JPH07106910A - Chip type piezoelectric resonator and its production - Google Patents

Abstract

PURPOSE:To obtain an external electrode that has a suppressed solder bite and has the improved soldering performance by forming a 2nd layer of copper and a 3rd layer of silver on a 1st layer having its soldering performance deteriorated by the barrel polishing. CONSTITUTION:When plural chip type piezoelectric resonators 1 are produced, a mother main surface electrode part serving as a 1st layer 43 is previously formed by caking of the copper paste in the state of a sandwich structure where both main surfaces of a mother piezoelectric substrate are covered with a mother shearthing resin layer. The sandwich structure is divided into pieces and undergoes the barrel polishing. Then the copper is plated on the layer 43 by a dry process so that a 2nd layer 44 is formed. The silver is plated on the layer 44 in a dry process and a 3rd layer 45 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip type piezoelectric resonator and a method of manufacturing the same, and more particularly to improvements in the structure and method of forming external electrodes.

[0002]

2. Description of the Related Art Piezoelectric resonators are used, for example, as filters, oscillators, discriminators, etc., and generally have leads. However, in recent years
Surface mounting technology has been adopted in order to reduce the size of electronic devices, and along with this, there is also a demand for chip-type piezoelectric resonators of this type without lead wires.

[0003]

[Related Application] In order to satisfy the above-mentioned demand, the applicant of the present application filed a patent application directed to “chip type piezoelectric resonator and its manufacturing method” on October 19, 1992, for example, in Japanese Patent Application No. 4-280008. Filed as an issue. In this earlier application, a chip-type piezoelectric resonator and a method for manufacturing the same are proposed as described below.

FIG. 2 is a perspective view showing the external appearance of the chip-type piezoelectric resonator 1 proposed in this earlier application. The chip-type piezoelectric resonator 1 includes a rectangular parallelepiped chip 8 having two main surfaces 2 and 3 parallel to each other and four end surfaces 4 to 7 connecting the main surfaces 2 and 3. A plurality of external electrodes 9 to 11 are formed on the outer surface of the chip 8. Each of these external electrodes 9 to 11 is formed so as to surround the chip 8, and has a main surface electrode portion 12 located on the main surfaces 2 and 3 and an end surface electrode portion 13 located on the end surfaces 4 and 6, respectively. Have.

The chip 8 also includes a piezoelectric substrate 14 extending in parallel with the main surfaces 2 and 3, and exterior resin layers 15 and 16 respectively covering both main surfaces of the piezoelectric substrate 14. Although not shown, on the main surface of the piezoelectric substrate 14, a plurality of vibrating electrodes facing each other with the piezoelectric substrate 14 sandwiched therebetween and a plurality of vibrating electrodes connected to the vibrating electrodes and electrically connected to the end face electrode portions 13 respectively. A terminal electrode is formed.

Such a chip type piezoelectric resonator 1 is shown in FIG.
Through the steps shown in FIG. 7 respectively.

First, as shown in FIG. 3, a mother piezoelectric substrate 17 is prepared. The mother piezoelectric substrate 17 has piezoelectricity and is made of piezoelectric ceramic such as PZT. A part of the mother piezoelectric substrate 17 is enlarged and shown in FIG.

Referring to FIG. 4, divided vibrating electrodes 18 and 19 are formed on one main surface of mother piezoelectric substrate 17, and vibrating electrodes 18 and 1 are formed on the other main surface.
The vibrating electrode 20 facing 9 is formed. Further, terminal electrodes 21, 22 and 23 are formed so as to be connected to the vibrating electrodes 18, 19 and 20, respectively. These one set of vibrating electrodes 18 to 20 and terminal electrodes 21 to 23 provide elements for one piezoelectric resonator 1, and the mother piezoelectric substrate 17 is provided with these plural sets of vibrating electrodes 18 to 2.
0 and terminal electrodes 21 to 23 are formed.

