JPH1013155A - Crystal oscillator with frequency-adjusting function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a small crystal oscillator eliminating the need for a function for adjusting an oscillation frequency outside of the crystal oscillator by providing a voltage-variable capacitor element (PEAC) for adjusting the oscillation frequency inside the package of the crystal oscillator. SOLUTION: A voltage applied on the PEAC element 4 is changed from an outside, so that the electrostatic capacitance of the PEAC element 4 is changed, load capacitance is adjusted and a desired frequency is obtained. That is, a positive voltage is applied to the adjustment terminal 6 of the PEAC element 4, so that the synthetic capacitance becomes larger, load capacitance is increased and the oscillation frequency of the crystal oscillator 1 becomes low. When a negative voltage is applied on the adjustment terminal 6 of the PEAC element 4, the combined capacitance of the PEAC element is decreased, the load capacitance is reduced and the oscillation frequency becomes high. Thus, the combined capacitance of the PEAC element 4 is increased/decreased, so that load capacitance is changed and the oscillation frequency of an oscillation circuit is adjusted through the use of the crystal oscillator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage-variable capacitive element, such as a crystal oscillator for generating a reference frequency signal for an apparatus such as a mobile communication device or a measuring device, which requires a high-precision frequency. More specifically, the present invention relates to a crystal resonator that uses a floating electrode MOS capacitance element (hereinafter, referred to as a PEAC element) and adjusts its oscillation frequency.

[0002]

2. Description of the Related Art A conventional crystal unit has a function of adjusting an oscillation frequency outside the crystal unit. This is because the desired oscillation frequency cannot be obtained due to variations in the series resonance frequency of the crystal unit and variations in the load capacitance of the oscillation circuit, such as transistor base capacitance, substrate stray capacitance, and capacitor capacitance. to cause. Therefore, when using a conventional crystal unit, a trimmer capacitor to adjust the oscillation frequency, or a laser trimming capacitor or a laser trimming resistor that irradiates a laser to adjust the capacitance or resistance value, or The PEAC element has been mounted on the board as an independent individual component.

[0003]

In the conventional crystal unit, components for adjusting the oscillation frequency are required on the oscillation circuit for the above-described reasons. FIG. 8 is an example of a related art showing a case where a trimmer capacitor is used as a component for adjusting the oscillation frequency. In the figure, reference numeral 1 denotes a quartz oscillator, which is indicated by a dotted line 101.
Are enclosed in the same package. 2 is an inverter, 3 is a feedback resistor, 5 is a capacitor, and 7 is a trimmer capacitor. By turning the rotor of the trimmer capacitor 7, the oscillation frequency of the crystal oscillator can be set to a desired value. However, an oscillation circuit using a trimmer capacitor has the following problems in terms of mounting and performance.

[0004] In the industrial field where mounting is strongly required to be small and thin, particularly in the field of mobile communications, the height and mounting area of the trimmer capacitor are problematic. It is a barrier. In terms of performance, the rotor of the trimmer capacitor is rotated to adjust the oscillation frequency, but it is difficult to make fine adjustments because the rotor has backlash. In addition, there is a problem that the capacitance changes due to an impact due to a drop or a collision, and the oscillation frequency deviates from a desired value.

Further, the act of turning the rotor of the trimmer capacitor to adjust the frequency is difficult to automate, and is a major industrial problem. Next, when adjusting the oscillation frequency using a laser trimming capacitor or laser trimming resistor that adjusts the capacitance and resistance by irradiating a laser, the characteristic value can be changed only in one direction. The value cannot be returned. For example, once the resistance value has been increased, the resistance value cannot be reduced, and the oscillation frequency change due to the secular change of the crystal unit may not be adjusted sufficiently.

Further, when the crystal unit and the PEAC element are mounted on a substrate as independent packages, the mounting area is increased, and the bare chip cannot be used to increase the reliability of the PEAC element. There is also a problem that costs are high, such as using a package.

[0007]

In order to solve the above problems, the present invention provides a PEAC for adjusting an oscillation frequency.
The device was provided in a crystal oscillator package. This allows
By changing the voltage applied to the PEAC element from the outside, the capacitance of the PEAC element can be changed, the load capacity can be adjusted, and a desired frequency can be obtained. SUMMARY OF THE INVENTION An object of the present invention is to provide a small-sized crystal resonator which does not require a function of adjusting the oscillation frequency outside the crystal resonator.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method for manufacturing a crystal resonator in a container.
This is provided with an EAC element, and will be described with reference to FIG. In FIG. 1, a portion surrounded by a dotted line 100 in the figure corresponds to a crystal oscillator with a frequency adjustment function of the present invention, 1 is a crystal oscillator, 2 is an inverter, 3 is a feedback resistor, and 4 is PEA.
C element, 5 is a capacitor, and 6 is an adjustment terminal.

