JP2004064651A - Surface-mounted piezoelectric oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the prior art problem that IC component placed within a recessed portion of an insulating substrate creates distortion by a stress due to thermal expansion of adhesive placed directly above the components through resins, changes an oscillation frequency, and reduces reliability. <P>SOLUTION: A surface-mounted piezoelectric oscillator has an IC component unit 2 provided with an insulating substrate 5 having a recessed portion 6 for IC component mounting all over the substrate, a plurality of upper electrodes 11 placed on a top surface of a wall 10 surrounding the recessed portion, and resins 12 filled in the recessed portion for covering the IC components; and a piezoelectric oscillator 3 provided with a package 20 having a bottom electrode 26 connected to the upper electrodes when the package is mounted above the IC component unit, and a piezoelectric oscillating element 22 hermetically housed in the package. A non-electrode area 10a in which no upper electrode exists within the top surface wall of the insulating substrate composing the IC component unit and a bottom outside of the package of the piezoelectric oscillator facing the non-electrode area are joined with an insulating adhesive 30. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement of a piezoelectric oscillator such as a crystal oscillator, and more particularly to a surface mount type piezoelectric oscillator in which a packaged piezoelectric vibrator is fixedly integrated on an IC component unit on which an IC component is mounted.
[0002]
[Prior art]
Due to the rapid progress in price reduction and miniaturization accompanying the spread of mobile communication devices such as mobile phones, the price, size and thickness of piezoelectric oscillators such as crystal oscillators used in these communication devices have also been reduced. The demand for conversion is increasing. In response to such demands, not only are crystal oscillators packaged, but also oscillator circuits including frequency adjustment circuits and frequency temperature compensation circuits are integrated and integrated into ICs to reduce the number of components. .
3 (a), 3 (b), 3 (c) and 3 (d) are an external perspective view of a conventional surface mount piezoelectric oscillator, a perspective view of an IC component unit, a sectional view showing an assembling procedure, and a vertical sectional view of a finished product. It is. The piezoelectric oscillator 101 is of a type in which a packaged piezoelectric vibrator 103 is fixed on an IC component mounting package (IC component unit) 102.
The IC mounting package 102 has a concave portion 106 formed at the center of the upper surface of an insulating substrate 105 made of an insulating material such as ceramic, and an IC chip or IC package (IC package) is mounted on an IC component mounting pad 107 provided on the inner bottom surface of the concave portion. In the following, each of the electrodes on the IC component 108 side is fixed on each pad 107 using solder or the like. The recess 106 is surrounded by a rectangular annular outer wall 110.
External electrodes 109 for surface mounting on a motherboard (not shown) are formed on the bottom surface of the substrate 105, and four upper electrodes 111 are formed on the upper surface of each outer wall 110 surrounding the recess 106. Each external electrode 109 is connected to each pad 107 and each upper electrode 111 via a connection conductor (not shown). The IC component 108 mounted in the concave portion 106 may cause a problem such as dew condensation or the like occurring on its electrode or the like due to contact with air, thereby causing a short circuit or the like. Filling (potting) covers the outer surface of the IC component to block it from outside air.
The piezoelectric vibrator 103 has a configuration in which a piezoelectric vibration element 122 is housed in a concave portion 121 of a box-shaped package body 120 made of ceramic or the like, and the concave portion 121 is hermetically sealed with a lid 123. The piezoelectric vibrating element 122 has an excitation electrode formed on a main surface of a piezoelectric substrate such as a quartz substrate, and a lead electrode extending from the excitation electrode to an edge of the piezoelectric substrate is connected to a pad 125 arranged in the recess 121. On the other hand, a bottom electrode 126 that is electrically connected to the pad 125 is exposed on the bottom surface of the package body 120 while being fixed. The four bottom electrodes 126 provided are connected and fixed to the four upper electrodes 111 of the IC mounting package 102 in a one-to-one correspondence with solder or a conductive adhesive.