As described above, the piezoelectric resonator 1 is an energy trap type dual mode piezoelectric resonator utilizing the thickness extensional vibration mode, which has the divided vibration electrodes 18 and 19 and the vibration electrode 20 facing the divided vibration electrodes 18 and 19. The following measures are taken to secure the vibration space.

First, bank-shaped adhesive layers 24 and 25 are formed on each main surface of the mother piezoelectric substrate 17 so as to surround each region of the mother piezoelectric substrate 17 corresponding to each vibration region of the piezoelectric resonator 1. , For example, by printing.

On the other hand, a plurality of cover sheets 26 respectively covering the spaces surrounded by the adhesive layers 24 and 25 described above.
Mother sheets 28 and 29 formed with Nos. 27 and 27, respectively, are prepared. These mother sheets 28 and 29
Preferably has an insulating property and is made of, for example, a high heat resistant polyimide sheet. Mother sheet 2
In each of 8 and 29, preferably, the plurality of cover sheets 26 and 27 are held by connecting portions 30 and 31 that are narrower than the cover sheets 26 and 27. Also, the mother sheets 28 and 29 are
It is preferable to have the same external dimensions as the mother piezoelectric substrate 17.

Mother sheets 28 and 2 as described above
9 is arranged so as to cover each main surface of the mother piezoelectric substrate 17 so that the cover sheets 26 and 27 are bonded to the adhesive layers 24 and 25. At this time, as described above, if the outer dimensions of the mother sheets 28 and 29 are made equal to the outer dimensions of the mother piezoelectric substrate 17, the alignment between the mother sheets 28 and 29 and the mother piezoelectric substrate 17 is performed. Is easy.

Next, as shown in FIG. 5, the mother piezoelectric substrate 17 described above is fitted into the frame 32 together with the mother sheets 28 and 29, and in that state, both main surfaces of the mother piezoelectric substrate 17 are respectively attached. The uncured exterior resin 33 is poured so as to cover. This exterior resin 33 is then heated and thereby cured. As described above, since the cover sheets 26 and 27 are held by the comparatively thin connecting portions 30 and 31, when the exterior resin 33 is poured, the connecting portions 30 and 31 hardly block the flow of the exterior resin 33. Instead, the exterior resin 33 can sufficiently sneak into the gap between each of the connecting portions 30 and 31 and the mother piezoelectric substrate 17.

Next, the mother piezoelectric substrate 17 is taken out from the frame 32. As shown in FIG. 6 on both main surfaces of the mother piezoelectric substrate 17.
As shown in, the mother exterior resin layers 34 and 35 provided by the exterior resin 33 described above are respectively formed.

Next, the sandwich structure 36 in which both main surfaces of the mother piezoelectric substrate 17 are covered with the mother exterior resin layers 34 and 35 as described above is subjected to a plane polishing process. That is, in order to improve the dimensional accuracy in the thickness direction of the chip 8 of the chip-type piezoelectric resonator 1 to be obtained shown in FIG. 2 and the flatness of the main surfaces 2 and 3, the outer surface of each of the mother exterior resin layers 34 and 35 is increased. Are lap-polished, for example.

Next, as shown in FIG. 6, the external electrodes 9 to 11 shown in FIG. 2 are formed on both main surfaces of the sandwich structure 36.
The mother main surface electrode portions 37 to be the respective main surface electrode portions 12 are formed in stripes.

Next, the sandwich structure 36 is cut along the cut lines 38 and 39. By this cutting, the chips 8 for the individual piezoelectric resonators 1 are obtained, as shown in FIG. The terminal electrodes 21 to 23 described above are exposed on the end surface 4 of the chip 8. Further, the main surface electrode portion 12 provided by the mother main surface electrode portion 37 is formed on the main surface 2 above the chip 8, and the main surface 3 below the chip 8 is also not shown, Similar main surface electrode portion 12
Are formed.

