Trelic’s picture of the week 09/2017

Why are there so many wires in this picture?

 

 

When you test something, you need a way to analyse the effect of the test. Sometimes visual inspection is enough, but often it is important to somehow measure the functionality of the tested structures. Especially during reliability testing (accelerated life testing, environmental testing, you name it!) it is important to measure some output whether your sample fails or not. Measured quantity depends on the structure and can be voltage, weight or resistance to mention just a few examples.

There are two possibilities to utilize the measurements. First is to do the measurements after certain testing intervals at ambient conditions. Second is to measure in real time during testing (in situ). The first option requires possibly less preparation before testing, but it also gives much less feedback from the test. With real-time testing the exact failure times can be determined, and it is possible to follow how the failures occur (for example, does the measured quantity change dramatically or does the change develop slowly over time).

Real-time measurements are especially important if intermittent failures are typical for the tested materials or structures. This means that a failure can be seen at testing conditions, but the measured factor fully or partially attains its original state at ambient conditions. These kinds of failures are very typical for example for polymer structures and for interconnections. Polymers have often such failures because they have time-dependent mechanical behaviour. This means that during testing a part may deform and cause failure, but after testing the deformation may recover sooner or later and the part recovers its functionality. Sometimes real-time measurements are not possible, but if they are, we highly recommend them.

You probably already guessed why are there so many wires in the picture above. We measured the resistance of these test structures in real-time during testing to monitor their exact behaviour. It takes some time to attach the wires, but after that the reliable measurement system will do the work for us.