JPS5947888B2 - Manufacturing method of surface acoustic wave device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface acoustic wave device used in a wave wave device, a delay line, etc., and a method for manufacturing the same.

The manufacturing method of the surface acoustic wave device includes a method for manufacturing a surface acoustic wave device.
The process includes the process of forming electro-mechanical converter electrodes, the process of performing an end face reflection prevention process, the process of separating each element chip, the process of bonding each element chip, and the assembly process of packaging.

Among these, the end face reflection prevention process is a process specific to surface acoustic wave devices, and when the surface acoustic wave is reflected at the end face of the element and input to the output side electromechanical converter, the main signal ripple in frequency characteristics as a time-delayed signal,
This causes deterioration of the overall electrical characteristics of this device, such as deterioration of pulse delay characteristics.

For this purpose, end face reflection prevention treatment from the element end face is required.

Conventionally, the following methods have been considered as means for preventing end face reflection.

(a) Sound absorbing material is provided on the end face and the surface of the substrate in the vicinity thereof.

(b) A resin-based sound absorbing material is applied and cured on the end face and the surface of the substrate in the vicinity thereof.

(c) The cross-sectional shape of the end face of the element chip is formed into a round shape so as to guide and absorb surface acoustic waves to the back surface.

1) Providing irregularities on the substrate surface near the end face of the element chip.

(e) Providing unevenness on the end face of the element chip.

However, among these conventional technologies, (a) and (b)
Issues such as sound absorber shape, thickness, reliability),
In particular, it has drawbacks such as unresolved heat resistance, strength, moisture resistance, and aging problems.

Regarding (c), since each element chip must be processed individually after being separated into each element chip, processing time is required and it is not easy.

Regarding (d), since steps such as sandblasting and etching must be used, the cost increases due to an increase in photoresist steps and an increase in the number of photoresist masks required.

However, if the desired unevenness can be formed, it is advantageous in terms of temperature characteristics and reliability, but normally, the desired unevenness is created by missing holes during cutting, but there is a risk of the crank getting in, and it is difficult to control the shape. In addition, there is a lack of reproducibility, and no concrete methods have been announced that are easy to control, guarantee reproducibility, and are inexpensive, especially when it comes to shape control. The purpose of the present invention is to eliminate the various drawbacks of the above-mentioned conventional techniques, and to improve the frequency characteristics and pulse delay characteristics of surface acoustic wave devices at low cost without adding any particular steps. An object of the present invention is to provide a method for manufacturing a surface acoustic wave device with improved performance.

The main point of the present invention is that, in order to achieve the above object, a metal film with strong adhesion to the substrate is attached on the cut margin when cutting the piezoelectric substrate into each element chip. When the metal film portion separates by applying stress, the substrate material under the metal film is to be ruptured together.

If the shape of the metal film is a linear figure with unevenness about the size of the wavelength of the surface acoustic wave, unevenness about the same size as the wavelength can be formed on each element end face.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the method for manufacturing a surface acoustic wave device according to the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram of a cross-sectional structure in each step of a method for manufacturing a surface acoustic wave device according to the present invention.

In FIG. 1, 1 is a piezoelectric substrate, 2 is a metal thin film, 3 and 4 are electrodes, 5 is a boundary metal portion, and 6 is an element chip.

Briefly explaining this flowchart below, FIG. 1a shows a piezoelectric substrate 1 whose surface has been polished, and FIG.
This figure shows a state in which a metal thin film 2 is formed by a well-known vapor deposition method, and in this state, it is formed into a shape having a cross-sectional structure of C by a well-known photoetching method.

In this state, a desired element chip 6 is formed by cutting while ensuring a cutting margin on the boundary metal portion 5, and a cross-sectional structure as shown in FIG. d can be obtained.

After this, it will be sent to the next process (not shown) up to the package sealing process.

FIG. 2 is a top model view of the structure shown in FIG. 1.

Reference numeral 7 indicates a cutting line on the boundary metal portion 5, and the other symbols are the same as in FIG.

Although FIG. 2 shows the case of three elements before division and cutting, it is clear that the same applies to a case where a large number of these elements are two-dimensionally arranged in a rectangular arrangement.

As shown in FIG. 2, the electrodes 3, 4 and the boundary metal part 5
The metal pattern is used to form one photomask at the same time, and especially the pattern of the boundary metal part 5 is
As shown in this figure, each boundary metal part 5 is formed of a metal thin film that has irregularities of the same size as the wavelength of the surface acoustic wave on both sides and strongly adheres to the piezoelectric substrate 1, so when cutting each boundary metal part 5, At the time of cutting, cutting stress is applied to the piezoelectric substrate 1 and the boundary metal part 5, so that by separating the boundary metal part 5, the wavelength of the surface acoustic wave of the boundary metal part is approximately the same along the cutting line of the piezoelectric substrate 1. The element chip 6 of the piezoelectric substrate 1 is shaped according to the degree of unevenness.
unevenness is formed on the side surface.

FIG. 3 is a partial model diagram showing the uneven shape 8 on the side surface of the element chip 6, and the other end is not shown.

Therefore, the surface acoustic waves that reach the end of the element without being converted into electrical signals by the electrodes 3 and 4 are scattered by the end face having the uneven shape 8, and what effect does this have on the f-characteristic of the end face reflection? is significantly reduced.

Further, the boundary metal portion 5 of each element chip is formed by incorporating the boundary metal portion pattern into a photomask used for forming the electric-mechanical converter electrodes 3 and 4.
, 4 may be formed at the same time, so they can be formed without adding any new process.

Therefore, the present invention can be achieved inexpensively.

In addition, the present invention provides a sound absorbing material tape on the end face of the element chip and its vicinity, applying and curing a resin sound absorbing material,
Similarly, it can be used in combination with the element chip of a surface acoustic wave device, which reduces the effect of unnecessary waves by forming unevenness on the surface acoustic wave propagation surface near the end face of the element chip, to completely reduce unnecessary waves. There is no need to state it again.

As described above, according to the present invention, deterioration of frequency characteristics and deterioration of pulse delay characteristics due to ripples caused by end face reflection can be easily prevented with good reproducibility and reliability, and without requiring any additional steps. , can be reduced.

Therefore, there is no increase in time or cost, and it can be easily used in combination with other methods such as pasting sound absorbing material on the end face and its vicinity, coating and curing resin sound absorbing material, etc., so that the effects can be combined. This is a significant contribution to this field.

[Brief explanation of drawings]

FIG. 1 is a flow explanatory diagram of the main parts of the method for manufacturing a surface acoustic wave device according to the present invention, and FIG.
FIG. 3 is an explanatory perspective view of the end of the element chip of the surface acoustic wave device according to the present invention (the other end is not shown). 1...Piezoelectric substrate, 2...Metal thin film,
3.40. ...Electrical/mechanical converter electrode, 5,...
, , boundary metal part, 60. . 00. Element chip, 7,... Division cutting allowance,
8. , , , Split fracture side.

Claims (1)

[Claims] 1. A surface acoustic wave device having a first step of forming a large number of electrical/mechanical transducers on the surface of a piezoelectric substrate, and a second step of dividing the piezoelectric substrate between adjacently formed electrical/mechanical transducers. In the manufacturing method, a step of forming a metal thin film having an uneven pattern in the propagation direction of the surface acoustic wave is provided before the second step at the dividing position of the surface of the piezoelectric substrate on the side where the electromechanical transducer is formed. . A method of manufacturing a surface acoustic wave device, characterized in that the division in the second step is performed at the boundary of the metal thin film.