Next, as shown in FIG. 2, the principal surface electrode portion 12
An end face electrode portion 13 is formed so as to be continuous with each. These end face electrode portions 13 are respectively the terminal electrodes 21 shown in FIG.
To 23 are electrically connected. In this way
A desired chip type piezoelectric resonator 1 is obtained.

[0019]

As shown in FIG. 8, the above-mentioned mother main surface electrode portion 37 has a predetermined pattern of a copper paste containing a copper powder 41 coated with a silver film 40 and a thermosetting resin 42. And is solidified by heating. The reason why the copper paste having such a composition is used is as follows.

First, with such a copper paste, the copper paste can be solidified by hardening the thermosetting resin 42.
Heating at a relatively low temperature such as 0 ° C. or lower is sufficient. When a high temperature of, for example, 300 ° C. or higher is required for solidification of the copper paste, the Curie point of the piezoelectric ceramic forming the mother piezoelectric substrate 17 is exceeded, and the mother piezoelectric substrate 1
7 deteriorates, and the mother exterior resin layers 34 and 35 also deteriorate.

Further, the presence of the thermosetting resin 42 contained in the copper paste can strengthen the adhesive force between the mother exterior resin layers 34 and 35.
Therefore, even if the sandwich structure 36 bends,
The mother main surface electrode portion 37 is connected to the mother exterior resin layers 34 and 3
No peeling from each of the 5

Further, the copper powder 4 on which the silver film 40 is formed
Since it contains 1, the oxidation on the surface of the copper powder 41 is prevented, and good solderability can be obtained.

However, after obtaining the chip 8 shown in FIG. 7 and before forming the end face electrode portion 13 shown in FIG.
In order to prevent disconnection between the main surface electrode portion 12 and the end surface electrode portion 13, barrel polishing is performed at the stage of the chip 8 shown in FIG. This barrel polishing acts not only on the edge portion of the chip 8 but also on the surface of the principal surface electrode portion 12. As a result, if the principal surface electrode portion 12 is cut to the position shown by the alternate long and short dash line in FIG. 8, the copper powder 41 is exposed on the surface and is oxidized, so that the solder in the principal surface electrode portion 12 is soldered. Wearability is reduced.

Therefore, an object of the present invention is to provide a chip type piezoelectric resonator and a method for manufacturing the same, which does not cause deterioration in solderability of the principal surface electrode portion of the external electrode as described above.

[0025]

According to the present invention, first, a rectangular parallelepiped chip having two main surfaces parallel to each other and four end surfaces connecting these main surfaces and an outer surface of the chip are formed. And a plurality of external electrodes each having a main surface electrode portion located on the main surface and an end surface electrode portion located on the end surface, wherein the chip has a piezoelectric substrate extending parallel to the main surface, and a piezoelectric substrate. Of the piezoelectric substrate, the plurality of vibrating electrodes facing each other with the piezoelectric substrate sandwiched therebetween, and the end face electrode portions electrically connected to the vibrating electrodes, respectively. In order to solve the above-mentioned technical problem, the main surface electrode portion is a copper paste applied on the end surface, which is directed to a chip-type piezoelectric resonator in which a plurality of terminal electrodes connected to is formed. A first layer formed by solidification, a second layer formed by dry plating copper on the first layer, and a third layer formed by dry plating silver on the first layer I am trying.

Further, in the method of manufacturing the chip-type piezoelectric resonator according to the present invention, the step of preparing a mother piezoelectric substrate having piezoelectricity and the step of preparing the mother piezoelectric substrate on the main surface of the mother piezoelectric substrate so as to face each other with the mother piezoelectric substrate sandwiched therebetween. Forming a plurality of sets of vibrating electrodes and terminal electrodes for a plurality of piezoelectric resonators each including a plurality of vibrating electrodes and a plurality of terminal electrodes connected to the vibrating electrodes, and covering both main surfaces of the mother substrate. Forming the exterior resin layer as described above, forming a first layer of the main surface electrode portion of the external electrode by applying a copper paste on the exterior resin layer in a predetermined pattern and solidifying the copper paste, and each of the terminal electrodes. So as to be exposed on the split surface, the mother piezoelectric substrate is split together with the exterior resin layer and the first layer to obtain chips for a plurality of piezoelectric resonators, a step of barrel polishing the chips, and Then, an end face electrode portion that is electrically connected to each terminal electrode and continuous with each main surface electrode portion is formed on the divided surface of each chip, and a second layer and a second layer formed by copper dry plating on the first layer are formed. And a step of forming respective third layers by silver dry plating.

