| 摘要 |
PURPOSE:To increase the attenuation effect to spurious waves propagated on a crystal plane under a coated film, by reducing the reflection of spurious waves due to the boundary of coated film, through the forming of a sound absorbing film with thick coated film pattern and thin coated film pattern. CONSTITUTION:In a surface acoustic wave filter provided with an electrode pattern and sound absorbing pattern with an input transducer and an output transducer on a piezoelectric crystal substrate, the sound absorption film provided at the end of the substrate is constituted as a double form. A layer 11 under the sound absorption film is made thinner by using a screen with much mesh to form a coating film with high pattern accuracy and the film is dried, then thicker parint is made as an upper layer 12 by using a screen with less mesh at the inside on the sound absorption film printed as above. |
