JP4284143B2 - Piezoelectric oscillator - Google Patents

Description

  The present invention relates to a piezoelectric oscillator used in an electronic device such as a portable communication device.

  Conventionally, piezoelectric oscillators such as temperature-compensated crystal oscillators have been widely used in electronic devices such as portable communication devices.

  As such a conventional piezoelectric oscillator, for example, as shown in FIG. 3, a concave portion 25 is provided on the upper surface, and a plurality of external terminals 22 are provided on the lower surface. The crystal resonator element 24 and the IC element 26 for controlling the oscillation output of the crystal resonator element 24 are accommodated, and the opening of the recess 25 is formed by a conventionally known seam welding (resistance welding) or the like with a metal lid 27. An airtightly sealed structure is known (for example, see Patent Document 1).

  The concave portion 25 of the wiring board 21 has a stepped step on its inner periphery, and the IC element 26 is mounted on the lower stage and the crystal vibration element 24 is mounted on the upper stage, and both elements are placed in the concave section 25. By arranging the elements so as to partially overlap each other, the piezoelectric oscillator is configured to be smaller than when both elements are arranged in parallel in the recess 25.

Further, in such a conventional piezoelectric oscillator, after the assembly is completed, the inspection of the crystal resonator element 24, the inspection of the IC element 26, and the operation check of the entire crystal oscillator are performed. Non-defective / defective products were selected based on the results of each inspection.
Japanese Unexamined Patent Publication No. 2003-101348 (FIGS. 1, 3, and 5)

  By the way, when a defect is found in the crystal resonator element 24 during the inspection of the crystal resonator element 24 described above, it is extremely complicated to remove the crystal resonator element 24 and replace it with another crystal resonator element 24. Since the production efficiency is greatly reduced by the replacement work, the wiring substrate 21 on which the crystal resonator element 24 is mounted is usually discarded without replacing the crystal resonator element 24 with a non-defective product. ing.

  However, in the conventional piezoelectric oscillator described above, the IC element 26 is disposed below the crystal resonator element 24. Therefore, when a defect is found in the crystal resonator element 24 in the inspection of the crystal resonator element 24, the crystal resonator element If the wiring board 21 on which the circuit board 24 is mounted is discarded as it is, the normal IC element 26 disposed below the crystal vibrating element 24 is discarded, and parts are wasted, which increases the manufacturing cost. Had the disadvantage of incurring.

  The present invention has been devised in view of the above-described drawbacks, and its purpose is to mount a piezoelectric vibration element and an IC element on a wiring board, and then to find out if a defect is found during inspection of each element. An object of the present invention is to provide a piezoelectric oscillator excellent in productivity that can be effectively used for assembling products without wasting normal elements.

The piezoelectric oscillator of the present invention, the first wiring board that the opening of the recess and the recess which is open to the top surface having a enclose supporting unit, causes mounting the second wiring board, the first In a piezoelectric oscillator in which a piezoelectric vibration element and an IC element for oscillation control are arranged in a storage area surrounded by an inner surface of a concave portion of a wiring board and a lower surface of the second wiring board, the piezoelectric vibration element and the IC element One of the elements is mounted on the bottom surface of the recess, the other element is mounted on the lower surface of the second wiring board, and the wiring conductor and the second wiring board of the first wiring board connected to both elements The wiring conductor is electrically connected by a connecting portion made of a conductive connecting material, and the support portion and the lower surface of the second wiring board are positioned inside the connecting portion along the opening of the concave portion. provided that comprises a conductor material, and said first wiring board Is characterized in that the allowed hermetically sealing the housing area by joining in beauty / or sealing material is coupled to the second ground terminal for external connection through the wiring conductor of the wiring board.

  Furthermore, in the piezoelectric oscillator of the present invention, the IC element is composed of a flip chip type IC whose base material is formed of single crystal silicon, and a ground conductor layer is attached to the main surface opposite to the mounting surface of the IC element. It is characterized by being.

  Furthermore, in the piezoelectric oscillator according to the present invention, a plurality of terminals for external connection are arranged in parallel on one surface of the lower surface of the first wiring substrate and the upper surface of the second wiring substrate, and the other surface is disposed on the other surface. The shield conductor layer is deposited.

