JP2003158440A - Joining member, piezoelectric vibration device using the joining member, and manufacturing method for the piezoelectric vibration device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joining material whose supply amount can be fine and constant and to obtain a piezoelectric vibration device with excellent characteristics by using such a joining member. SOLUTION: The joining member B is a fine particle which is spherical on the whole and comprises a core B1, a conductive film B2 which is formed on the core surface, and a thermoplastic resin film B3 which is formed on the surface of the conductive film. On electrode pads 12 and 16, the joining member B is mounted and a crystal diaphragm 2 is so mounted that lead-out electrodes 211 and 221 face the top part of the joining member B. The joining member B is interposed and heated up to specific temperature and then naturally cooled to carry out electromechanical joining.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joining member, particularly to a joining member used for joining an electronic element in a piezoelectric vibrating device or the like, and to a piezoelectric vibrating device using the joining material and a method for manufacturing the same. .

[0002]

2. Description of the Related Art Piezoelectric vibrating devices such as crystal oscillators and crystal filters are dominated by surface mount type using a ceramic package, and in order to cope with ultra miniaturization in this type as well, An increasing number of configurations do not use an elastic support made of a metal support to support the crystal diaphragm. However, in order to secure impact resistance even when the elastic support is not used, a silicon-based conductive resin adhesive is often used when fixing the crystal diaphragm to the ceramic package. The silicone-based conductive resin adhesive has flexibility even after being cured, and can relieve external stress acting on the crystal diaphragm. In addition, when the flexibility after curing is not so required, not only the silicone resin but also the urethane resin or the epoxy resin may be used.

As is well known, a conductive resin adhesive is a conductive filler such as silver added and dispersed in a resin such as silicon resin at a predetermined ratio, and its conductivity basically depends on the ratio of the conductive filler added. However, if the proportion of addition is high, an appropriate viscosity cannot be obtained, and the workability in bonding may decrease. In order to solve such a problem, for example, in Japanese Patent Application Laid-Open No. 1-294784, the structure of the conductive filler is devised, and two kinds of scale-like metal powders having different sizes are kneaded so that the reliability of the conductive bonding is improved. It is disclosed that the property is improved.

Usually, the mounting of the crystal diaphragm on the package is
First, a small-diameter dispenser was used to apply an appropriate amount of a conductive bonding material to the external lead-out electrodes of the package, and a quartz crystal diaphragm was mounted so that the lead-out electrodes correspond to the applied areas. However, recent miniaturization of electronic parts has been remarkable, and for example, the size of a quartz crystal diaphragm used for a piezoelectric vibrating device has been made extremely small and thin. For this reason, the lead-out electrode provided on the crystal diaphragm and the external lead-out electrode provided on the package in which the lead-out electrode is mounted are extremely small. In order to respond to such miniaturization, it is also necessary to make the discharge port of the dispenser small, but in such a case, the conductive filler is relatively large in size, so that only the conductive filler becomes clogged, and as a result, discharge The bonding material used was in a resin-rich state. If the bonding is performed in a resin-rich state, there are problems that it may cause poor conduction between the package and the crystal diaphragm, and that the aging characteristics are also unfavorable.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a bonding material capable of making the supply amount of the bonding material minute and constant, and further, such bonding The purpose is to obtain a piezoelectric vibrating device having good characteristics by using a member.

[Means for Solving the Problems]

The present invention has a basic structure in which a solid bonding material is used in place of the liquid bonding material that has been conventionally used, and the above-mentioned problems can be solved by the following characteristic structures.

As a constitution of the joining member, a joining member made of a fine granular or ultrathin sheet-like conductive core and a coating resin formed around the conductive core as described in claim 1, An example of the joining member is a fine granular or ultrathin sheet-shaped core, a conductive film formed around the core, and a coating resin formed on the upper surface of the conductive film, as shown in FIG. The fine granular shape may be spherical, tablet-like, or the like. Further, as disclosed in claim 4, the conductive film can be exemplified by a configuration made of a metal plating film or a conductive resin to which a conductive filler is added.

