Oscillator

Abstract: An oscillator in which organic substances derived from an active element fixing adhesive do not deposit on an oscillating element and in which when the active element or the oscillating element is damaged, other good parts that are not defective can be reused. In the oscillator, an active element 2 is mounted inside a first container 1 whose upper surface is opened, and not only the opening of the first container 1 is closed by an oscillating unit 3 having an oscillating element 6 incorporated therein, but also the oscillating unit 3 is attached onto the opening of the first container 1, so that second connecting electrodes 11a to 11d of a second container 5 of the oscillating unit 3 are electrically connected to first connecting electrodes 14a to 14d of the first container 1. As a result of this construction, the oscillating element and the active element can be accommodated in separate containers, which not only prevents organic substances derived from an active element fixing adhesive from being deposited on the oscillating element, but also parts that are not defective can be reused only by separating the first container from the second container if the active element or the oscillating element is damaged.

Description: BACKGROUND OF THE INVENTION The invention relates to an oscillator to be used as a reference frequency source of mobile communication equipments such as portable telephones. Generally, oscillators of this type have such structure that an oscillating element and an active element therefor are accommodated in a single container. Such an oscillator having both the active element and the oscillating element accommodated in a single container addresses the problem that organic substances emitted from a resin-containing adhesive used for fixing the active element deposit on the oscillating element to thereby deteriorate the oscillation characteristics of the oscillating element. To overcome this problem, the following technique has recently been proposed. The inside of a container having openings on both ends thereof is partitioned into two chambers, and the oscillating element is accommodated in one of the chambers and the active element in the other, so that deposition of organic substances emitted from the resin-containing adhesive used for fixing the active element on the oscillating element can be prevented. However, the aforementioned oscillator having two chambers is disadvantageous in terms of costs. That is, such oscillator is prepared by: first, mounting an oscillating element in one of the two chambers and sealing the corresponding opening of the chamber after frequency adjustments have been made; and then, mounting the active element in the other chamber and writing temperature compensation data to the active element. If the active element is damaged at the time of being mounted or at the time of writing the temperature compensation data, not only the active element but also the oscillating element must be disposed of together with the container. Hence, this type of oscillator has been costly. That is, if the active element is damaged, one may suggest that only the active element be removed from the other chamber of the container and replaced with a new one. However, in actuality, the active element is fixed by a resin-containing adhesive, so that the active element is not easy to remove, thus ending up in damaging also the container in some cases. EP 727872 discloses a piezoelectric oscillator including a semiconductor integrated circuit and a piezoelectric resonator. The piezoelectric resonator comprises a case with a cross-section of an elliptic or a track-like (combination of a rectangle and two semicircles) shape, wherein the semiconductor integrated circuit and an electronic component are molded with a resin into a very thin unit in the form of a surface-mounting structure. US 5025228 discloses a piezoelectric resonator consisting of a piezoelectric reed encased in a housing composed of a cap and a base. The resonator is based in a thermostatically-controlled containment consisting of an inner cell which is screwed into an outer cell. The cap of the resonator is folded over its entire outer surface to the sides and the bottom of the inner cell. US 4627533 discloses a ceramic package for a compensated crystal oscillator and has a three-layer body with a closed bottom upper cavity, a closed bottom lower cavity, and a through cavity in which the oscillator crystal is mounted. The upper cavity carries an oscillator network on a thin film hybrid, while the lower cavity carries the temperature compensation network on a thick film hybrid. SUMMARY OF THE INVENTION The object of the invention is, therefore, to provide an oscillator having such a structure that organic substances derived from an active element fixing adhesive do not deposit on an oscillating element and that if the active element or the oscillating element is damaged, other good parts that are not defective can be reused. This object is solved by an oscillator having the features as defined in claim 1. According to the invention, an oscillator of such structure that not only organic substances derived from an active element fixing resin-containing adhesive do not deposit on the oscillating element but also if the active element or the oscillating element is damaged, other good parts that are not defective can be reused. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an exploded perspective view of an oscillator according to a first embodiment; Fig. 2 is a perspective view showing an appearance of the first embodiment; Fig. 3 is a front view of the first embodiment; Fig. 4 is a plan view of the first embodiment; Fig. 5 is a side sectional view of the first embodiment; Fig. 6 is a plan view of a first container of the first embodiment with an active element attached; Fig. 7 is a half-sectional view of the front of the first container of the first embodiment; Fig. 8 is a plan view of the first embodiment with a shield plate of a second container removed; Fig. 9 is a sectional view of the front of the second container of the first embodiment; Fig. 10 is an electrical block diagram of the first embodiment; Fig. 11 is a sectional view of the front of an oscillator according to a second embodiment; Fig. 12 is a plan view of the second embodiment; Fig. 13 is an exploded sectional view of the front of the second embodiment; Fig. 14 is a sectional view of the front of a third embodiment; Fig. 15 is a plan view of the third embodiment; Fig. 16 is a sectional view of a main portion of the front of an oscillator according to a fourth embodiment; Fig. 17 is an exploded perspective view of an oscillator according to a fifth embodiment; and Fig. 18 is a sectional view of the front of the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the invention will now be described with reference to Figs. 1 to 18. First Embodiment Figs. 1 to 10 show the first embodiment. In Figs. 1 to 5, a first container 1 is formed of a laminated body of ceramic sheets, and is box-shaped with the upper surface thereof opened as shown in Figs. 1, 6 and 7. An active element 2 constructed of a bare chip is mounted inside the first container 1 while fixed by an adhesive. An oscillating unit 3 is attached onto an outer peripheral wall 4 of the first container 1 so as to cover the opening of the first container 1. As shown in Figs. 1, 8 and 9, the oscillating unit 3 has a second container 5, an oscillating element 6, and a shield plate 7. The second container 5 is formed of a laminated body of ceramic sheets with the upper surface thereof opened. The oscillating element 6 is constructed of a crystal oscillator mounted inside the second container 5. The shield plate 7 made of a metal plate is attached to the opening of the second container 5 as an exemplary sealing plate. The oscillating element 6 is hermetically sealed inside the second container 5 by welding the shield plate 7 to a seam ring 9 that is fixed onto an outer peripheral wall 8 of the second container 5. It may be noted that hermetic sealing may be implemented by glass, solder, Au-Sn alloys, and the like. As shown in Figs. 1 and 2, semicircular notches 10 are formed at four points on the outer peripheral surface of the outer peripheral wall 8 of the second container 5. As shown in Fig. 9, second connecting electrodes lla to lid are formed both on the inner sides of the notches 10 and on the bottom surface continuous to the notches 10. As shown in Fig. 10, the second connecting electrodes 11a and 11c these electrodes are electrically connected to the oscillating element 6, whereas the second connecting electrodes 11b and lid are electrically connected to the seam ring 9 to be grounded. On the other hand, the active element 2 mounted on the first container 1 is, as shown in Figs. 6 and 7, electrically connected to electrodes 13 by wires 12, and first connecting electrodes 14a to 14d, each of which is connected to either one of the electrodes 13, are arranged at four points on the outer peripheral wall 4 of the first container 1. The first connecting electrodes 14a to 14d and the second connecting electrodes lla to lid are electrically connected by a conductive adhesive A such as thermal hardening conductive resin or solder in such a manner that: the connecting electrode 14a is connected to the connecting electrode lla; the connecting electrode 14b is connected to the connecting electrode 11b; the connecting electrode 14c is connected to the connecting electrode 11c; and the connecting electrode 14d is connected to the connecting electrode lid. As a result, the oscillating element 6 is electrically connected to the active element 2. It may be noted that the active element 2 is connected through flip-chip mounting instead of connection through the wires 12. After electrical connection between the first electrodes 14a to 14d and second electrodes lla to lid has been completed, an adhesive seal resin 15 is applied over the outer peripheral portion of the bottom surface of the second container 5 as shown in Figs. 3 and 4. As a result, not only the second container 5 is bonded and fixed onto the upper surface of the outer peripheral wall 4 of the first container 1, but also the opening on the upper surface of the first container 1 is sealed by the second container 5 to thereby protect the active element 2. As a result of the opening being thus sealed, resin molding on the outer periphery of the active element 2 is no longer necessary. However, to give more reliable protection of the active element 2, resin molding over the outer periphery of the active element 2 may be made in addition to the sealing of the opening by the second container 5. Semicircular notches are arranged over the outer periphery of the first container 1, and electrodes 16a to 16n are arranged on the respective notches. Among these electrodes, the electrodes 16b, 16f, 16i, 16m extend not only on the corresponding notches but also to the bottom surface of the first container 1 continuous to such notches. The electrode 16b serves as an AFC terminal; the electrode 16f, a ground terminal; the electrode 16i, an oscillation output terminal (TCXO); and the electrode 16m, a power supply terminal (V DD ). Fig. 7 shows an example of the electrode 16i. Fig. 10 shows a configuration of this oscillator. Further, the other electrodes 16a, 16c, 16d, 16e, 16g, 16h, 16j, 16k, 161, 16n are inspecting electrodes. These electrodes are arranged at positions remote upward by a predetermined distance from the bottom surface of the first container 1. These electrodes are used to write data to a memory within the active element 2 and to carry out various types of inspections. Here, since these inspecting electrodes are arranged so as to be distanced from the bottom surface of the first container 1, there is no likelihood that conductive patterns on the board are short-circuited to the inspecting electrodes when the first container is mounted on the board. It may be noted that a varactor diode is arranged inside the active element 2 in addition to the memory. The oscillation frequency of the oscillating element 6 is controlled so as to stay substantially constant independently of temperatures by varying the voltage to be supplied to the cathode of the varactor diode so that the capacitance thereof is changed. Second Embodiment Figs. 11 to 13 show the second embodiment. It may be noted that the same parts and components as those of the first embodiment will be described while denoted by the same reference numerals. As shown in Figs. 11 to 13, the second embodiment is characterized in that a recessed step 4B is formed on the upper inner peripheral portion of an outer peripheral wall 4A of a first container 1A, so that a second container 5 is supported by such step 4B. That is, when the step 4B is formed on the upper surface of the first container 1A and the second container 5 is supported by the step 4B as shown in Figs. 11 and 13, the second container 5 can be positioned with respect to the first container 1A without having to perform special positioning operation. In addition, relative positions between the first