[0027]

According to the present invention, the main surface electrode portion of the external electrode has the first layer formed by solidifying the copper paste, the second layer formed by dry plating copper, and the dry plating silver. And a third layer formed by. here,
The first layer enables high adhesion with the exterior resin layer, and the second layer prevents solder erosion of the main surface electrode portion,
The third layer prevents copper oxidation.

[0028]

Therefore, according to the present invention, it is possible to obtain a chip type piezoelectric resonator provided with the main surface electrode portion of the external electrode which can provide excellent solderability.

In particular, according to the method of manufacturing a chip-type piezoelectric resonator according to the present invention, a plurality of chip-type piezoelectric resonators are obtained by finally dividing the mother piezoelectric substrate to obtain a large number of chip-type piezoelectric resonators. You can get it. In addition, since the first layer in the main surface electrode portion of the external electrode is formed before the above-mentioned division, the formation of such a first layer can be performed efficiently.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Substantially the same steps as the steps shown in FIGS. 2 to 7 described above are also applied to one embodiment of the present invention. Therefore, referring again to FIGS. 2-7, like reference numerals are used for corresponding elements to describe embodiments of the invention. Note that redundant description may be omitted.

In order to obtain the chip type piezoelectric resonator 1 shown in FIG. 2, the mother piezoelectric substrate 17 shown in FIGS. 3 and 4 is prepared. As described above, the mother piezoelectric substrate 17 has piezoelectricity and is made of a piezoelectric ceramic such as PZT. Vibrating electrodes 18 and 19 are formed on one main surface of the mother piezoelectric substrate 17, and a vibrating electrode 20 facing the vibrating electrodes 18 and 19 is formed on the other main surface. In addition, the terminal electrodes 21, 2 are connected to the vibrating electrodes 18, 19 and 20, respectively.
2 and 23 are formed. One piezoelectric resonator 1 includes a set of these vibrating electrodes 18 to 20 and terminal electrodes 21 to 2
3, a plurality of sets of vibrating electrodes 18 to 20 and terminal electrodes 21 to 23 for the plurality of piezoelectric resonators 1 are formed on the mother piezoelectric substrate 17.

Further, bank-shaped adhesive layers 24 and 25 are formed on each main surface of the mother piezoelectric substrate 17 by printing, for example, so as to surround the regions corresponding to the respective vibration regions of the piezoelectric resonator 1. To be done.

On the other hand, a plurality of cover sheets 26 respectively covering the spaces surrounded by the adhesive layers 24 and 25 described above.
Mother sheets 28 and 29 having sheets 27 and 27 formed therein are prepared. In each of the mother sheets 28 and 29, the plurality of cover sheets 26 and 27 are held by the relatively narrow connecting portions 30 and 31.

Mother sheets 28 and 2 as described above
9 is arranged so as to cover each main surface of the mother piezoelectric substrate 17 so that the cover sheets 26 and 27 are bonded to the adhesive layers 24 and 25.

Next, as shown in FIG. 5, the mother piezoelectric substrate 17 is fitted in the frame 32 together with the mother sheets 28 and 29, and the uncured exterior resin is formed on each main surface of the mother piezoelectric substrate 17. 33 are poured respectively. This exterior resin 33 is then heated and thereby cured.

Next, as shown in FIG. 6, the sandwich structure 36 including the mother exterior resin layers 34 and 35 provided by the exterior resin 33 and the mother piezoelectric substrate 17 is taken out from the frame 32. Next, the outer surface of each of the mother exterior resin layers 34 and 35 is flat-polished,
Thereby, the dimensional accuracy and flatness in the thickness direction are improved.