A thermoplastic resin or a thermosetting resin can be used as the coating resin. Examples of the thermoplastic resin include fluoropolymer resin and styrene resin, and examples of the thermosetting resin include epoxy resin. it can. When a thermosetting resin is used as the coating resin, the thermoplastic resin on the surface of the joining member is melted by heating during joining, and the conductive core or the conductive film on the lower surface electrically joins the joined members. The thermoplastic resin cures when the heating is released, but at this time, the thermoplastic resin mechanically joins the members to be joined. When a thermosetting resin is used as the coating resin, for example, it is made into a paste form together with a binder, and the members to be joined are made to adhere to each other in the initial stage of joining, and electrically joined by the conductive core or conductive film on the lower surface. Heat curing proceeds by heating. Note that a conductive material may be added to the coating resin to have conductivity. In this case, the reliability of conductive bonding between the members to be bonded is improved. As described above, since the liquid bonding material is basically not used, there is no problem that the conductive filler is clogged and the application area is enlarged, which have been problems in the past.

As described in claim 3, the core may be made of a cushioning material, and examples of the cushioning material include silicone resin and urethane resin having high elasticity. By giving the core a buffering function,
The mechanical or thermal shock resistance of the connected member can be improved. In particular, it works effectively in a structure with reduced mechanical strength such as an ultra-thin crystal diaphragm.

Further, as described in claim 7, a joining member may be constructed such that a large number of fine metal wires are penetrated through the resin sheet to secure conduction between the front and back sides. Conduction between the front and back can be ensured by a large number of thin metal wires.

Further, as described in claim 8, it may be a joining member in which a large number of fine metal particles are embedded in a resin sheet to secure conduction between the front and back. It is desirable to arrange the fine metal particles at a density such that they are in contact with each other. Since the resin sheet integrates the fine metal particles, it is easy to handle, and a large number of fine metal particles can ensure conduction between the front and back.

It is to be noted that a proposal of a structure in which thin thermoplastic resin is formed on the front and back sides of the joining member according to claim 7 or 8 is disclosed in claim 9. By interposing the member to be joined between the joining materials and heating, the thermoplastic joining material is melted and mechanically joined. In addition, the presence of the fine metal wires or the fine metal particles enables reliable electrical connection.

Further, as described in claim 10, claim 7
The resin sheet used for the joining member according to claim 9 may be made of a thermoplastic resin. By using a thermoplastic resin for the resin sheet, the members to be joined can be joined more efficiently.

It is preferable to apply each of the above-mentioned joining members to a piezoelectric vibration device. That is, as described in claim 11, the piezoelectric vibrating element having the excitation electrode formed is configured to be conductively bonded to the package through one or more bonding members according to claim 1 to claim 10. Good.
With the above configuration, since a liquid bonding material is not used as in the conventional case, the bonding material can be prevented from flowing out and the piezoelectric vibration element and the package can be bonded in a limited predetermined area.

As a twelfth aspect of the present invention, there is proposed a preferred method of manufacturing a piezoelectric vibration device using the joining member according to the present invention. That is, a piezoelectric vibrating element having an excitation electrode is formed on the external lead electrode formed on the package via one or a plurality of the joining members according to any one of claims 5 or 9 or 10. A step of mounting, and a step of heating at least the joining member arrangement region at a predetermined temperature to dissolve the thermoplastic resin of the joining member,
A step of electrically connecting the external lead-out electrode and the excitation electrode through the joining member by releasing the heating, and mechanically joining the package and the piezoelectric vibrating element with the thermoplastic resin. By manufacturing, it is possible to take advantage of the characteristic of the joining member that the thermoplasticity of the surface of the joining member is melted by heating at the time of joining, and the metal core or the conductive film on the lower surface is responsible for electrical joining between the members to be joined. The thermoplastic resin cures when the heating is released. At this time, the thermoplastic resin mechanically joins the members to be joined, and the electrical joining can be surely performed by the conductive member such as the conductive film. Since a liquid bonding material is basically not used as in the conventional case, there is no fear of the problems of the conductive filler being clogged and the application area being enlarged, which have been conventionally problems.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment according to the present invention will be described with reference to FIGS. 1, 2 and 3. FIG. 1 is a cross-sectional view of a joining member used in the present embodiment, FIG. 2 is an internal cross-sectional view showing an example in which the present joining member is applied to a surface mount type crystal resonator, and FIG. 3 is an enlarged view of a main part of FIG. Is.

