JP2010220152A - Surface-mounted crystal device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-mounted crystal oscillator which is less apt to cause changes in the temperature of a crystal piece, and even when it is exposed to wind of a fan, or the like, suppresses the occurrence of fluctuations in the oscillation frequency, and thereby attaining improved stability in short-term frequency. <P>SOLUTION: In the surface-mounted crystal device includes a container body 2, which houses therein at least the crystal piece 4 and includes at the outer bottom surface a recess in which a mounting terminal 10 is formed; and a metal cover 7, which is bonded to an opening end face of the container body 2 and seals the crystal piece 4. One principal surface of the metal cover 7, that serves as an outer surface of the surface-mounted crystal device, is covered with a heat-insulating material 18. Thus, even if the surface-mounted crystal device mounted on a mounting substrate is exposed to wind of a fan, or the like, the occurrence of fluctuations in the oscillation frequency is suppressed, thereby the short-term frequency stability is made satisfactory. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface-mount crystal device, and more particularly to a surface-mount crystal device that avoids fluctuations in oscillation frequency due to the influence of external heat.

(Background of the Invention)
Surface-mounted crystal devices such as surface-mounted crystal oscillators (hereinafter referred to as surface-mounted oscillators) are well known as frequency control elements and are small and light, so that they are particularly suitable for portable electronic devices such as mobile phones. Widely used as a frequency and time reference source. In recent years, with the miniaturization of electronic devices, the demand for miniaturization of surface mount oscillators has been further increased. One of such devices is a surface mount oscillator in which a crystal piece and an IC chip are accommodated in a container body and hermetically sealed with a metal lid.

(Example of conventional technology)
FIG. 6 is a cross-sectional view of a surface mount oscillator for explaining one conventional example. A surface-mounted oscillator 1 shown in FIG. 6 (see “Example of Prior Art” in Patent Document 1) accommodates an IC chip 3 and a crystal piece 4 in a container body 2, and a frame wall serving as an opening end surface of the container body 2. 5 A metal lid 7 is joined to a metal ring 6 provided on the upper surface. The container body 2 has a concave portion and a step portion, and is composed of a ceramic frame wall 5 and a bottom wall 8. The frame wall 5 includes a first frame wall 5a and a second frame wall 5b. And the container main body 2 is formed by laminating | stacking and baking the bottom wall 8, the 1st frame wall 5a, and the 2nd frame wall 5b.

  The IC chip 3 integrates each element such as an amplifier constituting the oscillation circuit, and has each IC terminal (not shown) on one main surface as a circuit function surface. Then, one main surface side of the IC chip 3 is fixed to the bottom surface of the recess of the container body 2 by, for example, ultrasonic thermocompression using bumps 9 (so-called flip chip bonding). Each IC terminal (for example, power source, ground, output, AFC terminal) of the IC chip 3 is electrically connected to mounting terminals 10 formed at the four corners of the outer bottom surface of the container body 2.

  As shown in FIG. 7, the crystal piece 4 extends, for example, extraction electrodes 12 from both excitation surfaces 11 to both ends of one end. Then, both sides of one end of the extraction electrode 12 are fixed to the stepped portion by the conductive adhesive 13 and electrically and mechanically connected to the crystal holding terminal 14. The crystal holding terminal 14 is electrically connected to a crystal terminal (not shown) of the IC chip 3.

  The metal lid 7 is joined to a metal ring 6 provided on the opening end surface of the container body 2 by seam welding, beam welding, or the like. The metal lid 7 is electrically connected to a ground terminal which is one of the mounting terminals 10 via a via hole (not shown). Then, the surface-mounted oscillator 1 based on these is surface-mounted by, for example, solder or the like by transporting a high-temperature furnace to a mounting board of a portable device.

JP 2007-288268 A

(Problems of conventional technology)
However, in the surface mount oscillator 1 having the above configuration, when mounted on the mounting board 15 as shown in FIG. 8, the oscillation frequency fluctuates due to the heat generated by the other electronic components 16 and the influence of the air blown by the fan 17. There was a problem to do. The fan 17 prevents the internal temperature of the portable device from rising due to heat generated by the electronic component 16.

  Specifically, the surface mount oscillator 1 is mounted on the mounting substrate 15 in the vicinity of an electronic component 16 that generates heat, for example, as an active element. At this time, the heat of the electronic component 16 is transmitted to the surface-mounted oscillator 1 through a conductive path including a ground pattern (not shown) formed on the mounting substrate 15, and in particular, the surface-mounted oscillator 1 is heated from the bottom surface.