Next, on the outer surfaces of the mother exterior resin layers 34 and 35, the mother main surface to be the first layer 43 (FIG. 1) of the main surface electrode portion 12 of each of the external electrodes 9 to 11 shown in FIG. The electrode part 37 is formed. In this embodiment, the mother main surface electrode portion 37 is formed by applying a copper paste in a predetermined pattern and solidifying it. Here, the copper paste may include the copper powder 41 on which the silver film 40 is formed as shown in FIG. 8 or the copper powder on which the silver film is not formed.

The sandwich structure 36 is then cut along the cut lines 38 and 39. By this cutting, a plurality of chips 8 for one chip-type piezoelectric resonator 1 as shown in FIG. 7 are obtained. On the end surface 4 of the chip 8, the terminal electrodes 21 to 23 are exposed. Note that, in FIG. 7, what is formed on the main surfaces 2 and 3 of the chip 8 is the first surface electrode portion 12 as a part of the first surface electrode portion 12.
Only layer 43. Therefore, in FIG. 7, the reference numeral “43” of the first layer is shown in parentheses. The chip 8 includes a piezoelectric substrate 14 extending in parallel with the main surfaces 2 and 3, and exterior resin layers 15 and 16 respectively covering both main surfaces of the piezoelectric substrate 14. Here, the piezoelectric substrate 14 is obtained by dividing the mother piezoelectric substrate 17, and the exterior resin layers 15 and 16 are obtained by dividing the mother exterior resin layers 34 and 35, respectively. .

Incidentally, the above-mentioned polishing and mother main surface electrode portion 3
The steps of forming and cutting 7 are sandwich structure 3
6 may be carried out while being held in the frame 32.

Next, the chip 8 is barrel-polished. As a result, the edge portion of the chip 8 is rounded and the surface of the first layer 43 is scraped off to some extent.

FIG. 1 is an enlarged sectional view showing a part of a chip type piezoelectric resonator 1 to be obtained by this embodiment. As shown in FIG. 1, the second layer 4 made of copper is formed on the first layer 43 by dry plating such as sputtering or vacuum deposition while using an appropriate mask (not shown).
4 is formed, and a third layer 45 made of silver is further formed thereon by the same dry plating. In this way, the principal surface electrode portion 12 is provided by the first layer 43, the second layer 44 and the third layer 45. Here, the first layer 43
Is bonded to each of the exterior resin layers 15 and 16 with a strong adhesive force, and the second layer 44 is connected to the main surface electrode portion 1
The solder erosion of No. 2 is prevented, and the third layer 45 improves the solderability of the main surface electrode portion 12. The functions of each of the second layer 44 and the third layer 45 are increased as the thickness of each is increased, but practically, each of them is 2 to 4 μm.
A moderate thickness is sufficient.

On the other hand, the end surface electrode portion 13 connected to the main surface electrode portion 12 is preferably formed as follows. Referring to FIG. 1, using a suitable mask (not shown), a first layer 46 of nickel-copper alloy having a thickness of about 1 μm is formed by dry plating such as sputtering, and the first layer 46 is formed thereon. The second layer 47 made of copper and the third layer 48 made of silver are formed by the same method with the same thickness as the second layer 44 and the third layer 45. This end face electrode part 1
3, the first layer 46 contributes to further prevention of solder erosion. In this way, the chip-type piezoelectric resonator 1 having the appearance as shown in FIG. 2 is obtained.

Although the present invention has been described above with reference to the illustrated embodiments, several modifications are possible within the scope of the present invention.

For example, the adhesive layers 24 and 25 and the cover sheets 26 and 27 are used in order to secure the vibration space in the chip type piezoelectric resonator 1, but the adhesive layers 24 and 25 and the cover sheets 26 and 27 may be replaced with other structures.

