JP2008113234A - Crystal oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystal oscillator of an excellent reflow characteristic having a crystal vibration element of a main electrode layer structure which does not lower adhesion strength between a support part and the crystal vibration element even though the crystal vibration element is made compact in accordance with compactness and the area of an extracting electrode is made small. <P>SOLUTION: In the crystal oscillator, an integrated circuit element including an oscillation circuit is mounted on the surface principal plane of an insulative substrate of a container of a recessed shape surrounding a first space part of the surface principal plane of the insulative substrate, the crystal vibration element connected to the integrated circuit element through a connection electrode part is housed in a container also having a recessed shape surrounding a second space part formed on the top surface of the first space part of the insulative substrate, the containers surrounding the first and the second space parts are connected through the connection electrode part, and a lid is mounted on the top edge part of an opening of the container surrounding the second space part to perform hermetic sealing. In the main electrode layer structure of the crystal oscillator, the number of sums of film thickness of the both sides of a ground main electrode layer made of a high-melting point metal attached to the front and rear faces of the internal crystal vibration element is ≥30 Å and ≤90 Å. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

      The present invention provides a main electrode layer structure in which the crystal resonator element itself is also miniaturized due to the miniaturization of the crystal resonator, and the adhesion strength between the support portion and the crystal resonator element is not reduced even when the lead electrode area is reduced. The present invention relates to a crystal oscillator having a good reflow characteristic, in which a crystal resonator element having the above is mounted.

      The crystal unit of the crystal oscillator, which is one of the independent electronic components, is formed on the front and back main surfaces of the crystal resonator element on the excitation electrode that excites the crystal resonator element and the base container that houses the crystal resonator element. A connection electrode for connecting to the support portion to be connected and a lead electrode for conductively connecting the excitation electrode and the connection electrode are formed. With the miniaturization of crystal resonators, small strip shapes have become mainstream as the shape of crystal resonator elements. In order to cope with further downsizing, conventionally, a conductive bonding material has been used as a conductive fixing means between the extraction electrode on the quartz-crystal vibrating element side and the support portion on the base container side.

      FIG. 5 is a cross-sectional view of a crystal resonator 50 showing a state in which a crystal resonator element 52 having various electrodes formed therein is housed in a base container 56 and conductively fixed by a conductive bonding material 58 as an example of the prior art. That is, on the front and back main surfaces of the crystal resonator element 52 constituting the crystal resonator element 52, the opposing excitation electrode 53 and the connection electrode 54 extending from the excitation electrode 53 to one short side of the crystal resonator element 52 are provided. A lead electrode 55 is formed to be electrically connected to the connection electrode 54 and to be electrically connected to the support portion 57 on the base container 56 side.

The crystal resonator element 52 configured as described above is disposed in the space of the base container 56 so as to be substantially parallel to the inner bottom surface of the base container 56. At that time, the conductive connection material 58 such as a silver paste containing a metal material such as silver is connected between the extraction electrode 55 on the crystal resonator element 52 side and the support portion 57 on the base container 56 side. . The conductive bonding material 58 also holds the crystal vibrating element 52 in the base container 56. The crystal resonator 50 is formed by disposing a metal lid 59 in the opening of the base container 56 in which the crystal resonator element 52 is mounted in the internal space and hermetically sealing the internal space of the base container 56. .
The following documents are disclosed about the crystal vibrating element 52 as described above.

JP 2002-050937 A

      Incidentally, the applicant has not found any prior art documents related to the present invention other than the prior art documents specified by the above prior art document information by the time of filing of the present application.

      However, as miniaturization of crystal resonators progresses, the crystal resonator element mounted inside the crystal resonator itself must be miniaturized, and as a result, a region where connection electrodes can be formed on the main surface of the crystal resonator element has become extremely large. Narrower and smaller lead electrode shape. Therefore, the area of the support part on the base container arranged within the formation area of the extraction electrode is also reduced, and as a result, the adhesive strength between the support part and the extraction electrode is weakened. There is a risk. Further, since the contact area is small, the strength for holding the crystal resonator element is also weak, and there is a high possibility that the crystal resonator element will drop off when a force is applied to the crystal resonator element from the outside. In order to avoid these problems, conventionally, when mounting the crystal resonator element on the support portion, the crystal resonator element is mounted on the support portion so that the conductive bonding material is covered to the side surface of the crystal resonator element. However, as a result, excessive stress was applied to the crystal resonator element itself from the conductive bonding material, making the vibration characteristics of the crystal resonator element unstable. There is a problem that the frequency fluctuation of the reflow characteristic may be increased.