The joining member B used in this embodiment is a fine particle having a spherical shape as a whole, and has a core B1, a conductive film B2 formed on the core surface, and a thermoplastic resin film B3 formed on the conductive film surface. Consists of. The core B1 is made of, for example, a silicon-based resin having a buffering function, and has a diameter of, for example, 0.01 to
It has a fine spherical shape of about 0.3 mm. The conductive film B2 formed on the core B1 is made of a conductive resin film. The conductive resin film is, for example, a silicon resin in which a conductive filler is dispersed, and has conductivity over the entire sphere. The shape of the conductive filler dispersed in the resin is flake-like or granular or a metal of a combination thereof, such as gold,
It is possible to select materials with excellent conductivity such as silver and copper,
Also, a plurality of metal materials may be dispersed. Note that, as the conductive film, a metal plating film or the like may be used instead of the conductive resin film.

The thermoplastic resin film B3 formed on the conductive film B2 has a structure coated with a fluoropolymer resin,
By heating the joining portion to a temperature above the melting temperature of the resin (for example, 250 ° C.), the coating of the thermoplastic resin film is partially removed, and the members to be joined are electrically connected by the lower conductive film.

Next, a surface mount type crystal resonator (piezoelectric vibrating device) bonded by the above-mentioned bonding member will be described with reference to FIGS. Surface mount type crystal unit
From a ceramic package 1 having a rectangular parallelepiped shape as a whole and having a recess serving as a base, a rectangular quartz crystal diaphragm 2 which is a piezoelectric vibrating element housed in the package, and a metal lid 3 joined to an opening of the package. Become.

The ceramic package 1 in cross section comprises a concave ceramic substrate 10 and a circumferential metal layer 11 formed on the bank 10a around the concave. Metal layer 11
Consists of a metallized layer made of W (tungsten) and an upper metal film layer formed on the metallized layer. The upper metal film layer is composed of a nickel plating layer in contact with the metallization layer and an extremely thin gold plating layer formed on the nickel plating layer. The thickness of each layer is, for example, about 10 to 20 μm for the metallized layer 11, about 2 to 6 μm for the Ni plating layer 12 a, and about 0.5 to 1.0 μ for the Au plating layer 12 b.
m.

On the inner bottom surface (corresponding to the base) of the ceramic package 1, electrode pads 12 and 16 serving as external lead-out electrodes are formed at both ends in the long side direction, and these electrode pads are connected electrodes 13 and 17, respectively. Via the electrodes, the electrodes are electrically drawn out to the bottom surface outside the package as the extraction electrodes 14 and 15. Although not shown, a ground electrode (not shown) electrically connected to the metallized layer 11 is formed on the bottom surface outside the package. The electrode pad formed on the base is formed by depositing N on the metallization layer made of W (tungsten) or Mo (molybdenum).
The i film layer and the Au film layer are formed in this order by plating or the like.

A rectangular crystal vibrating plate 2, which is a piezoelectric vibrating element, is mounted on the electrode pads 12, 16 so as to support both ends in the long side direction. A pair of excitation electrodes 21 and 22 are formed on the front and back surfaces of the crystal diaphragm 2, and are led out to the electrode pads 16 and 12 by the lead electrodes 211 and 221. Extraction auxiliary electrodes 212 and 222 are formed on the surfaces of the extraction electrodes 211 and 221 opposite to the joints with the electrode pads, and are electrically connected to the extraction electrodes.

