Reliability Lab Testing, Consulting, Training.

Ops a la Carte

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Engineering Success with Reliable Products.

HASS

What is “HASS”?

DEFINITION

A Highly Accelerated Stress Screen (HASS) is a process comprising a set of stresses performed to find potential defects on a product before it is shipped. The stresses are tailored to the product during the HASS Test Development process based on information gathered during the HALT testing process. The key to a successful HASS test is imposing just enough stress to expose defects without aging the product beyond what it is warranted for.

SITUATION

In today’s world of electronics, the reliability of components is getting better and better, and some of the old methods of in-spec screening and burn-in are not as effective as they once were. What is needed in today’s world of electronics and electromechanical devices is a more sophisticated method of screening whereby the screen is tailored and tuned to the product capabilities and weaknesses.

OBJECTIVE

The purpose of Highly Accelerated Stress Screening (HASS) is to develop an appropriate manufacturing screen for the product to identify and eliminate infant mortalities.

VALUE TO YOUR ORGANIZATION

The more effective the manufacturing screen, the fewer field failures due to infant mortalities.

RELIABILITY INTEGRATION

An example of Reliability Integration during HASS is as follows:

Using FMECA results to identify possible wear-out mechanisms that need to be taken into account for HASS

Certain wear-out failure modes are not easily detectable in HALT or even in HASS Development. Therefore, when wear-out failure modes are present, we must rely on the results of a FMECA to help determine appropriate screen parameters.

METHODOLOGY

  1. HASS Plan: The HASS Plan will outline the process from start to finish, including the equipment trade-off analysis, fixture design, screen development, proof of screen, screen implementation, trend analysis, and the transition from HASS to HASS Auditing (HASA). The plan will serve as the roadmap and can be used as a decision tool during the implementation process.
  2. Choice of Environmental Equipment/Location of Test: Performance of HASS will probably require specialized environmental equipment. If your facility does not have this equipment, we can help perform the “return on investment (ROI)” analysis to determine if it makes sense to purchase the equipment or to use outside test labs.

    If the ROI Analysis shows that it makes sense to purchase, we can help you choose the proper piece of equipment from the possible choices.

    If the ROI Analysis shows that it makes sense to use an outside test lab, we can help you decide which lab will best fit your short-term and long-term needs.

  3. Fixture Design/Qualification: Once the environmental equipment is identified, we can help you determine the number of products that can be tested at one time to maximize throughput and then we can design a thermal fixture and vibration fixture (if vibration is being used) that will accommodate this throughput.

    Once the fixture is designed and developed, it must be qualified to assure that it provides for uniform thermal airflow and uniform vibration energy (if vibration is being used) across all products.

  4. Development of Screen: After the fixture is complete and prior to the implementation of production HASS testing, Safety of HASS testing shall be performed. The purpose of this testing is to demonstrate that the chosen screen leaves products with sufficient life left in them to survive a normal lifetime of field use. Safety of HASS testing shall be accomplished by developing a HASS profile from the HALT results, and then taking one set of products (number of products to be screened at one time during Production HASS) and subjecting it to multiple passes of the proposed HASS. If a failure occurs, then the stress levels shall be reduced and the process repeated. This demonstrates that the selected HASS test leaves sufficient life in the product.
  5. Proof of HASS Strength: Some customers are also interested to determine if the chosen screen is strong enough to find defects. Because of the nature of HASS and the acceleration factors involved, this is usually assumed to be true. However, if proof is needed, then “No Problem Found (NPF)” samples from the field can be used, if available, to help confirm that the screen can find intermittent design issues.

    Another method that can be used is to “seed” a product with defects to assure that the screen is able to detect these types of defects. This is analogous to the process of testing software by inserting bugs and then assuring that the test routines are able to find the bugs. Both of these methods tend to be difficult and may be inconclusive. Therefore, an even better method is introduce the screen as is, to monitor the performance of the product in the field and to then “tune” the screen based on the field results. One method of accelerating this process is to run a higher number of screens at the inception of the screen and to then back off this number based on the screen results and how many screen cycles are needed to find each type of defect.

  6. Implementation of Screen: Once the screen is developed and the location of the test is known, then we can run this screen at the designated location and deliver the units back for final checkout and shipment.
  7. Trend Analysis: One key method of this process is to monitor field performance to determine if the screen is missing any infant mortality failures, and to then refine or “tune” the screen. This is a continual process.
  8. Move from HASS to HASA – The HASA Plan: For a high volume product, as the volume increases and the defect rate decreases, a HASS audit or HASA can then be applied. The key parameters to monitor to determine if a HASA is appropriate is the stability of the process and if the defect rate is at its target. The first step is to write a HASA Plan. This will outline the parameters to decide on such as Detection Shift Level, Alpha and Beta Risk Levels, and Sample Size.
  9. HASA Implementation: Once the HASA Plan is approved, the process is under control, and the defect rate is at its target, we can implement HASA. We can run this Audit at the designated location and deliver the units back for final checkout and shipment.
  10. HASA Monitoring: A key step of the HASA process is monitoring the performance of the product and making decisions when to increase/decrease sample sizes. We can perform this on-going statistical analysis to assure that the HASA process is running smoothly.

