Every product design that contains a microprocessor, circuit card, or electromechanical assembly can benefit from highly accelerated life testing (HALT) to increase the speed of development, eliminate design flaws, and keep the project within budget. The HALT technique shortcuts and avoids design problems by quickly exposing any weak links in a product or production process. As a result, these problems can be fixed before they become expensive field or manufacturing issues.
In effect, HALT ferrets out any weak links in the design process to make products better. It works by applying various stresses in steps to find a product’s weak spots, operational margins, and limits. These stresses may include vibrations, high temperature, rapid temperature changes, and more.
Stresses must be higher than normal to obtain time compression and accelerate aging. It’s important to note that HALT is not a pass-or-fail test. The stresses are increased until the product fails, not just increased to some predefined limits.
If undetected, most HALT failures will eventually cause problems in the field. The testing usually takes a few days or a few weeks, and some failures are easy and inexpensive to fix.
Such a proactive approach stands in contrast to traditional testing procedures, which typically consume weeks or months. Additionally, because many conventional test procedures call out minimum specifications and nothing more, traditional design verification testing checks only within specifications, missing design defects detectable by over-stress techniques. This leads to product failures in the field, costly product recalls, ongoing warranty expenses, and time-consuming support programs.
In contrast, HALT is a proven method of finding design defects. Without discovery, design defects often appear in end-use applications, causing product failures after release. But HALT increases product reliability by pushing a product to its operating limits and beyond. With HALT, a product is subjected to the outer margins of temperature, rapid thermal cycling, and vibration testing to rapidly uncover any design weaknesses.
“Most traditional testing checks the product up to the spec, but HALT goes way beyond that,” says Mike Silverman, managing partner of Ops Ala Carte LLC, a Saratoga, Calif., professional consulting firm that focuses on reliability engineering services. “For example, let’s say a cell-phone manufacturer says its product will work up to 50°C. Well, HALT will actually take that phone up to 70, 80, or 90°C in order to find any weaknesses before the product goes out the door. That in itself is acceleration, because we are accelerating any possible failure mechanisms and bringing them back into the laboratory so the customer doesn’t see them.”
“I would say that the main thing that accelerates products to market is that failures can be created much more quickly by using HALT than with standard reliability improvement techniques,” says consultant Ed Kyser, PhD. Based in Los Altos, Calif., Kyser’s company Reliability provides assessment and economic analysis of all aspects of reliability and quality improvement programs. “The reason: We’re stressing the product/component beyond its design limits. To me, that is the genius behind this kind of approach to finding faults and fixing them.”
After HALT has revealed any product weaknesses, proper root cause of failure analysis facilitates the corrective action necessary to improve the design. As a result, HALT reduces R&D costs, shortens the time-to-market, and increases product quality and reliability.
Ultimately, the benefits of increased product reliability help push up the bottom line of any manufacturer. In the long run, the outcome is higher customer satisfaction and confidence, increased company image and reputation, and increased market share.