JP5100211B2 - Crystal oscillator for surface mounting - Google Patents

Description

  The present invention has a surface mount crystal oscillator as a technical field, in particular, a temperature compensated crystal oscillator (hereinafter referred to as a temperature compensated oscillator) that prevents frequency fluctuation (drift) due to sudden heat generation upon power-on. )

(Background of the Invention)
The temperature compensated oscillator is small and light and has high frequency stability with respect to temperature change. Therefore, the temperature compensated oscillator is built in as a frequency source particularly in portable electronic devices whose temperature environment changes. One of such devices is a temperature compensated oscillator (TCXO) in a mobile phone, for example, and it is required to suppress frequency fluctuations at startup.

(Example of conventional technology)
FIG. 3 is a diagram for explaining a conventional example. FIG. 3A is a sectional view of a temperature compensated oscillator, FIG. 3B is a bottom view thereof, FIG. 3C is a plan view of a crystal piece, and FIG. The figure is a schematic circuit block diagram of a temperature compensated oscillator.

  The temperature compensated oscillator includes an IC chip 2 and a crystal piece 3 placed in a concave container body 1 having an inner wall step on one end side and a metal cover 4 covered. The container body 1 is made of a laminated ceramic having a bottom wall 1a and two layers of frame walls 1b, and has mounting terminals 5 on the outer bottom surface. Further, for example, the outside surface has a temperature compensation data writing terminal (not shown) and a crystal inspection terminal for measuring crystal vibration characteristics.

  The container body 1 has a circuit terminal (not shown) to which the IC chip 2 is fixed on the inner bottom surface serving as the recess bottom surface, and a crystal holding terminal to which the crystal piece 3 is fixed on the inner wall step. Usually, the bottom wall 1 a of the container body 1 is provided with a shield electrode 14 on the laminated surface as two layers (1 a 1, 1 a 2) and is connected to the ground terminal in the external terminal 5.

  The IC chip 2 has an IC terminal (not shown) on one main surface as a circuit function surface, and integrates the oscillation circuit 6 and the temperature compensation mechanism 7 excluding the crystal resonator 3A (crystal piece 3). Then, one main surface of the IC chip 2 faces the inner bottom surface of the container main body 1, and each IC terminal is fixed to the circuit terminal on the inner bottom surface by so-called ultrasonic thermocompression using, for example, bumps 8 (so-called flip chip bonding). .

  The oscillation circuit 6 includes, for example, an inverter amplification element made of CMOS (not shown) and a resonance circuit as a feedback circuit. The resonance circuit includes a crystal resonator (crystal piece 3) and a divided capacitor in the IC chip 2. The temperature compensation mechanism 7 has at least a temperature sensor composed of a resistor or the like that detects the ambient temperature, and generates a compensation voltage Vc in response to the ambient temperature. The compensation voltage Vc is generated by temperature compensation data from the write terminal based on a frequency temperature characteristic measured in advance.

  The quartz crystal piece 3 has, for example, an AT cut and has excitation electrodes 9 on both main surfaces, and extends extraction electrodes 10 on both sides of one end. Both ends of the extended end portion of the extraction electrode 10 are fixed to the crystal holding terminal of the inner wall step portion by the conductive adhesive 11. Then, it is electrically connected to the crystal terminal of the IC chip 2 to form a dividing capacitor and a resonance circuit. The metal cover 4 is joined to a metal ring 12 provided on the opening end surface of the container body 1 by seam welding or the like.

In such a case, a compensation voltage Vc by a temperature sensor made of, for example, a resistor of the temperature compensation mechanism 7 is applied to the voltage variable capacitance element 13 inserted in the oscillation circuit 6 (oscillation loop). As a result, the load capacity as viewed from the crystal resonator changes, and therefore, the frequency temperature characteristic (FIG. 6 described later), which becomes a cubic curve, which depends on the crystal resonator (crystal piece 3) in particular, is flattened, Increase frequency stability.
Japanese Patent Laying-Open No. 2003-101348 (for example, FIG. 1) Japanese Patent Application No. 2006-089233

(Problems of conventional technology)
However, in the temperature compensated oscillator having the above configuration, for example, when it is built in a mobile phone and intermittently operates as a PLL, the active element (transistor or the like) of the IC chip 2 operates when the power is turned on (at startup). There has been a problem of deteriorating frequency fluctuation characteristics when the power is turned on.

