifespan of a product? Probably not. Without field failures on the same or a similar product, establishing a time correlation is challenging. However, if you can replicate field failures in the lab under certain conditions, you can make a good correlation.   Is a rapid thermal cycling chamber with tri-axial vibration the only equipment you'll need? If that were true, I'd be wealthy. Just as a toolbox requires multiple tools, testing equipment should not rely solely on HALT, despite its value.   One positive industry shift is the increased sharing of non-proprietary information among engineers. To learn more about HALT, explore groups like the IEEE AST (Advanced Stress Testing) group, attend seminars, and join user groups. Sharing knowledge helps us avoid starting from scratch. Trustworthy sources are invaluable. Final Note When conducting HALT testing, rely on your product knowledge. Preplan with the end-use environment in mind. For plastics, know melting points. Keep an open mind during tests, recognizing product failures as learning opportunities, not personal failures. Collaborate with design, project, production engineers, management, and anyone offering valuable insights.   I enjoy working with HALT and wouldn't choose any other industry. Like BASF's motto, "We don’t make the _____ … we make it better," I help create better products, enhancing reliability, reducing costs, and improving safety. As a child, I wanted to bring world peace, but as an adult, I realize change is gradual. As a teacher and manufacturer, I see that each of us can contribute to a better world. You now have the opportunity to excel at your job, produce better products cost-effectively, and improve others' lives by making them safer, easier, and more reliable.

Understanding how HALT and HASS aid in creating a better product requires a grasp of these testing methods. We'll start with a brief overview of each, followed by the main highlights: VTC-9 HALT and HASS Chamber HALT (Highly Accelerated Life Test): During product development, HALT is used to detect early weaknesses by progressively increasing stress levels until the component fails. Afterward, weaker components are substituted with stronger ones, improving product reliability and potentially predicting an extended product lifespan. HALT is performed during the prototyping (design phase). HALT is a crucial tool for predicting potential failures throughout the product’s life. Furthermore, HALT helps identify the product's ultimate limits. HALT is an effective way to lower warranty costs by detecting possible failures before they occur in the field. HALT enhances the understanding of the product’s behavior. HALT is most effective when multiple stresses are applied simultaneously, such as temperature, vibration, voltage, temperature ramp rates, etc. HALT is also used during R&D stages to identify design flaws. HALT pushes a product to its failure point. Pushing a product to its limits through testing provides numerous benefits. HALT testing uncovers design issues that might not surface in real-world conditions for years. For example, it can identify exposed electrical connections prone to corrosion, mechanical supports that lack sufficient strength, or switches that might malfunction under the stress of intense vibration in cold environments. Through HALT testing, the engineering, QA, manufacturing, and program management teams can evaluate the results and integrate them into an updated design to address and remove flaws and weaknesses. VTC-32 HALT and HASS Chamber HASS (Highly Accelerated Stress Screening) is a production screening method designed to identify and eliminate weak components or failures. It accelerates the real-world lifespan of a product by applying multiple stresses, including temperature and vibration, and sometimes voltage and humidity. The main goal of HASS is to reveal latent defects that might have been introduced during manufacturing. These defects are usually related to design and should have been identified and removed through reliability enhancement testing in the design phase. HASS is conducted during the manufacturing (production) phase. HASS involves a series of tests that can be applied to anywhere from 1 to 100 percent of the outgoing products. HASS minimizes failures in the field. HASS subjects products to conditions more extreme than those they would typically encounter in the field. HASS serves as an inspection process. HASS applies stresses that reveal numerous flaws present in the production process, such as cold solder joints, loose hardware, defective components, etc. HASS identifies these flaws in the shortest time possible. HASS is an indicator of reliability. The expense and occurrence of product failures in the field can be very high. However, utilizing HASS enables manufacturers to detect failures before they happen in the field. This approach saves money, time, and reputation, while also decreasing the number of faults that must be managed in the field.

