Critical Temperature to Dielectric Degradation of Printed Circuit Board
Dielectric degradation of printed circuit board based on the thermal properties in an open-air environment was investigated. With increase of the temperature, the copper electrodes were oxidized from Cu 2O to CuO; the base material of epoxy laminate was thermally affected to the change of molecular structure and degradation of dielectric properties. With increase of the temperature, the capacitance and surface resistance decreased, the thermal stimulated current increased and showed a valley value near 450 K and a peak value near 490 K
Thermally stimulated discharge currents in high temperature dielectrics
The measurement of TSD (thermally stimulated discharge) currents in Nomex is reported. The TSD currents were measured by heating the sample at a uniform rate. Both the temperature and the current were measured using a strip chart recorder having a sensitivity of 2 mu V/mm and 10/sup -14/ A/mm, respectively. Detailed results are presented.<<ETX>>
Experimental characterization of board conduction sheets
A series of experiments assessing the impact of circuit board thermal conductivity on the thermal performance of air-cooled electronic component arrays is described. Simulated low-profile, surface-mount components in the form of small copper pieces with heat dissipating thick film resistors are employed. From one to five of these components are mounted in standardized square pitch arrays on three different circuit board samples: standard glass epoxy (k=0.26 W/m degrees K), three-layer (metal-glass epoxy-metal) board of moderate effective conductivity (k=1.14 W/m degrees K), and a three-layer high conductivity sample (k=35.9 W/M degrees K). These configurations were tested under forced and natural convection conditions. Profiles of board temperature were acquired using simultaneous thermocouple measurements. The data show that while convection accounts for approximately 80% of the component heat removal in forced air-cooling on the glass epoxy board, conduction to the board can carry nearly all (96%) of the heat load in natural convection cooling on a highly metalized board. The use of moderate conductivity boards increases the effective heat transfer area of a component by a factor of three or more.<<ETX>>