In this embodiment, the oscillating circuit is a Colpitts-type oscillating circuit including an inverter amplifier composed of an inverter 2 and a feedback resistor 3 and a crystal unit 1. The oscillation frequency of the Colpitts-type oscillation circuit is a certain frequency depending on the series resonance frequency of the crystal unit 1, the load capacitance determined by the base capacitance of the transistor, the stray capacitance of the substrate, the capacitance of the capacitor, and the like. However, these factors vary, and the oscillation frequency does not always reach a desired value. Therefore, a desired frequency can be obtained by changing the capacitance of the PEAC element 4 and adjusting the load capacitance.

Next, the configuration and operation of the PEAC element 4 will be described with reference to FIGS. The PEAC element 4 applies a negative or positive voltage to the adjustment terminal 6 with respect to the N-type substrate to cause a tunnel current to flow through the thin SiO ₂ film, and inject and eject electrons to the floating electrode. First, when a positive voltage is applied to the adjustment terminal 6, electrons flow out of the floating electrode, the depletion layer formed immediately below the floating electrode is narrowed, and the depletion layer capacitance C _DEP is increased. Combined capacitance C _P at this time PEAC element 4 increases. Conversely, when a negative voltage is applied, electrons flow into the floating electrode, the depletion layer formed immediately below the floating electrode expands, and the depletion layer capacitance C _DEP decreases. Combined capacitance C _P at this time PEAC element 4 is small. Thus, the capacity of the PEAC element 4 can be changed.

In the PEAC element 4, the number of electrons in the floating electrode is kept constant unless an electric field sufficient to cause a tunnel current to flow through the floating electrode. PEAC
The capacitance of the element 4 is kept constant. That is, the PEAC element 4 is an element that can change the capacity electrically and replaces the trimmer capacitor that changes the capacity mechanically.

Next, a method of adjusting the oscillation frequency of the crystal unit will be described. For example, assuming that the crystal oscillator oscillates at a frequency higher than a desired frequency in the oscillation circuit wired as shown in FIG.
, The combined capacitance Cp of the PEAC element 4 increases, the load capacitance also increases, and the oscillation frequency of the crystal resonator decreases. In this way, lower the frequency,
A desired oscillation frequency can be obtained. When the crystal resonator shown in FIG. 1 oscillates at a frequency lower than the desired frequency, when a negative voltage is applied to the adjustment terminal 6 of the PEAC element 4, the combined capacitance Cp of the PEAC element 4 becomes smaller, and the load capacitance becomes smaller. And the oscillation frequency increases. in this way,
The frequency can be increased to a desired oscillation frequency.

As described above, by increasing or decreasing the combined capacitance of the PEAC element 4, the load capacitance can be changed and the oscillation frequency of the oscillation circuit using the crystal oscillator can be adjusted.

[0014]

【Example】

Embodiment 1 An embodiment will be described with reference to the drawings.
4A and 4B show a crystal resonator according to an embodiment of the present invention. FIG. 4A is an exploded view, and FIG. 4B is a sectional view. The crystal oscillator includes a container 15, a crystal oscillator 16, and a PEAC element 18. The container 15 includes a container body 14 and a lid 11,
The container body 14 includes the ring 12 and the base 13. The container 15 is made of ceramic, glass, metal, or the like. In this embodiment, an example using a laminated ceramic is used.

A method for forming a crystal resonator will be described.
First, the PEAC element 18 is fixed to the bottom of the container body 14 and near the step 17, and is connected to the conductive pattern by bonding. Thereby, conduction between the terminal formed on the outer surface of the container body 14 and the PEAC element is established as shown in FIG. Next, the crystal vibrating body 16 is moved to the container body 1.
4 are electrically and mechanically connected to and held by a stepped portion 17 formed at both corners using a conductive adhesive or the like. Then, the container body 14 and the lid 11 are joined by seam welding to obtain the crystal resonator of the present invention. At this time, the inside of the container is sealed with a vacuum or an inert gas such as nitrogen.

As described above, the PEAC element 18 is fixed to the bottom of the container body 14 and close to the step 17, so that when an external impact is applied to the crystal unit,
It is possible to avoid contact with the side of the crystal vibrating body 16 that does not hold large vibration displacement, and it is possible to reduce the distance between the PEAC element and the crystal vibrating body, thereby contributing to the thinning of the crystal vibrator.

(Embodiment 2) FIGS. 5A and 5B are exploded views, and FIG. 5B is a cross-sectional view of a crystal resonator according to an embodiment of the present invention. As shown in FIG. 7, the PEAC element has a wire 19 in which the bending of the quartz oscillator is wire-bonded.
It has a holding part for suppressing. The holding part is a wire provided on the PEAC element, but electrically
It is insulated from the circuit of the C element. That is, the wire of the holding unit is in a floating state.

