The thermosetting resin investigated in this study was a mixture of bis-maleimide and bis-cyanate, frequently referred to as BT (bis-maleimide triazine). For printed circuit board applications, a brominated epoxy resin was blended with BT to impart flame resistance. Resin curing was extensively investigated using a combination of thermoanalytical techniques (thermal analysis, heated-cell infrared spectroscopy, dynamic mechanical analysis, and microdielectrometry). Differential scanning calorimetry indicated a minimum of two separate reactions. Fourier-transform infrared spectroscopy provided more detailed information on the cross-linking reactions during the curing. The onset of cyclotrimerization was found to appear at 150°C, correlating with one of the peaks observed in the differential scanning calorimetry measurements. Dynamic mechanical methods were used to investigate the viscosity profile during simulated lamination temperature profiles. Microdielectrometry performed simultaneously with parallel-plate rheometry provided further insight into the physical changes that occur during lamination.
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