JPS5912814Y2 - surface acoustic wave device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an electrode shape of a surface acoustic wave element.

Surface acoustic wave elements mutually convert electrical signals and surface acoustic waves using piezoelectricity.

Using its frequency characteristics and delay time characteristics, filters,
Used for delay lines, etc.

Piezoelectric materials include piezoelectric ceramics such as PZT, single crystals such as lithium niobate, and piezoelectric thin films such as zinc oxide, but piezoelectric thin films are superior in terms of characteristics and cost.

When this piezoelectric thin film is used in a surface acoustic wave device, glass is usually used as an insulating substrate.

Input/output electrodes using crossed comb electrodes are provided on this glass substrate, and a piezoelectric thin film is formed on the glass substrate provided with these electrodes.

Zinc oxide is used as the piezoelectric thin film, and is manufactured by sputtering zinc, combining it with oxygen, and depositing it on the substrate.

In order to obtain sufficient gain as a surface acoustic wave element, the film must be sufficiently thick to improve piezoelectricity.

However, when the film thickness is increased, a problem arises in that the glass substrate may break.

This phenomenon of glass substrate cracking is thought to be caused by stress caused by the thin film.

When the film thickness is thin, the glass does not break, but as the film thickness increases, the distortion of the crystal structure of the thin film increases.
It is thought that stress is accumulated due to this distortion, and when the stress exceeds a certain value, the glass breaks.

When we observed the phenomenon of glass breaking mentioned above, the following points became clear.

FIG. 1 is a perspective view of a commonly used surface acoustic wave device, in which electrodes are formed on a glass substrate 11.

The electrodes are connected to a cross-comb electrode 12, a pad 13 for connecting each electrode to the outside, and a conductive path 14 connecting the pads.

The conductive path 14 has input and output electrodes on both sides of the electrode fingers of the intersecting comb-shaped electrode 12 located on two straight lines, and is parallel to the end surface of the glass substrate 11.

When manufacturing a surface acoustic wave device, a large number of electrode patterns are arranged on a single glass substrate, and this is cut to manufacture a single device.

When dividing this glass substrate, the glass was often broken along the lines along the conductive paths 14.

This is thought to be because this line is a discontinuous line between the glass surface and the metal surface used for the electrode, and stress is locally concentrated and becomes the largest at that line.

Since this line coincides with the cutting line of the glass substrate, the force applied when dividing the glass substrate is combined with the force to cause the glass substrate to break.

Moreover, it may cause the glass substrate to be destroyed during sputtering.

The purpose of the present invention is to prevent the glass substrate from cracking as described above, and achieves this purpose by preventing stress from concentrating on a specific portion.

The present invention achieves the above objectives by changing the pattern of the electrodes.

The following description will be made according to the embodiment shown in FIG.

As described above, intersecting comb-shaped electrodes 22 and pads 23 for connecting each electrode to the outside are provided on the glass substrate 21.

A conductive path 24 connecting the interdigitated electrode 22 and the pad 23 is provided, but it is provided so as to extend in a direction different from the propagation direction of the surface acoustic wave so that the conductive path 24 is not located on a straight line.

In other words, the conductive path 24 connecting the crossed comb electrode 22 and the external circuit extends in a direction at an angle to the common electrode 25 connecting the ends of the electrode fingers of the crossed comb electrode 22. It is connected to a pad 23 provided near the edge of the substrate 21.

The conductive path 24 is also no longer parallel to the end surface of the glass substrate 21.

Such an electrode arrangement can be easily constructed by simply changing the mask used when forming the electrodes by photoetching.

According to the present invention, the direction of the force applied when dividing the glass substrate does not coincide with the line where the stress increases, so that cracking of the glass substrate can be reduced.

Moreover, the stress on the glass substrate is dispersed, and the glass is less likely to break even when force is applied from the outside.

Thereby, the manufacturing yield of the surface acoustic wave device is improved, and a highly reliable surface acoustic wave device can be obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a conventional surface acoustic wave element, and FIG. 2 is a perspective view of an embodiment of the present invention. 11, 21...Glass substrate, 12.22...
...Cross comb electrode, 13.23...Pad,
14.24... Conductive path, 25... Common electrode.

Claims (1)

[Scope of utility model registration request] In a surface acoustic wave element formed by forming a piezoelectric thin film on the surface of a glass substrate provided with interdigitated electrodes, a conductive path connecting the interdigitated electrodes and an external circuit is arranged in the direction of propagation of the surface acoustic wave and the direction of propagation of the surface acoustic wave. A surface acoustic wave element characterized by extending in a direction different from the direction perpendicular to the propagation direction.