  According to the piezoelectric oscillator of the present invention, the second wiring board is placed on the upper surface of the first wiring board having the recess, and the piezoelectric region is piezoelectrically surrounded by the inner surface of the recess and the lower surface of the second wiring board. The vibration element and the IC element for oscillation control are disposed, and one of the piezoelectric vibration element and the IC element is disposed on the bottom surface of the concave portion of the first wiring board, and the other element is disposed on the lower surface of the second wiring board. Since the piezoelectric vibration element and the IC element are separately inspected because they are mounted separately, it is possible to assemble a piezoelectric oscillator using only those that have passed the inspection. Even if the problem is discovered, it is relatively easy to remove the second wiring board from the first wiring board, so that normal elements are mounted without significantly reducing the overall production efficiency. It is possible to replace the wiring board you are. Therefore, normal elements without defects are not wasted, and the manufacturing cost of the piezoelectric oscillator can be kept low.

  In addition, according to the piezoelectric oscillator of the present invention, the accommodation area of the piezoelectric vibration element and the IC element provided between the first wiring board and the second wiring board is hermetically sealed with the annular sealing material. Since the sealing material is arranged on the inner side of the connection part for electrically connecting the first wiring board and the second wiring board, these connection parts are arranged in the first wiring board. And the second wiring board can be exposed to the outside. Therefore, even after the piezoelectric oscillator is assembled, by inspecting each element and the like without disassembling the piezoelectric oscillator, the probe needle for inspection or the like is brought into contact with the connection portion or the connection pad. be able to.

  Furthermore, according to the piezoelectric oscillator of the present invention, the sealing material is formed of a conductive material, and the sealing material is used for external connection via the wiring conductors of the first wiring board and / or the second wiring board. By connecting to the ground terminal, when the piezoelectric oscillator is used, the storage area of the piezoelectric vibration element and IC element is surrounded by the sealing material held at the ground potential, so that noise from the outside is not generated. It is possible to satisfactorily shield the entry into the storage area with the sealing material, and to stably operate the piezoelectric vibration element and the IC element disposed in the storage area.

  Furthermore, according to the piezoelectric oscillator of the present invention, the IC element is composed of a flip-chip IC made of single crystal silicon, and a ground conductor layer is attached to the main surface opposite to the mounting surface of the IC element. Since the IC element electronic circuit and the piezoelectric vibration element are partitioned by the ground conductor layer, part of the noise generated by the IC element is absorbed well by the ground conductor layer. It is possible to effectively prevent the electrical characteristics of the piezoelectric vibration element from becoming unstable due to the noise generated by.

  Furthermore, according to the piezoelectric oscillator of the present invention, a plurality of external terminals for external connection are arranged in parallel on either one of the lower surface of the first wiring board and the upper surface of the second wiring board. By adhering the shield conductor layer to the surface of the substrate, it is possible to satisfactorily shield the external noise from entering the storage area of the piezoelectric vibration element or the IC element with the shield conductor layer. It becomes possible to always stably operate the piezoelectric vibration element and the IC element disposed in the storage area.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an exploded perspective view showing an example in which a piezoelectric oscillator according to an embodiment of the present invention is applied to a surface-mount crystal oscillator, and FIG. 2 is a cross-sectional view of the crystal oscillator of FIG. Is roughly constituted by a first wiring board 1, a second wiring board 4, a crystal vibration element 7 as a piezoelectric vibration element, and an IC element 8 for oscillation control.

  The first wiring board 1 is formed by laminating a plurality of ceramic layers made of a ceramic material such as glass-ceramic or alumina ceramic, and a predetermined wiring conductor 2 is formed between the surface and adjacent ceramic layers. In addition, a via-hole conductor or the like for electrically connecting the wiring conductors is embedded in the interior, and a shield conductor layer 6 is deposited and formed on the lower surface over substantially the entire surface.

  On the upper surface of the first wiring substrate 1, a recess 3 and an annular support portion 1 a surrounding the opening of the recess 3 are provided. The IC element 8 is accommodated. For this reason, a pair of mounting pads 2 a that are electrically connected to the corresponding vibration electrodes 7 a of the crystal resonator element 7 via the conductive connecting material 9 are provided on the bottom surface of the recess 3.

