JPH0685591A - Manufacture of chip-type piezoelectric element - Google Patents

Abstract

PURPOSE:To always properly form a cavity for a vibration space at a chip-type piezoelectric element which can be mounted on the surface and is armoured by resin. CONSTITUTION:A mother board 21 formed plural piezoelectric resonators 29 is prepared on a piezoelectric substrate 22, dams 30a for surrounding vibration areas are formed on the respective main faces of the mother board 21 and after a void forming member 30 is charged into the dams 10a, the thermosetting armour resin is applied so as to cover both of the faces of the mother board 21 and set. At the same time, the cavity forming member 30 is moved into the armour resin and as a result, the cavity for the vibration space. The plural chip-type piezoelectric resonators are provided by dividing the mother board 21 covered with the armour resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a chip type piezoelectric resonator used as a chip type filter, an oscillator, a discriminator, or the like.

[0002]

2. Description of the Related Art Piezoelectric resonators conventionally used as filters, oscillators, and discriminators have generally been leads.

However, in recent years, surface mounting technology (SMD) has been adopted in order to miniaturize electronic devices, and along with this, this type of piezoelectric resonator also has a chip type without a lead wire. Is required. A specific example of such a chip type piezoelectric resonator will be described with reference to FIGS. 11 to 13.

As shown in FIGS. 11 to 13, the piezoelectric resonator 1 includes a piezoelectric substrate 2. Divided vibrating electrodes 3 and 4 are formed on one main surface of the piezoelectric substrate 2,
On the other main surface, a vibrating electrode 5 facing the vibrating electrodes 3 and 4 is formed. These vibrating electrodes 3, 4 and 5
To the terminal electrodes 6, 7 and 8, respectively,
These terminal electrodes 6 to 8 are located at the edges of the piezoelectric substrate 2.

This piezoelectric resonator 1 is an energy trap type dual-mode piezoelectric resonator utilizing a thickness extensional vibration mode, which has divided vibration electrodes 3 and 4 and a vibration electrode 5 facing them. On both sides of the piezoelectric substrate 2,
Resin plates 11 and 12 made of polyphenylene sulfide (PPS) having cavities 9 and 10, respectively, are arranged at locations corresponding to the vibrating electrodes 3 to 5, and are bonded to the piezoelectric substrate 2 by adhesives 13 and 14. Further, as shown in FIG. 13, external electrodes 15, 16 and 71 are formed on the outer surface of the piezoelectric resonator 1,
It is electrically connected to the terminal electrodes 6, 7 and 8, respectively.

Such a chip-type piezoelectric resonator 1 has the advantages that it is small and can be surface-mounted.

[0007]

However, although the resin plates 11 and 12 are bonded to the piezoelectric substrate 2 with the adhesives 13 and 14, the bonding strength is relatively weak, and as a result, the vibration of the piezoelectric resonator 1 occurs. There is a problem in that the effect of suppressing spurious by suppressing unnecessary vibrations in parts other than the parts does not appear.

Further, since the adhesives 13 and 14 are used, there is a problem that moisture easily enters from the interface between the piezoelectric substrate 2 and the resin plates 11 and 12, and the moisture resistance is poor.

Further, the resin plates 11 and 1 are mounted on the piezoelectric substrate 2.
Since 2 is adhered by the adhesives 13 and 14, it is difficult to align the vibrating electrodes 3 to 5 with the cavities 9 and 10 of the resin plates 11 and 12, which is an obstacle to automation.

Therefore, an object of the present invention is to provide a method for manufacturing a chip type piezoelectric resonator which can solve the above-mentioned problems.

[0011]

The method for manufacturing a chip type piezoelectric resonator according to the present invention is characterized by including the following steps in order to solve the above-mentioned technical problems.

