A novel approach of depositing embedded resistors

This paper examines a novel approach of depositing embedded resistors through the deposition of carbon paste onto the substrate by means of aerosol-based deposition. This technique demonstrated good dimensional control - resistance tolerance reached +/-8 percent for the various resistor sizes evaluated. This is an encouraging result, given that current subtractive or additive techniques exceed 15 percent tolerance without laser trimming (Jillek, 2005). However, the atomization process changes the sheet resistivity of the carbon paste, which creates a challenge for this technique. The effect of temperature and moisture on the embedded resistors were also investigated. The resistors seem to be consistent and stable even after moisture exposure-the resistance values show minimal change (~0.5 percent) after exposure to MST level 3. However, after baking at 125degC for two hours, resistance decreases approximately two percent. The resistors revert back to original values after being exposed to room temperature for 48 hours. This indicates that the carbon paste is almost saturated after fabrication and exposure to normal room conditions. The effect of thermal shock is slightly more apparent. Resistance experienced a maximum reduction of one percent after TS 700 cycles. Further investigation at elevated temperatures revealed an inverse relationship between resistance and the temperature. At 150degC, resistance had a maximum reduction of about four percent, which implies that thermal treatment has a greater effect on resistance. This correlates to the greater energy and electron movement at elevated temperatures, which increases the conductive current through the paste