[0003]
By the way, in the piezoelectric oscillator having the above-described configuration, when the connection strength between the IC component unit 102 and the piezoelectric vibrator 103 depends exclusively on the solder connection between the upper electrode 111 and the bottom electrode 126, etc. Since the connection strength is not sufficient, it is common to connect the upper surface of the resin 112 cured after filling and the lower surface (non-electrode region) of the package body 120 with the insulating adhesive 130. Specifically, as shown in FIGS. 3B and 3C, a state in which an appropriate amount of adhesive 130 is applied to the center of the upper surface of resin 112 and a binder such as solder is applied to the upper surface of each upper electrode 111 Then, the piezoelectric vibrators 103 are overlapped, and then the adhesive and the solder are cured. In addition, before the solder or the like is cured, the piezoelectric vibrator 103 is positioned and fixed on the IC component unit 102 by the adhesive 130, so that the displacement during the solder curing process can be prevented.
[0004]
[Problems to be solved by the invention]
However, when a structure in which the resin 112 and the bottom surface of the package body 120 are connected by using the adhesive 130 is employed, the characteristics as an oscillator fluctuate due to a change in ambient temperature, and the characteristics are stable. There is a problem that will not be. That is, when the ambient temperature rises above a predetermined allowable temperature, the adhesive 130 expands and deforms. At this time, the ceramic constituting the insulating substrate 105 also thermally expands, but the expansion coefficient of the adhesive 130 is much higher. When the adhesive 130 expands, the IC component 108 is pressed downward through the thin portion of the resin 112, and distortion occurs in the entire IC component and the terminals of the IC component. Due to this distortion, the characteristics of the entire oscillator fluctuate, and the oscillation frequency fluctuates.
As described above, conventionally, an IC component is mounted in a concave portion provided on one surface of an insulating substrate, and then the resin is filled in the concave portion to embed the IC component, and then the resin portion covering the upper surface of the IC component is formed. In a piezoelectric oscillator with a structure in which a piezoelectric vibrator is stacked on an insulating substrate with the adhesive applied, and the electrodes are connected by soldering, etc., the stress caused by the thermal expansion of the adhesive due to the temperature change causes the piezoelectric oscillator to be directly under the adhesive. In this case, the IC component located at the position (1) is pressurized to generate distortion, and the frequency of the oscillator fluctuates.
The present invention has been made in view of the above, and an IC component disposed in a recessed portion of an insulating substrate is distorted by a stress caused by thermal expansion of an adhesive disposed immediately above the resin through a resin, causing oscillation. It is an object of the present invention to propose a surface mount type piezoelectric oscillator that solves the conventional problem that the frequency is changed and the reliability is reduced.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, an invention according to claim 1 includes an insulating substrate having a concave portion for mounting an IC component on one surface, an IC component mounting pad formed on an inner bottom surface of the concave portion, and surrounding the concave portion. A plurality of upper electrodes disposed on the upper surface of the annular outer wall, an external electrode for surface mounting exposed on the outer bottom of the insulating substrate, a connection conductor for electrically connecting the IC component mounting pad, the upper electrode and the external electrode, and A package comprising: an IC component unit having a resin filled in the recess to cover the IC component; and a bottom electrode connected to the upper electrode when placed on the upper surface of the IC component unit. And a piezoelectric vibrator having a piezoelectric vibrating element hermetically housed in the package, and a non-electrode region where no upper electrode is present on the upper surface of the outer wall of the insulating substrate constituting the IC component unit; Between the package outer bottom surface of the piezoelectric vibrator facing the non-electrode region, characterized by being joined by an insulating adhesive.
When fixing the piezoelectric vibrator on the IC component unit, the connection strength is not enough if only the electrodes are electrically and mechanically connected by soldering or the like. However, conventionally, since the adhesive is disposed directly above the IC component, there is a problem that the IC component is affected by distortion due to thermal expansion of the adhesive and the oscillation frequency fluctuates.
In the present invention, as a portion to which the insulating adhesive is applied, a portion where there is no possibility of adversely affecting the IC component, that is, a non-electrode region on the upper surface of the outer wall of the insulating substrate is selected. The IC component unit and the piezoelectric vibrator can be mechanically and firmly connected.
