How Environmental Stress Screening Reduces Potential Field Failures?
Environmental Stress Screening (ESS) refers to a testing process involving subjecting a newly assembled or manufactured product, usually an electronic, to environmental stresses. This series of testing is important for the purpose of identifying and eliminating the latent defects of an electronic product that are usually introduced during the product manufacturing process.
The possible defects exposed through the ESS are not usually able to be detected by a simple electrical testing or visual inspection. The defects may be either as a result of poor workmanship or defective parts.
The ESS is designed to expose possible electronic equipment manufacturing process defects by subjecting 100% products groups to environmental stimuli set or to an environmental stimulus (for example, thermal cycling and random vibration). That is done for a time that is programmed to force the occurrence of failures before product shipment or equipment fielding.
The testing conditions electronic equipment is subjected are usually set to mimic the same conditions that the equipment will be exposed to in the real world. ESS thus prepares electronic equipment for its real-world use and application.
When an ESS is conducted or applied, failures exposure is normal. This marks the major difference between Environmental Stress Screening and conventional certification testing since with the latter; a failure-free operation is required as reliability proof.
"When an ESS is conducted or applied, failures exposure is normal. This marks the major difference between Environmental Stress Screening and conventional certification testing"
Temperature Cycling Advantages
There are numerous ESS process types to choose from including temperature cycling. Various studies conducted have established that among the different types of ESS processes available, the screening process type which is most effective is temperature cycling.
While numerous studies have established that both random vibration and thermal (temperature) cycling are the most effective screening processes for pinpointing latent defects, however, if only a single screening or testing is to be employed, then temperature cycling is considered to be the most effective for latent defects identification.
As stated by the ESSEH (Environmental Stress Screening of Electronic Hardware) guidelines, temperature cycling is often able to expose latent product defects of about two-thirds more compared with the random vibration process, ranked as the second most effective screening process for identifying flaws.
One important aspect of the process of screening is stress uniformity. The Temperature cycling process provides a stress environment that is uniform.
This advantage is important since all the product areas are subjected to the same stress amount throughout the screening process. Other methods of screening do not provide stress uniformity.
Temperature cycling is also advantageous because the process takes less time to be performed compared with other stress processes. This enables latent defects to be exposed in the form of failures very quickly. Temperature cycling has a higher overall efficiency even if the vibration process has a cycle time that is much shorter.
Temperature cycling basic parameters include temperature change rate, temperature extremes, number of cycles, and uniformity of temperature across a product.
You should design the environment a product is to be subjected to in the early design stage. Environment design should not be just an afterthought because you are faced with a problem.
Some of the issues to be clearly designed and addressed in the early stage of design include Mode of Transport (air, sea, and land), geographic considerations, operating environment, and safety.
For the product screening to be as effective as possible, the temperature that the product is subjected to should be extremely apart. Adhere to the board components temperature limitations. The minimum temperature range, hot and cold, ought to be100C. The air temperature change rate influence on the part ought to be 5C to 20C per minute, with temperature uniformity across all the equipment or products housed in the chamber being the emphasis.
To decide the required number of cycles for the preferred temperature stress rate, the ESS process must be supervised carefully. You can start with around 30 numbers of cycles and keep an eye on failures. The cycle's number is able to be reduced until the failures percentage begins to plunge and this is vital for achieving an efficient screen.
For an ESS program to achieve long term success, that will greatly depend on how well there is monitoring of results. After an effective implementation, if you want to measure the return on investment, then you have to rely on monitoring.
Reviewing a screening program may be necessary due to different reasons. For example, if their in field failures increase or new assembly methods. Being able to determine the underlying cause of a failure is essential for the purpose of addressing the problem or issue.
Being able to determine the underlying cause of a failure is essential for the purpose of addressing the problem or issue.
Always remember that manufacturing problems usually contribute to a huge share of failures. Monitoring the ESS program is necessary for the reason that it is based on analysis of field failure and therefore, it is only reasonable that analysis must be relied on in the course of the process.
ESS serves the purpose of reducing potential field failures; it is not an end result. And so, monitoring is important for the purpose of evaluating the change in manufacturing processes, part selection, and screen effectiveness to enable the adoption of the appropriate course of action.
"ESS serves the purpose of reducing potential field failures; it is not an end result. And so, monitoring is important"
ESS testing chamber by Testlabs
Testlabs offer ESS test chambers that meet IEC 60068-2-14: 2009. Customer can choose the size and performance from different models offered or customize the test chambers according to specified test requirements.
Testlabs's ESS chambers are featured with model style look, easy to operate controller and high performance and reliable compressor.