JPH03214916A - Manufacture of surface acoustic wave element - Google Patents

Abstract

PURPOSE:To prevent the characteristic of a surface acoustic wave element from being changed due to adhesion by curing an adhesives at a glass dislocation temperature or below after an element chip is adhered by a flexible adhesives, applying degassing processing at the glass dislocation temperature or over and applying heat treatment for a prescribed time or over at the glass dislocation temperature or below so as to eliminate the distortion of the element chip. CONSTITUTION:A flexible adhesives 12 made by using composition ratio of one for a major agent and three for a curing agent is coated to a chip mount part 10b of a terminal board 10, and a surface acoustic wave element 14 is placed on the chip mount base 10b and adhered. Then heat treatment is applied for nearly two hours at a temperature below the glass dislocation temperature Tg (nearly 100 deg.C) of the flexible adhesives 12 to cure the flexible adhesives 12. Then degassing processing to eliminate the evaporation component of the excess curing agent or the like is applied, in which heat treatment is applied for nearly six hours at a temperature over the glass dislocation temperature Tg (nearly 100 deg.C) of the flexible adhesives 12. Then heat treatment is implemented for a long time at a temperature below the glass dislocation temperature Tg (nearly 100 deg.C) of the flexible adhesives 12 to eliminate distortion caused by the curing of the adhesives.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a surface acoustic wave device in which a device chip is bonded to a chip mounting portion using an adhesive.

[Prior Art] Surface acoustic wave elements are elements such as filters, resonators, and oscillators that utilize surface acoustic waves. As shown in FIG. 3, a normal surface acoustic wave element includes a chip lI placement part 10 of a terminal block 10 in which an electrode bin 10a is formed.
A surface acoustic wave element chip 14 with electrodes formed on the surface of the piezoelectric substrate is die-bonded to b with an adhesive l2,
It has a structure in which a cap 16 is placed over it. However, in conventional surface acoustic wave devices, stress is applied to the device chip 14 due to the hardening of the adhesive 12 that fixes the back surface of the device chip 14, causing distortion and changing the characteristics of the surface acoustic wave device. ? Moreover, since the stress applied to the element chip 14 varies depending on the type and amount of adhesive, the adhesive area, curing conditions, changes in adhesive over time, etc., the characteristics of the surface acoustic wave element vary greatly. For example, using a lithium tetraborate (LizB40) single crystal substrate as the piezoelectric substrate of the element chip 14,
When manufacturing a z-band surface acoustic wave filter, element chip 1
Figure 4 shows the change in the center frequency caused by die bonding 4 to the chip mounting section Job. FIG. 4(a) shows the center frequency of the element chip 14 before die bonding, and FIG. 2(b) shows the center frequency of the element chip 14 after die bonding. Before die bonding, the average value of the center frequency was 414.062 Mllz, but after die bonding, the average value of the center frequency was 4 1 3.980 MHz, about 82 Kllz (approximately 200 p for the center frequency of 414.062 Mllz).
pm) decreases. That is, the average value of the center frequency changes by about -82 KHz (about -200 ppm). Moreover, the variation in the center frequency increases. [Problems to be Solved by the Invention] As described above, in conventional surface acoustic wave devices, when the device chip is die-bonded using adhesive, the characteristics of the surface acoustic wave device change, and the surface acoustic wave device is not fixed as it is. There was a problem with this.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for manufacturing a surface acoustic wave device in which the characteristics do not change even when the device chip is bonded to the chip mounting portion. [Means for Solving the Problems] The above object is to provide a bonding process in which a surface acoustic wave element chip is bonded to a chip mounting portion using a flexible adhesive, and a bonding process at a temperature below the glass transition temperature of the flexible adhesive. a first heat treatment step in which the visible adhesive is cured by heat treatment; and a desorption step in which volatile components are removed from the visible adhesive by heat treatment at a temperature equal to or higher than the glass transition temperature under an atmospheric pressure of 1 atmosphere or less. It is characterized by comprising a second heat treatment step of performing gas treatment, and a third heat treatment step of performing heat treatment at a temperature below the glass transition temperature for a predetermined period of time or more to remove distortion of the surface acoustic wave element chip. This is achieved by a manufacturing method for surface acoustic wave devices. [Function] According to the present invention, after bonding element chips with a flexible adhesive, the adhesive is cured at a temperature below the glass transition temperature, and then degassing is performed at a temperature above the glass transition temperature. Since the distortion of the element chip is removed by heat treatment for a predetermined period of time below, the characteristics of the surface acoustic wave element do not change due to adhesion, and moreover, stable element characteristics can be ensured over a long period of time. [Example] A method for manufacturing a surface acoustic wave device according to an example of the present invention will be explained with reference to FIG. An example will be explained in which a 400 MHz band surface acoustic wave resonator filter is manufactured using a lithium tetraborate (Li.Bt07) single crystal substrate as the piezoelectric substrate of the element chip 14. In this example, as the visible adhesive An epoxy adhesive is used. For example, the main ingredient is Ecobond (ECCOBO).
ND) 45 Clear, Catalyst (CATAL) as hardening agent
I ST) 1 Use a flexible epoxy adhesive (manufactured by Grace) using 5 clear. First, a flexible adhesive 12 prepared at a ratio of 1 part base material and 3 parts curing agent is applied to the chip mounting portion 10b of the terminal block 10 (step SIO). Next, the surface acoustic wave element chip 14 is placed on the chip. Mounting table 10b
(Step Sit). Next, heat treatment is performed at a temperature below the glass transition temperature Tg (approximately 100° C.) of the flexible adhesive 12, for example, approximately 85° C., for approximately 2 hours to harden the flexible adhesive 12 (Step 31 2). The reason for curing at a temperature lower than the glass transition temperature Tg is that if the temperature is higher than the glass transition temperature Tg, the flexible adhesive 12 itself undergoes metamorphosis, gas generation due to volatile components, and changes in the hardness of the adhesive occur, causing the element to deteriorate. This is because the deterioration and frequency change of the chip 14 progresses significantly. Next, in a vacuum of -76 mmHg, for example, a temperature higher than the glass transition temperature Tg (about 100 °C) of the visible adhesive 12,
For example, heat treatment is performed at approximately 100° C. for approximately 6 hours, and degassing treatment is performed to remove volatile components such as excess curing agent (Step 813). This degassing treatment ensures the stability of the surface acoustic wave device's characteristics even when stored at high temperatures for long periods of time. Next, the glass transition temperature T of the flexible adhesive 12
(Step 314) FIG. 2 shows the relationship between heat treatment time and frequency change amount. As is clear from the figure,
The center frequency (which had changed by -400 ppm after the degassing treatment, that is, it had decreased by 400 ppm) gradually recovered as the heat treatment time progressed. It reaches the pre-bonding state (approximately Oppm) in about 140 hours, and becomes completely stable after more than 500 hours. Therefore, about 1
It can be seen that the distortion caused by the curing of the adhesive is almost completely removed by heat treatment for 50 to 200 hours or more. Thereafter, wire bonding is performed and a cap 16 is placed and sealed to complete the surface acoustic wave element.