System Description The humidification systems provided with Hanse Environmental, Inc. chambers utilize the latest in ultrasonic nebulization principles to generate the moisture required in the chamber. The ultrasonic nozzle uses air and water under pressure. Atomized water leaving the nozzle is hit by the air reflected by the resonator as sound waves.  It is then nebulized into very small particles, like a fog, and rapidly absorbed by the air. The resonator is adjusted at the factory for maximum atomization and proper fog pattern. The fog pattern can be narrowed by moving the resonator further from the nozzle tip, and conversely, widened by moving the resonator closer to the tip. The water used in the humidification system can be demineralized by the optional  D.I. bottle. In addition, a water quality light is included to monitor the quality of the water generated by the D.I. bottle. The D.I. bottles are a mixture of bed resin that contains positive and negative charged resins.  These resins remove the minerals from the water. The D.I. bottle supplied with the Hanse Chamber is a 1 cubic foot bottle. Installation The nozzle(s) is installed at the factory for proper distribution of the moisture introduced into the chamber. Even though the nozzle(s) is designed for the temperature extremes experienced in the normal operation of the chamber, it is recommended that the nozzle(s) be removed when humidification testing is not being performed. The nozzle(s) mounting brackets are designed for ease of installation and removal. The direction of the nozzle(s) has been determined at the factory to maximize the distribution of the moisture within the chamber and should be maintained within the configuration. The nozzle(s) is  provided with hose connections that can be made within the confines of the chamber when installing or removing it. This will reduce the time required to go into humidification testing. Operation The water and air supply to the nozzle(s) is regulated by in-line pressure regulators. The water pressure to the nozzle(s) is adjusted at the factory to provide the proper amount of moisture to the chamber. The air regulator should be adjusted to maintain the air pressure to the nozzle(s) at a  minimum of 15 psi above the water line pressure. This is necessary to provide enough air pressure to open the water valve internally to the nozzle. This will  allow atomization to begin. The air and water supplies to the nozzle(s) are controlled by 24 vdc control valves. The valves are controlled by the mode of operation of the chamber. When the humidification mode is disabled, Event 4 (digital out 4), the water supply is turned off ,and the line(s) is vented to drain. Similarly, the air lines are turned off and ported to exhaust also. This prevents an inadvertent operation of the system. When humidity is called for, Event 4 (digital out 4) enabled, and the nozzle(s) have been installed in the chamber, the water valve opens applying pressure to the nozzle(s). In addition, when the set point is above the humidity level in the chamber, the air valve opens which applies air pressure to the nozzle(s). This air pressure results in the opening of the water valve internal to the nozzle(s) and the atomization process is started. As the humidity level in the chamber reaches the set point, the control system will start controlling the air valve to take control of the humidity level in the chamber. The valve will remove air pressure from the nozzle(s) for longer and longer periods to control the humidity level within the set point parameters. If the humidity function is turned off, Event 4 (digital out 4), then the system reverts back to the condition described above and the air and water lines are ported to exhaust condition. At this point the nozzle(s) can be safely removed from the chamber once they have cooled off. If during normal operation of the humidification system the water quality light goes from green to red, the D.I. bottle should be scheduled for regeneration at the earliest possible time with out interrupting a test. The water quality light may indicate red if the system has been sitting for some time between operation. To test if the water is OK, run a small amount of water through the system. The light will turn green immediately if the D.I. bottle is OK. If the system is going to be operated for long periods of time in the humidification mode, it is recommended that a second D.I. bottle be installed with the water quality light in the line between the bottles. In this matter, if the light indicates that the water quality from the first bottle is not in spec, the water is still being treated by the second bottle and will continue to meet the water quality requirements of the system. When the humidification test is completed, put a second bottle in the place of the first bottle, have the first bottle regenerated and place it no the location of the second bottle. In this matter you will utilize the bottles to their maximum, and not regenerate them unnecessarily. Maintenance The humidification nozzle(s) do not require routine maintenance. The water supplied to them should be free of debris and suspended solids, and it is recommended that a 10 micron filter be installed between the chamber and the water supply. This will prevent premature plugging of the nozzle tip. The D.I. water bottles will require periodic regeneration that is dependent on the frequency of use and the quality of the raw water system. If the chamber is to be installed in a location that has particularly hard water or water with high mineral content, it is recommended that a second D.I. bottle be installed, or a small Reverse Osmosis system be installed ahead of the D.I. bottle(s) to extend their life. This system can be sized by the factory and local installation arranged if desired. Regeneration of the D.I. bottles can be done by any qualified pure water vendor. In Michigan, call Hi-Tech Environments at (810) 620-3333 for the name of the nearest qualified vendor or to arrange for replacement bottles.