  FIG. 5 is a typical start-up characteristic diagram when the temperature compensated oscillator is turned on. The vertical axis in the figure is the frequency deviation Δf / f0, and Δf is the difference frequency (f−f0) between the actual oscillation frequency f and the reference frequency f0. However, the reference frequency f0 is an oscillation frequency (nominal frequency ± α ppm) at room temperature of 25 ° C. Therefore, when the frequency deviation Δf / f0 is 0, the reference frequency f0 is obtained.

  According to this, the oscillation frequency f changes abruptly after the power is turned on (H1) and rises slowly, and the oscillation frequency stabilizes (saturates) after about 10 seconds to several tens of seconds (Ha time). The power-on (H1 time) here is, for example, 2 to 3 msec after power-on according to user standards. Therefore, the frequency fluctuation characteristics after that deteriorate due to a sudden change in the oscillation frequency from the time of power-on (H1).

  The frequency fluctuation characteristic is expressed as Δ (fx−fy) / f0 as the difference between the frequency deviation Δfx / f0 at Hx from the power-on and the frequency deviation Δfy / f0 at Hy. Therefore, in this case (FIG. 5), a large difference is produced between the frequency deviations Δf1 / f0 and Δf2 / f0 when the power is turned on (H1) and after a few seconds (H2). make worse.

  For these reasons, the steep slope (differential coefficient) of the start-up characteristic in the temperature compensated oscillator deteriorates the frequency variation characteristic at start-up when the power is turned on. In short, the frequency variation characteristic deteriorates as the temperature rise characteristic due to rapid heat generation of the IC chip becomes steeper. The deterioration of these frequency fluctuation characteristics is assumed to be caused by the following.

  That is, as shown in FIG. 6, for example, if a crystal resonator (quartz piece) is operating at a vibration frequency that is a reference frequency f0 at room temperature of 25 ° C., the temperature T 1 ( For example, it operates at an oscillation frequency that becomes an oscillation frequency (frequency deviation Δf / f is Appm) at 27 ° C. In this case, the oscillation frequency at a temperature T 1 (27 ° C.) higher than the normal temperature 25 ° C. is lower than the reference frequency f 0 based on the frequency temperature characteristics.

  Therefore, the temperature compensation mechanism in the IC chip 2 generates a compensation voltage Vc based on the resistance value of the temperature sensor so as to return to the reference frequency f0. In this case, since the IC chip 2 and the crystal piece 3 are arranged apart from each other, the temperature of the crystal piece 3 is lower than that of the IC chip 2. Therefore, the temperature sensor integrated on the IC chip 2 is higher than the operating temperature of the crystal piece 3.

  From these, the compensation voltage Vc increases rapidly as the temperature rise due to heat generation of the IC chip 2 when the power is turned on (H1 time), and gradually becomes an appropriate value over time. Therefore, it is presumed that the start-up characteristic after the power is turned on becomes the above-described FIG. 5, and the frequency fluctuation characteristic is deteriorated.

  These problems are caused not only by the heat generation of the IC chip 2 at the time of starting the temperature compensated oscillator that operates intermittently, but also by the heat generation of the set substrate even in the case of the temperature compensated oscillator that is always operated for GPS using PLL in combination. The same occurs because the temperature of the chip 2 rises. The rapid temperature rise of the set substrate occurs, for example, when a functional circuit other than a transmission / reception system that is constantly operating is operated.

  Regardless of the temperature-compensated oscillator, even in the case of a normal surface-mount oscillator, the frequency temperature characteristic can be adversely affected, so it is important to suppress the temperature rise of the IC chip. For example, as shown in FIG. 4, the frequency-temperature characteristic (solid line), which becomes a normal cubic curve as the temperature rises, jumps on the high and low temperature side and becomes a high frequency as shown by the dotted line.

(Object of invention)
An object of the present invention is to provide a surface mount oscillator having an improved heat dissipation effect to suppress the temperature rise of an IC chip, and in particular, to provide a temperature compensated oscillator in which frequency fluctuation based on a sudden temperature change is reduced. To do.

(Focus technology and new findings)
The present invention focuses on Patent Document 1 by the present applicant. In other words, an opening is provided on the outer bottom surface of the container body, an exposed surface is used as an electrode, and a blocking layer is provided between the set substrate and the air layer to avoid the influence of heat from the set substrate and the temperature of the IC chip Focused on technology to avoid. The inventors have found that a temperature increase can be suppressed as described below, particularly when a metal film connected to an external terminal is provided on the exposed surface of the opening.