The excitation electrode and the extraction electrode are in contact with the crystal vibrating plate 2, and the first Cr film layer 21 having a thickness of about 16 Å is provided.
a and 22a, and Au film layers 21b and 22b having a thickness of about 5000 angstroms are formed in this order by a sputtering method or a vacuum deposition method. A second Cr film layer 22c having a thickness of about 10 Å is formed on the upper surfaces of the excitation electrode 22 and the extraction electrode on the electrode pad side (that is, the upper surface of the Au film layer).

The above-mentioned joining member B is used for joining the ceramic package 1 and the crystal diaphragm. That is, the bonding member B is mounted on the electrode pads 12 and 16, and the crystal vibrating plate 2 is mounted on the bonding member B so that the extraction electrodes 211 and 221 correspond to each other. Then, the joining member B is interposed, the joining member B is heated to a predetermined temperature, and then naturally cooled, thereby performing electromechanical joining. As shown in FIG. 3, the conductive film of the bonding member conductively bonds the electrode pad and the extraction electrode, and the thermoplastic resin mechanically bonds by surface tension.
The heating temperature may be selected as the temperature at which the thermoplastic resin layer B3 is melted as described above, but it may not be completely melted or may be partially softened and melted. The heating method may be to heat the entire ceramic package,
A method of locally heating only the bonding portion may be used, but in any case, the bonding can be efficiently performed by advancing the bonding while applying pressure to the bonding portion of the crystal diaphragm in order to promote the bonding. It should be noted that the bonding member B may be used in plural at one position, although it depends on the size and the bonding area.

The metal lid 3 has Kovar as a base material, the surface of which is plated with Ni (not shown), and a silver brazing material S is formed in a circumferential shape corresponding to the metal layer 11. . Then, the metal lid 3 is mounted on the metal layer 11 in a vacuum atmosphere or an inert gas atmosphere, and in this state, it is heated by a local heating method such as beam welding or seam welding, and hermetically sealed by brazing.

In the above-mentioned embodiment, the bonding member is exemplified as a micro spherical member, but the bonding member is not limited to a spherical member and may have another shape. For example, as shown in FIG. 4, a core B11 made of a thin sheet-shaped silicon resin may be coated with a conductive film B21, and a thermoplastic resin layer B31 may be formed on the upper surface thereof. Further, as shown in FIG. 5, the core B12 may be formed of a thin silicon resin having irregularities, the conductive film B22 may be coated on the core B12, and the thermoplastic resin layer B32 may be formed on the upper surface of the core B12. . By forming the unevenness on the core in this manner, it is possible to increase the chances that the conductive film portion of the bonding member comes into contact with the electrode pad or the like of the member to be bonded, and ensure electrical connection. In addition to the above, the shape of the joining member such as a tablet can be selected.

Further, as the coating resin, a thermosetting resin may be used instead of the thermoplastic resin. In this case, a thermosetting resin is made into a paste together with a binder, for example, to adhere the members to be joined at the initial stage of joining the ceramic package 1 and the crystal diaphragm, and to electrically connect them by the conductive core or conductive film on the lower surface. It is advisable to carry out bonding and heat curing to proceed.

A second embodiment according to the present invention will be described with reference to FIGS. 6, 7 and 8. 6 is a cross-sectional view of the joining member used in the present embodiment, FIG. 7 is an internal cross-sectional view showing an example in which the present joining member is applied to a surface mount type crystal resonator, and FIG. 8 is an enlarged view of a main part of FIG. 7. Is. Note that the same structural parts as those of the first embodiment will be described using the same numbers, and a partial description thereof will be omitted. In this example, the structure of the joining member and the supporting form of the crystal diaphragm are different.