Overview HanseView allow for remote control through text files. This can be done on a local computer or via file sharing. Basic concept is that a command written to a text file is read by HanseView then executed and output placed to a text file. This remote control capability allows for test stand integration. You can then use 1 of two models. Have test stand send set point commands or profile start stop commands to control chamber then read back current status. Other option is to have test stand read only status and react to conditions and time to perform necessary equipment test. Video Tutorial Simple Demonstration Note on Version 3 HanseView program directory is been moved out of Program directoy and placed by default C:\HanseView instead of C:\Program Files\HanseView. Run: Notepad Open: "C:\Program Files\HanseVIEW\Chamber.INI" Find Section: "[System Parameters]" Add or Change:Remote Control File=C:\Program Files\HanseVIEW\RemoteControl.txt Save & Close file Run: HanseVIEW Run: NotePad Open: "C:\Program Files\HanseVIEW\RemoteControl.txt" Type: run Save the File Hanseview will start with stop code "Remote Start" Defining Remote Control File C:\Program Files\HanseVIEW\Chamber.INI contains section [System Parameters]Remote Control File=C:\Program Files\HanseVIEW\RemoteControl.txt This specifies the file you will write to. HanseVIEW will only load new setting on startup For Status see included "RemoteControl.txt" file and "RemoteControl.status" response file HanseVIEW tracks changes to the file and executes ASCII text commands written to the text file. Basic Commands Run Start the currently loaded profile to run stop Stops currently executing test status Writes current time/date and test status to RemoteControl.Status file (text file) load c:\Program Files\HanseVIEW\Profiles\Default.vcm Loads profile Default.vcm into the controller Added manual controls to file interface in 2.2.3 mant sp,rate Manual set point and rate for temperature manv sp,rate Manual set point and rate for vibration mana hex Manual auxiliaries see table bellow. This is a conversion of 16 bit binary to hex. First bit is Aux 16 last bit is Aux 1 Sample Programs: Sample BASIC Program to run chamber fileno=FreeFile() Open "c:\Program Files\HanseVIEW\RemoteControl.txt" for output as fileno Open "c:\Program Files\HanseVIEW\RemoteControl.txt" for output as fileno Open "c:\Program Files\HanseVIEW\RemoteControl.txt" for output as fileno Print#fileno,"run" Close fileno Sample BASIC Program to stop chamber fileno=FreeFile() Print#fileno,"stop" Close fileno Sample BASIC Program to load a profile fileno=FreeFile() Print#fileno,"load c:\Program Files\HanseVIEW\Profiles\Default.vcm" Close fileno Notes These samples assume both programs are running on same computer. UNC network name can be substituted for "c:\Program Files\ChamberView\" to run remotely. Appropriate error handling ust be added for unavailable files or machines. Actual "RemoteControl.txt" file spec is defined in HanseVIEW setup, but it should be local to HanseVIEW controller due to poll rates. We generally put the Remote Control file in a directory by itself with read/write privileges if network access is desired. Response file is always C:\Program Files\HanseVIEW\RemoteControl.status If network access is desired this directory is shared with Read/Only Attributes. Status File Format If you install the demo & HanseVIEW software on same computer this should also work for you. If you ran HansVIEW PRIOR to running the demo the first time, you would need to restart HanseVIEW to activate the remote control. Example Status File. Please note yours will change based on what options and inputs are selected. It is bes to make your prgram search the Varaible name to find it's value May 29, 2014 14:34:29 Channel 3 Temp Below Low Limit Data directory C:\HanseVIEW\Data\AAR\Thermal Test Out\Heat Step Test Out Elapsed Time 0:00:06 Remaining Time 1:55:3600 Profile Segment 1 Vibration1 Process Variable  0.000000 Vibration2 Process Variable  0.000000 Vibration3 Process Variable  0.000000 Vibration4 Process Variable  0.000000 Vibration Controller Process Variable 0.000000 Vibration SetPoint -299.899994 Product Process Variable 25.000000 Air Process Variable 25.000000 Temperature Setpoint -299.899994 Temperature3 Process Variable  -56094.765625 Temperature4 Process Variable  -56094.765625 Temperature5 Process Variable  -56135.703125 Temperature6 Process Variable  -56135.703125 Temperature7 Process Variable  -56135.703125 Temperature8 Process Variable  -56094.765625 Temperature9 Process Variable  -56094.765625 Temperature10 Process Variable  -56135.703125 Temperature11 Process Variable  -56135.703125 Temperature12 Process Variable  -56135.703125 Temperature13 Process Variable  -56133.664063 Temperature14 Process Variable  -56133.664063 Temperature15 Process Variable  -56133.664063 Temperature16 Process Variable

Ford Motor Company has been using Hanse Environmental testing systems for years. See the video below by Ford on the use of our testing systems.