(First solving means)
As described in claim 1 of the present invention, an IC chip having an IC terminal connected to the mounting electrode on the inner bottom surface of the concave container body having mounting electrodes at the four corners of the outer bottom surface In a crystal oscillator for surface mounting in which a crystal piece that is electrically connected to the IC chip is integrated, an opening extending between the mounting electrodes is formed in a central region of the outer bottom surface of the container body. And an exposed surface by the opening has a metal film.

(Second solution)
According to the fourth aspect of the present invention, an IC chip having an IC terminal electrically connected to the mounting electrode and at least an oscillation circuit is fixed to the inner bottom surface of the concave container body having mounting electrodes at four corners of the outer bottom surface. Further, in the surface-mount crystal oscillator in which the IC chip and the crystal piece that is electrically connected are integrated, the central region of the outer bottom surface of the container body has an opening, and the exposed surface by the opening Has a metal film connected via a wiring pattern to either the mounting electrode or an IC terminal connected to the mounting electrode.

(Difference between the first and second solution means)
In the first solution, the opening is formed between the mounting electrodes, and the metal film may be connected to the mounting electrode or not. In the second solution, the metal film is connected to the mounting electrode, and the opening is The basic difference is that it may be formed between the mounting electrodes.

(Claims 1 and 2)
With such a configuration according to claims 1 and 2 (first and second solving means), since an opening is formed on the outer bottom surface of the container body, it corresponds to the opening between the set substrate. Thus, an air layer (space) is generated. In this case, this air layer is lower than the temperature of the container body and the set substrate. Since the metal film is formed on the exposed surface of the opening, the heat on the outer bottom surface of the container body is absorbed by the metal film and radiated from the metal film to the space.

  In particular, the inner bottom surface of the container body faces the circuit function surface on which the active elements of the IC chip are formed, and the heat radiated from this is directly transferred. Therefore, the heat dissipation effect from the opening and the metal film provided on the outer bottom surface which is the opposite surface of the inner bottom surface of the container body is great. In these cases, both the heat generation of the IC chip in the container main body and the temperature increase due to conduction from the set substrate are effective.

  For example, the heat due to the temperature rise of the set substrate is dominated by heat transfer from the mounting electrode connected to the set substrate and heat transfer from the outer bottom surface facing the set substrate. In this case, heat transfer from the mounting electrode is radiated to the space by the opening. In addition, heat transfer from the outer bottom surface prevents the radiant heat from the set substrate by the space formed by the opening as a heat insulating layer.

(Claim 1)
According to the first aspect of the present invention, since the opening on the outer bottom surface is formed across the mounting electrodes, the exposed area of the outer bottom surface and the volume of the space (air layer) due to the opening are increased. Therefore, the heat dissipation effect from the outer bottom surface (opening) of the container body to the air layer can be enhanced.

(Claim 2)
According to a second aspect of the present invention, the metal film provided on the exposed surface of the opening is connected to the mounting electrode and the IC terminal via a wiring pattern. Therefore, in the case of a temperature rise due to heat generation of the IC chip, particularly heat from the IC terminal of the IC chip is transferred to the metal film through the wiring pattern. Further, when the temperature of the set substrate is increased, heat from the mounting electrode is transferred to the metal film through the wiring pattern.

  Therefore, in any case, heat is transferred to the metal film through the IC terminal, the mounting electrode, and the wiring pattern having the highest heat conduction. Thereby, the heat dissipation effect from the metal film to the space in the opening is also increased, and the temperature rise of the IC chip is suppressed.

(Embodiment section)
According to a second aspect of the present invention, in the first aspect, the metal film is connected to either the mounting electrode or an IC terminal connected to the mounting electrode through a wiring pattern. In the third aspect of the present invention, in the second aspect, the mounting electrode connected to the metal film is a ground terminal.

  According to claim 5 of the present invention, in claim 4, the mounting electrode connected to the metal film is a ground terminal. The surface mount crystal oscillator according to claim 6, wherein the opening is formed between the mount electrodes.

  The dependent claim 2 corresponds to the claim 4, and the claim 4 has a configuration corresponding to the claim 1. The effect is as described above, and the description thereof is omitted. Further, in the third and sixth aspects, since the metal film is connected to the ground terminal, an electrical adverse effect is eliminated as compared with the case where it is connected to other mounting electrodes such as an output and a power source.

  According to a seventh aspect of the present invention, in the first aspect, the IC chip includes a temperature compensation mechanism for an oscillation frequency having a temperature sensor. In the temperature compensated oscillator according to this, since the temperature rise due to the heat generation of the IC chip is suppressed by heat radiation, the frequency variation characteristic is maintained well.

  According to an eighth aspect of the present invention, in the first or fourth aspect, the crystal piece is disposed in the container body together with the IC chip and hermetically sealed. This clarifies a configuration in which an IC chip and a crystal piece are accommodated and hermetically sealed in one concave container body (so-called one-room type).

  In this case, the IC chip is fixed to the inner bottom surface of the container main body, and the crystal piece is fixed to the inner bottom surface together with the IC chip, for example, even if the crystal piece is fixed to the inner wall step of the container main body and positioned above the IC chip. Even if it is located, it includes both cases.

  According to the ninth aspect of the present invention, in the first or fourth aspect, the crystal piece is hermetically sealed in a vibrator container having a bottom surface bonded to the opening end surface of the container body, and is electrically connected to the IC chip. This clarifies a configuration in which an IC chip is fixed to the inner bottom surface of the container body having a concave shape, and a separate surface-mounted vibrator is joined to the opening end face (so-called joining type).

  FIG. 1 is a diagram of a temperature compensated oscillator for explaining an embodiment of the present invention. FIG. 1 (a) is a sectional view and FIG. 1 (b) is a diagram of an outer bottom surface. 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.

  As described above, the temperature compensated oscillator includes the bottom wall 1a and the frame wall 1b. The temperature compensation oscillator has a concave shape having mounting electrodes 5 at the four corners of the outer bottom surface and writing terminals and crystal inspection terminals (not shown) on the outer surface. The container body 1 is provided. An IC chip 2 is fixed to the inner bottom surface of the container body 1 by flip chip bonding, and both ends of one end portion of the crystal piece 3 from which the extraction electrode 10 extends are held on the inner wall step portion.

  And the opening end surface of the container main body 1 is sealed with the metal cover 4, and the IC chip 2 and the crystal piece 2 are hermetically sealed. The planar external dimensions of the temperature compensated oscillator here are 2.5 × 2.0 mm as standard values, and the height (thickness) is 0.8 mm. Also, here, the bottom wall layer 1a of the container body 1 has two layers (1a1, 1a2) and has a shield electrode 14 connected to the mounting electrode 5 on the laminated surface. The IC chip 2 has a temperature compensation mechanism having an oscillation circuit and a temperature sensor, and the temperature compensation mechanism generates a compensation voltage based on the temperature sensor.

  And in this embodiment, the opening part 15 is provided in the center area | region in the lowest layer which is the lower layer 1a1 of the bottom wall layer 1a used as the outer bottom face of the container main body 1. FIG. Here, the opening 15 is formed across a pair of mounting electrodes 5 on both sides of the opposing long side. The shield electrode 14 is exposed as it is on the exposed surface of the opening 15 (the surface of the upper layer 1a2).

  The thicknesses of the upper layer 1a1 and the lower layer 1a2 of the bottom wall layer 1a are the same, and are approximately 90 μm. However, the thickness of the mounting electrode of the lower layer 1a1 is excluded. The plane area of the opening 15 is set to 1.3 × 0.9 mm. For example, the area of the write terminal and the crystal inspection terminal provided on each surface of the outer surface is 0.45 × 0.44 mm and the total area (for four) is 0.792 mm 2. Furthermore, the area of each mounting electrode 5 is larger than 0.45 × 0.60 mm and the total area of 1.08 mm 2. The mounting electrode 5 is formed with a gap between the inner periphery of the lower layer 1a1.

  In such a configuration, as described in the column of the effect of the invention, the opening 15 provided on the outer bottom surface of the container main body 1 and the shield electrode 14 as a metal film have a temperature higher than that of the container main body 1 and the set substrate. The heat generated from the IC chip 2 and the heat conducted from the set substrate are released into the space in the lower opening.

In these cases, the rapid heat generation of the IC chip 2 enhances the heat dissipation effect by the large-area opening 15 extending between the mounting electrodes and the shield electrode (metal film) 14 connected to the mounting electrode as the ground terminal 15. In particular, the heat of the bottom wall 1 a including the circuit function surface due to heat generation of the IC chip 2 and the radiant heat directly transferred from the IC terminal to the IC terminal is radiated from the opening 15.