That is, first, a mother substrate is prepared on which a plurality of piezoelectric resonance elements each including a vibrating electrode facing each other with the piezoelectric substrate sandwiched and terminal electrodes connected thereto are prepared on the piezoelectric substrate. Next, a bank is formed on each main surface of the mother substrate so as to surround each vibration region of the piezoelectric resonance element. Next, a cavity forming material is provided in these bank. Then, a thermosetting exterior resin is applied in an uncured state so as to cover both main surfaces of the mother substrate. Next, the exterior resin is cured and the cavity forming material is transferred into the exterior resin, and as a result, a cavity for the vibration space is formed. Next, the mother substrate covered with the exterior resin is divided into individual piezoelectric resonance elements so that the terminal electrodes are exposed on the division surfaces, and a plurality of chip-type piezoelectric resonators are obtained.

[0013]

According to the present invention, the bank is formed in a state of being aligned with each of the vibration regions of the plurality of piezoelectric resonance elements provided by the mother substrate, and the cavity forming material is provided in the bank, and then the mother substrate is formed. The exterior resin is applied so as to cover both main surfaces of. The above-mentioned cavity forming material moves into the exterior resin when the exterior resin is cured, and as a result, forms a cavity for the vibration space in relation to the vibration region of the piezoelectric resonance element. Therefore, it is possible to form a cavity in the exterior resin that is always properly aligned with the vibration region.

Further, the exterior resin is applied so as to cover both main surfaces of the mother substrate in an uncured state, and is cured in that state. Therefore, a large adhesive strength can be obtained between the exterior resin and the mother substrate, and as a result, unnecessary vibrations other than the vibration part of the piezoelectric resonator can be sufficiently suppressed. Moreover, the humidity resistance of the obtained piezoelectric resonator can be improved.

Further, according to the present invention, since the mother substrate covered with the exterior resin is finally divided to obtain a plurality of chip type piezoelectric resonators, a large number of chip type piezoelectric resonators can be efficiently obtained. it can. Here, as described above, since the cavity is always formed by the bank in a proper shape,
Since the cavities do not expose a part of the cavities, the manufacturing yield can be improved.

[0016]

1 is a perspective view showing a chip type piezoelectric resonator 20 obtained by a manufacturing method according to an embodiment of the present invention. In order to obtain such a piezoelectric resonator 20, the steps shown in FIGS. 2 to 8 are performed.

First, as shown in FIG. 2, a mother substrate 21
Is prepared. A part of the mother substrate 21 is enlarged and shown in FIG. The mother substrate 21 is provided with a piezoelectric substrate 22 made of piezoelectric ceramic. Divided vibrating electrodes 23 and 24 are formed on one main surface of the piezoelectric substrate 22, and these vibrating electrodes 23 and 24 are formed on the other main surface. The vibrating electrode 25 is formed so as to face the. Vibrating electrode 2
3, 24 and 25 have terminal electrodes 26, 2 respectively.
7 and 28 are connected. These one set of vibrating electrodes 23
25 to 25 and the terminal electrodes 26 to 28 constitute one piezoelectric resonance element 29, and the mother substrate 21 provides a plurality of piezoelectric resonance elements 29.

The piezoelectric resonance element 29 is composed of divided vibration electrodes 23 and 24 and a vibration electrode 25 facing them.
Is a dual-mode piezoelectric resonator of energy trapping type that utilizes the thickness longitudinal vibration mode, and the following treatment is performed to secure the vibration space. That is, the bank 30 a is formed on each main surface of the mother substrate 21 so as to surround each vibration region of the piezoelectric resonance element 29. Figure 2
In FIG. 3 and FIG. 3, only the bank 30a formed on one main surface of the mother substrate 21 is shown, but a similar bank is also formed on the other main surface. These bank 30a is formed by printing ink, resin, etc., for example. Next, the cavity forming material 30 made of, for example, wax is provided in the bank 30a.