The present invention is not limited to the above embodiments, and various modifications are possible. For example, the flexible adhesive is not limited to the epoxy adhesive used in the above embodiments, but other types of flexible adhesives may be used. When using other visible adhesives, the heat treatment temperature in each step also differs depending on the adhesive used. [Effects of the Invention] As described above, according to the present invention, after bonding element chips with a visible adhesive, the adhesive is cured at a temperature below the glass transition temperature, and then degassed at a temperature above the glass transition temperature. Later, the device chip was heat-treated at a temperature below the glass transition temperature for a predetermined period of time to remove distortion, so that the characteristics of the surface acoustic wave device did not change due to adhesion, and the surface acoustic wave device had stable characteristics for a long period of time. can be manufactured.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a method for manufacturing a surface acoustic wave device according to an embodiment of the present invention, FIG. 2 is a graph showing the relationship between heat treatment time and frequency change amount in the method for manufacturing a surface acoustic wave device, and FIG. is an exploded view of the surface acoustic wave device, and FIG. 4 is a graph showing the change in center frequency before and after bonding in the surface acoustic wave filter. In the figure, lO...terminal block 10a...electrode pin 10b...chip mounting part 12...adhesive 14...element chip 16...cap heat 9JL physical temperature = 85'C 2nd Three cranes

Claims (1)

[Scope of Claims] An adhesion step of adhering a surface acoustic wave element chip to a chip mounting portion with a flexible adhesive; and a heat treatment at a temperature below the glass transition temperature of the flexible adhesive to a first heat treatment step for curing the flexible adhesive; and a degassing step for removing volatile components from the flexible adhesive by heat treatment at a temperature equal to or higher than the glass transition temperature under an atmospheric pressure of 1 atmosphere or lower. 2, and a third heat treatment step of removing distortion of the surface acoustic wave device chip by performing heat treatment at a temperature equal to or lower than the glass transition temperature for a predetermined period of time or more. Production method.