      The present invention has been conceived in view of the above-mentioned drawbacks, and therefore, the purpose of the present invention is to reduce the area of the extraction electrode as the crystal resonator element itself is downsized by downsizing the crystal unit of the crystal oscillator. Means for ensuring the adhesive strength between the support portion and the extraction electrode without reducing the adhesion strength between the support portion and the crystal resonator element even when the amount of the conductive bonding material that can be used is limited compared to the conventional case. It is an object of the present invention to provide a crystal oscillator having a good reflow characteristic, in which a crystal resonator element having a main electrode layer structure in which the influence of a residual stress on a crystal base plate irrespective of this is reduced is mounted.

      The crystal oscillator according to the present invention is an integrated circuit in which an oscillation circuit is incorporated on the front main surface of the insulating base in a concave container surrounding the first space provided on the front main surface of the insulating base. An element is mounted and electrically connected to the previous integrated circuit element through a connection electrode in a concave container surrounding the second space formed on the upper surface of the first space of the insulating substrate. The container that surrounds the first space and the container that surrounds the second space are joined via the connection electrode portion, and an opening of the container that surrounds the second space In a quartz oscillator in which a lid is placed and hermetically sealed on the upper edge, the sum of the thicknesses of both surfaces of the base main electrode layer made of a refractory metal attached to the front and back surfaces of the previous quartz resonator element is 30 mm. As described above, it is characterized by being 90 mm or less.

The crystal oscillator according to the present invention is characterized in that, in the above configuration, the base main electrode layer is made of chromium (Cr).

      According to the crystal oscillator of the present invention, the oscillation circuit is incorporated on the front main surface of the insulating base in the concave container surrounding the first space provided on the front main surface of the insulating base. An integrated circuit element is mounted and electrically connected to the previous integrated circuit element through a connection electrode portion in a concave container surrounding the second space formed on the upper surface of the first space of the insulating substrate. A container that surrounds the first space part and a container that surrounds the second space part are joined via the connection electrode part, and the container that surrounds the second space part. In a quartz oscillator in which a lid is placed on the upper edge of the opening and hermetically sealed, the sum of the film thickness on both sides of the base main electrode layer made of a refractory metal attached to the front and back surfaces of the previous crystal resonator element Is 30 mm or more and 90 mm or less, and the residual main electrode layer is made thin by reducing the Cr film thickness. Since it is easy to release the force, the frequency fluctuation of the reflow characteristic (the characteristic that causes the frequency fluctuation as a result of the release of the residual stress in the crystal vibration element by heating when the crystal oscillator is reflow mounted on the mounting circuit board) It becomes possible to suppress.

      Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol in each figure shall show the same object.

      FIG. 1 is a cross-sectional view of the crystal oscillator according to the embodiment of the present invention taken along line XX ′ shown in FIG. 2, and FIG. 2 shows a second space in which the lid 4 is removed from the crystal unit of the crystal oscillator of the present invention. It is the top view which looked at the part 9 from the upper surface. The crystal oscillator shown in FIG. 1 is provided with an electrode terminal 19 on the lower surface of an insulating substrate 10 having a first space portion 15 for accommodating the integrated circuit element 7, and the first space portion 15 for accommodating the integrated circuit element 7. The integrated circuit element 7 is mounted on the upper surface of the insulating substrate 10 having the above. In addition, a side wall surrounding the first space portion 15 of the insulating substrate 10 having the first space portion 15 that houses the integrated circuit element 7 is provided on the side wall 13, and a plurality of writings are provided on the outer side surface of the wall body 13. A control terminal 11 is formed. Further, as shown in FIG. 1, the upper surface of the wall body 13 has a structure in which the crystal resonator 1 in which the crystal resonator element 5 is accommodated is placed and fixed.

      In FIG. 1, a crystal resonator 1 includes, for example, a substrate 2 made of a ceramic material such as glass-ceramic and alumina ceramic, and side walls 3 and 42 made of a ceramic material similar to the substrate 2, such as an alloy, Kovar, phosphor bronze, or the like. The crystal resonator 1 is configured by attaching the side wall 3 to the upper surface of the substrate 2 and mounting and fixing the lid 4 on the upper surface of the substrate 2, and is positioned inside the side wall 3. A crystal resonator element 5 is mounted on the upper surface of the substrate 2 to be operated.