A Tutorial by Lloyd W. Condra, Hanse Environmental, Inc. Environmental stress screening (ESS) is one of the most widely used of all accelerated reliability tests. It precipitates latent defects, which are detectable only with the application of stress. Latent defects are introduced into the product during manufacturing, since design-related defects should have been detected and eliminated by reliability-enhancement testing during the design phase. Figure 1 illustrates the ESS concept. ESS is effective only for a product with an infant-mortality region, which is indicated by a decreasing initial failure rate in Figure 1. The optimum ESS time is t0, since at that point, all the infant-mortality defects have been screened out. If ESS ends before t0, the product still contains infant-mortality defects which will be found by the user of the product. If ESS ends after t0, useful life is consumed without improving the failure rate. The failure rate may not be zero even after t0. The failures occurring after t0 are not infant-mortality failures though, and they must be dealt with in ways other than ESS. Many attempts have been made to prescribe standard ESS processes, but since ESS processes are product-specific, the most effective ones are based on a knowledge of the product, its potential defects and the stresses that cause them.1,2,3,4 An effective ESS process generates valuable data which can be used to improve the product as well as to screen out defects. Unfortunately, when ESS is viewed only as a requirement imposed by the customer or the market, its full benefits are not realized. The compliance-based approach treats ESS like a cookbook process, in which the product is exposed to a standard set of stresses, at standard levels, for standard lengths of time. Little attention is given to the failure mechanisms, to how they are distributed in time, or to how the failure data can be used to improve the product. Compliance-based ESS provides few benefits other than satisfying a customer-imposed requirement. Compliance-based ESS users can incur unnecessary expense. Table 1, 2 shows a typical ESS program implemented by a manufacturer of aerospace electronics equipment. From a physics-of-failure point of view, these conditions are practically identical and, with minor modification, they could all be conducted in a single environmental test chamber. Since the compliance-based approach does not bring this level of understanding to the process, each condition was implemented as stated, and a separate test chamber was required for each one. The physics-of-failure approach to ESS is based on an understanding of the potential types of latent defects in the product, the failure mechanisms and the stresses that cause them.5,6,7 The ESS conditions are set up to precipitate those defects, and the data is used to determine their causes and distributions. Failure data is communicated to the appropriate design and manufacturing personnel and used to make changes to improve the product. If it is properly set up and operated, a physics-of-failure ESS process can be extremely cost-effective. Setting Up the ESS Process ESS is product unique, since each product has its own set of potential defects and since the applied ESS stresses affect each product differently. Even though the ESS process must be set up individually for each product, there are many common features of both products and stresses which cause many ESS processes to be similar. The stresses applied in ESS are expected to precipitate manufacturing defects. They are not necessarily those the product will see in service. The two most common ESS stresses for electronic products are temperature cycling and vibration. They may be applied sequentially or simultaneously. It is critical that electronic equipment be monitored during ESS. This is the only way to detect failures under extreme conditions. More importantly, the stresses used in ESS can induce reversible damage not detected in tests conducted at ambient conditions. This induced damage is itself a latent defect, and the ESS process can actually cause early field failures. Reducing or Eliminating ESS Since ESS is an inspection step, it does not add value to the product and should be reduced or eliminated as quickly as possible. This cannot be done without proper justification, which requires relevant data. ESS must be set up to provide data which can be used to reduce or eliminate it. The following eight steps illustrate what should be done: 1. Collect failure rate data during the ESS process. Failure data must be collected, not just at the beginning and the end, but during the ESS process. It is not enough to know that failures occurred; their time of occurrence must be recorded. Data from all ESS attempts, whether or not there was a failure, must be collected and recorded. 