An integrated SAW sensor with direct write antenna

This paper presents a wafer-level integrated SAW sensor that uses conventional thin-film fabrication for the SAW, and the direct write of a thicker dissimilar metal for the antenna. An automated thermal spray process deposits the antenna conductor onto the SAW substrate, providing ease of fabrication, optimal film thickness, superior adhesion, and application specific materials. Results will highlight the direct printing of thick copper traces onto whole LiNbO₃ wafers. The design of a 915 MHz meandered dipole antenna with low mismatch loss and maximized radiation efficiency over a 7% SAW fractional bandwidth is demonstrated. Experimental performance results of antennas fabricated on standard FR4 and on-wafer by the direct write process are contrasted. Temperature sensors are fabricated on YZ-LiNbO₃ and their wireless performance is evaluated.