      The crystal resonator 1 has a crystal resonator element 5 accommodated in a second space 9 surrounded by the upper surface of the substrate 2, specifically, the inner surface of the side wall 3 and the lower surface of the lid body 4. A lid 4 is placed and hermetically sealed, a pair of mounting pads connected to the excitation electrode 6 of the crystal resonator element 5 on the upper surface of the substrate 2, and an insulating property to be described later on the lower surface of the substrate 2. A plurality of second connection electrode portions 17 connected to the wall body 13 on the base 10 are provided, and these pads and terminals are connected via a wiring pattern on the surface of the substrate 2 and via holes embedded in the substrate. The corresponding devices are electrically connected to each other.

      On the other hand, the crystal resonator element 5 accommodated in the crystal unit 1 is formed by attaching and forming a pair of excitation electrodes 6 on both main surfaces of a crystal base plate cut by a predetermined crystal axis, and from the outside. When the fluctuating voltage is applied to the quartz base plate via the pair of excitation electrodes 6, a thickness shear vibration occurs at a predetermined frequency. The excitation electrode 6 is formed of a base main electrode layer 22 made of a chromium (Cr) layer which is a refractory metal and an upper main electrode layer 23 made of an Au layer.

      Here, the lid 4 of the crystal unit 1 is connected to an electrode terminal 19 for a ground terminal described later via the second connection electrode unit 17 of the crystal unit 1 and the first connection electrode unit 18 of the insulating base 10. If it is allowed to be used, the lid 4 made of metal is connected to the reference potential at the time of use, and a shielding function is given. Good protection from the action. Therefore, the lid 4 of the crystal unit 1 is connected to the electrode terminal 19 for the ground terminal via the second connection electrode unit 17 of the crystal unit 1 and the first connection electrode unit 18 of the insulating substrate 10. It is preferable to keep it.

      The insulating substrate 10 having the first space 15 for accommodating the integrated circuit element 7 to which the above-described crystal resonator 1 is attached has a substantially rectangular shape, and is made of glass cloth base epoxy resin or polycarbonate. , A resin material such as epoxy resin or polyimide resin, or a ceramic material such as glass-ceramic or alumina ceramic.

      The insulating substrate 10 having the first space 15 for accommodating the integrated circuit element 7 has four electrode terminals 19 (a power supply voltage terminal, a ground terminal, an oscillation output terminal, an oscillation control, respectively) at the four corners on the lower surface of the substrate region. Are formed on the outer periphery of the wall 13 between the four corners, and on the outer side surface of the wall 13 between the four corners. A write control terminal 11 is provided.

      The four electrode terminals 19 provided on the lower surface of the insulating base 10 having the first space portion 15 that accommodates the integrated circuit element 7 serve as terminals for connecting the crystal oscillator to a mounting circuit board such as a mother board. When the crystal oscillator is mounted on the mounting circuit board, it is electrically connected to the circuit wiring of the mounting circuit board via a conductive bonding material such as solder.

      In addition, the wall 13 provided on the upper surface of the insulating base 10 having the first space 15 for accommodating the integrated circuit element 7, and the insulating base having the first space 15 for receiving the integrated circuit element 7. The insulating substrate 10 having the first space 15 for accommodating the integrated circuit element 7 while ensuring a predetermined interval necessary for disposing the integrated circuit element 7 between the crystal unit 1 and the crystal unit 1. The first connection electrode portion 18 is connected to the second connection electrode portion 17 of the crystal resonator 1 through the solder layer 12.

      Further, a plurality of electrode pads are provided in the central region of the insulating base 10 having the first space 15 for accommodating the integrated circuit element 7 described above, and the connection of the integrated circuit element 7 to these electrode pads. The insulating property in which the integrated circuit element 7 has the first space portion 15 is obtained by electrically and mechanically connecting the pad via a conductive bonding material 8 such as an Au bump, solder, or anisotropic conductive adhesive. It is attached to a predetermined position on the substrate 10.

      The integrated circuit element 7 has, on its circuit forming surface (lower surface), a temperature sensing element such as a thermistor for detecting the ambient temperature state, a memory for storing temperature compensation data for compensating the temperature characteristics of the crystal vibration element 5, A temperature compensation circuit that corrects the vibration characteristics of the crystal resonator element 5 according to a temperature change based on the temperature compensation data, an oscillation circuit that is connected to the previous temperature compensation circuit and generates a predetermined oscillation output, and the like are provided. The oscillation output generated by the oscillation circuit is used as a reference signal such as a clock signal after being output to the outside.