2. Prepare a plot of failure rate vs time. This is the type of plot shown in Figure 1. If the failure rate decreases with time, there is an opportunity to reduce it if proper product improvements can be made. If the curve is constant, or if it increases with time, the ESS process cannot be effective because either there are no infant-mortality defects or the wrong stresses, or levels thereof, are being used. If this is the case, ESS should be modified or discontinued and some other means of product improvement must be implemented. ESS may be conducted anywhere in the manufacturing process flow. Table 2 shows some examples of the types of stresses used for ESS at the component, subassembly, assembly and system levels for electronic equipment.8 Table 38 shows the types of defects which may be detected by temperature cycling and vibration. The specific levels of ESS stresses are selected to precipitate the relevant defects in a relatively short time, and yet not consume a significant portion of the life of non-defective items. For electronic equipment, the lower end of the temperature cycling range is usually from -40(degree)C to -50(degree)C, and the upper end is from +75(degree)C to +85(degree)C. The rate of temperature change can also be important. Figure 2 illustrates the effects of temperature rate-of-change on surface-mount transistor lifting.7 Selecting the vibration level can be quite challenging, especially if the defects are susceptible to a range of frequencies. In general, multiaxis, repetitive shock vibration is much more effective and efficient than single-axis vibration. Simultaneous temperature cycling and vibration also are much more efficient than either separate or sequential application of the two stresses. 3. Analyze failures and separate them according to failure mechanism. All failures must be analyzed in order to take corrective action. It is truly amazing that many ESS operations do not include any structured method to analyze the failures and to provide the results to those who can take the proper corrective action. 4. Prepare plots of failure rate vs time for each failure mechanism. After this is done, the criteria of Step 2 must be applied to each failure mechanism. Again, only failure mechanisms with decreasing failure rates can be attacked with ESS. 5. Improve the product. Without using the data generated by ESS to improve the product, including design, components, materials and processes, there is no hope of reducing or eliminating the ESS process. If the staff responsible for the ESS process is not the staff responsible for designing and manufacturing the product, it is important that good communication take place between the two groups. 6. Collect and analyze ESS data for the improved product. If the proper steps have been taken to improve the product, then the area under the infant-mortality region of the failure rate vs time curve should be smaller. This may result from either a reduced slope of the curve or from a shorter time in which it reaches a constant failure rate. 7. Modify ESS conditions to reflect the new failure rates. As failure mechanisms are eliminated, the stresses that precipitate them may be eliminated. If they occur in shorter times, then the duration of the ESS process may be shortened. In some cases, additional stresses or increased levels may have to be introduced to detect failure mechanisms which were not expected. If this is the case, care must be taken to avoid introducing irrelevant failures. 8. Reduce or eliminate ESS as warranted. If the ESS process has been set up properly, and if the proper data is collected and used effectively, it will result in a continuously improving product. Eventually, a point will be reached where the ESS process may be reduced significantly or eliminated entirely. It may also be possible to reduce the frequency of ESS by going from a 100% screen to a sample screen. The effectiveness of ESS ultimately must be evaluated economically. This analysis is based on the cost to conduct ESS, the cost of field failures, and the frequency of occurrence of field failures.7,9,10,11,12,13,14 ESS costs include the cost of capital equipment, the recurring cost of conducting the process, the cost of analyzing and repairing failures, and the risk of actually introducing new failures into the product. The benefit is in the reduced costs of field failures. Effectiveness of ESS The references contain many examples of the successful use of ESS. AT&T called its process environmental stress testing (EST) to emphasize the fact that the company used the results to make product improvements.15 The process combined temperature step stress and temperature cycling between -20(degree)C and +70(degree)C for circuit card assemblies. Figure 3 shows a plot of failures vs the number of cycles in the EST process. From the data in Figure 3, the investigators concluded that the optimum number of temperature cycles was 16. In addition to the improvement in outgoing quality, the investigators tracked field failure results. They reported a five-fold improvement in product which had been exposed to EST, compared to product which was not exposed to EST. Although