Design of metallization layers for PZT piezoelectric ceramics and joining to 4J29 Kovar alloy

Abstract

To enhance the bonding strength of PZT ceramics/4J29 Kovar alloy joints, the metallization layers on PZT ceramics were strategically designed, fabricated, and optimized. Subsequently, the metallized PZT ceramics were successfully joined with the 4J29 Kovar alloy using Sn-3.0Ag-0.5Cu (SAC305) solder. In this study, the wetting behavior, joining mechanism and the effect of metallization layers thickness on the joining strength were investigated. The (Ti + Ni + Au) multilayer structure enhances wetting, as Au dissolves into the solder to improve wetting, while Ni serves as a barrier to prevent direct contact between the solder and Ti, thereby ensuring the integrity of the metallization layer. The joining mechanism for PZT ceramics/solder and solder/4J29 Kovar alloy involves the reaction between Ni (in the metallization layer) and Sn (in the solder), and Sn diffusion into 4J29 Kovar alloy, respectively. The highest joint strength of 29.0±1.4 MPa was achieved with (Ti + Ni + Au) metallization layers (Ti:100 nm, Ni:1000 nm, Au:300 nm), marking a 120% improvement over the adhesive currently used for joining PZT ceramics to 4J29 Kovar alloy. Our work presents a promising method for joining PZT ceramics with 4J29 Kovar alloy, which is applied in transducers as a core component for oil logging.