A method for forming a crystal resonator will be described.
First, the PEAC element 18 is disposed and fixed such that the PEAC element 18 is located at the bottom of the container body 14 and the holding section is below the end on the side not holding the quartz oscillator 16. Next, PEAC element 1
8 is connected to the conductive pattern formed on the bottom of the container body 14 by wire bonding as in the first embodiment.
Thereby, as shown in FIG. 6, the terminal C formed on the outer surface of the container body 14 and the charge injection terminal (I
NJECTION TERMINAL) Connect to connect the T _G of the terminal D and the PEAC element, by connecting the capacitor terminal T _C terminal B and PEAC element, PEAC element electrically connected is taken. Next, the quartz oscillator 16 is
Electrically and mechanically connected to the step 17 formed at both corners of the container body 14 using a conductive adhesive or soldering,
Hold. Then, the container body 14 and the lid 11 are joined by seam welding to obtain the crystal resonator of the present invention. At this time, the inside of the container is sealed with a vacuum or an inert gas such as nitrogen.

By providing the holding portion, when an external impact is applied to the crystal resonator, the deflection of the non-held side of the crystal vibrating body 16 having a large vibration displacement is supported by bonding, and the crystal piece is broken. And breakage can be prevented. Further, in the present invention, the holding unit is provided on the same chip as the PEAC element 18, but it is needless to say that the same effect can be obtained without providing the holding unit on the same chip. For example, an electrode pattern may be formed on the container body 14, and the holding portion may be formed by bonding in the same manner as in the above embodiment.

[0020]

The present invention is embodied in the form described above, and has the following effects as compared with the case where the PEAC element is provided outside the crystal unit. Since the inside of the crystal unit is sealed with vacuum or an inert gas such as nitrogen, the PEAC element can be mounted with a bare chip.
Manufacturing costs can be reduced. In addition, since the quartz vibrator has a structure that does not contact the inner wall of the container except for its supporting portion, it can be configured so that a space exists inside the container. By utilizing the space, the height and mounting area of the bare chip do not affect the size of the crystal resonator container, and the frequency adjustment function can be provided with the same size as the conventional crystal resonator alone. As a result, the number of components can be reduced, and the mounting area can be reduced. The frequency adjustment function of the crystal unit according to the present invention controls the oscillation frequency after taking into account variations in the series resonance frequency of the crystal unit and variations in the load capacitance due to variations in the base capacitance, stray capacitance, and capacitance of the transistor. It can be adjusted electrically.

Further, since the variation of the series resonance frequency of the crystal unit can be adjusted by the PEAC element, the frequency adjustment accuracy in the manufacturing process of the crystal unit can be relaxed, and the high-precision adjustment is performed on the oscillation circuit only once. . However, in a high-precision quartz crystal resonator, the frequency is adjusted by milling the electrodes of the crystal oscillator using a technique such as laser trimming or ion milling. It becomes troublesome twice.

Further, unless an electric field sufficient to cause a tunnel current to flow through the electrodes in the PEAC element, the number of electrons in the electrodes is kept constant, and new electrons are injected.
Unless it is poured out, the capacitance of the PEAC element is kept constant. Therefore, unlike the case where a trimmer capacitor is used, it is resistant to impact such as dropping or collision, thermal stress such as reflow, washing with organic solvent, etc. Extremely strong.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a schematic view of a configuration of a PEAC element used in the present invention.

FIG. 3 is an equivalent circuit diagram of a PEAC element used in the present invention.

FIG. 4 is a configuration diagram of a crystal resonator according to an embodiment of the present invention.

FIG. 5 is a configuration diagram of a crystal resonator according to an embodiment of the present invention.

FIG. 6 is an explanatory view of mounting a quartz oscillator showing one embodiment of the present invention.

FIG. 7 is an explanatory diagram of a PEAC element showing one embodiment of the present invention.

FIG. 8 is a conventional circuit diagram for explaining the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crystal oscillator 2 Inverter 3 Feedback resistor 4 PEAC element 5 Capacitor 6 Adjustment terminal 100 Crystal oscillator with frequency adjustment function

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H03H 9/19 H03H 9/19 A (72) Inventor Fumio Kimura 1-chome Nakase, Mihama-ku, Chiba-shi, Chiba No. 8 Inside Seiko Electronic Industries Co., Ltd. (72) Inventor Takashi Konno 1-8 Nakase Nakase, Mihama-ku, Chiba City, Chiba Pref.

Claims (2)

[Claims] In a quartz oscillator in which a quartz oscillator is disposed in a container made of ceramic, glass or metal, a voltage variable capacitor for adjusting an oscillation frequency and a voltage is applied to the voltage variable capacitor. A crystal resonator with a frequency adjustment function, characterized by having an oscillation frequency adjustment terminal of (1). 2. The crystal unit with a frequency adjustment function according to claim 1, further comprising a holding unit for suppressing deflection of the crystal unit.