JPH02166909A - Method for performing fine adjustment on delay time of surface acoustic wave delay line - Google Patents

Abstract

PURPOSE:To perform fine adjustment on delay time with high accuracy by forming a film of thermoplastic resin polyparaxylene(parylene) on the surface of a substrate by a room temperature chemical vapor phase reaction method(room temperature CVD method), and controlling the thickness of the film. CONSTITUTION:After a surface acoustic wave(SAW) delay line 4 is inputted to a vapor deposition room 2 and is mounted on a jig 7 for measuring group delay characteristic, the vapor deposition room 2 is set in a vacuum state by evacuating by an exhaust system pump 3. And the thermoplastic resin parylene is introduced from an evaporation part 1 to the vapor deposition room 2 as measuring the delay time of the SAW delay line 4 by a network analyzer 5, and a shutter 9 is opened, and the parylene is deposited on the surface of the substrate of the SAW delay line 4, and the shutter 9 is closed at a time when it coincides with targeted delay time. In such a way, it is possible to perform the fine adjustment on the delay time with high accuracy as monitoring the delay time by a measuring instrument at a room temperature without occurring a thermal defect on the SAW delay line.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for fine-tuning the delay time of a surface acoustic wave (SAW) delay line in the manufacture of the same.

(Prior art) In the manufacturing process of a SAW delay line, factors that change the delay time (manufacturing deviation factors) include (1) variation in the sound speed of the substrate, (2) film thickness of electrode fingers, and (3) film within the wafer. Examples include thickness distribution. Even if these manufacturing deviation factors are controlled, a variation in delay time of about 0.3% occurs.

For this reason, it is difficult to adjust the delay time of SAW delay lines, which are normally manufactured with a delay time deviation of about 0.5%, to within the desired deviation using only normal processes due to the factors mentioned above. Recognize. In the end, it reduces the yield,
Decreases productivity.

Therefore, after manufacturing the SAW delay line, while monitoring the delay time with a measuring device, an insulating thin film (for example, 51
02) A method has been devised in which the film is deposited by t' sputtering or vacuum evaporation, and the delay time is finely adjusted.

(Problems to be Solved by the Invention) However, in the method of depositing 3102 and the like on the substrate surface by sputtering or vacuum evaporation, the temperature rise during film formation may cause thermal problems to the SAW delay line. The delay time changes depending on the temperature characteristics, and even if you adjust the delay time while monitoring it with an angle measuring device, it will change when the temperature returns to room temperature, making it difficult to make accurate fine adjustments. Ta.

The present invention was made to solve these drawbacks, and it is possible to measure the delay time with high precision while monitoring the delay time with a measuring device at room temperature without causing any thermal damage to the SAW delay line. The purpose is to allow fine adjustments.

(Means for Solving the Problems) The present invention uses a room-temperature chemical vapor phase reaction method (hereinafter referred to as "room-temperature CVD method") to prepare thermoplastic resin parylene while monitoring the delay time of a SAW delay line using a group delay characteristic measuring instrument or the like. In this method, fHi of parylene is formed by depositing it on the substrate surface of the SAW delay line, and the thickness of the formed parylene film is controlled to finely adjust the delay time.

(Function) The advantages of parylene film are: (1) Enables uniform WJ coating without pinholes (2) Easy to control film thickness (3) Excellent insulation properties and solvent resistance (4) Stress resistance It is effective as a coating material for finely adjusting the delay time on the substrate surface of a SAW delay line. Since this kind of thermoplastic resin parylene is formed into a film by the normal temperature CVD method,
There is no need to cause thermal trouble to the SAW delay line.

As a result, a SAW delay line with a delay time deviation of 0.1% or less can be efficiently designed and manufactured with high yield.
Furthermore, the variable amount of the delay time according to the present invention is about 2%, which is a range in which the insertion loss does not increase, which is sufficiently large compared to the manufacturing deviation, and can contribute to improving productivity.

(Example) Fig. 1 is a diagram showing an example of an apparatus for carrying out the method of the present invention, and Fig. 2
The figure is an enlarged view of the area around the SAW delay line in the deposition chamber, where 1 is the evaporation part of the thermoplastic resin parylene, 2 is the deposition chamber, 3 is the exhaust system pump, 4 is the SAW delay line, and 5 is the area for measuring group delay characteristics. Network analyzer, 6 is a cover for exposing the board surface 7
8 is a jig for measuring group delay characteristics, 8 is a coaxial cable for measurement, 9 is
is the shutter.

To operate this, first cover the SAW delay line 4 with the substrate surface exposure cover 6 so that only the substrate surface is exposed.
After putting the SAW delay UJ4f:M into the deposition chamber 2 and attaching it to the group delay characteristic measurement jig 7, the inside of the deposition chamber 2 is evacuated by the exhaust system pump 3 to create a vacuum. and SAW delay line 4
While measuring the delay time of
It is introduced into the vapor deposition chamber 2 from above. Then open shutter 9 and SAW delay! As parylene is deposited on the surface of the substrate 4, the propagation speed of the surface wave slows down due to the mass of the parylene, and the delay time of the SAW delay line 4 increases. Therefore, the shutter 9 is closed when the desired delay time coincides with the end of the deposition of the thermoplastic resin parylene.

(Effect of the invention) This method allows fine adjustment of the delay time while constantly monitoring the group delay time characteristics of the SAW delay line at room temperature, so the delay time can be adjusted in real time.
There are advantages not available with conventional methods. Further, there are advantages in that the yield is improved and it is possible to design and manufacture a highly accurate SAW delay line with a delay time deviation of 0.1% or less.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of an apparatus for carrying out the method of the present invention, and FIG.
The figure is an enlarged view of the area around the SAW delay line inside the deposition chamber. DESCRIPTION OF SYMBOLS 1... Evaporation part, 2... Vapor deposition chamber, 3... Exhaust system pump, 4... SAW delay line, 5... Network analyzer, 6... Cover for substrate surface exposure 7... Group delay characteristic measurement jig, 8... Coaxial cable for measurement, 9... Shutter

Claims (1)

[Claims] In a method of finely adjusting the delay time of a surface acoustic wave delay line while monitoring the delay time with a measuring device, thermoplastic resin poly para
ene) (hereinafter referred to as parylene) is deposited on the surface of the substrate of the surface acoustic wave delay line by a room temperature chemical vapor reaction method to form the parylene film, and the film is formed while monitoring the delay time with a measuring device. A method for finely adjusting the delay time of a surface acoustic wave delay line, characterized in that the delay time is finely adjusted by controlling the thickness of the parylene film.