connecting electrodes 14a to 14d and second connecting electrodes lla to lid can also be set correctly, which not only allows both connecting electrodes to be electrically connected reliably, but also allows the upper opening of the first container 1A can be sealed by the second container 5 reliably. Third Embodiment Figs. 14 and 15 show the third embodiment. It may be noted that the same parts and components as those of the first and second embodiments will be described while denoted by the same reference numerals. As shown in Figs. 14 and 15, the third embodiment is characterized in that an outer peripheral wall 4C of a first container 1B is made higher than in the second embodiment. More specifically, the upper surface of the first container 1B is extended upward to second connecting electrodes lla to lid of a second container 5, and a shield electrode 17 is arranged on the upper surface of the outer peripheral wall 4C so as to extend all along the periphery thereof as shown in Fig. 15. The shield electrode 17 is electrically connected to an electrode 16f serving as a ground terminal through a conductive path 20 that is formed inside the outer peripheral wall 4C shown in Fig. 14. Therefore, this shield electrode 17 not only makes it hard for external noise to be picked up by the connecting portions of the first and second connecting electrodes, but also prevents electrostatic destruction of the active element 2 by an operator touching the active element 2 with his or her finger. Since the conductive adhesive A is made hard to insert into the connecting portions of the first connecting electrodes 14a to 14d and second connecting electrodes lla to lid by extending the outer peripheral wall 4C upward, notches 18 extending as high as to a step 4B are formed in the inner surface portions of the outer peripheral wall 4C so as to correspond to the first connecting electrodes 14a to 14d and second connecting electrodes lla to lid and the conductive adhesive A is charged into such notches 18. As a result, electric connection between the first connecting electrodes 14a to 14d and second connecting electrodes 11a to 11d is stabilized. Further, the first and second connecting electrodes can be electrically connected easily as well as reliably in this way, the area occupied by the first and second connecting electrodes can be reduced accordingly, which in turn contributes to further preventing infiltration of external noise into the first and second electrodes. It may be noted that the conductive adhesive A is charged not as high as to the upper inner portion of the notches 18 and that the upper portion is covered by a bonding seal resin 15 lest the shield electrode 17 should be short-circuited to the first connecting electrodes 14a to 14d and second connecting electrodes lla to lid inadvertently. Fourth Embodiment Fig. 16 shows the fourth embodiment. It may be noted that the same parts and components as those of the first to third embodiments will be described while denoted by the same reference numerals. As shown in Fig. 16, the fourth embodiment is characterized in that a hole 19 whose diameter is tapered toward the lower portion of a first container 1C is formed in a step 4B portion confronting first connecting electrodes 14a to 14d. When the first container 1C and the second container 5 are bonded and fixed, a redundant conductive adhesive A is charged into this hole 19 to prevent short-circuiting by a conductive adhesive A spreading outside the first connecting electrodes 14a to 14d and second connecting electrodes lla to lld inadvertently. In this case, if the hole 19 is straight, the conductive adhesive A disadvantageously leaks outside the first container 1C. Therefore, the hole 19 must be structured so that the diameter thereof is tapered in order to prevent leakage. Further, in case of a thermal hardening conductive resin being used as a conductive adhesive A, this hole 19 works to exhaust the gas which is generated during thermal hardening of the thermal hardening conductive resin. The first container 1C and the second container 5 may be fixed by soldering. However, contaminant such as flux may be attached to the active element 2 so that it may cause some defects. Accordingly, in order to eliminate such defects, the thermal hardening conductive resin is preferable. While each of the first and second containers is made of a laminated body of ceramic sheets in the aforementioned modes of embodiment, these containers may also be made of glass, ceramics, glass epoxy materials, and the like. Fifth Embodiment Figs. 17 and 18 show the fifth embodiment. It may be noted that the same parts and components as those of the first to fourth embodiments will be described while denoted by the same reference numerals. As shown in Figs. 17 and 18, the fifth embodiment is characterized in that an active element 2 and an oscillating element 6 are interposed between a shield plate 7 and a conductive layer 21. That is, in Fig. 17, the active element 2 is mounted on a die-bonding area 22, is connected to electrodes 13 of a first container 1 with wires 12, and has the entire part thereof coated with a protective resin 23. Here, the first container 1 is formed by laminating ceramic sheets (la to ld), and the conductive layer 21 is formed between the ceramic sheets lc and ld by printing and is grounded through the internal wiring. As a result of this construction, effects of electromagnetic fields caused by the wiring patterns of the mother board and effects of electromagnetic fields derived from other devices and circuits close to the mother board can be shielded at the time of mounting the oscillator onto the mother board. Hence, an oscillator with stable output frequency can be implemented. As described in the foregoing, the invention is characterized not only as accommodating the oscillating element and the active element in separate containers, but also as stacking these containers one upon another. Therefore, there is no likelihood that organic substances emitted from the bond formed by a resin-containing adhesive for fixing the active element onto the oscillating element will deposit, so that deterioration of oscillating characteristics due to deposition of organic substances and the like can be prevented. Further, even if the active element or the oscillating element is damaged, what is needed is only replace either the first container or the second container. That is, any good parts that are not defective can be reused. Hence, an oscillator that is extremely advantageous also in terms of costs can be implemented.