The joining member C used in this embodiment is shown in FIG.
As shown in FIG. 3, a sheet-shaped base material (resin sheet) C1 made of silicon resin is provided with a large number of metal wires (fine metal wires) C2.
And a thin thermoplastic resin film C3 is formed on the front and back surfaces of the sheet. The thermoplastic resin film C3 is made of a fluoropolymer resin and is set to have a film thickness similar to that of the tip portion of the metal wire. It is also possible to provide a thin adhesive material on the front and back surfaces of the joining member and mechanically join the members to be joined without forming the thermoplastic resin film. Alternatively, the sheet-shaped base material may be made of a thermoplastic resin.

As shown in FIG. 7, the electrode pads 12,
A rectangular crystal vibrating plate 2 which is a piezoelectric vibrating element is mounted on 16 (not shown), and one end in the long side direction is cantilevered. A pair of excitation electrodes 21 and 22 are formed on the front and back surfaces of the crystal diaphragm 2, and extraction electrodes 211 and 221 are provided.
(211 is not shown)
It is pulled out to the part. Each of the extraction electrodes 211, 221 is provided with an extraction auxiliary electrode 21 on the opposite surface of the extraction electrode 211, 221 with the crystal diaphragm interposed therebetween.
2, 222 (212 is not shown) are formed correspondingly. An insulating auxiliary support base 18 is integrally formed with the ceramic package 1 on the other end of the crystal diaphragm in the long side direction. The crystal vibration plate is attached to the electrode pads 12 and 16 and the auxiliary support base 18. It is supported in the installed state.

The joining member C is mounted on the electrode pads 12 and 16, and the extraction electrodes 211 and 22 are provided above the joining member C, respectively.
The crystal diaphragm 2 is mounted so that 1 corresponds exactly. Then, the joining member C is heated to a predetermined temperature with the joining member C interposed, and then naturally cooled to perform electromechanical joining.
The heating temperature may be selected as the temperature at which the thermoplastic resin layer C3 is melted as described above, but it may not be completely melted or may be partially softened and melted. The heating method may be to heat the entire ceramic package,
A method of locally heating only the bonding portion may be used, but in any case, the bonding can be efficiently performed by advancing the bonding while applying pressure to the bonding portion of the crystal diaphragm in order to promote the bonding.

In the above-mentioned embodiment, the structure in which the metal wire is penetrated as the joining member is illustrated. However, as shown in FIG. 9, for example, the conductive resin sheet D1 is used as the conductive core, and the thermoplastic resin film D2 is provided on the front and back sides thereof. May be formed. A thin metal film may be used as the conductive core instead of the conductive resin sheet.

Further, as shown in FIG. 10, the resin sheet E1
It is also possible to use a joining member E in which a large number of fine metal particles E2 are embedded in the above to secure conduction between the front and back surfaces and a thermoplastic resin film is formed on the front and back surfaces. It is desirable that the fine metal particles E2 are arranged at a density such that they are in contact with each other. Resin sheet E1
Since the fine metal particles are integrated with each other, the handling is good, and a large number of fine metal particles E2 can ensure conduction between the front and back.

Further, as the example of the piezoelectric vibrating device, the example of the crystal oscillator is shown, but it is of course applicable to other piezoelectric vibrating devices such as a crystal filter, a crystal oscillator or a surface acoustic wave device.

[0035]

According to the present invention, the resin on the surface of the joining member mechanically connects the members to be joined, and the metal core or the conductive film serves to electrically join the members to be joined. Since a liquid bonding material supplied by a dispenser is not used unlike the conventional case, the problems that the conductive filler is clogged and the application area is increased, which have been problems in the past. Therefore,
It is possible to obtain a bonding material that is easy to handle and that can supply a minute and constant amount of the bonding material.

According to the third aspect, by providing the core with a cushioning function, the mechanical or thermal shock resistance of the connected member can be improved. In particular, it works effectively in a structure such as an ultra-thin crystal diaphragm having poor impact resistance, and can improve the impact resistance of the members to be joined.