In this embodiment, the outer surface of the container body has a writing terminal and a crystal inspection terminal that are electrically connected to the IC chip 2, and the mounting electrode 5 is provided on the outer bottom surface. Therefore, the heat dissipation effect can be enhanced together with these heat dissipation effects, and a rapid temperature rise can be avoided. However, since the opening 15 and the exposed shield electrode (metal film) 14 are directly under the IC chip 2 to release the above-described direct heat transfer and have the largest area, the effect thereof is the greatest.

  In this example, since the mounting electrode 5 is formed with a gap from the inner periphery of the lower layer 1a1, an electrical short circuit with the shield electrode 14 exposed to the opening 15 during mounting by solder reflow on the set substrate is prevented. it can.

(Other matters)
In the above embodiment, the opening 15 is provided across the pair of opposing mounting electrodes 5 of the container body 1, but two sets of opposing mounting electrodes are formed in a cross shape, for example, as shown in FIG. It may be formed between 5 and the area of the opening may be increased. And the opening part 15 may open | release and communicate with both ends, and may improve the fluidity | liquidity of the air layer in the opening part 15. FIG.

  Further, the example in which the IC chip 2 is disposed on the inner bottom surface of the container body 1 and the crystal piece 3 is disposed on the inner wall stepped portion is shown. However, the IC chip 2 and the crystal piece 3 are parallel to the inner bottom surface of the container body 1 (horizontal direction). The same applies to the case of fixing in parallel. Further, even when a surface-mounted vibrator (vibrator container) in which a crystal piece is hermetically sealed is fixed to and electrically connected to the opening end face of the container body 1 to which the IC chip 2 is fixed to the inner bottom surface, similarly. Applicable.

  Further, the IC chip 2 is flip chip bonding in which the circuit function surface having the IC terminal is fixed and directly electrically connected, but the non-circuit function surface of the IC chip 2 is fixed and electrically connected by wire bonding. The same applies to the case of connection.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure of the temperature compensation oscillator explaining one Embodiment of this invention, The figure (a) is sectional drawing, The figure (b) bottom view. It is a bottom view of the temperature compensation oscillator explaining the other example of this invention. FIG. 2A is a cross-sectional view of a temperature compensated oscillator, FIG. 1B is a bottom view, and FIG. 1C is a plan view of a crystal piece. It is a circuit block diagram of a temperature compensated oscillator for explaining a conventional example. It is a starting characteristic figure of the temperature compensation oscillator explaining a prior art example. It is a frequency temperature characteristic diagram of a crystal oscillator for explaining a conventional example. It is a frequency temperature characteristic diagram of a crystal oscillator for explaining a conventional example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Container body, 2 IC chip, 3 Crystal piece, 4 Metal cover, 5 Mounting terminal, 6 Oscillation circuit, 7 Temperature compensation mechanism, 8 Bump, 9 Excitation electrode, 10 Lead electrode, 11 Conductive adhesive, 12 Metal ring, 13 voltage variable capacitance element, 14 shield electrode, 15 opening.

Claims (2)

Have a upper and lower four corners of the outer bottom surface of the bottom wall layer composed of two layers two pairs of opposing mounting electrodes, in said bottom surface of the container body having a bottom inner and concave with inner wall step portion And an IC chip having an IC terminal electrically connected to the mounting electrode and having an oscillation circuit,
Wherein the above of the IC chip of the container body which is fixed an IC chip is held at one end on both sides in the inner wall stepped section to integrate the quartz piece for connecting the IC chip and electrically, of the concave of the container body A crystal oscillator for surface mounting in which an opening end face is hermetically sealed with a metal cover ,
The IC chip includes a temperature compensation mechanism of an oscillation frequency having a temperature sensor, and the fixing of the IC chip to the inner bottom surface of the container body is by flip chip bonding.
The central region of the outer bottom surface of the container body has an opening formed in a cross shape across the two sets of opposing mounting electrodes in the central region of the lower layer, and the exposed surface by the opening includes the in the mounting electrodes and have a metal film which is connected via a wiring pattern on one of IC terminals connected to the mounting electrodes was conducted from the heating and the set substrate of said IC chip heat be released into the space in the opening Improve the heat dissipation effect,
The mounting electrode has a gap between the inner periphery of the opening formed in the lower layer and prevents an electrical short circuit with the metal film during mounting during solder reflow. Oscillator. In claim 1 ,
The mounting electrode surface-mount crystal oscillator which is a ground terminal connected to the metal film.