  The support portion 1a functions as a support surface for supporting a second wiring board 4 to be described later, and a corresponding connection of the second wiring board 4 is provided on the outer peripheral side of the support portion 1a. A plurality of connection pads 2b are provided which are electrically connected to the pads 5b via conductive connection materials such as solder.

  When the first wiring board 1 is made of a ceramic material such as glass-ceramic, the wiring conductor 2 and the surface of a ceramic green sheet obtained by adding and mixing an appropriate organic solvent or the like to the ceramic material powder, for example. The conductor paste or the like is printed and applied in a predetermined pattern, and a plurality of these are laminated and press-molded, followed by firing at a high temperature. The recess 3 is formed by forming a rectangular through-hole in the center of the ceramic green sheet disposed in the upper region of the ceramic green sheet used for manufacturing the first wiring board 1. It is formed.

  The crystal resonator element 7 mounted on the bottom surface of the concave portion of the first wiring substrate 1 described above has a pair of vibration electrodes 7a attached and formed on both main surfaces of a crystal piece cut along a predetermined crystal axis. Thus, when an externally varying voltage is applied to the crystal piece via the pair of vibrating electrodes 7a, thickness-shear vibration is caused at a predetermined frequency.

  The crystal resonator element 7 is mounted on the bottom surface of the concave portion of the first wiring board 1 by electrically connecting the pair of vibration electrodes 7a to the corresponding mounting pads 2a on the bottom surface of the concave portion through the conductive adhesive 9. It is electrically connected to the corresponding connection terminal of the IC element 8 via the wiring conductor 2 of the first wiring board 1 and the wiring conductor 5 of the second wiring board 4 described later.

  Since such a first wiring board 1 has a shield conductor layer 6 on its lower surface, the shield conductor layer 6 is used as the wiring conductor 2 of the first wiring board 1 or a second wiring board described later. When the crystal oscillator is used, the shield conductor layer 6 is held at the ground potential by being connected to the ground terminal 10a for external connection via the four wiring conductors 5. Thereby, it is possible to satisfactorily shield the external noise from entering the storage area of the crystal resonator element 7 and the IC element 8 with the shield conductor layer 6 and to arrange the crystal resonator element 7 disposed in the storage area. Further, it is possible to protect the IC element 8 better than unnecessary electric action from the outside, and to always operate these elements 7 and 8 stably. Therefore, the shield conductor layer 6 is preferably attached to the lower surface of the first wiring board 1.

  On the other hand, the second wiring board 4 is formed by laminating a single ceramic layer or a plurality of ceramic layers made of the same ceramic material as the first wiring board 1 described above, for example, alumina ceramics. An external terminal 10 such as a power supply voltage terminal, a ground terminal, an oscillation output terminal, and an oscillation control terminal is formed on the upper surface, and the connection pad 5b is disposed on the lower surface so as to face the connection pad 2b of the first wiring board 1 described above. However, a mounting pad 5 a for mounting an IC element is provided at a position facing the recess 3.

  The second wiring board 4 is for supporting the IC element 8 on the lower surface and a plurality of external terminals 10 on the upper surface and closing the opening of the recess 3. A crystal resonator element 7 and an IC element 8 are disposed in a storage area surrounded by the lower surface of the substrate 4 and the inner surface of the recess 3.

  As the IC element 8 mounted on the lower surface of the second wiring board 4 described above, for example, a flip chip type IC element having a plurality of connection terminals on the mounting surface is used. A temperature sensing element (thermistor) for detecting the ambient temperature state and temperature compensation data for compensating the temperature characteristics of the crystal vibration element 7 are stored on the circuit forming surface, and the vibration of the crystal vibration element 7 is based on the temperature compensation data. There are provided a temperature compensation circuit that corrects the characteristics according to a temperature change, an oscillation circuit that is connected to the temperature compensation circuit and generates a predetermined oscillation output, and the oscillation output generated by the oscillation circuit is externally provided. After being output, it is used as a reference signal such as a clock signal, for example.