some ESS practitioners believe that the process should always be conducted on 100% of the product, a sample EST process has been implemented successfully.15 One two-stage ESS process for laser diodes was comprised of a steady-state burn-in at 165(degree)C and 10 kA/cm216 The results showed that unscreened lasers had a medium lifetime of about 600 h, compared to about 6,000 h for screened lasers. for 2 h prior to assembly, and a second steady-state burn-in at 70(degree)C for 150 h after assembly. In another study on laser diodes, AlGaAs laser diodes were exposed to an ESS process consisting of operation under power in inert atmospheres.17 The results are shown in Table 5. Again, significant improvement in operating reliability was obtained for products which had been exposed to ESS. If a product has a very low failure rate, the design and operation of the ESS process can be quite complex. McClean reported the use of a technique called highly accelerated stress audit to screen printed-circuit card assemblies.18 The screening stresses were temperature cycling and vibration, with power being applied during the process. As the name implies, the test was applied on a sample basis. As noted in these examples, the development and operation of an ESS process must be highly customized to the product being screened. Perhaps the greatest benefit of ESS is the hands-on knowledge and experience about the product gained by those who design and manufacture it. For this reason, it is not a good idea to assign the ESS process to a reliability department or a third-party screening organization with limited capability to change the design or manufacturing processes. Alternatives to ESS ESS is effective only when the product has an infant-mortality region. If this is not the case, other methods must be used. Some other methods which also involve the application of stresses are ongoing reliability testing (ORT), ongoing accelerated life testing and periodic requalification. ORT exposes a small sample, for example, less than 1% of production on a regular basis, to stresses at or slightly above the operating range for periods ranging from a few days to a few weeks. All failures are analyzed, and the data is used to improve the product. At the conclusion of the test, the surviving samples are shipped as regular product. Ongoing accelerated life testing is similar to ORT, except that the stresses are somewhat higher, and the test is continued until the samples fail. Since this is a destructive test, the sample sizes may be somewhat smaller than those of ORT, especially if the product is an expensive one. Periodic requalification involves the repetition of the qualification procedure, or an abbreviated version of it, on a periodic basis (usually once or twice per year). This type of test had its beginning in some of the U.S. military standards. Since periodic requalification does not involve a wide range of sample lots and since it is expensive, it is losing popularity. Summary The overall purpose of ESS is to assure that, once a product is qualified, there will be no uncontrolled variations in the individual items during the production phase. The application of stresses is necessary to detect some defects which cannot be observed by functional or visual observation. The only realistic way to develop and operate an effective ESS process is to use the physics-of-failure approach. This requires an understanding of the product, and knowledge of the types of defects and the types of stresses which precipitate them. Almost by definition, a significant amount of trial and error is associated with developing efficient ESS processes; but once the basic knowledge is gained, it can be applied to a wide range of products. In most cases where ESS has been implemented, it has proven to be quite effective in reducing overall product costs. References 1. MIL-STD-2164 (EC), Military Standard Environmental Stress Screening Process for Electronic Equipment. 2. DoD-HDBK-344 (USAF), Environmental Stress Screening of Electronic Equipment. 3. Environmental Stress Screening Guide, Technical Report No. AD-A206, U.S. Army, Ft. Belvoir, VA, January 1989. 4. Environmental Stress Screening Guidelines for Assemblies, Institute of Environmental Sciences, March 1990. 5. Pecht, M., and Lall, P., "A Physics of Failure Approach to Burn-In," Proceedings of the ASME Winter Annual Meeting, 1993. 6. Lambert, R.G., "Case Histories of Selection Criteria for Random Vibration Screening," The Journal of Environmental Sciences, January-February 1985, pp. 19-24. 7. Smithson, S.A., "Effectiveness and Economics--Yardsticks for ESS Decision," Proceedings of the Institute for Environmental Sciences, 1990. 8. Mandel, C.E.N., Jr., "Environmental Stress Screening," Electronic Materials Handbook, Vol. 1, ASM International, Materials Park, OH, 1989, pp. 875-876. 9. Smith, W.B., and Khory, N., "Does the Burn-In of Integrated Circuits Continue to be a Meaningful Course to Pursue?," Proceedings of the 38th Electronic Components Conference, IEEE, 1988, pp. 507-510. 