  On the other hand, the surface mount oscillator 1 is cooled from the metal lid 7 by the air blown from the fan 17 that air-cools the heat in the portable device. From this, it was confirmed that the oscillation frequency of the surface-mounted oscillator 1 fluctuates due to the following causes (inference), and the short-term stability of the frequency in the order of, for example, 100 msec is deteriorated.

  That is, the surface-mounted oscillator 1 is heated from the bottom by the heat of the electronic component 16 and is simultaneously cooled from the metal lid 7 by the blowing (air cooling) of the fan 17. However, the air-cooling heat generated by blowing air from the fan 17 is not stable as compared with the heat applied from the mounting board 15 via the conductive path. Therefore, the internal temperature of the surface mount oscillator 1 does not become uniform, and fluctuations occur. From this, it is assumed that the oscillation frequency fluctuates based on the frequency-temperature characteristics of the crystal resonator (crystal piece 4). When there is no fan 17, that is, when no wind is applied to the surface-mounted oscillator 1, fluctuations in the oscillation frequency can be almost ignored.

  In particular, due to the recent miniaturization of the surface mount oscillator 1, the heat capacity of the surface mount oscillator 1 has been reduced. Therefore, the temperature of the crystal piece 4 is sensitively changed by the air blown by the fan 17, and the oscillation frequency is likely to fluctuate. For example, this problem is remarkable in the surface-mounted oscillator 1 having a planar outer shape of 2.5 mm × 2.0 mm or less. These cause the same problem even when the temperature compensation type is adopted.

(Object of invention)
It is an object of the present invention to provide a surface mount oscillator that suppresses the occurrence of fluctuations in the oscillation frequency and improves the short-term stability of the frequency, even when the temperature of the crystal piece is unlikely to change and the wind of a fan or the like hits.

  According to the present invention, as shown in the claims (Claim 1), at least a crystal piece is accommodated and a container body having a recess in which a mounting terminal is formed on an outer bottom surface is bonded to an opening end surface of the container body. And a crystal device for surface mounting comprising a metal lid that hermetically encloses the crystal piece, wherein one main surface of the metal lid that is an outer surface of the surface mount crystal device is covered with a heat insulating material; To do.

  With such a configuration, even when a fan or other wind hits a surface-mount crystal device mounted on a mounting substrate, it is possible to improve the short-term stability of the frequency by suppressing the occurrence of oscillation frequency fluctuations. . This is because wind from a fan or the like mainly hits the metal lid that is the upper part of the crystal device, but one main surface of the metal lid that is the outer surface of the crystal device is covered with a heat insulating material. Therefore, the temperature inside the crystal device becomes uniform, and the temperature change of the crystal piece hardly occurs.

(Embodiment section)
In Claim 2 of this invention, it is set as the structure by which the outer surface of the said container main body was covered with the heat insulating material in Claim 1. Moreover, in Claim 3 of this invention, it is set as the structure covered with the heat insulating material in Claim 2 except the said mounting terminal of the said container main body. As a result, even if wind from the fan or the like hits the outer surface or outer bottom surface of the container body, the temperature change of the crystal piece is less likely to occur, and the occurrence of fluctuations in the oscillation frequency is further suppressed to improve the short-term stability of the frequency. it can.

  In Claim 4 of this invention, it is set as the structure in which the said heat insulating material is resin in Claims 1-3. Moreover, in Claim 5 of this invention, it is set as the structure in which the said heat insulating material is a heat resistant tape in Claims 1-3. This clarifies the insulation.

It is sectional drawing of the surface mount oscillator explaining 1st Embodiment of this invention. It is sectional drawing of the surface mount oscillator explaining 2nd Embodiment of this invention. It is sectional drawing of the surface mount oscillator explaining 3rd Embodiment of this invention. It is a figure showing the change of the frequency deviation by the ventilation in this invention. It is a figure showing the change of the frequency deviation by the ventilation in one prior art example. It is sectional drawing of the surface mount oscillator explaining a prior art example. It is a perspective view of a crystal piece. It is a side view when a surface mount oscillator and an electronic component are mounted on a mounting board.

(First embodiment, corresponding to claims 1, 4, and 5)
FIG. 1 is a sectional view of a surface mount oscillator for explaining a first embodiment of the present invention. In addition, the same number is attached | subjected to the same part as a prior art example, and the description is simplified or abbreviate | omitted.