  The plurality of connection terminals provided on the upper surface of the IC element 8 are arranged so as to correspond to the mounting pads 5a provided on the lower surface of the second wiring board 4, and these connection terminals are connected to each other. The IC element 7 is attached to the second wiring substrate 4 by individually bonding to the corresponding mounting pad 5a via a conductive connecting material such as Au, Au—Sn alloy, solder, or conductive adhesive. At the same time, the connection terminal of the IC element 8 is electrically connected to the external terminal 10.

  Such a second wiring board 4 is manufactured by a method similar to that of the first wiring board 1 described above, and in order to attach it to the first wiring board 1, first the second wiring board 1 is used. The IC element 8 having the substrate 4 attached to the lower surface thereof is located in the recess 3 of the first wiring substrate 1, and the corresponding connection pads of both the wiring substrates 1 and 4 are connected to each other through the conductive connection material. It is placed on the first wiring board 1 so as to face each other, and then, heat or the like is applied to the conductive connecting material to bond it to both connection pads. The vibration electrode of the vibration element 7 is electrically connected to the connection terminal or the like of the IC element 8 via the wiring conductors 2 and 5 of the wiring boards 1 and 4.

  In the present embodiment, the upper surface of the second wiring board 4 functions as a mounting surface when the crystal oscillator is mounted on an external wiring board such as a mother board, and the external terminals 10 are soldered or the like. The crystal oscillator is mounted on the external wiring board by being electrically connected to the corresponding circuit wiring of the external wiring board via the conductive connecting material.

  As described above, in the present embodiment, since the crystal resonator element 7 is mounted on the bottom surface of the concave portion of the first wiring substrate 1 and the IC element 8 is mounted on the lower surface of the second wiring substrate 4, The inspection of the element 7 and the IC element 8 is performed separately, and the crystal oscillator can be assembled using only those that have passed the inspection.

  Even if a defect is found in the crystal resonator element 7 or the IC element 8 after the crystal oscillator is assembled, the operation of removing the second wiring board 4 from the first wiring board 1 is not limited to the crystal resonator element. 7 and the IC element 8 are simpler than the case where they are removed from the wiring board, and can be replaced with a wiring board on which normal elements are mounted without greatly reducing the overall production efficiency. Therefore, the normal crystal resonator element 7 and the IC element 8 having no defects are not wasted, and the manufacturing cost of the crystal oscillator can be kept low.

  Furthermore, in the present embodiment, the IC element 8 is constituted by a flip chip type IC, and a ground conductor layer 8a is attached to the main surface opposite to the mounting surface. For this reason, the electronic circuit of the IC element 8 and the crystal resonator element 7 are partitioned by the ground conductor layer 8a, whereby a part of noise generated by the IC element 8 is absorbed well by the ground conductor layer 8a. Thus, it is possible to effectively prevent the electrical characteristics of the crystal resonator element 7 from becoming unstable due to noise generated by the IC element 8. Therefore, in order to stabilize the electrical characteristics of the crystal resonator element 7, the IC element 8 is constituted by a flip chip IC, and the ground conductor layer 8 a is covered on the main surface opposite to the mounting surface of the IC element 8. It is preferable to keep it on.

  Note that a write control terminal (not shown) for writing temperature compensation data to the temperature compensation circuit of the IC element 8 is, for example, on the side surface of the first wiring board 1, the upper surface of the second wiring board 4, and the like. The probe needle of the data writing device is applied to these write control terminals, and temperature compensation data corresponding to the temperature characteristics of the crystal resonator element 7 is written in the memory provided in the temperature compensation circuit of the IC element 8 Thus, the temperature compensation data is stored in the temperature compensation circuit. Such a writing control terminal is arranged in an external spare part provided integrally with the wiring boards 1 and 4 at the time of manufacture, and after the temperature compensation data has been written, the spare part is provided. If it is separated from the wiring boards 1 and 4 together with the write control terminal, there is an advantage that the crystal oscillator can be miniaturized.

  And between the first wiring board 1 and the second wiring board 4 described above, more specifically, between the support portion 1 a of the first wiring board 1 and the lower surface of the second wiring board 4. Has a sealing material 11 disposed in an annular shape along the opening of the recess 3 inside the connection portion between the wiring boards 1 and 4, and the sealing material 11 and the inner surface of the recess The storage area of both elements 7 and 8 surrounded by the lower surface of the second wiring board 4 is hermetically sealed.

