QMT Features: April 2012
Benefits of environmental testing
Manufacturers can save cost and time by considering compliance and testing requirements at the beginning of their journey, rather than at the end. By Jean-Louis Evans, MD. at TÜV SÜD Product Service and TÜV SÜD BABT.

Environmental testing ensures that products operate in a physical environment such as extreme climatic conditions, at altitude or in the ocean. It is often a contractual requirement demanded by the defence, aerospace, automotive, rail and maritime industries; where the operating environments are harsh and safety, functionality and reliability are critical

For some manufacturers, environmental testing is a customer (sometimes mandatory) requirement, while others do it voluntarily to differentiate their products against a competitor, or to support any defence against a warranty claim.

To remain competitive, manufacturers are coming under increasing pressure to extend their warranty terms to three or five-years. There is also a growing customer demand for 25 years’ fault-free service in applications where access for maintenance and repair is difficult, such as sub-sea applications, power generation and distribution. In such circumstances, it would of course be highly risky to offer extended warranties without extensive testing to back them up.

The cost of the environmental testing can be set against the cost of failures in the field and loss of brand reputation. Furthermore, considering environmental requirements right from the earliest stages of product design yields a better product, gets it to market faster and with much lower design corrections costs.
This article looks at just three important aspects of environmental testing – packaging test, conventional testing and highly accelerated life test (HALT),

Packaging test
Many products which are designed for a benign environment suffer their highest stress during transportation. This means that manufacturers have the choice of designing suitable packaging that protects the product, over-engineering it so that it is tough enough to survive, or just putting the product in a box and allowing for the cost of replacing damaged goods.

There is a variety of standards for packaging design and testing covering dangerous goods. However, the level of damage currently experienced in transit suggests that many manufacturers may not fully understand the environment, even though the packaging test process is increasingly a condition of transit assurance.

Environmental test
The ability of products to operate and survive against physical stresses such as extreme climate, changes in temperature, vibration and shock is commonly used to demonstrate compliance through a rigorous testing regime. These physical environments can be reproduced in the laboratory under repeatable conditions and can simulate the actual environment. In addition, it is possible to develop tests that combine environments to simulate “real life” scenarios, such as rain then sunshine, flying through clouds, the dust and heat of the desert, etc.

With time to market getting ever shorter, there is never enough time to fully test the long-term reliability of a product. Reliability evaluation that takes weeks is unlikely to uncover all potential failure modes and will not yield a statistically significant number of failures unless many products are tested.

Highly Accelerated Life Testing (HALT) is a technique that accelerates the life testing process of electronic products, where there has been considerable success in the automotive, aerospace, and rail and power electronics industries.

The basic principle behind the HALT process relies on two environmental effects that are known to affect reliability in electronic components, namely thermal and mechanical stresses.

HALT uses thermal and mechanical stimuli, applied separately and then together, to determine the product’s operating and destruct limits. It is particularly valuable at the development or prototype stage and, when coupled with power cycling and product specific stresses, has been proved to expose design flaws within hours.

This is also a cost-effective, compressed product test method which applies real tests earlier in the design/development process, rapidly characterises and identifies design flaws, achieves shorter time to market with a ‘mature’ product, and reduces field returns. Typically taking from three to five days to identify potential problems early in a product’s design cycle, HALT has gained widespread acceptance across manufacturing sectors.
HALT results can also be used to set test limits for production screening. Highly accelerated stress screening (HASS) uses the same equipment as HALT, but as operating and destruct limits are known, it can be used to screen HALT-tested products. This means that screening test time is a fraction of the time of conventional stress screening tests and faults due to production variations become apparent very quickly. Additionally, you take so little life out of the product during a HASS screen, you can (and people do) use deliverable product for HASS!

HASS is widely used in automotive electronics applications, such as vehicle lighting controls and in the aerospace industry, where deliverable product is sometimes used.

In addition, if you used HALT during design, it can prove useful as a cost reduction tool. Most manufacturers will, at some stage, consider reducing material and component costs once the product is safely established on the market. The use of HALT on the initial product, and then on re-designs, will enable cost reductions to be implemented without jeopardising reliability. This is because if the products show comparable results during HALT, they will compare on durability. We have seen this done very effectively on automotive components and electronic power supplies, where manufacturers continually look to save costs without compromising performance.

Companies operating in both civil and military avionics as well as telecommunications are frequent HALT users. This is because of its success in quickly detecting and fixing design flaws in products that have proved to be very robust and reliable in service as the demand for safer, ever more reliable products increases. Interest in HALT is also rapidly growing among other manufacturers, particularly those producing safety-critical products, as well as companies with a strong brand name or extended warranty to defend.

Effective environmental testing
For manufacturers to be assured of the optimum environmental performance of their products, they should ensure that they are fully aware of the known and potentially damaging environments that their product may experience during its life.

For many, working with a specialist organisation can bring a number of benefits, including up to date information on test standards, the right methods to use and state-of-the-art test facilities. Significant cost and time saving will be realised in the long run by getting things right first time, invoking specialist knowledge at the earliest design stages, and considering compliance and testing requirements at the beginning of your journey, rather than at the end. l
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