Further, according to claim 7, it is possible to ensure the conduction between the front and back sides by the large number of thin metal wires.

Further, according to the eighth aspect, since the fine metal particles are integrated with the resin sheet, the handling is good, and the plurality of fine metal particles can ensure the conduction between the front and back.

According to the tenth aspect, by using the resin sheet as the thermoplastic resin, the members to be joined can be joined more efficiently.

According to the eleventh aspect, since the liquid bonding material is not used as in the conventional case, the bonding material is prevented from flowing out and the piezoelectric vibrating element and the package are bonded in a limited predetermined area. It is possible to obtain a piezoelectric vibrating device having good characteristics.

According to the twelfth aspect, the thermoplasticity of the surface of the joining member is melted by heating at the time of joining, and the characteristic of the joining member is utilized in that the metal core or the conductive film on the lower surface is responsible for electrical joining between the members to be joined. You can The thermoplastic resin cures when the heating is released. At this time, the thermoplastic resin mechanically joins the members to be joined, and the electrical joining can be surely performed by the conductive member such as the conductive film. Since a liquid bonding material is basically not used as in the conventional case, the problems of the conductive filler clogging and the increase of the coating area, which have been conventionally problems, are eliminated. Therefore, it is possible to obtain a piezoelectric vibration device having good characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a joining member according to a first embodiment.

FIG. 2 is an internal cross-sectional view of the piezoelectric vibration device according to the first embodiment.

FIG. 3 is an enlarged view of a main part of FIG.

FIG. 4 is a cross-sectional view showing another example of a joining member.

FIG. 5 is a cross-sectional view showing another example of a joining member.

FIG. 6 is a cross-sectional view of the joining member according to the second embodiment.

FIG. 7 is an internal cross-sectional view of the piezoelectric vibration device according to the second embodiment.

FIG. 8 is an enlarged view of a main part of FIG.

FIG. 9 is a cross-sectional view showing another example of a joining member.

FIG. 10 is a cross-sectional view showing another example of a joining member.

[Explanation of symbols]

1 Ceramic package 10 Ceramic substrate 11, 71 Metal layer 2,8 Crystal diaphragm 3,9 Metal lid B, C, D joining members

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Claims (12)

[Claims] 1. A joining member comprising a fine granular or ultrathin sheet-like conductive core and a coating resin formed around the conductive core. 2. A fine granular or ultrathin sheet-shaped core,
A joining member made of a conductive film formed around the core and a coating resin formed on the upper surface of the conductive film. 3. The joining member according to claim 1, wherein the core is made of a cushioning material. 4. The joining member according to claim 2, wherein the conductive film is made of a metal plating film or a conductive resin to which a conductive filler is added. 5. The joining member according to claim 1, wherein the coating resin is a thermoplastic resin. 6. The joining member according to claim 1, wherein the coating resin is a thermosetting resin. 7. A joining member in which a large number of thin metal wires are penetrated through a resin sheet to secure conduction between the front and back. 8. A joining member in which a large number of fine metal spheres are embedded in a resin sheet to secure conduction between the front and back. 9. The joining member according to claim 7, wherein a thin resin is formed on the front and back of the resin sheet. 10. The joining member according to claim 7, wherein the resin sheet is made of a thermoplastic resin. 11. A piezoelectric vibrating element having an excitation electrode formed,
A piezoelectric vibration device conductively bonded to a package through one or a plurality of bonding members according to any one of claims 1 to 10. 12. A piezoelectric device having an excitation electrode formed on an external lead electrode formed on a package via one or more bonding members according to claim 5, 9 or 10. A step of mounting a vibrating element, a step of heating at least the joining member disposition region at a predetermined temperature to melt the thermoplastic resin of the joining member, and a step of releasing the heating to lead to the outside through the joining member. A method of manufacturing a piezoelectric vibrating device, comprising the steps of electrically connecting an electrode and the excitation electrode and mechanically bonding the package and the piezoelectric vibrating element by curing the thermoplastic resin.