JPH04280506A - Manufacture of resin package piezoelectric component - Google Patents

Abstract

PURPOSE:To improve the non-defective rate by employing cavity forming members whose melting points differ from each other to form a cavity so as to prevent wax from remaining on a piezoelectric vibration element. CONSTITUTION:Piezoelectric vibration elements 12,14 to which two kinds of wax 22,24 are dripped are dipped in package resin 26 made of a thermosetting resin. Then the resin 26 is heated and a solvent included in the resin 26 is evaporated and air bubbles are caused in the resin 26. When the internal temperature of the resin 26 gradually increases and reaches a melting point TA of the wax 22, the wax 22 starts being absorbed by the resin 26. When the temperature further rises and reaches a melting pint TB of the wax 22, the wax 24 starts being absorbed by the resin 26. The cavity for a vibration electrode is formed to a part to which the wax 22, 24 are dripped by the absorption of the wax 22, 24 by the resin 26. Thus, the cavity is surely formed and the remaining of the wax to the vibration electrode is avoided, the non-defective rate is improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a resin-clad piezoelectric component, and more particularly to a method of manufacturing a resin-clad piezoelectric component in which two or more cavities are formed to secure a vibration space for a piezoelectric vibrating element.

0002

2. Description of the Related Art FIG. 3 shows a composite trap as an example of a conventional piezoelectric component of this type. This composite trap 1
, one end of a terminal 3 is connected to the piezoelectric vibrating element 2, one end of a terminal 5 is connected to the piezoelectric vibrating element 4, and the terminals 3 and 5 are connected with solder 6 at the other end. Then, wax 7 as a cavity forming material is dripped onto the vibrating parts of the piezoelectric vibrating elements 2 and 4, and then the piezoelectric vibrating elements 2
and 4 are covered with an exterior resin 8, and the exterior resin 8 is further heated and hardened. The wax 7 is absorbed into bubbles generated when the solvent in the exterior resin 7 evaporates when the exterior resin 8 is heated and hardened, thereby forming cavities in the vibrating portions of the piezoelectric vibrating elements 2 and 4.

0003

[Problems to be Solved by the Invention] However, the amount of air bubbles in the exterior resin 8 increases almost in proportion to the heating time, whereas the wax 7 melts rapidly once it reaches its melting point, so it is difficult to maintain a sufficient amount of the wax 7. In some cases, it is not absorbed into the exterior resin 8 and remains on the vibrating electrode. This is remarkable in the portion sandwiched between the two piezoelectric vibrating elements 2 and 4, where the amount of exterior resin 8 is smaller than the amount of wax 7.

Possible ways to solve this problem include using a wax with a low melting point and allowing sufficient heating time, or heating at a higher temperature to increase the amount of bubbles generated per unit time. . However, in the former method, since the wax melts at a low temperature, the wax that cannot enter the bubbles mixes with the exterior resin and adheres to the vibrating electrode portion. Further, in the latter method, although the amount of bubbles generated is sufficient for the amount of wax, there is a problem that if the temperature is too high, the characteristics of the piezoelectric vibrating element will deteriorate.

[0005] Therefore, the main object of the present invention is to provide a method of manufacturing a resin-clad piezoelectric component in which the piezoelectric vibrating element is not deteriorated and the cavity forming material is not left behind.

[0006]

[Means for Solving the Problems] The present invention provides a resin-clad piezoelectric component having at least one piezoelectric element and forming two or more independent cavities in relation to the piezoelectric element in the exterior resin covering the piezoelectric element. A method of manufacturing a resin-clad piezoelectric component is characterized in that cavity forming materials having different melting points are used to form a cavity.

[0007]

[Effect] The exterior resin hardens at approximately 150°C, but when heating is started to harden the exterior resin, bubbles are gradually generated within the exterior resin, and one of the cavity forming materials melts at a relatively low temperature. Begin to. Therefore, one of the cavity forming materials is first absorbed into the air bubbles within the exterior resin. Thereafter, as time passes, the number of air bubbles in the exterior resin increases, and one of the cavity-forming materials is absorbed by the air bubbles and diffuses into the surrounding resin as well. Then, as time passes, the other cavity-forming material also melts, and is therefore also absorbed into the bubbles one after another. At this time, since the temperature is high (≦150° C.), more air bubbles are formed, and the other cavity forming material is also completely absorbed. In this way, by using cavity forming materials with different melting points, there is a time difference in absorption into the exterior resin,
As a result, each cavity forming material is completely absorbed by the time the exterior resin is completely cured.

[0008]

According to the present invention, since the cavity forming material is completely absorbed into the exterior resin, wax does not remain on the piezoelectric vibrating element, and the yield rate can be increased. Furthermore, since there is no need to raise the temperature to a particularly high temperature, problems such as deterioration of the characteristics of the piezoelectric vibrating element do not occur. The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0009]

[Embodiment] The composite trap 10 shown in FIG. 1 includes two piezoelectric vibrating elements 12 and 14 in which vibrating electrodes (not shown) are formed on both principal surfaces of a piezoelectric substrate made of, for example, ceramic.
including. A terminal 16 is connected to the piezoelectric vibrating element 12, and a terminal 18 is connected to the piezoelectric vibrating element 14, respectively. When the piezoelectric vibrating element 10 is viewed from the side, the terminals 16 and 18 are
The sides of each terminal not connected to the piezoelectric vibrating element are connected with solder 20 in a V-shaped state.

