IEC 60068-2-14 Test guidelines updated

IEC 60068-2-14: The test standard for thermal cycling of electrical equipment has been updated with the collaboration of Weiss Technik. The focus is mainly on the interaction between the test piece and the test parameters.

A car is started in the morning after a cold night in the parking lot - the engine and electronics start and warm up quickly. This is just one of the many everyday situations in which electrical products are sometimes exposed to extreme and abrupt cold and heat. Temperature-induced load testing provides insight into how the units respond to these conditions. They also provide insight into sustainability, vulnerability and damage mechanisms.

Laboratories and manufacturers that perform tests on temperature changes are guided, among other things, by the IEC 60068-2-14 standard. The test criteria are currently under review due to improvements in testing technology, particularly in the measurement and analysis of the test sample. Christian Haack, head of development at Weiss Technik, played a role in this. As chairman of the IEC Technical Committee TC 104, he also took responsibility for revising the standard. “For this purpose, I mainly collected user knowledge and practical experience from the industry, trade associations and various international committees to incorporate this into the update of the standard,” says Haack.

Hot and cold: stronger focus on the test piece

The change to the standard, which does not change the basic test method, puts the emphasis on the sample. This is because specimens heat or cool differently depending on their material, weight and processing, and each specimen responds differently to the test conditions. Any wear or damage will also be uneven. Additional sample curves and tolerances for temperature levels have been added to the standard for guidance. This improves, among other things, the comparability of tests. Sensors can be attached to the test piece to measure the responses to temperature changes. Advantage: The test piece can be measured in many places and its behavior can be recorded live. Cameras installed in the test chamber also provide images for visual evaluation.

Three test procedures: Includes shock testing

The test variants are divided into the designations Na, Nb and Nc. Na refers to a temperature jump test that involves huge differences in heat or cold: for example, an abrupt drop from 100 degrees Celsius to minus 50 degrees Celsius and back again – both at maximum cooling and heating power. The thermal shock test is performed using flap shock devices that cool or heat the sample via air valves. Alternatively, it can be performed with car models in which the test piece is shuttled between heating and cooling chambers, similar to a frozen pizza being pushed directly from the refrigerator into a hot oven. Nb is a ramp test, which involves a linear controlled temperature change – cooling and heating in gradual steps. Due to the gradual temperature change, the reaction of the sample during the defined post-tempering can be observed. For this reason, this test method is also considered the experimental precursor of the Na temperature jump test. Finally, Nc represents a test method where liquid induces the temperature changes instead of air. The test is performed using the two-bath method, which, due to the high conductivity of liquids, significantly improves heat and cold transfer, even with abrupt temperature changes.

Quality and experience: standard reflects testing practice

The guideline is primarily intended for the qualification, validation and development of electrical products. It is used for quality assurance and to identify causes and mechanisms of damage, ultimately leading to unit approval. Even mechanical products and components can be tested with this test method. Because the testing methodology has not changed, laboratories and manufacturers can largely continue to use their existing testing equipment, depending on the type of test. Weiss Technik devices such as the ShockEvent, TempEvent, ClimeEvent and LabEvent, some of which can reach temperatures as low as minus 70 degrees Celsius, are ideal for these tests. With the direct involvement of Weiss Technik, the Reiskirchen-based company's decades of experience in the field of test chambers and environmental simulation became an essential part of revising the standard.

Source:  https://www.weiss-technik.com/en/news/detail/iec-60068-2-14~n36113