[0006]
According to a second aspect of the present invention, an insulating substrate having a concave portion for mounting an IC component on one surface, an IC component mounting pad formed on an inner bottom surface of the concave portion, and an annular outer wall surrounding the concave portion are disposed on the upper surface. A plurality of upper electrodes, an external electrode for surface mounting exposed on the outer bottom of the insulating substrate, a connection conductor for electrically connecting the IC component mounting pad to the upper electrode and the external electrode, and a coating for covering the IC component. A package comprising: an IC component unit having a resin filled in the recess; a plurality of bottom electrodes connected to the upper electrode when placed on the top of the IC component unit; and A piezoelectric vibrator having a piezoelectric vibrating element hermetically housed therein, wherein the plurality of upper electrodes include at least two grounding upper electrodes, and the plurality of bottom electrodes are each of the grounding upper electrodes. electrode A ground bottom electrode having a one-to-one correspondence is provided, and one of the ground top electrodes and the ground bottom electrode facing the one ground top electrode are joined by an insulating adhesive. It is characterized by having done.
In the case where the outer shape of the insulating substrate is constant, if the volume of the concave portion is increased, the width of the upper surface of the outer wall located on the outer periphery of the concave portion is inevitably reduced, so that the amount of the insulating adhesive applied is reduced, and the width is increased. When a necessary and sufficient amount of adhesive is applied to the upper surface of the outer wall, it is more difficult to secure a stronger bonding force.
Therefore, the present invention focuses on the fact that two of the four upper electrodes formed on the upper surface of the outer wall are grounding upper electrodes for grounding the metal lid of the piezoelectric vibrator, and only one of them is insulated. By using it as a region to which the adhesive is applied, the bonding strength is enhanced. The function of grounding the metal lid can be sufficiently realized by electrically connecting the other grounding upper electrode and the grounding bottom electrode on the lower surface of the piezoelectric vibrator.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
1 (a), 1 (b), 1 (c) and 1 (d) are external perspective views of a surface-mounting electronic component (piezoelectric oscillator) according to an embodiment of the present invention, a perspective view of an IC component unit, and an AA cross-sectional view. And BB sectional drawing.
The surface-mounted piezoelectric oscillator 1 is of a type in which a piezoelectric vibrator 3 packaged on an IC component mounting package (IC component unit) 2 is fixed.
The IC mounting package 2 has a concave portion 6 formed at the center of the upper surface of an insulating substrate 5 made of an insulating material such as ceramic, and an IC chip or an IC package (hereinafter, referred to as an IC chip or IC package) on an IC component mounting pad 7 provided on the bottom surface inside the concave portion. , IC components) 8 and the electrodes of the IC components 8 are fixed on the IC component mounting pads 7 using solder or the like.
External electrodes 9 for surface mounting are formed on the bottom surface of the insulating substrate 5, and a plurality (four in this example) of upper electrodes are provided at appropriate places on the upper surface of the annular outer wall 10 protruding so as to surround the recessed portion 6. 11 are formed. The external electrode 9 is connected to the IC mounting pad 7 and the upper electrode 11 via a connection conductor (not shown). The IC component 8 mounted in the recess 6 may be in contact with air, which may cause a problem such as dew condensation on the electrode or the like and cause a short circuit. Therefore, the insulating resin 12 is filled in the recess 6. (Potting) to isolate from outside air. The insulating resin 12 is filled in the recess 6 so as to cover the entire outer surface of the IC component 8 in a state of being melted by an injector or the like, and then cured.
The piezoelectric vibrator 3 has a configuration in which a piezoelectric vibrating element 22 is accommodated in a concave portion 21 of a box-shaped package body 20 made of ceramic or the like, and the concave portion 21 is hermetically sealed with a metal lid 23. The piezoelectric vibrating element 22 is formed by forming two excitation electrodes on a main surface of a piezoelectric substrate such as a quartz substrate, and a lead electrode extending from each excitation electrode to an edge of the piezoelectric substrate is disposed in the recess 21. While being connected and fixed to the pads 25, four bottom electrodes 26 electrically connected to the pads 25 and the metal lid 23 are exposed on the bottom surface of the package body 20. Each bottom electrode 26 is connected and fixed to the four upper electrodes 11 of the IC mounting package 2 in one-to-one correspondence with solder or a conductive adhesive. Four bottom electrodes 26 are provided, two of which are ground bottom electrodes, which are connected to the metal lid 23 via a connection conductor (not shown) and are grounded. The remaining two bottom electrodes 26 are electrically connected to the two excitation electrodes of the piezoelectric vibrating element 22, respectively.