Wax is dripped onto the vibrating electrode portions of the piezoelectric vibrating elements 12 and 14 thus formed. Wax 22 is dripped onto the vibrating electrode portion of the piezoelectric vibrating element 12, and wax 24 is dripped onto the vibrating electrode portion of the piezoelectric vibrating element 14, respectively. The melting points of waxes 22 and 24 are moderately lower than the heating temperature of exterior resin 26, which will be described later, and the melting points of waxes 22 and 24 are different from each other. Here, the melting point of the wax 22 is TA, and the melting point of the wax 24 is TB. The melting point of each wax may be lower than the other, but in this example, wax 2
The melting point TA of wax 24 is lower than the melting point TB of wax 24.

In this way, the piezoelectric vibrating elements 12 and 14 on which the two types of waxes 22 and 24 have been dripped are coated with an exterior resin 2 made of a thermosetting resin such as an epoxy resin.
Dip at 6. Then, the exterior resin 26 is heated and hardened at about 150°C. By heating the exterior resin 26, the solvent contained in the exterior resin 26 evaporates and bubbles are generated within the exterior resin 26. The temperature inside the exterior resin 26 also gradually increases, and when the melting point TA of the wax 22 is reached, the wax 22 begins to be absorbed into the exterior resin 26. and,
When the temperature inside the exterior resin 26 further increases and reaches the melting point TB of the wax 24, the wax 24 melts into the exterior resin 26.
begins to be absorbed. By absorbing the waxes 22 and 24 into the exterior resin 26, the waxes 22 and 24
A cavity for the vibrating electrode is formed in the area where the liquid is injected.

That is, when heating is started to harden the exterior resin 26, bubbles are gradually generated within the exterior resin 26, and one wax 22 begins to melt at a relatively low temperature TA. Therefore, one wax 22 is first absorbed into the air bubbles within the exterior resin 26. Thereafter, as time passes, the number of bubbles in the exterior resin 26 increases, and the wax 22 is absorbed by the bubbles and diffuses into the surrounding resin. Then, as time passes, the temperature inside the exterior resin 26 also becomes high (≦
150° C.), the other wax 24 also melts, and is therefore also sequentially absorbed into the bubbles. At this time, since the temperature is high, more air bubbles are formed, and the wax 24 is also completely absorbed. In this way,
By using waxes 22 and 24 with different melting points, there is a time difference in absorption into the exterior resin 26, so that each wax 22 and 24 is completely absorbed into the exterior resin 26 by the time the exterior resin 26 is completely cured. Absorbed.

In this way, the waxes 22 and 24 are
Since it is absorbed into the exterior resin 26 in stages, the amount of air bubbles generated in the exterior resin 26 and the amount of each wax 22 and 24 absorbed into the exterior resin 26 match well, and each wax 2
2 and 24 are smoothly and completely absorbed into the exterior resin 26. As a result, a cavity is reliably formed and no wax remains on the vibrating electrode portion, resulting in a high yield rate.

Note that if the melting point TB of the wax 24 is set at a temperature at which the wax 22 will be sufficiently absorbed,
The absorption of each wax takes place better. However, this is not a condition; TA < TB or TA > TB
That's fine. This method uses a single trap 3 as shown in Figure 2.
It can also be used in the production of 0. The single trap 30 shown in FIG. 2 includes one piezoelectric vibrating element 32 to which a terminal 34 is connected. Wax 22 is applied to the vibrating electrode portion on one main surface of the piezoelectric vibrating element 32, and wax 24 is applied to the vibrating electrode portion on the other main surface.
is instilled. In this way, the piezoelectric vibrating element 32 dripped with the waxes 22 and 24 is covered with the exterior resin 36 made of a thermosetting resin similar to the aforementioned exterior resin 26, and the exterior resin 36 is cured. At this time, the same two-stage absorption of the waxes 22 and 24 as described above is performed, and all the waxes are completely absorbed into the exterior resin 36.

[0015] In each of the above embodiments, a trap using an energy trapping type piezoelectric vibrating element has been described, but the present invention is applicable to any piezoelectric component using a similar energy trapping type piezoelectric vibrating element (or resonant element). Of course, it can also be used for piezoelectric filters, for example. Furthermore, although wax was used as a cavity forming material,
In this invention, other than wax, known cavity forming materials such as paraffin may be used. However, since paraffin undergoes a phase change from a solid to a gas without passing through a liquid phase, the term "melting point" should be understood to include not only the temperature at which it changes from a solid to a liquid, but also the temperature at which it directly changes from a solid to a gas.

[Brief explanation of the drawing]

FIG. 1 is an illustrative side cross-sectional view showing one embodiment of the present invention.

FIG. 2 is an illustrative side cross-sectional view showing another embodiment of the invention.

FIG. 3 is an illustrative side cross-sectional view showing a conventional technique.

[Explanation of symbols]

10...Composite trap 12,1
4, 32...Piezoelectric vibration element 16, 18, 34...Terminal 22, 24...Wax 26, 36...Exterior resin

Claims (1)

[Claims] 1. A method of manufacturing a resin-clad piezoelectric component having at least one piezoelectric element and forming two or more independent cavities in association with the piezoelectric element in an exterior resin covering the piezoelectric element, wherein the cavity 1. A method for manufacturing a resin-clad piezoelectric component, characterized in that cavity forming materials having different melting points are used to form the piezoelectric component.