The chip-type piezoelectric resonator 1 shown in the drawing is
Although the energy trapping type dual mode piezoelectric resonator utilizing the thickness longitudinal vibration mode is used, the present invention can be applied to other types of piezoelectric resonators.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view showing a part of a chip-type piezoelectric resonator 1 according to an embodiment of the present invention.

FIG. 2 is a perspective view showing an external appearance of the chip-type piezoelectric resonator 1 shown in FIG.

3 is a perspective view showing a mother piezoelectric substrate 17 and mother sheets 28 and 29, which are prepared to obtain the chip-type piezoelectric resonator 1 shown in FIG. 1, separated from each other.

FIG. 4 is an enlarged perspective view showing a part of the mother piezoelectric substrate 17 shown in FIG.

5 is a perspective view showing a step of pouring an exterior resin 33 so as to cover each main surface of the mother piezoelectric substrate 17 shown in FIG.

FIG. 6 is a sandwich structure 3 in which a mother principal surface electrode portion 37 is formed after the exterior resin 33 shown in FIG. 5 is cured.
It is a perspective view showing 6.

7 is a perspective view showing the appearance of a chip 8 obtained by cutting the sandwich structure 36 shown in FIG.

8 is a cross-sectional view showing an enlarged composition of the principal surface electrode portion 12 shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chip type piezoelectric resonator 2,3 Main surface 4-7 End surface 8 Chip 9-11 External electrode 12 Main surface electrode part 13 End surface electrode part 14 Piezoelectric substrate 15,16 Exterior resin layer 17 Mother piezoelectric substrate 18-20 Vibration electrode 21 -23 Terminal electrode 33 Exterior resin 34,35 Mother exterior resin layer 37 Mother main surface electrode part 38,39 Cutting line 40 Silver film 41 Copper film 42 Thermosetting resin 43 First layer 44 Second layer 45 Third layer

Claims (2)

[Claims] 1. A rectangular parallelepiped chip having two main surfaces parallel to each other and four end surfaces connecting the main surfaces,
And a plurality of external electrodes, each of which is formed on the outer surface of the chip and has a main surface electrode section located on the main surface and an end surface electrode section located on the end surface, wherein the chip is the main surface A piezoelectric substrate extending in parallel with the piezoelectric substrate, and an exterior resin layer covering both main surfaces of the piezoelectric substrate, and a plurality of vibrating electrodes facing each other with the piezoelectric substrate sandwiched between the piezoelectric substrate and the main surface of the piezoelectric substrate. A plurality of terminal electrodes connected to the vibrating electrodes and electrically connected to the end face electrode parts respectively are formed. In the chip-type piezoelectric resonator, the main face electrode parts are copper provided on the end faces. A first layer formed by solidifying the paste, a second layer formed by dry plating copper on the first layer, and a first layer formed by dry plating silver on the first layer. A chip-type piezoelectric resonator having three layers. 2. A mother piezoelectric substrate having piezoelectricity is prepared, and a plurality of vibrating electrodes facing each other with the mother piezoelectric substrate sandwiched therebetween and a plurality of vibrating electrodes connected to the vibrating electrode are provided on the main surface of the mother piezoelectric substrate. Forming a plurality of sets of vibrating electrodes and terminal electrodes for a plurality of piezoelectric resonators each including a terminal electrode, forming an exterior resin layer so as to cover both main surfaces of the mother substrate, and on the exterior resin layer A copper paste is applied in a predetermined pattern and solidified to form a first layer of the main surface electrode portion of the external electrode, and the mother piezoelectric substrate is attached to the exterior resin layer so that each of the terminal electrodes is exposed on the divided surface. And divided together with the first layer to obtain chips for a plurality of piezoelectric resonators, barrel-polishing the chips, and then electrically connecting each of the terminal electrodes to the divided surface of each of the chips. And forming an end face electrode portion connected to each of the main face electrode portions, and forming a second layer by copper dry plating and a third layer by silver dry plating on the first layer, respectively. A method for manufacturing a chip-type piezoelectric resonator, comprising: