Life Predict and Simulation of the Copper Wire in Flexible Printed Circuit Board
Fatigue failure of the circuit board's research focuses on the influence to the circuit board of vibration of rigid circuit board type, distribution of Electronic Components on the board etc. And there is relatively little research to the flexible circuit board's fatigue life research. Local stress-strain method is used to predict the fatigue life. Simulate actual fatigue test load conditions to established finite element model of flexible printed circuit board. Perform fatigue analysis under the periodicity stress. Drawn fatigue life of copper wire in different loading conditions. There is guiding significance to the follow-up test.
Numerical Fatigue Life Prediction of IGBT Module for Electronic Locomotive
: In this study, the thermomechanical stress and fatigue analysis of a high voltage and high current (3,300 V/ 1200 A) insulated gate bipolar transistor (IGBT) module used for electric locomotive applications were performed under thermal cycling condition. Especially, the reliability of the copper wire and the ribbon wire were compared with that of the conventional aluminum wire. The copper wire showed three times higher stress than the aluminum wire. The ribbon type wire showed a higher stress than the circular type wire, and the copper ribbon wire showed the highest stress. The fatigue analysis results of the chip solder connecting the chip and the direct bond copper (DBC) indicated that the crack of the solder mainly occurred at the outer edge of the solder. In case of the circular wire, cracking of the solder occurred at 35,000 thermal cycles, and the crack area in the copper wire was larger than that of the aluminum wire. On the other hand, when the ribbon wire was used, the crack area was smaller than that of the circular wire. In case of the solder existing between DBC and base plate, the crack growth rate was similar regardless of the material and shape of the wire. However, cracking occurred earlier than chip solder, and more than half of the solder was failed at 40,000 cycles. Therefore, it is expected that the reliability of the solder between DBC and base plate would be worse than the chip solder.
Reduction of patient exposure during dental radiography.
We investigated the effect of using additional accessories with a conventional X-ray machine to reduce patient exposure during full-mouth dental radiography. LiF extruded-rod thermoluminescent dosimeters were placed in 23 anatomical sities of a Randophantom and the phantom was exposed to a Turkish dental X-ray machine operated at 60 kV, 10 mA for 0.5 sec periods. Maximum reductions were observed at the eyes (80%), in the thyroid (70.6%). under the collar bone (59.9% average) and the gonads