The above-mentioned provision of the cavity forming material 30 is preferably carried out as shown in FIG. First, as shown in FIG. 4 (a), after forming a bank 30a on the main surface of the mother substrate 21, as shown in FIG. 4 (b), at a substantially central portion of a region surrounded by the bank 30a, The cavity forming material 30 is dropped. The wax used as the cavity forming material 30 becomes liquid by being heated, and thus such dropping is possible. The cavity forming material 30 dropped in this manner is shown in FIG.
As shown in (c), it spreads within the bank 30a. In Figure 4,
Although only the bank 30a and the cavity forming material 30 formed on the one main surface of the mother substrate 21 are illustrated, the mother substrate 21
The same operation is performed on the other main surface of. In addition,
In order to increase the fluidity of the cavity forming material 30 from the state shown in FIG. 4 (b) to the state shown in FIG. 4 (c),
The cavity forming material 30 may be heated. This heating is preferably performed by blowing hot air, for example, on each main surface of the mother substrate 21. This is because, for example, if the entire mother substrate 21 is heated, the cavity forming material 30 provided on the downward facing main surface may fall off due to heating.

On the other hand, as shown in FIG. 5, a frame 31 made of, for example, a resin into which the above-mentioned mother substrate 21 can be fitted almost exactly is prepared. This frame 31 has a temperature (for example, 150 ° C.) at the time of heat curing of the exterior resin described later.
It is taken into consideration that it does not deform or melt. Further, when the outer side surface 32 of the frame 31 is used as a reference plane for cutting, which will be described later, it is desirable that the flatness is good.

Further, it is preferable to provide the frame 31 with a means capable of fixing the mother substrate 21 to be inserted therein to substantially the center of the frame 31 in the thickness direction. In this example,
The shelves 33 are provided inside the opposite sides (for example, short sides) of the frame 31.

As shown in FIG. 6, the mother substrate 2 described above is used.
1 is fitted in the frame 31, and in that state, the uncured exterior resin 3 is formed on one surface of the mother substrate 21 as shown in FIG.
4 is poured. As the exterior resin 34, for example, an epoxy thermosetting resin liquefied by a solvent is used, and an appropriate amount of filler such as silica or talc is added thereto. The exterior resin 34 is dried by, for example, natural drying, and the frame 31 is attached to the mother substrate 2
After the exterior resin 34 does not flow out even if it is reversed together with 1, the frame 31 is provided with the mother substrate 21 and the exterior resin 34.
Along with this, the exterior resin 34 is poured again onto the other surface of the mother substrate 21 in this state. The exterior resin 34 is also naturally dried, for example.

Next, the exterior resin 34 poured in two steps as described above is, for example, at 150 ° C. for 30 minutes,
Heat cured. At this time, the cavity forming material 30 described above
Migrate into the exterior resin 34, and as a result, a cavity for the vibration space is formed.

Next, in order to improve the dimensional accuracy and flatness in the thickness direction of the chip-type piezoelectric resonator 20 (FIG. 1) to be obtained, the outer surface of each exterior resin 34 is polished together with the frame 31. This polishing is performed, for example, by rubbing polishing using a polishing plate. As a result, a sandwich structure 35 in which both surfaces of the mother substrate 21 are covered with the exterior resin 34 as shown in FIG. 8 is obtained.

Next, as shown in FIG. 8, this sandwich structure 35 is provided with the frame 31 and the outer surface 32 of the frame 31.
Is taken as a reference plane and cut along the cutting lines 36 and 37. By this cutting, the mother substrate 21 is divided into individual piezoelectric resonance elements 29, and the terminal electrodes 26 to
28 is exposed on the cut surface. In this way, the chip-type piezoelectric resonator 20 as shown in FIG. 1 is obtained.

The above-mentioned polishing and cutting steps are
It may be implemented with the sandwich structure 35 taken out from the frame 31.

Next, as shown in FIG. 9, on the surface of the chip type piezoelectric resonator 20 where at least the terminal electrodes 26 to 28 are exposed, the external electrodes 38 which are electrically connected to the terminal electrodes 26 to 28, respectively. ~ 40 are applied, for example by printing and baking a conductive paste.

In this embodiment, all the terminal electrodes 26 to 28 of the chip type piezoelectric resonator 20 are exposed on the same surface, but such terminal electrodes may be exposed on different surfaces. In that case, external electrodes may be provided on each of these surfaces.

Further, as shown in FIG. 10, the external electrodes 3 which are electrically connected to the terminal electrodes 26 to 28 of the chip type piezoelectric resonator 20.
8a, 39a, 40a may be formed not only on one side surface of the chip-type piezoelectric resonator 20 but also on at least one of the upper and lower surfaces, and further on the other side surface. By doing so, when the chip-type piezoelectric resonator 20 is mounted on the circuit board, soldering thereof can be reliably achieved. It should be noted that, of the external electrodes 38a to 40a, the portions formed on the upper surface and / or the lower surface of the chip-type piezoelectric resonator 20 are printed in advance with a conductive paste and baked in the state of the sandwich structure 35 shown in FIG. It may be given by the method of.

In the above-described embodiment, if the color of the bank 30a is different from the colors of the piezoelectric substrate 20 and the exterior resin 34, when the bank 30a is exposed by cutting at an improper position, Can be easily visually identified. Thus, the exposed bank 30a is not sufficiently sealed by the exterior resin 34 and should be a defective product.

[Brief description of drawings]

FIG. 1 is a perspective view showing an external appearance of a chip type piezoelectric resonator 20 obtained according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a mother substrate 21 prepared to obtain the chip-type piezoelectric resonator 20 shown in FIG.

3 is an enlarged perspective view showing a part of the mother board 21 shown in FIG.

FIG. 4 is a cross-sectional view for explaining a step of providing a cavity forming material 30 in the bank 30a shown in FIGS. 2 and 3.

5 is a perspective view showing a frame 31 used to obtain the chip-type piezoelectric resonator 20 shown in FIG.

6 is a perspective view showing a state in which the mother board 21 shown in FIG. 2 is fitted into the frame 31 shown in FIG.

FIG. 7 is an exterior resin 34 on the mother substrate 21 shown in FIG.
It is a perspective view showing the state of pouring.

8 is a perspective view for explaining a cutting step of a sandwich structure 35 obtained after curing the exterior resin 34 shown in FIG.

9 is a perspective view showing a state where external electrodes 38 to 40 are formed on the chip-type piezoelectric resonator 20 shown in FIG.

10 is a perspective view showing a state in which external electrodes 38a to 40a are formed on the chip-type piezoelectric resonator 20 shown in FIG.

11 is an exploded perspective view showing elements included in a conventional chip-type piezoelectric resonator 1. FIG.

12 is a sectional view of the chip-type piezoelectric resonator 1 shown in FIG.

13 is a perspective view showing the external appearance of the chip-type piezoelectric resonator 1 shown in FIG.

[Explanation of symbols]

 20 Chip Type Piezoelectric Resonator 21 Mother Substrate 22 Piezoelectric Substrate 23-25 Vibration Electrode 26-28 Terminal Electrode 29 Piezoelectric Resonance Element 30a Bank 30 Cavity Forming Material 34 Exterior Resin 36, 37 Cutting Line 38-40, 38a-40a External Electrode

Claims (1)

[Claims] 1. A mother substrate on which a plurality of piezoelectric resonant elements each including a vibrating electrode facing each other with the piezoelectric substrate sandwiched therebetween and terminal electrodes connected to the vibrating electrodes are prepared, and each of the piezoelectric resonant elements is prepared. Is formed on each main surface of the mother substrate so as to surround the vibration region of the mother substrate, a cavity forming material is provided in the bank, and then a thermosetting exterior resin is formed so as to cover both main surfaces of the mother substrate. Is applied in an uncured state, the exterior resin is cured, and the cavity forming material is transferred into the exterior resin, as a result, a cavity for a vibration space is formed, and then covered with the exterior resin. And a step of dividing the mother substrate for each of the piezoelectric resonance elements so that the terminal electrodes are exposed on the division surface to obtain a plurality of chip-type piezoelectric resonators. Manufacturing Method.