Accordingly, two of the four upper electrodes 11 connected in a one-to-one correspondence with the four bottom electrodes are upper electrodes for grounding, and the other two are upper electrodes for excitation.
A characteristic configuration of the present invention is that the non-electrode region 10a where the upper electrode 11 does not exist on the upper surface of the outer wall 20 of the insulating substrate 5 that constitutes the IC component unit 2, and the piezoelectric vibrator 3 that faces the non-electrode region 10a The point is that the outer body (non-electrode region 20a) of the package body 20 is joined with the insulating adhesive 30. As the insulating adhesive 30, an epoxy-based or silicone-based adhesive is used. These insulating adhesives 30 exhibit a much stronger bonding force than a conductive adhesive obtained by kneading silver powder into a binder.
[0008]
As an assembly procedure, first, as shown in FIG. 1B, the IC component 8 is mounted in the concave portion 6 of the insulating substrate and filled with the resin 12, and then the non-electrode region on the upper surface of the annular outer wall 20 is formed. An appropriate amount of the adhesive 30 is applied to the non-electrode region 10 a on the upper surface of the wide portion located between the upper electrodes 11. Further, after applying a binder such as solder or a conductive adhesive on the upper electrode 11, the piezoelectric vibrator 3 is positioned on the IC component unit 2 and the overlapping binder is cured. At this time, the displacement of the electrodes is prevented by the adhesive effect of the adhesive 30. After the adhesive 30 and the binder are cured, the bonding strength between the IC component unit 2 and the piezoelectric vibrator 3 can be increased by the strong bonding force of the adhesive 30.
According to the piezoelectric oscillator according to this embodiment, the adhesive 30 which is easily thermally expanded due to the temperature rise is arranged on the upper surface of the outer wall which is separated from the IC component 8 in the recessed portion 6. Mechanical stress due to expansion is not applied to the IC component 8, and the possibility that the oscillation frequency fluctuates is greatly reduced.
[0009]
Next, FIG. 2 is a perspective view of an insulating substrate constituting a piezoelectric oscillator according to another embodiment of the present invention. This insulating substrate 5 is configured such that the planar shape of the recess is larger than that of the example of FIG. When the shape of the component housed in the recess 6 is large or the number of components is large, the planar shape of the recess must be increased, and the width of the non-electrode region 10a located between the upper electrodes 11 is narrow. Has become. Therefore, it is difficult to apply a sufficient amount of the adhesive 30 to the non-electrode region 10a having such a small width, and the adhesive force of only a small amount of the adhesive makes the IC component unit 2 and the piezoelectric vibrator 3 strong. It is difficult to fix to.
Therefore, in this embodiment, one of the two grounding upper electrodes constituting the four upper electrodes 11 is used as an adhesive application area. In other words, of the four upper electrodes 11a to 11d, two upper electrodes 11a and 11b are excitation upper electrodes connected to the two excitation electrodes forming the piezoelectric vibration element 22 via the excitation bottom electrodes, respectively. The remaining two upper electrodes 11c and 11d are grounding upper electrodes respectively connected to the metal lid 23 via the grounding bottom electrode. In the present embodiment, while applying an appropriate amount of the insulating adhesive 30 to the upper surface of the one grounding upper electrode 11d to cut off the conduction with the corresponding one grounding bottom electrode, the mechanical bonding force is increased, With respect to the other grounding upper electrode 11c, conduction with the corresponding other grounding bottom electrode is ensured to secure the shield by the metal lid 23.
Therefore, also in this embodiment, since the adhesive which is easily thermally expanded due to the temperature rise is arranged on the grounding upper electrode on the upper surface of the outer wall separated from the IC component 8 in the recess 6, even if the adhesive is thermally expanded. In addition, mechanical stress due to thermal expansion is not applied to the IC component 8, and the possibility that the oscillation frequency fluctuates is greatly reduced.
On the other hand, the shield effect by grounding the metal lid 23 can be sufficiently ensured by electrically connecting the other grounding upper electrode 11c to the other grounding bottom electrode.
Note that the manufacturing procedure is not actually performed for each individual piece, but is performed by a batch process using a sheet-shaped insulating substrate base material in which a large number of insulating substrates are connected in a sheet shape.