  A surface-mounted oscillator 1 shown in FIG. 1 accommodates an IC chip 3 and a crystal piece 4 in a container body 2, and a metal lid 7 on a metal ring 6 provided on the upper surface of a frame wall 5 serving as an opening end surface of the container body 2. Are joined. The container body 2 has a concave portion and a step portion, and is composed of a ceramic frame wall 5 and a bottom wall 8. The frame wall 5 includes a first frame wall 5a and a second frame wall 5b. And the container main body 2 is formed by laminating | stacking and baking the bottom wall 8, the 1st frame wall 5a, and the 2nd frame wall 5b.

  The IC chip 3 is fixed to the bottom surface of the recess of the container body 2 by, for example, ultrasonic thermocompression using a bump 9. The quartz crystal piece 4 is electrically and mechanically connected to the quartz crystal holding terminal 14 by a conductive adhesive 13 on both sides of one end portion where the extraction electrode 12 is extended. The metal lid 7 is joined to the metal ring 6 provided on the open end surface of the container body 2 by seam welding, beam welding, or the like using the base material as Kovar.

  In such a case, first, the ceramic bottom wall 8, the first frame wall 5a, and the second frame wall 5b are formed. On the bottom wall 8 and the first frame wall 5a, metallized layers of the mounting terminal 10 and the crystal holding terminal 14 are formed by printing tungsten (W), respectively. Then, the container body 2 is formed by laminating and firing the bottom wall 8, the first frame wall 5a, and the second frame wall 5b.

  Next, the metal ring 6 is joined to the opening end surface of the container body 2 using a brazing material (eg, silver brazing) (not shown). The metal ring 6 is formed, for example, by punching using a die or the like using a base material as Kovar. Then, a nickel (Ni) film is provided on the surface of the metallized layer by electrolytic plating or electroless plating, and a gold (Au) film is further provided on the surface of the nickel film to form the mounting terminal 10 and the crystal holding terminal 14. .

  In the IC chip 3, an IC terminal (not shown) formed on one main surface that is a circuit function surface is electrically and mechanically fixed to the bottom surface of the recess of the container body 2 by ultrasonic thermocompression using the bumps 9. The crystal piece 4 is a rectangular AT-cut crystal diaphragm. And the excitation electrode 11 and the extraction electrode 12 are formed by thin film formation means, such as a vacuum evaporation method and sputtering method.

  Thereafter, the crystal piece 4 is fixed to the crystal holding terminal 14 formed on the step portion of the container body 2 by the conductive adhesive 13. Next, the metal lid 7 is joined to the metal ring 6 formed on the opening end surface of the container body 2 by seam welding. Finally, a resin 18 as a heat insulating material is applied to one main surface of the metal lid 7 which is the outer surface of the container body 2 and cured.

  With such a configuration, even when the wind of the fan 17 strikes the surface-mounted oscillator 1 mounted on the mounting substrate, it is possible to improve the short-term stability of the frequency by suppressing the occurrence of fluctuations in the oscillation frequency. This is because the wind of the fan 17 mainly hits the metal lid 7 which is the upper part of the surface mount oscillator 1, but one main surface of the metal lid 7 which is the outer surface of the surface mount oscillator 1 is covered with the resin 18. Therefore, the temperature inside the surface mount oscillator 1 becomes uniform, and the temperature change of the crystal piece hardly occurs.

  Here, the base material of the container body 2 often uses alumina as a ceramic. The thermal conductivity of alumina is about 30 (W / Km) at room temperature. On the other hand, the base material of the metal lid 7 is Kovar, and the thermal conductivity is about 17 (W / Km) at room temperature. Therefore, it is considered that the effect is small even if only one main surface of the metal lid 7 having a lower thermal conductivity than the container body 2 is covered with the resin 18. However, for example, in the surface mount oscillator 1 having a planar outer shape of 2.5 mm × 2.0 mm, the area of one main surface of the metal lid 7 is about 5.0 mm 2, and the area of one outer surface of the long side of the surface mount oscillator 1 Is about 2.0 mm 2. Therefore, when the surface mount oscillator 1 receives wind from one direction, the metal lid 7 receives more wind than the outer surface. Further, for example, in the arrangement of the fan 17 shown in FIG. 8, it is considered that the wind mainly hits the metal lid 7. Therefore, even when only one main surface of the metal lid 7 is covered with the resin 18, a sufficient effect can be obtained.

