High-temperature storage and thermal shock studies of passive component attach materials

In this work, the high temperature testing of passive component attach materials is reported. The target operating temperature for this research was 200°C to 225°C. The four materials chosen for the study were Ablestik (71-1) silver filled polyimide, EPO-TEK (E3081) silver-filled epoxy, Grace Specialty Polymers (CS6000) silver filled silicone, and Indalloy´s (IND. 183) 88Au/12Ge eutectic solder. The two board materials selected for study were 96% alumina ceramic substrates and high temperature cyanate ester circuit boards. Resistors and capacitors were selected as the passive components. Since eutectic Sn/Pb solder terminations were unusable at these temperatures, end terminations for both the resistors and capacitors were Pd/Ag and Au. The test pattern was of a series resistor chain of eight 0-ohm resistors (120 mil×60 mil) and three independent 12 μF ceramic multilayer capacitors (750 mil×650 mil). The storage temperatures selected were 175°C, 250°C, and 300°C. The cyanate ester boards were tested in the 175°C and 250°C ambients, while the ceramic substrates were tested in the 250°C and 300°C environments. The polymer based component attach materials were tested at 175°C and 250°C, while the Au/Ge solder was tested at 300°C. Thermal shock studies have been performed through 910 liquid to liquid cycles with a temperature range from -55°C to 200°C. Both Pd/Ag and Au terminated components on cyanate ester circuit boards and some ceramic substrates were included in these thermal shock rests