[0010]
【The invention's effect】
As described above, according to the present invention, the IC component disposed in the recessed portion of the insulating substrate is distorted by the stress caused by the thermal expansion of the adhesive disposed immediately above via the resin, and the oscillation frequency fluctuates. , And the conventional problem that reliability is reduced can be solved.
According to the first aspect of the present invention, since a portion where the insulating adhesive is applied has no possibility of adversely affecting the IC component, that is, a non-electrode region on the upper surface of the outer wall of the insulating substrate is selected. , The IC component unit and the piezoelectric vibrator can be mechanically and firmly connected.
According to the invention of claim 2, two of the four upper electrodes formed on the upper surface of the outer wall are focused on the grounding upper electrode for grounding the metal lid of the piezoelectric vibrator. Is used as a region to which the insulating adhesive is applied, whereby the bonding strength can be enhanced. The function of grounding the metal lid can be sufficiently realized by electrically connecting the other grounding upper electrode and the grounding bottom electrode on the lower surface of the piezoelectric vibrator.
[Brief description of the drawings]
FIGS. 1A, 1B, 1C, and 1D are external perspective views of a surface mount electronic component (piezoelectric oscillator) according to an embodiment of the present invention, a perspective view of an IC component unit, and AA. Sectional drawing and BB sectional drawing.
FIG. 2 is a perspective view of an insulating substrate constituting a piezoelectric oscillator according to another embodiment of the present invention.
3 (a), (b), (c) and (d) are external perspective views of a conventional surface mount piezoelectric oscillator, a perspective view of an IC component unit, a perspective view showing an assembling procedure, and a longitudinal section of a finished product. Area view.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Surface mount type piezoelectric oscillator, 2 Package for mounting IC components (IC component unit), 3 Piezoelectric vibrator, 5 Insulating board, 6 Depression, 7 Pad for mounting IC components, 8 IC components, 9 External electrodes, 10 Outer wall, 10a non-electrode region, 11 upper electrode, 11a, 11b upper electrode for excitation, 11c, 11d upper electrode for ground, 12 insulating resin, 20 package body, 20a non-electrode region, 21 recess, 22 piezoelectric vibration element, 23 metal cover , 25 pads, 26 bottom electrode, 30 insulating adhesive.

Claims (2)

An insulating substrate having a concave portion for mounting an IC component on one surface, an IC component mounting pad formed on an inner bottom surface of the concave portion, a plurality of upper electrodes disposed on an upper surface of an annular outer wall surrounding the concave portion; An external electrode for surface mounting exposed on the outer bottom of the substrate, a connection conductor for electrically connecting the IC component mounting pad, the upper electrode, and the external electrode, and a recess filled to cover the IC component. An IC component unit comprising a resin;
A piezoelectric vibrator including a package having a bottom electrode connected to the upper electrode when mounted on the upper surface of the IC component unit, and a piezoelectric vibrating element hermetically housed in the package. And
The non-electrode region where the upper electrode does not exist on the upper surface of the outer wall of the insulating substrate constituting the IC component unit, and the outer bottom surface of the package of the piezoelectric vibrator facing the non-electrode region are joined with an insulating adhesive. A surface-mount type piezoelectric oscillator characterized in that: An insulating substrate having a concave portion for mounting an IC component on one surface, an IC component mounting pad formed on the inner bottom surface of the concave portion, a plurality of upper electrodes disposed on an upper surface of an annular outer wall surrounding the concave portion, An external electrode for surface mounting exposed on the outer bottom of the substrate, a connection conductor for electrically connecting the IC component mounting pad, the upper electrode, and the external electrode, and a recess filled to cover the IC component. An IC component unit comprising a resin;
A package including a plurality of bottom electrodes connected to the upper electrode when mounted on the top surface of the IC component unit, and a piezoelectric vibrator including a piezoelectric vibrating element hermetically housed in the package; Has,
The plurality of upper electrodes includes at least two grounding upper electrodes,
The plurality of bottom electrodes include a ground bottom electrode in a one-to-one correspondence with each of the ground top electrodes,
The surface mounting according to claim 1, wherein one of the grounding upper electrodes and a grounding bottom electrode facing the one grounding upper electrode are joined by an insulating adhesive. Type piezoelectric oscillator.

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