      Here, as shown in FIGS. 1 and 2, the characteristic part of the present invention is that the insulating substrate 10 in a concave container surrounding the first space 15 provided on the front main surface of the insulating substrate 10. An integrated circuit element 7 in which an oscillation circuit is incorporated is mounted on the front main surface of the same, and also has a concave shape surrounding the second space portion 9 formed on the upper surface of the first space portion 15 of the insulating substrate 10. The crystal resonator element 5 electrically connected to the integrated circuit element 7 through the connection electrode portions 17 and 18 is accommodated in the container, and the container surrounding the first space portion 15 and the second space portion 9 are accommodated. In the crystal oscillator in which the enclosing container is joined via the connection electrode portions 17 and 18 and the lid 4 is placed on the upper edge of the opening surrounding the second space 9 and hermetically sealed, Sum of film thicknesses on both sides of base main electrode layer 22 made of a refractory metal attached to the front and back surfaces of element 5 30Å or more, as the following 90 Å, it is possible to suppress the frequency variation of the reflow characteristics at reducing the chromium (Cr) film thickness used as a base main electrode layer 22. The graph of FIG. 3 shows how the frequency fluctuation of the reflow characteristic is suppressed to a small level. Here, the vertical axis of FIG. 3 is the frequency change rate ΔF (ppm) due to reflow of the crystal oscillator, and the horizontal axis is the sum (Å) of the film thicknesses of both surfaces of the chrome-film crystal resonator element 5 used for the base main electrode 22. is there. FIG. 3 shows that when the sum of the film thicknesses of chromium (Cr) is 90 mm or less, the frequency change rate by reflow heating (peak temperature: about 240 ° C. to 260 ° C.) is stable at −0.5 ppm or less. . In this experiment, the Cr film thickness is controlled by fixing the discharge power to 0.21 kW and changing the transport speed. Conventionally, the sum of the film thickness of the base main electrode layer is about 150 mm (conveying speed 3000 to 5000 pps), the frequency change rate in reflow heating is as large as about -1.5 ppm, and it is highly accurate such as for GPS. There is a possibility that it is not preferable for a crystal oscillator that requires the As for the upper main electrode layer 23, an Au layer having a thickness of about 3500 to 4000 mm is formed as the upper main electrode layer 23.

      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, chromium (Cr) is used for the base main electrode layer 22 as shown in FIG. 1, but instead of this, nickel (Ni), titanium (Ti ), Nichrome, aluminum (Al), silver (Ag), or other metal material may be used to form the underlying main electrode layer, and this case is also included in the technical scope of the present invention. There is no.

1 is a schematic cross-sectional view of a crystal oscillator according to an embodiment of the present invention as viewed from the side. In addition, the lower figure of FIG. 1 is the figure which expanded a part (21) of the upper figure. It is the schematic top view which looked at the 2nd space part which is the part of a crystal oscillator of the crystal oscillator concerning embodiment of this invention from upper direction. It is a graph which shows the relationship between the reflow frequency change rate (vertical axis), and the Cr film thickness (horizontal axis) used as a base main electrode layer of the crystal oscillator concerning embodiment of this invention. It is the rough side surface sectional view which looked at the crystal oscillator part of the crystal oscillator from which the conventional crystal oscillation element was carried in the horizontal direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Crystal oscillator 2 ... Board | substrate 3 ... Side wall 4 ... Cover body 5 ... Quartz vibration element 6 ... Excitation electrode 7 ... Integrated circuit element 8 ... Conductive joining Material 9 ... second space 10 ... insulating base 11 ... write control terminal 12 ... solder layer 13 ... wall 15 ... first space 17 ... 2nd connection electrode part 18 ... 1st connection electrode part 19 ... Electrode terminal 21 ... Conductive bonding material 22 ... Underlayer main electrode layer 23 ... Upper layer main electrode layer 24 ... Supporting part

Claims (2)

An integrated circuit element in which an oscillation circuit is incorporated is mounted on the front main surface of the insulating base in a concave container surrounding the first space provided on the front main surface of the insulating base. A quartz crystal resonator element electrically connected to the integrated circuit element through a connection electrode portion in a concave container surrounding the second space portion formed on the upper surface of the first space portion of the insulating substrate. The container enclosing the first space part and the container enclosing the second space part are joined via the connection electrode part, and the container enclosing the second space part In a crystal oscillator in which a lid is placed on the upper edge of the opening and hermetically sealed,

A crystal oscillator characterized in that the sum of the film thicknesses of both surfaces of a base main electrode layer made of a refractory metal attached to the front and back surfaces of the crystal resonator element is 30 mm or more and 90 mm or less.       2. The crystal oscillator according to claim 1, wherein the base main electrode layer is made of chromium (Cr).

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