Power cycling test

Unlike lead, tin exhibits anisotropy, e.g., coefficient of thermal expansion that varies by a factor of 2 in different crystallographic directions. As discussed in Sec. III.C, this condition can lead to large internal stresses and thermal ratcheting in tin alloys that does not occur in lead-based solders. These effects are anticipated during normal thermal and power cycling tests with no... 

Microelectronic solder joints are subjected to a number of failure mechanisms such as thermal cycle cracking, electromigration, thermomigration, corrosion, etc. Any new solder alloy must satisfy all of these requirements simultaneously. Power cycle testing stresses an assembly in a manner that closely repUcates actual appUcation use conditions. 

It is not practical to determine the contact resistance in power connectors. The resistance of the connection of a specified length of conductor on each side of the connector is measured and is called the overall resistance or the connection resistance. One industry specification (32) defines the included lengths and requites the stabiUty of the connection resistance to be within 5% of its average value throughout the heat-cycle test. 

The Ta/Nb flotation was accomplished using collector RS702. This collector is composed of amine acetate, phosphoric acid esters and hydroxamate. Collector RS702 is a powerful collector, capable of floating a variety of niobium minerals that are contained in the flotation feed. Metallurgical results obtained from a continuous locked-cycle test are shown in Table 23.14. 

Fuel Cell Power Train Tested on the R40 Driving Cycle... 

Infant-mortality period. In the early period of failures, accelerated stress tests such as burn-in, power cycling, temperature cycling, and vibration as well as highly accelerated stress and life testing are used. These methods are used to screen out parts that are inherently not reliable and prevent the delivery of dead on arrival parts to a customer. While this consumes some early life of an assembly by stress screening, the remaining population begins the useful life period or the flat area of the bathtub. 

Shikano M., Kobayashi H., Koike S., Sakaebe H., Ikenaga E., Kobayashi K, Tatsumi K Investigation of positive electrodes after cycle testing of high-power Li-ion battery cells II An approach to the power fading mechanism using hard X-ray photoemission spectroscopy, J. Power Sources 2007, 174,795-799. 

To determine the best operation range, a large number of different cycle tests with variations of depth of discharge, power and temperature were performed. For cell tests, hundreds of test channels had been operated over several years. A test channel is a bidirectional DC power supply which can be programmed to charge and discheu ge the... 

Figure 21.5 Example of a load cycling aging test profile (power versus test duration) illustrating the relative power during dynamic cycling phase for lOmin (a) and an initial 1 h polarization curve measurement followed by 2 h dynamic cycling phase and another polarization curve measurement (b). Courtesy of FCTES. ...

Development and demonstration of the S-CO2 Brayton cycle power converter. Turbine and compressors need to be developed for utilization in S-CO2 Brayton cycle tests. A key question concerns whether an axial flow compressor can be used near the critical point. The recuperators and cooler in the cycle are compact Printed Circuit Heat Exchangers (PCHEs) for which the performance and efficiency with S-CO2 needs to be validated. A complete S-CO2 Brayton cycle power converter including a heat source, turbine, load, high and low temperature recuperators, compressors, cooler, and supporting components for control and operation needs to be constructed and demonstrated at a sufficiently large scale ... 

Another widely used expression may be found in IPC-SM-785. This expression tries to account for the effect of power cycling and the dwell time in the thermal profile it also makes it possible to make predictions for one component or solder joint geometry based on data for another similar one. In its most simplified form, the acceleration factor for tests meeting the preceding criteria for FR-4 and eutectic Sn-Pb solder joints may be approximated as... 

After 500 h accelerated lifetime testing on an automotive PEM fuel cell stack with idling cycles, load changing cycles, high-power cycles, and start-stop cycles, the stack performance clearly deteriorated. As shown in Figure 10.21, the average cell voltage curve of every cell from 1 to 14 cells is lower than for cells 15-100. 

Another form of thermal cycling test, which is gaining popularity for high power dissipation components, is based on varying the die temperature by switching the power supplied to the test specimens on and off with a period which is about twice the thermal time constant of the package ( 7 min). However, it is not yet clear how the results of this thermal cycling test compare with the older test. 

---