10. Pantic, D., "Benefits of Integrated-Circuit Burn-In to Obtain High Reliability Parts," IEEE Transactions on Reliability, Vol. R-35, No. 1, 1986, pp. 3-6. 11. Shaw, M., "Recognizing the Optimum Burn-In Period," Quality and Reliability Engineering International, Vol. 3, 1987, pp. 259-263. 12. Huston, H.H., Wood, M.H., and DePalma, V.M., "Burn-In Effectiveness - Theory and Measurement," Proceedings of the International Reliability Physics Symposium, IEEE, 1991, pp. 271-276. 13. Suydo, A., and Sy, S., "Development of a Burn-In Time-Reduction Algorithm Using the Principles of Acceleration Factors," Proceedings of the International Reliability Physics Symposium, IEEE, 1991, pp. 264-270. 14. Trindade, D.C., "Can Burn-In Screen Wearout Mechanisms?: Reliability Modeling of Defective Subpopulations--A Case Study," Proceedings of the International Reliability Physics Symposium,IEEE, 1991, pp. 260-263. 15. Parker, P.T., and Harrison, G.L., "Quality Improvement Using Environmental Stress Screening,"AT&T Technical Journal, July-August, 1992, pp. 10-23. 16. Chik, K.D., and Devenyi, T.F., "The Effects of Screening on the Reliability of AlGaAs/GaAs Semiconductor Lasers," IEEE Transactions on Electron Devices, Vol. 35, No. 7, July 1988, pp. 966-969. 17. Tang, W.C., Altendorf, E.H., Rosen, H.J., Web, D.J., and Vettiger, P., "Lifetime Extension of Uncoated AlGaAs Single Quantum Well Lasers by High-Power Burn-In in Inert Atmospheres,"Electronics Letters, Vol. 30, No. 2, January 20, 1994, pp. 143-145. 18. McClean, H., "Highly Accelerated Stressing of Products With Very Low Failure Rates,"Proceedings of the Institute of Environmental Sciences, 1992. About the Author Lloyd Condra wrote this article while employed as a consultant to Hanse Environmental, Inc. Today, he is a Principal Engineer at Boeing Company in Seattle. Previously, he was affiliated with AT&T Bell Labs, Medtronics and Eldec. Mr. Condra is a graduate of Leigh University with an M.S. degree in material engineering, and is the author of two technical reference books. Hanse Environmental, Inc., 235 Hubbard St., Allegan, MI 49010, (269) 673 8638.

Since the early 1980's there has been much discussion regarding various approaches and methods in the use of environmental stress screening and Halt/HASS to markedly improve product quality and life.  Unfortunately, there was widespread misunderstanding and misapplication of the methodology . . . . and some still remains.  Accordingly, we have listed the "Seven Deadly Sins of HALT/HASS". 1. Thermal cycling chamber air instead of product. Environmental chambers with high rates of air temperature change may not qualify as a HALT/HASS chamber.  Simply cycling chamber air temperature is not sufficient.  HALT/HASS requires thermal stimulation of the product. Thermal cycling must cause the product to physically expand and contract at a relative high rate of change over a number of stress cycles.  That is why you cannot simply use traditional environmental simulation chambers or sell them with a "HALT/HASS" label. 2. Vibration levels measured on table instead of product. As in product thermal stimulation, HALT/HASS requires a product vibration response.  Measurement of the input is not measurement of the product response to 6dof vibration. 3. Putting latent defects into product. HASS overstress, whether, thermal, vibration, humidity, or other, can well cause new latent defects, which were not there to begin with. Each product is different.  It is vitally important to determine the optimum stress levels empirically when establishing a HASS production screen. 4. Taking out too much product life. HASS screening during manufacturing can take unneeded life out of a product. If the screen is set too high or the one screen fits all approach. 5. Not tailoring HASS stress to product. It is imperative that the HASS screens be tailored to the product.  The one screen fits all approach does not work.  The screen level may be too low or to high  for some products.  If too low it can  allow potential infant mortality defects to be undetected.  If too high it can take unneeded life out of the product. 6. Not functionally testing product while undergoing HALT/HASS. Intermittent part failures can go undetected unless they are functionally tested while undergoing HALT/HASS.  The level of detectably must be high in order to obtain the results desired. 7. Over design of product as a result of improper HALT. HALT is essentially an exploratory stress test to find part defects and to replace weak parts with robust parts.  However, care must be taken that the product is not subjected to HALT undue overstress and consequential redesign.  Misapplication of HALT can result in an over designed product that is not commercial viable. WE CAN HELP Our long term experience with HALT/HASS seminars, installations, and practitioners worldwide is a valuable resource that we welcome you to draw on. Please do not hesitate to contact us.