As the material of the sealing material 11, a bonding material such as an Au—Sn alloy or solder is preferably used, and when both the wiring boards 1 and 4 are bonded using such a bonding material, An annular metallized layer (not shown) is provided on both the support portion 1a and the lower surface of the second wiring board 4 in order to firmly bond the sealing material 11 to the wiring boards 1 and 4, respectively. The storage area hermetically sealed with the sealing material 11 is filled with an inert gas such as N ₂ gas or Ar gas in order to stabilize the electrical characteristics of the crystal resonator element 7 and the like.

  As described above, the housing regions of the elements 7 and 8 provided between the first wiring board 1 and the second wiring board 4 are hermetically sealed with the annular sealing material 11, and the sealing material 11 is arranged on the inner side of the connection portion that electrically connects the first wiring board 1 and the second wiring board 4, so that these connection portions are connected to the first wiring board 1 and the second wiring board 1. The wiring board 4 can be exposed to the outside. Therefore, even after the crystal oscillator is assembled, by inspecting the elements 7 and 8 without disassembling the crystal oscillator, the probe needle for inspection or the like is brought into contact with the connection portion or the connection pad. It can be done easily.

  At this time, if one end of the connection pads 2b and 5b provided on the wiring boards 1 and 4 is led out to the side face of the first wiring board 1 or the side face of the second wiring board 4, a probe needle for inspection or the like can be provided. It becomes easy to make it contact with a connection part, and the workability | operativity of a test | inspection can be improved. Therefore, it is preferable that one end of the connection pads 2 b and 5 b provided on the wiring boards 1 and 4 is led out to the side face of the first wiring board 1 and the side face of the second wiring board 4.

  Further, when the sealing material 11 is made of a conductor material such as an Au—Sn alloy or solder, the sealing material 11 is connected to the ground terminal 10 a for external connection via the wiring conductor 5 such as the second wiring substrate 4. Thus, when the crystal oscillator is used, the storage area of the crystal resonator element 7 and the IC element 8 is surrounded by the sealing material 11 held at the ground potential GND. Therefore, the sealing material 11 satisfactorily shields external noise from entering the storage area provided between the first wiring board 1 and the second wiring board 4. At the same time, it is possible to better protect the crystal resonator element 7 and the IC element 8 disposed in the storage area from unnecessary electrical action from the outside, and to always operate these elements 7 and 8 stably. . Therefore, the sealing material 11 is formed of a conductive material, and the sealing material 11 is grounded for external connection via the wiring conductors 2, 5, etc. of the first wiring board 1 and the second wiring board 4. It is preferable to connect to the terminal 10a.

  When the second wiring board 4 is mounted on the first wiring board 1, the sealing material 11 is, for example, on the support portion 1 a of the first wiring board 1 or the second wiring board 4. An Au—Sn alloy or the like is applied to one of the lower surfaces of the wiring board so as to form a predetermined annular pattern, and then the annular pattern is heated and melted at a high temperature to be bonded to the metallized layer of the other wiring board. By interposing, it is interposed between the first wiring board 1 and the second wiring board 4. Further, when the sealing material 11 is bonded to both the wiring boards 1 and 4 simultaneously with the connection between the connection pads 2a and 5a, both the sealing material 11 and the conductive connection material are formed of an Au—Sn alloy. It is preferable to keep it.

Further, a flow prevention made of an inorganic material such as Al ₂ O ₃ between the support region of the first wiring substrate 1 and the second lower surface of the wiring substrate 4 and between the intervening region of the sealing material 11 and the connection portion. If a film, a groove, a convex portion, or the like is formed so as to surround the sealing material 11, when the sealing material 11 is formed of a conductor material such as an Au—Sn alloy or solder, There is an advantage that it is possible to effectively prevent the stopping material 11 from flowing toward the connecting portion and attempting to short-circuit. Therefore, the flow prevention made of an inorganic material such as Al ₂ O ₃ between the support region of the first wiring substrate 1 and the second lower surface of the wiring substrate 4 and between the intervening region of the sealing material 11 and the connection portion. It is preferable to form a film, a groove, a convex portion or the like so as to surround the sealing material 11.