CASE STUDIES/OPTIONS

The following case studies and options provide example approaches. We shall tailor our approach to meet your specific situation.

  1. Developing a HASS Profile and Proving the Screen Is Safe: A Computer manufacturer needed for us to help them develop a HASS profile that would be safe and to prove that there was sufficient life in the product. For them, we ran a Safety of HASS to assure that the screen was not damaging.
  2. Developing a HASS Profile and Optimizing the Screen: A Telecommunications manufacturer was having a lot of field issues and needed their screen to be optimized to assure that it was as strong as possible yet still safe. For them, we ran both a Safety of HASS as well as a Proof-of-HASS Strength to optimize their screen.
  3. Transitioning from HASS-to-HASA: A Medical Device company was a high volume manufacturer and decided early on that they needed to be running HASA. For them, we developed a HASS-to-HASA implementation strategy. First, we developed a screen using the Safety-of-HASS and Proof-of-HASS techniques. Then, during the low volume pilot production, we ran HASS. Then, as the product started approaching the volume ramp-up, we transitioned them from HASS-to-HASA.

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Email Us: info@OPSaLaCarte.com

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OPS A La Carte, Engineering Success with Reliable Products. We are a leading reliability engineering consulting firm since 2001. We have helped many companies create robust products and elevate them to great success, even become the leader in their industry. We are known for providing the whole gamut of reliability lab testing, consulting, and training. With over 25 reliability engineer-experts around the world, with diverse backgrounds and experience, we serve both domestic and global businesses in all areas of reliability, in depth and width. Hi, my name is Jay Muns, owner and CEO. I have more than 30 years of experience in engineering and business operations.

OPS A La Carte have produced very high-quality results for us, with fast turnaround times. Their engineers are the best in their field, are a pleasure to work with, and their work is of the highest standards available. This has helped us obtain critical product approvals…” We help companies see from outside of their forest and understand what they didn’t know before. Companies come to us out of three scenarios: First, when their products fail. We help put out the fire by identifying problems and providing solutions. Second, after a product is designed, to check the box and move on with getting their product into the marketplace. The best is third: to get engaged early, by including reliability as a part of their initial product design goals. This will save time, money and energy. It is much better to have a worry-free product that addresses reliability issues upfront, than dealing with deficiencies after a product is developed, or worse, already manufactured and sold to the end users. Being proactive with reliability engineering will save a business tons of money and trouble. In all scenarios, you receive professional expertise with integrity and at a fair price. Many of our clients are repeat customers for years because of the value we consistently deliver.

Our ENGINEER-consultants each have over 20 years of experience and perform lab testing, consulting and training based on actual reliability science. They follow well established industry standards, such as “HALT” (highly accelerated life test,) and “HASS” (highly accelerated stress screen.) These engineers evaluate, make recommendations and validate results based on highly relevant lab data, co-relating to real world data. Whether your company has a reliability department or not, you can take advantage of our entire testing-consulting-training package, or any portion of it. We also offer Failure analysis and safety certification services such as UL, CE, and other environmental testing services, like solar, UV, SALT spray testing, ESD (electro-static discharge,) and EMC (electro-magnetic compatibility.)

“Ops A La Carte trained us to use HALT methodology as a proactive tool, to root out key failures in our early and advanced prototypes, and that made it possible for us to deliver dependability that our customers demand, in pilot and production units."“...OPS has played a key role in our evolution from a research company to a manufacturer of ‘mission-critical’ components.” A couple of companies describe our HALT/HASS training as “highly informative, engaging and exciting.” “The benefit far exceeds the price."

Our mission is to enable companies to create their happy customers, with a well-engineered product. By helping our clients understand the real problems and the real solutions, we help improve their careers and reputations. Achieving the win-win-win results for our clients and their customers is our ultimate satisfaction. We have a family-like company culture with positive energy and great teamwork. An improved and reliable product is our own small way to contribute to a better humanity and a slightly better world. Call us at (408) 654-0499, or email us at info@opsalacarte.com, or visit our website www.opsalacarte.com. Thank you!

A couple of our clients' testimonials:

"The expert team at OPS assisted us in evaluating the available reliability testing possibilities, and with their help, we crafted a customized test program precisely sized to meet the needs of our project. The resulting program proved to our team, our customers, and our regulatory auditors that our product was robust, met its reliability goals effectively, and satisfied all safety risk factors."

"...Ops A La Carte worked with us to develop a testing program based on HALT and HASS to effectively assess low-temperature operation capability and screen the boards for assembly and component defects. They then facilitated and supported the HALT and HASS testing effort. It was quicker and more efficient than we had expected. The boards for the first four strings have been delivered. We are looking forward to working with them through completion of the project."