Multi-Band SAW Wiring Buffer Layer to Prevent Metal Cracks

A buffer layer is introduced between the metal wiring layer and the electrode layers to serve as an intermediary. This buffer layer prevents direct contact between the metal wiring layer and electrode layers, thereby eliminating the harmful effect of voids and cracks that occur when metal is directly formed on electrode layers. The buffer layer acts as a mediator that maintains electrical connectivity while preventing structural defects.

The buffer layer is formed in advance before the metal wiring layer is deposited. This preliminary cushioning layer provides a protective interface that prevents the formation of voids and cracks during subsequent metal layer formation processes. By preparing this protective layer beforehand, the durability of the metal wiring layer is ensured before any harmful defects can occur.

The buffer layer serves multiple functions simultaneously: it acts as a physical barrier to prevent voids and cracks, provides a uniform base for metal wiring layer formation, and maintains electrical connectivity between different electrode layers with different thicknesses. This multi-functional approach simplifies the overall structure by replacing the need for complex metal gap management with a single universal buffer layer.

The buffer layer is selectively formed only in regions where metal wiring layers will be deposited over electrode layer interfaces. This localized application maintains the optimal local quality of electrode layers for filter performance while adding complexity only where necessary for structural integrity. The buffer layer is present exactly where needed to prevent defects without unnecessarily complicating other regions.