  Thus, the crystal oscillator described above applies a predetermined voltage to the crystal resonator element 7 from the outside to vibrate the crystal resonator element 7 at a predetermined resonance frequency, and a predetermined oscillation signal corresponding to the resonance frequency of the crystal resonator element 7. Is generated and amplified by the IC element 8 and the obtained signal is output to the outside via the external terminal 10 to function as a crystal oscillator. In the crystal oscillator according to the present embodiment, a temperature compensation circuit or the like is provided inside the IC element 8, and therefore the frequency of the oscillation signal output to the outside depends on the temperature state of the crystal oscillator 7 when used. It will be corrected.

  In addition, this invention is not limited to the above-mentioned embodiment, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention.

  For example, in the above-described embodiment, the surface-mount type crystal oscillator using the crystal resonator element as the piezoelectric resonator element has been described as an example, but instead of this, another piezoelectric resonator element such as a SAW filter is used as the piezoelectric resonator element. The present invention is also applicable when using.

  In the embodiment described above, the crystal resonator element 7 is mounted in the recess 3 of the first wiring board 1 and the IC element 8 is mounted on the lower surface of the second wiring board 4. Then, the IC element 8 may be mounted in the recess 3 of the first wiring board 1, and a piezoelectric vibration element such as a crystal vibration element may be mounted on the lower surface of the second wiring board 4.

  Further, in the above-described embodiment, the external terminals 10 are provided on the upper surface of the second wiring board 4, but instead, the external terminals 10 may be provided on the lower surface of the first wiring board 1. good. In that case, the upper surface of the second wiring board 4 is used to form the shield conductor layer 6.

  Further, in the above-described embodiment, the flip chip type IC is used as the IC element 8, but other IC elements, for example, a type of IC that is bonded to the mounting pad of the wiring board by a conventionally known wire bonding or the like. You may make it comprise a piezoelectric oscillator using an element.

It is a disassembled perspective view which shows the example which applied the piezoelectric oscillator which concerns on one Embodiment to this invention to the crystal oscillator. It is sectional drawing of the crystal oscillator of FIG. It is sectional drawing of the conventional piezoelectric oscillator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st wiring board 1a ... Support part 2 ... Wiring conductor of 1st wiring board 2a ... Mounting pad for piezoelectric vibration elements 2b ... Connection pad of 1st wiring board DESCRIPTION OF SYMBOLS 3 ... Concave part 4 ... 2nd wiring board 5 ... Wiring conductor of 2nd wiring board 5a ... Mounting pad for IC elements 5b ... Connection pad of 2nd wiring board 6. ..Shield conductor layer 7 ... Piezoelectric vibration element (crystal vibration element)
DESCRIPTION OF SYMBOLS 8 ... IC element 8a ... Ground conductor layer 9 ... Conductive connection material 10 ... External terminal 10a ... Ground terminal 11 ... Sealing material

Claims (3)

A first wiring board that the opening of the recess and the recess which is open to the top surface having a enclose supporting unit, causes mounting the second wiring board, wherein a concave inner surface of the first wiring board In a piezoelectric oscillator in which a piezoelectric vibration element and an oscillation control IC element are arranged in a storage region surrounded by a lower surface of a second wiring board,
One of the piezoelectric vibration element and the IC element is mounted on the bottom surface of the recess, and the other element is mounted on the lower surface of the second wiring board, and the first wiring board connected to both elements Electrically connecting the wiring conductor and the wiring conductor of the second wiring board at a connection portion made of a conductive connecting material;
The support portion and the lower surface of the second wiring board are arranged at an inner position than the connection portion along the opening of the concave portion, and are made of a conductive material, and the first wiring board and / or A piezoelectric oscillator, wherein the storage area is hermetically sealed by bonding with a sealing material connected to a ground terminal for external connection via a wiring conductor of a second wiring board . 2. The IC element according to claim 1, wherein the IC element is formed of a flip chip type IC having a base material made of single crystal silicon, and a ground conductor layer is attached to a main surface opposite to the mounting surface of the IC element. The piezoelectric oscillator according to 1. A plurality of terminals for external connection are arranged in parallel on one of the lower surface of the first wiring substrate and the upper surface of the second wiring substrate, and a shield conductor layer is attached to the other surface. The piezoelectric oscillator according to claim 1 or 2, wherein

Images