Claims: An oscillator comprising: a first container (1) formed by a first upper surface with a first opening, a first bottom surface and a first outer peripheral wall (4); an active element (2) being mounted inside the first container (1); and an oscillating unit (3), said oscillating unit comprising: a second container (5) formed by a second upper surface with a second opening, a second bottom surface and a second outer peripheral wall (8); an oscillating element (6) being mounted inside the second container (5); and a seal plate (7) being attached to said second opening of the second upper surface of the second container; characterized in that said oscillator further comprises: an external electrode (13) being arranged so as to extend from a portion of said first outer peripheral wall to said first bottom surface, a first connecting electrode (14a,..., 14d) being arranged on the first outer peripheral wall (4) of the first container (1), a second connecting electrode (11a,...,11d)being arranged so as to extend from a portion of said second outer peripheral wall (8) to the second bottom surface, wherein said second connecting electrode (11a,...,11d) of the oscillating unit (6) is electrically connected to the first connecting electrode (14a,...,14d) of the first container (1), and said oscillating unit (6) being mounted onto the first peripheral wall (4) of the first container (1) so as to cover said first opening of the first container (1). An oscillator according to claim 1, wherein an inspecting electrode is arranged on an outer peripheral surface of the first outer peripheral wall of the first container, and the inspecting electrode is positioned so as to be remote upward by a predetermined distance from the bottom surface of the first container. An oscillator according to claim 1, wherein an adhesive sealing resin is arranged on an outer peripheral portion of the second bottom surface of the second container. An oscillator according to claim 1, wherein a recessed step is formed inside an upper inner peripheral portion of the first outer peripheral wall of the first container, and the second container is supported by the step. An oscillator according to claim 4, wherein not only the upper surface of the first outer peripheral wall of the first container is arranged so as to be higher than the second connecting electrode of the second container, but also a shield electrode is arranged on the upper surface of the outer peripheral wall of the first container. An oscillator according to claim 4, wherein a notch is arranged at a position not only on an inner surface side of the first outer peripheral wall of the first container but also corresponding to the second connecting element of the second container so as to extend downward from the upper surface side of the first outer peripheral wall of the first container to the upper surface of the step. An oscillator according to claim 6, wherein an electrode is arranged on an inner surface of the notch. An oscillator according to claim 6, wherein a conductive adhesives charged only into a lower portion from the opening of the notch. An oscillator according to claim 4, wherein a hole is arranged at a position not only on the bottom surface of the step of the first container but also corresponding to the second connecting electrode on the bottom surface of the second container. An oscillator according to claim 9, wherein the hole of the step of the first container is such that a diameter thereof is tapered downward. The oscillator of claim 1, comprising: a conductive body on the first bottom surface of the first, a shield plate covering the second opening of the second upper surface of the second container, wherein the first container and the second container are electrically connected so that the conductive body and the shield plate are electrically grounded. An oscillator according to claim 11, wherein not only the first container is formed by laminating ceramic layers, but also the conductive body is formed by interposing a conductive layer between the laminated ceramic layers.

Inventors: KIMURA AKIO, KONDO SHUJI, SATOH YUKI, SUZUKI MITSUO, KIMURA, AKIO, KONDO, SHUJI, SATOH, YUKI, SUZUKI, MITSUO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, VICTOR COMPANY OF JAPAN, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD., VICTOR COMPANY OF JAPAN, LIMITED
Application year: 1997
Main classification: H03L1
IPC codes: H01L23, H03B5, H03H9