The Problem The short lifecycle of today's electronic products creates many pressures for rapid development and manufacture of new products, or product upgrades, in order to stay ahead in the competitive market place. Take for instance, the short model life of computers and printers. A new model appears every few months. Time-to-market is short, and customers expect the new models to work "out of the box" each and every time. These pressures can result in compromised product development and/or manufacturing problems caused by part, process, and workmanship defects. The result is increased manufacturing costs, warranty costs, impacted profit margins, and sadly worse, customer dissatisfaction with resulting loss of market share. The ESS Solution Environmental Stress Screening (ESS), is the solution. It typically utilizes thermal cycling with or without vibration to precipitate latent defects, the so-called "early life defects" which appear during the early life stage of product use. The "bathtub curve" illustrates the life cycle of a product with early life and wear out defects. ESS requires rapid product thermal cycling over a wide temperature range. The objective is to stress components by means of differential expansion rates of the various mounted components, solder connections, and the component mounting assembly itself to precipitate the early life defects. Vibration is likewise utilized to further fatigue the product. Determination of the proper levels are typically determined by increasing environmental stress in step-by-step level. It is an empirical procedure which is different for each product configuration. HALT / HASS HALT/HASS are two applications of the ESS concept. The HALT test is utilized during product development.  It determine initial weakness in the product by increasing stress level in steps to the component destruct levels. Then it replaces weak components with more rugged ones, thereby increasing product reliability. Resulting estimates of improved product life and warranty can be also be accomplished. For example, by applying HALT to a UUT (Pre Halt), we find destruct levels for a given stress-vs-time. By analyzing these failures and then making corrections, we are then able to receive a more robust UUT (Post Halt).  By relating Pre & Post Halt results found in actual use (Field Stress), an estimate of the improved life and subsequent warranty extension are possible. Example of Warranty Improvement Using HALT The HASS process is a production screen to assure that weak components are precipitated (failed). HALT experience and the step stress empirical evaluation is used to establish a good screen. It is important that the level of stress is tailored to the product. There is no one-stress-fits-all. Furthermore,  the product must be functional tested while undergoing stress to detect failures and intermittents. 100% production screening is initially recommended. Subsequently, lot screen sampling may be possible. The HASS screen should be evaluated over time to assure it is doing its job.

Hanse is proud to introduce one of the most advanced integrated touch screen systems on the market. It allows for complete chamber control from the touch panel. It has advanced capabilities including: 12 Channels of Vibration analysis maximum 14 Thermal Couples of input maximum

Why Hanse Environmental builds the best HALT/HASS Chambers on the market. 1. Up to 100Grms 6DoF vibration (US Patent). This is twice that of the industry! 2. 50% reduction in air consumption for vibrators. This is a real cost savings. 3. Three-year unconditional warranty for the vibration system and controller. Best in the industry. 4. New air plenum that reduces electrical and LN2 consumption. Our unique cyclonic airflow results in real utility cost savings. 5.  SCR control of heating elements. Adjusts heating KW to that required by the thermal load and temperature change rate requirements. This reduces electrical usage. 6. We do not use a proprietary controller that is only available from Hanse. We use a Watlow Programmer/Controller affording ready access and support from the Programmer/ Controller manufacturer. Replacements are available worldwide.

Hanse Environmental, Inc. in cooperation with Samwell Testing (China) and Engineering Services (Mexico) held two seminars in China during March 2009. The first seminar was in Beijing on March 17, 2009. The second seminar was in Shanghai, March 20, 2009. Attendees at the seminars represented more than thirty companies who are seeking ways to design and build more reliable products for the markets they serve. Hanse Environmental had a great time introducing the HALT/HASS Systems in China!