  Further, the same effect can be obtained by using a heat-resistant tape instead of the resin 18 as a heat insulating material. Next, a description will be given of measurement results regarding fluctuations in oscillation frequency due to air blowing when heat-resistant tape is used as the heat insulating material. FIG. 4 is a graph showing changes in the oscillation frequency of the first embodiment using a heat-resistant tape as a heat insulating material. FIG. 5 is a graph showing a change in oscillation frequency in the above-described conventional example (the metal lid 7 or the like is not covered with a heat insulating material). The surface mount oscillator 1 used in this measurement outputs an oscillation frequency of 16 MHz at a temperature of 45 degrees. Then, an environment substantially the same as the environment shown in FIG. 8 is prepared, and the surface mount oscillator 1 is blown from the fan 17 for about 60 seconds (t1 to t2) with the temperature of the surface mount oscillator 1 being 45 degrees. The frequency deviation in the order of 100 msec was measured.

  As apparent from the graph, the oscillation frequency fluctuates due to the blowing in both the first embodiment (the heat insulating material is a heat-resistant tape) and the conventional example. However, in the surface mount oscillator of the first embodiment (the heat insulating material is a heat-resistant tape), the fluctuation of the oscillation frequency is about 0.01 ppm. On the other hand, in the conventional surface mount oscillator, the fluctuation of the oscillation frequency is about 0.03 ppm. Therefore, in this example, the fluctuation of the oscillation frequency can be reduced to about one third in the first embodiment (the heat insulating material is a heat-resistant tape) compared to the conventional example. This improves the short-term stability of the oscillation frequency.

(Embodiment 2 corresponds to claims 1, 2, and 4)
FIG. 2 is a cross-sectional view of a surface mount oscillator for explaining a second embodiment of the present invention. In addition, the same number is given to the same part as previous embodiment, and the description is simplified or abbreviate | omitted.

  In the surface mount oscillator of the second embodiment, the surface mount oscillator 1 is formed in the same manner as in the first embodiment. And in 2nd Embodiment, the resin 18 used as a heat insulating material is apply | coated to the outer side surface of the container main body 2, and it is made to harden | cure. Thereby, even if the wind of the fan 17 hits the outer surface of the container body 2, the temperature change of the crystal piece 4 hardly occurs, the occurrence of oscillation frequency fluctuations can be further suppressed, and the short-term frequency stability can be improved. .

(Embodiment 3 corresponds to claims 1, 2, 3, and 4)
FIG. 3 is a cross-sectional view of a surface mount oscillator for explaining a third embodiment of the present invention. In addition, the same number is given to the same part as previous embodiment, and the description is simplified or abbreviate | omitted.

  In the surface mount oscillator of the third embodiment, the surface mount oscillator 1 is formed in the same manner as in the first embodiment. And in 2nd Embodiment, the resin 18 used as a heat insulating material is apply | coated and hardened to the outer side face of the container main body 2, and the outer bottom face except the mounting terminal 10 of the container main body 2. FIG. Thereby, even if the wind of the fan 17 hits the outer bottom surface of the container main body 2, the temperature change of the crystal piece 4 hardly occurs, the occurrence of oscillation frequency fluctuations can be further suppressed, and the short-term frequency stability can be improved. .

(Other matters)
As shown in claim 5, also in the second and third embodiments, a heat-resistant tape may be used in place of the resin 18 as a heat insulating material as in the first embodiment. In each of the above embodiments, the surface-mounted oscillator is shown as an example of the crystal device. However, the same effect can be obtained in the case of the temperature-compensated crystal oscillator (TCXO) that houses the IC chip 3 having the temperature compensation circuit. The same applies to the case where a surface-mount crystal resonator is used as the crystal device.

  DESCRIPTION OF SYMBOLS 1 Surface mount oscillator, 2 Container body, 3 IC chip, 4 Crystal piece, 5 Frame wall, 6 Metal ring, 7 Metal lid, 8 Bottom wall, 9 Bump, 10 Mounting terminal, 11 Excitation electrode, 12 Extraction electrode, 13 Conductivity Adhesive, 14 crystal holding terminal, 15 mounting board, 16 electronic component, 17 fan, 18 resin.

Claims (5)

  A crystal for surface mounting comprising a container body having at least a concave portion in which a crystal piece is accommodated and mounting terminals are formed on an outer bottom surface, and a metal lid which is bonded to the opening end surface of the container main body and hermetically encloses the crystal piece. In the device, a surface mount crystal device, wherein one main surface of the metal lid serving as an outer surface of the surface mount crystal device is covered with a heat insulating material.   2. The crystal device for surface mounting according to claim 1, wherein an outer surface of the container body is covered with a heat insulating material.   3. The surface-mount crystal device according to claim 2, wherein an outer bottom surface of the container body excluding the mounting terminal is covered with a heat insulating material.   4. The surface mount crystal device according to claim 1, wherein the heat insulating material is a resin.   4. The surface-mount crystal device according to claim 1, wherein the heat insulating material is a heat-resistant tape.